4-rotor anyone
Senior Member
Joined: Nov 2001
Posts: 2,284
That's good.
I've gotta pull the mock up soon to send the plates to Jeff. Just need to secure the exhaust center section while I have access to a primaflow muffler. We won't use it in the final product, but it's useful for aligning the center section while building the header.
It's great the exchange rate will end up costing us less than we thought. All the parts, not including shipping are 4995 x .7 = $3496USD
The grand total will probably be around 10k for everything (rotor housings, carbs etc) but provide the performance of a typical modern 50k sports car.
I've gotta pull the mock up soon to send the plates to Jeff. Just need to secure the exhaust center section while I have access to a primaflow muffler. We won't use it in the final product, but it's useful for aligning the center section while building the header.
It's great the exchange rate will end up costing us less than we thought. All the parts, not including shipping are 4995 x .7 = $3496USD
Senior Member
Joined: Nov 2001
Posts: 2,284
Any word on your intermediate late?
I got the mockup out and torn down. We've gotta get the intermediate plates inspected before sending them to Jeff. We'll also go with an S6 front plate for the big oil pump and an S5 or S6 rear plate. I just hope it doesn't throw Jeff for a loop, with the missmatched coolant seal area.
It turns out we will most likely have the rotating assembly balanced as well. The owner figured if he's spending this much on a project of this magnitude, he might as well spend a fractional amount more for a better end result. Plus it means we won't need to come up with four rotors of the same letter, although starting with all letter C is prefered (two fronts, two rears).
I got the mockup out and torn down. We've gotta get the intermediate plates inspected before sending them to Jeff. We'll also go with an S6 front plate for the big oil pump and an S5 or S6 rear plate. I just hope it doesn't throw Jeff for a loop, with the missmatched coolant seal area.
It turns out we will most likely have the rotating assembly balanced as well. The owner figured if he's spending this much on a project of this magnitude, he might as well spend a fractional amount more for a better end result. Plus it means we won't need to come up with four rotors of the same letter, although starting with all letter C is prefered (two fronts, two rears).
Senior Member
Joined: Feb 2003
Posts: 212
From: Iowa Baby....Oh-Yea
Still have not heard anything on the missing iron...I did tell Jeff that I would give it annother few weeks though.
I think it would be a waste not to have it balanced. Are you going to have the rotors themselves balanced and corrected to the same weights? All of mine are within 2 grams and balanced so it doesnt matter which one goes where, and if I ever have to replace one its not a problem to get the same weight since it will have to be machined anyways=)
I think it would be a waste not to have it balanced. Are you going to have the rotors themselves balanced and corrected to the same weights? All of mine are within 2 grams and balanced so it doesnt matter which one goes where, and if I ever have to replace one its not a problem to get the same weight since it will have to be machined anyways=)
Senior Member
Joined: Nov 2001
Posts: 2,284
We got the intermediate plates inspected and ended up purchasing three good used ones because ours had a little too much step wear. We also got an S6 front plate and an S5 T2 rear plate. The S6 front will allow for a large FD oil pump. The S5 rear plate has the thicker iron where it's needed but still has the oil banjo bolt at the lower corner.
We still need to pick up some stationary gears so we can send everything to Jeff. We also need to weigh an '83-'85 rotor to within 1 gram +/- so he can accurately machine the counterweights. Then when we get everything back we'll have the rotating assembly dynamically balanced, counterweights trimmed(?), oil slingers removed etc.
Speaking of ever replacing something, we might just go with the MFR rotor housings since they'll always be the same should one of ours ever need to be replaced. Compared to custom peripheral ported rotor housings, if we can't get the same person to do the replacement as did the original run of four, we'll be SOL as far as getting them to be the same. They'd get close, but there would be some differences. Meh, maybe I'm worrying too much.
We still need to pick up some stationary gears so we can send everything to Jeff. We also need to weigh an '83-'85 rotor to within 1 gram +/- so he can accurately machine the counterweights. Then when we get everything back we'll have the rotating assembly dynamically balanced, counterweights trimmed(?), oil slingers removed etc.
Speaking of ever replacing something, we might just go with the MFR rotor housings since they'll always be the same should one of ours ever need to be replaced. Compared to custom peripheral ported rotor housings, if we can't get the same person to do the replacement as did the original run of four, we'll be SOL as far as getting them to be the same. They'd get close, but there would be some differences. Meh, maybe I'm worrying too much.
Senior Member
Joined: Feb 2003
Posts: 212
From: Iowa Baby....Oh-Yea
If the person makes a jig for Pporting the housings there shouldnt be a problem making a replacement. Maybe by the time I'm ready to do mine you'll be ready as well then I can just do all four at the same time.
Senior Member
Joined: Nov 2001
Posts: 2,284
I'm getting asked some 4 rotor questions in email and I felt my response is worthy of this thread. My comments are below.
I convinced the owner of the GSL-SE to go with 12A rotors because it meant the tranny could remain in its stock location so there was no need to cut a new hole in the tranny tunnel for the shifter and/or modify the shifter housing and shift rod length; the driveshaft could remain stock so if we break it, it's easy to replace without having to have it shortened, and the total power output will be a little easier on the stock rear end. Some say the stock rears can handle around 400 or 450 HP. Or was that torque? The 4 rotor 12A will have at least 400HP and probably more, but being based on a 12A and peripheral ported, the low end torque figures will be lower than if it had smaller ports and based on a 13B. Of course all bets are off for high RPM. Also the front sway bar can remain, which is something the 2nd gen guys need to remove or modify when installing a 20B in their '86-'92 cars. Plus the owner knows how to keep trannies and rear diffs alive better than most people.
S4 parts are fine to use. Their intermediate plates have three studs on one side and two threaded holes on the other which I suppose can be adapted. You can not use GSL-SE intermediates because you would have no coolant seals. Refer to the change-over from '85 to '86 when Mazda moved the coolant seals from the rotor housings to the side plates. A stupid move on their part because lots of leaks were the result due to minor imperfections in the castings. They have since moved them back to the rotor housings for the RX-8.
We chose GSL-SE intermediate plates because they have studs on both sides. The 12A rotor housings obviously have coolant seals in them. We are also going with a 3rd gen front plate and an '89 to '92 S5 Turbo II rear plate for the oil line banjo bolt location and it's stronger than S4 or GSL-SE. But what about the coolant seals? You can fill them on '86 and later side plates and that's what we'll do. We have to fill the side ports anyway to run peripheral ports. We'll use Devcon.
12A rotors and housings are 70mm while 13B are 80mm. That extra 40mm of length caused too many problems in the GSL-SE engine bay so we went with 12A stuff. I built a mock-up and used 12A and 13B dowel pins to align everything and some welded 12A tension bolts to hold it all together. The front mount capability of the '85 and older front covers could have been used but the intermediate plates were right above the main crossmember so a mid mount solution was much more feasible. Plus the extra 128 pounds and the increase in power on the aluminum front cover worried me a little.
Hardened stationary gears are easy to buy from Racing Beat. Cryo? I couldn't tell you. Probably heat treated and case hardened like the stock eccentric shafts. Jeff Bruce can machine hardened gears just as easily as stock gears because only the gear part is hardened. They come with bearings. I believe stock bearings are appropriate here because with two extra stationary and rotor bearings bleeding off oil pressure and volume, plus the less likelyhood of shaft flex with the extra support, the larger clearance of race bearings didn't make any sense. I want as much oil pressure at low RPM as possible because, being a street car, it's expected to spend some of its time down there.
We'll be using some Weber 51 IDA carbs. The owner doesn't care for the complication of EFI. A reliable and dead-simple ignition solution is to mod an '81-'85 dizzy to move the trailing pickup some 135° or 225° away from the leading pickup so the front rotors, which are phased 180° apart just like any 2 rotor engine, can be fired together every 180° of shaft rotation. That covers leading. For trailing, which technically won't be trailing anymore, it will fire the rear rotors every 180° of shaft rotation, but it will be offset from the front set by 90°. Were you able to follow all that?
Perhaps a better explanation is since the dizzy shaft spins half speed, and the stock reluctor has four tips, only two tips pass by a pickup every 360° of eccentric shaft rotation. Leave the leading pickup in its stock position and it will function fine on the rotor pair which is phased 180° apart just like any 2 rotor engine which employs a direct fire ignition system with dual leading sparks like DLIDFIS or 2GCDFIS (simultaneously fired or sometimes incorrectly refered to as wasted spark). Both rotors will get adequate spark. Did you know some rotor housings came stock without the trailing holes machined? Interesting piece of trivia for you.
Since trailing does nothing for power in an NA (naturally aspirated), but many have proven that simultaneously fired leading does improve things over single fired leading, it's no problem to employ the trailing pickup for the other rotor pair. The only problem is moving it so the reluctor tips will pass by 90° after they pass by the leading pickup. You can't move it 90° inside the dizzy housing because the reluctor tips are at 90° and the dizzy shaft spins half the speed of the eccentric shaft. One degree of movement in the dizzy housing equals two degrees at the eccentric shaft. The stock location for the trailing pickup is about 187° offset counterclockwise from the leading pickup. A relcutor tip passes by the leading pickup and then about 15 eccentric shaft degrees later, another reluctor tip, on the opposite side of the reluctor, passes by the trailing pickup. If I could delay that other tip from passing by the trailing pickup until 90° of eccentric shaft rotation have occured, I'd be in business. That means moving it about 45° away from its stock position or precisely 135° away from the leading pickup.
I was the first to use a MegaSquirt with a 20B. I was able to get dual leading sparks out of it by doubling the input 6-1 trigger signal. The input signal is hard coded to the output ignition trigger events but the injection events were adjustable so by doubling the incoming trigger signal from my 12-1 wheel (a modded stock CAS by removing four teeth instead of two), and calling the engine a V12, the MegaTune tach read correctly and the injection events were basically whatever I wanted. It worked as far as I could tell. I don't know how to tune and didn't have an O2 sensor at the time. I still don't know how to tune and the 20B is going into as 1st gen a little later this year. The engine needs a rebuild though. I was going to install it, get it running again and then rebuild it. There's nothing like the problems that arise from a fresh rebuild and trying to get a MegaSquirt tuned at the same time.
Anyway the point of the paragraph above is to say that I was able to get dual leading sparks out of the MegaSquirt for my 20B and it worked. No need for trailing. Plus it's NA with no plans to go turbo any time soon. I assume your 4 rotor will also be NA. At least with the 4 rotor, the ignition can get away with as little as two outputs instead of three. You could probably call it a wasted spark 4 cylinder with DIS if I remember my MS nomenclature correctly.
Oh, I bet you're curious about the ignitors and coils I used. For DLIDFIS, one pickup signal is shared between two ignitors, and each ignitor has its own coil, and each coil goes to a leading spark plug. Only the pickup signal is shared. It sparks both leading plugs together every 180° of eccentric shaft rotation. One rotor is at TDC (top dead center) and the other is in its exhaust phase. Igniting the trailing edge of the AF (air/fuel) mixture in the 'squish zone' of the exhaust phase rotor improves emmissions substantially and seems to increase power and smoothness. Starting is much easier. If you have an air fuel mixture guage, the LEDs tend to stabilize instead of producing a light show. That is assuming your tuning is right or at least close. A better ignition can cover for shoddy tuning. Since a 100% correct tune is not possible over the entire rev range and driving conditions, improving the ignition is a no-brainer. Especially if you've got a stock distributor based setup like on the 1st gens and older. Some people have said the stock 2nd gen ignition systems are weak, but they're actually very powerful. Don't read all your information from one source (including me - do more research).
As for the ignitors themselves, some MegaSquirt people like to use GM HEI ignitors. I've bench tested them with the MS with good results and used them on DLIDFIS projects. I've also used stock J-109s from the 1st gens here and there and with the MegaSquirt. I didn't like the results when using the stock ignitors in 2nd gens (located in the base of the coil holder). Maybe I need to do more research, but they would start to miss where the J-109s and GM HEIs wouldn't when connected to the MS.
I have used stock Diamond coils and some Bosch aftermarket coils for DLIDFIS. The 20B had three J-109s and three Diamond coils and ran great ignition-wise as far as I could tell. The 12A based 4 rotor will probably have two GM HEIs and two 2nd gen leading dual output coils. This idea reduces the complication by half of what it would have been had I gone with my original idea of using four ignitors and four coils. The dual outputs will work perfectly on each rotor pair that's offset by 180° because most of the power goes to the spark plug which needs it i.e. the one which is compressed and about to fire. The other is in its exhaust phase and requires very little voltage for the spark to jump due to the increased ionization present around the spark plug and the lower pressure. Basically on a kettering ignition system (points and transistor like J-109, GM HEI, stock 2nd gen), the harder it is for the spark to jump, the higher the voltage goes up. The nice thing about kettering is it produces a long duration spark compared to CDI (capacitive discharge ignition) systems like MSD, Crane etc. CDI works ok on turbos where the higher pressure due to boost, retarded ignition, and higher octane required to prevent knock etc would be too much for kettering. However you want a long duration spark, fair amount of advance and low octane on an NA for best power. CDI works on an NA, but in my and others' experience, kettering is best on a rotary if for no reason other than the long duration spark is particularly well suited to the long combustion chamber of a rotary. The MSD boasts multistrike sparks, but they only occur at low RPM. The rotary loves to be at high RPM and a peripheral port will spend most of its time up there. If the dual 2nd gen coils don't work out, I know DLIDFIS will. No need for two clunky red boxes.
I don't know how many others have attempted a 4 rotor with the MegaSquirt. You might be the first. One other person (patman) has gotten a 20B to run, but he went a different direction. You might be able to get away with two 2nd gen leading coils and use the stock ignitors since they were designed to be triggered by a 5 volt square wave output from an ECU. This is bordering on the edge of my knowldege base here. I experienced problems with them but I believe others have used them just fine.
Hmm, I suppose I should ask whether you're wanting to use the MegaSquirt for ignition only, or whether fuel injection is also planned. Not that I'd be any help in that regard, but maybe I could list some alternatives, if there are any (like carbs). I've already described how to do the ignition with a modded dizzy. Do you understand at which degrees each rotor reaches TDC? Do you understand the basics of ignition now? Do you want to use peripheral ports or side ports? Or both? What type of car will it go in? The engine will be 13B based (26B) since you're wanting to use S4 cores, right? Will it fit in the engine bay? I guess what I'm asking is how much research have you done thus far, and how many gaps have yet to be filled.
Jeff
Thanks for taking the time to reply Jeff. I really do appreciate it.
Your choice of three GSL-SE intermediate plates is strictly because of the mounting simplicity? As well as location in the engine bay, I take it the rotors and housings are diffirent lengths from other choices? I have S4 cores sitting around and want to use what I have here. I also work at a machine shop so fabricating a subframe wouldnt be all too difficult for me.
Hardened Stationary Gears...Im assuming cryo treated?
Ignition is something I still need to do much research on. As a shot from the hip I assumed that Megasquirt would have a programable application I could adapt.
Let me know what you think. Thanks again for the info.
J Gandy
Your choice of three GSL-SE intermediate plates is strictly because of the mounting simplicity? As well as location in the engine bay, I take it the rotors and housings are diffirent lengths from other choices? I have S4 cores sitting around and want to use what I have here. I also work at a machine shop so fabricating a subframe wouldnt be all too difficult for me.
Hardened Stationary Gears...Im assuming cryo treated?
Ignition is something I still need to do much research on. As a shot from the hip I assumed that Megasquirt would have a programable application I could adapt.
Let me know what you think. Thanks again for the info.
J Gandy
S4 parts are fine to use. Their intermediate plates have three studs on one side and two threaded holes on the other which I suppose can be adapted. You can not use GSL-SE intermediates because you would have no coolant seals. Refer to the change-over from '85 to '86 when Mazda moved the coolant seals from the rotor housings to the side plates. A stupid move on their part because lots of leaks were the result due to minor imperfections in the castings. They have since moved them back to the rotor housings for the RX-8.
We chose GSL-SE intermediate plates because they have studs on both sides. The 12A rotor housings obviously have coolant seals in them. We are also going with a 3rd gen front plate and an '89 to '92 S5 Turbo II rear plate for the oil line banjo bolt location and it's stronger than S4 or GSL-SE. But what about the coolant seals? You can fill them on '86 and later side plates and that's what we'll do. We have to fill the side ports anyway to run peripheral ports. We'll use Devcon.
12A rotors and housings are 70mm while 13B are 80mm. That extra 40mm of length caused too many problems in the GSL-SE engine bay so we went with 12A stuff. I built a mock-up and used 12A and 13B dowel pins to align everything and some welded 12A tension bolts to hold it all together. The front mount capability of the '85 and older front covers could have been used but the intermediate plates were right above the main crossmember so a mid mount solution was much more feasible. Plus the extra 128 pounds and the increase in power on the aluminum front cover worried me a little.
Hardened stationary gears are easy to buy from Racing Beat. Cryo? I couldn't tell you. Probably heat treated and case hardened like the stock eccentric shafts. Jeff Bruce can machine hardened gears just as easily as stock gears because only the gear part is hardened. They come with bearings. I believe stock bearings are appropriate here because with two extra stationary and rotor bearings bleeding off oil pressure and volume, plus the less likelyhood of shaft flex with the extra support, the larger clearance of race bearings didn't make any sense. I want as much oil pressure at low RPM as possible because, being a street car, it's expected to spend some of its time down there.
We'll be using some Weber 51 IDA carbs. The owner doesn't care for the complication of EFI. A reliable and dead-simple ignition solution is to mod an '81-'85 dizzy to move the trailing pickup some 135° or 225° away from the leading pickup so the front rotors, which are phased 180° apart just like any 2 rotor engine, can be fired together every 180° of shaft rotation. That covers leading. For trailing, which technically won't be trailing anymore, it will fire the rear rotors every 180° of shaft rotation, but it will be offset from the front set by 90°. Were you able to follow all that?
Perhaps a better explanation is since the dizzy shaft spins half speed, and the stock reluctor has four tips, only two tips pass by a pickup every 360° of eccentric shaft rotation. Leave the leading pickup in its stock position and it will function fine on the rotor pair which is phased 180° apart just like any 2 rotor engine which employs a direct fire ignition system with dual leading sparks like DLIDFIS or 2GCDFIS (simultaneously fired or sometimes incorrectly refered to as wasted spark). Both rotors will get adequate spark. Did you know some rotor housings came stock without the trailing holes machined? Interesting piece of trivia for you.
Since trailing does nothing for power in an NA (naturally aspirated), but many have proven that simultaneously fired leading does improve things over single fired leading, it's no problem to employ the trailing pickup for the other rotor pair. The only problem is moving it so the reluctor tips will pass by 90° after they pass by the leading pickup. You can't move it 90° inside the dizzy housing because the reluctor tips are at 90° and the dizzy shaft spins half the speed of the eccentric shaft. One degree of movement in the dizzy housing equals two degrees at the eccentric shaft. The stock location for the trailing pickup is about 187° offset counterclockwise from the leading pickup. A relcutor tip passes by the leading pickup and then about 15 eccentric shaft degrees later, another reluctor tip, on the opposite side of the reluctor, passes by the trailing pickup. If I could delay that other tip from passing by the trailing pickup until 90° of eccentric shaft rotation have occured, I'd be in business. That means moving it about 45° away from its stock position or precisely 135° away from the leading pickup.
I was the first to use a MegaSquirt with a 20B. I was able to get dual leading sparks out of it by doubling the input 6-1 trigger signal. The input signal is hard coded to the output ignition trigger events but the injection events were adjustable so by doubling the incoming trigger signal from my 12-1 wheel (a modded stock CAS by removing four teeth instead of two), and calling the engine a V12, the MegaTune tach read correctly and the injection events were basically whatever I wanted. It worked as far as I could tell. I don't know how to tune and didn't have an O2 sensor at the time. I still don't know how to tune and the 20B is going into as 1st gen a little later this year. The engine needs a rebuild though. I was going to install it, get it running again and then rebuild it. There's nothing like the problems that arise from a fresh rebuild and trying to get a MegaSquirt tuned at the same time.
Anyway the point of the paragraph above is to say that I was able to get dual leading sparks out of the MegaSquirt for my 20B and it worked. No need for trailing. Plus it's NA with no plans to go turbo any time soon. I assume your 4 rotor will also be NA. At least with the 4 rotor, the ignition can get away with as little as two outputs instead of three. You could probably call it a wasted spark 4 cylinder with DIS if I remember my MS nomenclature correctly.
Oh, I bet you're curious about the ignitors and coils I used. For DLIDFIS, one pickup signal is shared between two ignitors, and each ignitor has its own coil, and each coil goes to a leading spark plug. Only the pickup signal is shared. It sparks both leading plugs together every 180° of eccentric shaft rotation. One rotor is at TDC (top dead center) and the other is in its exhaust phase. Igniting the trailing edge of the AF (air/fuel) mixture in the 'squish zone' of the exhaust phase rotor improves emmissions substantially and seems to increase power and smoothness. Starting is much easier. If you have an air fuel mixture guage, the LEDs tend to stabilize instead of producing a light show.
As for the ignitors themselves, some MegaSquirt people like to use GM HEI ignitors. I've bench tested them with the MS with good results and used them on DLIDFIS projects. I've also used stock J-109s from the 1st gens here and there and with the MegaSquirt. I didn't like the results when using the stock ignitors in 2nd gens (located in the base of the coil holder). Maybe I need to do more research, but they would start to miss where the J-109s and GM HEIs wouldn't when connected to the MS.
I have used stock Diamond coils and some Bosch aftermarket coils for DLIDFIS. The 20B had three J-109s and three Diamond coils and ran great ignition-wise as far as I could tell. The 12A based 4 rotor will probably have two GM HEIs and two 2nd gen leading dual output coils. This idea reduces the complication by half of what it would have been had I gone with my original idea of using four ignitors and four coils. The dual outputs will work perfectly on each rotor pair that's offset by 180° because most of the power goes to the spark plug which needs it i.e. the one which is compressed and about to fire. The other is in its exhaust phase and requires very little voltage for the spark to jump due to the increased ionization present around the spark plug and the lower pressure. Basically on a kettering ignition system (points and transistor like J-109, GM HEI, stock 2nd gen), the harder it is for the spark to jump, the higher the voltage goes up. The nice thing about kettering is it produces a long duration spark compared to CDI (capacitive discharge ignition) systems like MSD, Crane etc. CDI works ok on turbos where the higher pressure due to boost, retarded ignition, and higher octane required to prevent knock etc would be too much for kettering. However you want a long duration spark, fair amount of advance and low octane on an NA for best power. CDI works on an NA, but in my and others' experience, kettering is best on a rotary if for no reason other than the long duration spark is particularly well suited to the long combustion chamber of a rotary. The MSD boasts multistrike sparks, but they only occur at low RPM. The rotary loves to be at high RPM and a peripheral port will spend most of its time up there. If the dual 2nd gen coils don't work out, I know DLIDFIS will. No need for two clunky red boxes.
I don't know how many others have attempted a 4 rotor with the MegaSquirt. You might be the first. One other person (patman) has gotten a 20B to run, but he went a different direction. You might be able to get away with two 2nd gen leading coils and use the stock ignitors since they were designed to be triggered by a 5 volt square wave output from an ECU. This is bordering on the edge of my knowldege base here. I experienced problems with them but I believe others have used them just fine.
Hmm, I suppose I should ask whether you're wanting to use the MegaSquirt for ignition only, or whether fuel injection is also planned. Not that I'd be any help in that regard, but maybe I could list some alternatives, if there are any (like carbs). I've already described how to do the ignition with a modded dizzy. Do you understand at which degrees each rotor reaches TDC? Do you understand the basics of ignition now? Do you want to use peripheral ports or side ports? Or both? What type of car will it go in? The engine will be 13B based (26B) since you're wanting to use S4 cores, right? Will it fit in the engine bay? I guess what I'm asking is how much research have you done thus far, and how many gaps have yet to be filled.
Jeff
Senior Member
Joined: Nov 2001
Posts: 2,284
I want to get this guy on the forum because I'm just about out of information, and he seems pretty serious.
I went through all my A material with the last email. I'm not sure what more I can tell you. I guess I'll reread your email and try to answer some key points.
I assumed only the gear part of the stationary gear was hardened because it doesn't make sense to harden the rest of it. The hardening is to reduce wear but make it too hard and it becomes brittle and can crack (cracking was the problem with early gears). Either way, Jeff Bruce said he can machine hardened gears. All he does is machine the base down a little so it'll fit in the intermediate plates.
I still think stock bearings are best, even for operation above 8500 because the shaft flex issue of 2 rotor engines most likely doesn't exist in a 4 rotor. Also the lighter the rotors, the less likelyhood of flexing.
Speaking of lighter rotors, you need to do more research in that area. For a 13B, I'd only use S5 rotors. Get them dynamically balanced along with the shaft and counterweights. You'll need to find someone nearby who can do that.
For ignition, the MS set to 4 cylinder DIS mode should work, maybe. It depends whether you want dual leading sparks only or single leading and trailing sparks. I'm the only person who thinks dual leading is superior to single fire leading and trailing. Of course I have a deeper understanding of rotary ignition than most people. I'm sure others would disagree. Hey, my stuff works for me.
Since you want to run a turbo some day, maybe you should just go with single leading and trailing sparks, fired together, requiring 8 seperate coils and ignitors. It'll be a wiring nightmare. Good luck fitting it all under the hood.
Please note that you can't use 4 dual output coils where each coil's dual outputs go to the same rotor housing. That doesn't work. Something about the pressure and the spark energy. Anyway the only correct way to use a dual output coil is if one side is in compression and the other is in exhaust. It works this way on rotaries and pistons. Remember that part about the ionized exhaust around the spark plug in my last email?
My way is deceptively simple. Two dual output coils; one to each 180° phased pair of rotors just like a stock 2nd gen.
Next I'll describe the firing order.
L1 0°
L3 90°
L2 180°
L4 270°
Easy enough. To get an idea of where the dual leading sparks come in, just remember that L1 and L2 are phased 180° apart and can be sparked at the same time. Same goes for L3 and L4, which can also be sparked at the same time, but the event must happen 90° after L1 and L2. It's so simple it's counter intuitive.
The end result looks like this.
L1+L2 0°
L3+L4 90°
L1+L2 180°
L3+L4 270°
We're still sparking at the same timing intervals, but instead of sparking each plug individually, we're sparking the two that are phased 180°. Then 90° later, the other set. Simple, elegant, very easy to fit and diagnose.
The above can be accomplished with a dizzy or a CAS. I've already described how to do it with a simple mod to the dizzy and a couple of GM HEI ignitors. The other way is with a CAS. The CAS will send a signal to the ECU, and the ECU will output a trigger signal to the stock ignitor in the base of each coil. This solution is more elegant and high-tech but requires a middle man (ECU) while the dizzy solution is perfect for carbs. Either way, it's far easier to deal with than a 20B.
So for right now since you plan on doing an NA setup first, I'd go with the two 2nd gen leading coils and not worry about trailing. The dual leading sparks will cover for the loss of trailing and add more than if you had single leading sparks with or without trailing (believe me, the difference trailing makes is not noticeable, but dual leading vs single leading is noticeable). Dyno tests have proven trailing does nothing for power. Numerous tests by 1st gen and early rotary owners (who upgraded from points or a hacked-in electronic dizzy from a 1st gen) have really fallen in love with the extra power and smoothness/driveability of my leading direct fire ignition upgrade. I wouldn't be caught dead doing anything less on my rotaries. I guess that's where my true passions are.
Again you need to do more research on rotors. I don't know of anyone who fills rotors to change the compression. 20B rotors are the same as S5 T2 9.0:1. I'll run my 20B NA because I don't know how to tune and it's an early engine. If it was a B series or later, I could get away with a large single. It's ok though since it's going into a 1st gen. I always have the option to turbo it in the future, but I'll keep it small because too much power will make it untractable. You need to examine just how much power you can get away with in an FD.
You should start with S5 T2 rotors and leave them at 9:1 compression. Don't bother with the NA rotors at 9.7 or whatever they are because you'll lose the ability to turbo it in the future. Besides, the early rotaries were 9.2 compression until the GSL-SE which went to 9.4 compression. I'd say 9.0 isn't much of an issue. The actual power loss or gain from different compression dish depths is actually quite minimal in NA form. I wouldn't lose sleep over it. Just go with S5 T2.
As for getting them lightened, it's costly and entirely up to you. We were going to use the lightest stock 12A rotor ever made; the '83-'85 which weigh about the same as S5 rotors if I remember correctly. And we were going to compensate for the extra rotating weight by using the lightest flywheel we can find that will fit our tranny. The car currently has a 1st gen tranny so we're stuck with no larger than 225mm. But that's not a bad thing because it is a smaller diameter than 240mm (T2) and therefore has less interia between shifts. I'm thinking a puck style clutch should hold the power and not weigh too much. This model appears more streetable than ACT and fits '83-'92 NA. http://cgi.ebay.com/ebaymotors/XTD-STAGE-3...1QQcmdZViewItem
What I think about exhaust is in order to make it streetable it will need a lot of muffling, which will kill power but is a necessary evil, unless an alternative could be found which would allow for quiet street driving but also provide the free flow that a peripheral port needs. Nothing like that exists. Either you can have small ports and lots of muffling, which might work, or large ports and almost no muffling but forget about driving it on the street. You can't have it both ways.
So I started looking for alternatives. I came up with an exhaust cutout with an electric valve. Either wire it up to a switch or maybe even the gas pedal so when it's mashed, the valve opens and the unmuffled (or maybe lightly muffled depending on where it's located in the system) is free to make as much noise as it wants. If we weren't going with MFR housings and their large ports, I don't think the exhaust cutout would be necessary because the power peak would be below 8 grand, but the owner insists on them so I had to come up with a solution that would allow it to be driven on the street but also flow well enough for the higher RPM these housings are capable of. Of course they will kill the low end but we figured having four of them will compensate for the loss down low, and the 1st gens are so light that even a street ported 12A has some get up and go down low.
If the thing idles below 2 grand, I'll be surprised. It's his project and his money. If I had my druthers I'd have gone with smaller ports that cost less than the MFR housings, and the 48mm IDA carbs, again for a lower cost than the 51mm, and stock apex seals since he has one or two sets of new Mazda seals already instead of buying 12 new carbon seals, and we'd need to keep the RPM below 8400, thus smaller ports would be necessary to hopefully peak at around 7k or so. The idle quality and street driveability would be much better as well with the total power output reduced a noticeable amount. It would probably feel faster since the torque would be lower in the RPM range and used more often. But then again, he's the type of person that actually enjoys driving a jungle cat. A smooth torquy low end isn't as important as high end power to him. He's from the old school of street ports, RB Holley carbs and a loud header exhaust. Low end torque and rotaries don't coexist in his mind. I'm the opposite where I'd prefer stock or near stock ports, a stock carb for the low end driveability and major ignition improvements with a well built, quiet but adequately flowing exhaust. I'll soon put my money where my mouth is when I get some of my projects going around here.
I suppose I could delve into the exhaust design we're working with. Racing Beat sells a long primary dual pipe exhaust system that consists of a short header that connects to a dual pipe center section which contains one presilencer per pipe, that then connects to a primaflow muffler which has a Y adaptor which funnels the pipes into a single 2.5" pipe before it enters the muffler. This system is very nice for a ported 12A or 13B whether NA or superchargerd. My owner also has a 5" Camden on a streetported 13B in an '81 GSL and it has enough torque to break the rear tires loose in gear on dry road. Perfectly adequate flow for that much power. He's never dynoed it so we don't know how much power it actually has, but he and Dave Atkins worked it out to around 195HP or so. So what happens if you double the HP? Of course the torque curve of a large periport will look different but it still crosses over at 5252RPM and with MFR ports, the power will keep building up probably to 10k or something like that. Scary to think about.
Wait a minute. What does the RB dual pipe system have to do with a 4 rotor project? He purchased the center section and two dissassembled header kits (the same 'road race' header that comes with the dual pipe system, only you weld it for custom applications) and two unflanged collector assemblies (Y adaptors). Each 180° rotor pair will collect into a Y adaptor and go down one pipe of the dual pipe center section. So the car will essentially have two single pipe center sections with a presilencer on each rotor pair. The nice part about this is since the rotor pairs will join together sooner, as per RB's short primary header instructions suggesting 10 to 18 inches as opposed to their long primary of 89 to 94 inches, it should allow enough room to fit it all under the hood and be quiet. RB also recommends 1.9 to 2.0" inner diameter. Their pipes are actually closer to 1.8, but such a small difference probably won't be a big deal, especially if we uncork it with the exhaust cutout.
Exhaust manifolds are the quietest. Short primary headers are louder and long primaries are the loudest. Think of a speaker box with two woofers. What happens when one is hooked out of phase? The bass disappears. They are phased 180° apart and cancel each other out. The same can be said for an exhaust manifold where the ports join very close to the engine. The further away they join, the louder the exhaust will be. Also, since only one port is flowing at any one time, it's ok to funnel two 2" OD pipes into a single 2" OD pipe as long as the angle at which they join is smooth at 30° to 40°.
The difference in exhaust noise between an RB dual pipe system and a single pipe system is quite appearant. The dual pipe system is quite a bit louder. Now imagine how my 4 rotor project will sound where each 180° pair of rotors flows into just one pipe of the dual pipe center section. Each pair will flow through one presilencer and come out quieter than if it had a 2 rotor engine. Well, maybe not quieter but certainly no louder. I've heard an RB dual pipe system without the muffler and it's dangerously loud. I've also heard the single pipe system without a muffler and it wasn't nearly as loud.
It's a question of acousticlly balancing with noise cancellation rather than that of impedance to flow, like what stock systems do. It's ingenious and elegant, kinda like my ignition idea, I think.
It's well known the Primaflow mufflers are somewhat restrictive in order to quiet the rotary enough to pass noise ordinances and sound good. That kind of restriction worries me. If the 4 rotor had smaller ports with power limited to around 300HP, it would be ok. However since the owner wants to use MFR housings, I have to install a cutout. Chances are the only place it will fit is within the single 2.5" pipe where it goes over the rear end, maybe. I'd rather not install two (one on each of the center section pipes) because it just adds complication and would cost twice as much, plus I'd lose the awesome 4 rotor sound and it would end up sounding more like two 12As reving together. No thanks. I want it to be loud and obnoxious, but quiet and streetable too. An exhaust cutout with an electric valve should give me what I want.
I'd say this email had a little more A material in it than I though. I don't think Ihave any more in me. I'm also not sure how much of it you'll find useful.
If you have no idea what I just talked about, I can give you some links to the RB exhaust components so you can get a visual. Maybe it'll help you design an exhaust sytem for your FD. Turbo rules don't apply to an NA unless you're going to turbo it some day. Then again, a turbo can quiet an exhaust some 50% but it also acts like an ugly cork in the system. My 20B could rev much faster than the PAC Performance RX-3 because mine was NA with a light steel flywheel and no clutch on it at the time (I was test firing it to check on ignition). I bet if it had an aluminum flywheel with a clutch and pressure plate, it would rev about the same. The Pac RX-3 had a large turbo and an automatic torque convertor. Both had very loud exhausts and sounded raspy and generally pretty awesome. I want something similar for the 4 rotor. Check here for the RX-3 http://www.geocities.com/cd23c/
I can send you the audio clip of my 20B if you want.
Anyway, here are the RB exhaust parts.
Disassembled Road Race Header Kit 74-85 (12A) (we got two)
http://www.racingbeat.com/resultset....rtNumber=16211
Street Port Center Section 79-85 RX-7
http://www.racingbeat.com/resultset....rtNumber=16398
Unflanged Collector Assembly (we got two)
http://www.racingbeat.com/resultset....rtNumber=16004
We still need to get this muffler.
http://www.racingbeat.com/resultset....rtNumber=16433
Hmm, reading the specs on that muffler, I sure am glad I have the option of adding a cutout.
Pports are the simplest.
Jeff Bruce can do any intermediate plate you want; with or without fuel injector holes.
Hmm, maybe you could buy us some MFR rotor housings with your discount. What are the rules on stuff like that?
Well, I think I've used up all my A meterial. You really should consider getting on the forum. There is a lot more to it than I can cover. Much of what I talk about is due to my assumption that the other person already has an idea of what I'm talking about. Several people on the forum could help fill in the gaps better than I could. Especially if it is FD-specific and powerFC/EFI specific and what not.
By the way, I posted our correspondence on the forum because it's filled with a ton of useful info. Perhaps others will read through it and fill in the gaps that I missed.
>I guess alot of your choices were for the specific application/vehicle. Alot of what I want to do wont be known until I get a front end to start fabricating things and test fitting with. Too bad most of the rollers ive seen all have all had front end damage and I cant seem to find any bare clips cut at the firewall. If I didnt have my streetported engine already in my FD I could get some preliminary notes taken.
>
> So it looks like your setup is what I was going to try out to begin with. Your right alot of your stuff is covered in the thread. Filling the coolant seal seats is the first thing I thought of when you mentioned that setup. Devcon? Ill do some research but ive never heard of it...?
>
> That was one of the questions I had on the stationary gears. I assumed they were machined and then hardened, I honestly didnt know that it was just the gears that were hardened...im curious why that is instead of treating the entire stationary gear.
>
> On that note I see you really like the idea of using the stock bearing. Personally I want to see just how far we can go on a build with used parts and wish to see some high RPM use. I would imagine if your build were geared more toward operation above 8500 race bearings would be your choice?
>
> Your choice on ignition setup...Definitly lost me. Pics of your work would hlep alot. I have done nothing with distributors other than replace them and clean up leads and rotor tips. Im a quick learner so I know its not beyond me however this would be the first time I have had to delv into something like this. In fact the Power FC setup is my first attempt at tuning and I plan on doing my own research and comparisons to tune that myself. I know its dangerous territory, however I feel if one takes there time and does the homework the risk can be reasonably minimised.
>
> For right now yes I do plan on doing an NA setup. The idea of a turbo was in the back of my head for HP figures only, the numbers ive seen from the NA engines running so far are more than adequate I think, however all of my builds tend to get a little extreem. Last year I put together a 13:1 4AGE for my corolla GTS and it was street driven. This 13B REW has a very large street port that I want to mate an R85 single with. My goal is to tune it to just over 500, as soon as I see that number im going to want the 4 rotor in it. From there the idea was to turbo the 4 rotor and limit my boost until I could learn to drive the car.
>
> From what Im seeing in these setups though there is alot of room for little things here and there, like header design and possibly filling in the rotor surface a bit to increase compression. I was looking at the MFR catalogue yesterday and saw that some of the 20Bs had extreemly light rotors, somewhere around 3700 grams compared to the 4300 or so grams of the S4 rotors I have now. So I had the idea of trying to use the 20B rotors as a base and possibly fill them in to raise compression. However teh S5 rotors have higher compression as it is. Im not sure if I want to try getting more compression from filling of teh rotor face on lighter rotors or simply start with S5 rotors that might be easier to source.
>
> I touched on Header design. The owner of teh machine shop I work at was teaching me about header lengths and design just the other day and there are a few combinations I can play with there to help an NA motor build power where i want it. I would really like to target the low end tourque issues ive been reading about however. This also has alot to do with the size porting I would have, so there are still alot of combinations I have to calculate before making those decisions. What do you think?
>
> Ill try and answere all the questions below. I can definitly start off by saying there are ALOT of gaps that need to be filled still. I had a really nice diagram that discribed TDC for each rotor, it was actually really easily understood. I need to look that thing up again, I should actually have it saved. I keep everything I come accross...even these emails, lol.
>
> I would think that it would be simplest to go with just PPorts...?
>
> If memory serves wasnt Bruces setup EFI? Thats the way I would like to go.
>
> I think I already discribed that it would be a 26B going into a FD. At this point I really dont know about fitment. There is a clutch issue I plan to remove my engine for, its doubtfull however I guess I could break down a front and rear plate and slide one of my random GSL-SE plates in as an intermediate and use it as a mock up as you did and play around with it for a while, take a few measurments and notes. My FD needs to be ready by June for a few events if I want to get into the MFR parts program. Are you familiar with it? If your a member of a sanctioning body and can prove your racing you can get MFR and OEM parts at a greatly reduced price. Thats the basic jist of it.
>
> Idealy I would have a front clip stipped bare to mock everything up with.
>
> It probably sounds like im in a bit over my head when I say that I dont understand the basics of ignition yet however with the learning im doing for the Power FC tuning and some help from you with this 4 rotor build im confident i will wrap my brain around it by the time im ready to start building an ignition system for it.
>
> What gaps need to be filled? There are nothing but gaps to me at this point, lol. Im simply very used to learning everything and doing it myself. It usually takes me a bit longer because of that however with me currently working at a machine shop I have too many resources around me to say that I cant learn to do this build with very little external hands on help.
>
> If im too far off track here and need a little critisism please dont hesitate to shake a finger or two at me. Direction and a little understanding/knowledge is what Im talking to you for in the first place.
>
> Thanks again Jeff. I look forward to your next reply.
>
> J Gandy
>
> So it looks like your setup is what I was going to try out to begin with. Your right alot of your stuff is covered in the thread. Filling the coolant seal seats is the first thing I thought of when you mentioned that setup. Devcon? Ill do some research but ive never heard of it...?
>
> That was one of the questions I had on the stationary gears. I assumed they were machined and then hardened, I honestly didnt know that it was just the gears that were hardened...im curious why that is instead of treating the entire stationary gear.
>
> On that note I see you really like the idea of using the stock bearing. Personally I want to see just how far we can go on a build with used parts and wish to see some high RPM use. I would imagine if your build were geared more toward operation above 8500 race bearings would be your choice?
>
> Your choice on ignition setup...Definitly lost me. Pics of your work would hlep alot. I have done nothing with distributors other than replace them and clean up leads and rotor tips. Im a quick learner so I know its not beyond me however this would be the first time I have had to delv into something like this. In fact the Power FC setup is my first attempt at tuning and I plan on doing my own research and comparisons to tune that myself. I know its dangerous territory, however I feel if one takes there time and does the homework the risk can be reasonably minimised.
>
> For right now yes I do plan on doing an NA setup. The idea of a turbo was in the back of my head for HP figures only, the numbers ive seen from the NA engines running so far are more than adequate I think, however all of my builds tend to get a little extreem. Last year I put together a 13:1 4AGE for my corolla GTS and it was street driven. This 13B REW has a very large street port that I want to mate an R85 single with. My goal is to tune it to just over 500, as soon as I see that number im going to want the 4 rotor in it. From there the idea was to turbo the 4 rotor and limit my boost until I could learn to drive the car.
>
> From what Im seeing in these setups though there is alot of room for little things here and there, like header design and possibly filling in the rotor surface a bit to increase compression. I was looking at the MFR catalogue yesterday and saw that some of the 20Bs had extreemly light rotors, somewhere around 3700 grams compared to the 4300 or so grams of the S4 rotors I have now. So I had the idea of trying to use the 20B rotors as a base and possibly fill them in to raise compression. However teh S5 rotors have higher compression as it is. Im not sure if I want to try getting more compression from filling of teh rotor face on lighter rotors or simply start with S5 rotors that might be easier to source.
>
> I touched on Header design. The owner of teh machine shop I work at was teaching me about header lengths and design just the other day and there are a few combinations I can play with there to help an NA motor build power where i want it. I would really like to target the low end tourque issues ive been reading about however. This also has alot to do with the size porting I would have, so there are still alot of combinations I have to calculate before making those decisions. What do you think?
>
> Ill try and answere all the questions below. I can definitly start off by saying there are ALOT of gaps that need to be filled still. I had a really nice diagram that discribed TDC for each rotor, it was actually really easily understood. I need to look that thing up again, I should actually have it saved. I keep everything I come accross...even these emails, lol.
>
> I would think that it would be simplest to go with just PPorts...?
>
> If memory serves wasnt Bruces setup EFI? Thats the way I would like to go.
>
> I think I already discribed that it would be a 26B going into a FD. At this point I really dont know about fitment. There is a clutch issue I plan to remove my engine for, its doubtfull however I guess I could break down a front and rear plate and slide one of my random GSL-SE plates in as an intermediate and use it as a mock up as you did and play around with it for a while, take a few measurments and notes. My FD needs to be ready by June for a few events if I want to get into the MFR parts program. Are you familiar with it? If your a member of a sanctioning body and can prove your racing you can get MFR and OEM parts at a greatly reduced price. Thats the basic jist of it.
>
> Idealy I would have a front clip stipped bare to mock everything up with.
>
> It probably sounds like im in a bit over my head when I say that I dont understand the basics of ignition yet however with the learning im doing for the Power FC tuning and some help from you with this 4 rotor build im confident i will wrap my brain around it by the time im ready to start building an ignition system for it.
>
> What gaps need to be filled? There are nothing but gaps to me at this point, lol. Im simply very used to learning everything and doing it myself. It usually takes me a bit longer because of that however with me currently working at a machine shop I have too many resources around me to say that I cant learn to do this build with very little external hands on help.
>
> If im too far off track here and need a little critisism please dont hesitate to shake a finger or two at me. Direction and a little understanding/knowledge is what Im talking to you for in the first place.
>
> Thanks again Jeff. I look forward to your next reply.
>
> J Gandy
I assumed only the gear part of the stationary gear was hardened because it doesn't make sense to harden the rest of it. The hardening is to reduce wear but make it too hard and it becomes brittle and can crack (cracking was the problem with early gears). Either way, Jeff Bruce said he can machine hardened gears. All he does is machine the base down a little so it'll fit in the intermediate plates.
I still think stock bearings are best, even for operation above 8500 because the shaft flex issue of 2 rotor engines most likely doesn't exist in a 4 rotor. Also the lighter the rotors, the less likelyhood of flexing.
Speaking of lighter rotors, you need to do more research in that area. For a 13B, I'd only use S5 rotors. Get them dynamically balanced along with the shaft and counterweights. You'll need to find someone nearby who can do that.
For ignition, the MS set to 4 cylinder DIS mode should work, maybe. It depends whether you want dual leading sparks only or single leading and trailing sparks. I'm the only person who thinks dual leading is superior to single fire leading and trailing. Of course I have a deeper understanding of rotary ignition than most people. I'm sure others would disagree. Hey, my stuff works for me.
Since you want to run a turbo some day, maybe you should just go with single leading and trailing sparks, fired together, requiring 8 seperate coils and ignitors. It'll be a wiring nightmare. Good luck fitting it all under the hood.
Please note that you can't use 4 dual output coils where each coil's dual outputs go to the same rotor housing. That doesn't work. Something about the pressure and the spark energy. Anyway the only correct way to use a dual output coil is if one side is in compression and the other is in exhaust. It works this way on rotaries and pistons. Remember that part about the ionized exhaust around the spark plug in my last email?
My way is deceptively simple. Two dual output coils; one to each 180° phased pair of rotors just like a stock 2nd gen.
Next I'll describe the firing order.
L1 0°
L3 90°
L2 180°
L4 270°
Easy enough. To get an idea of where the dual leading sparks come in, just remember that L1 and L2 are phased 180° apart and can be sparked at the same time. Same goes for L3 and L4, which can also be sparked at the same time, but the event must happen 90° after L1 and L2. It's so simple it's counter intuitive.
The end result looks like this.
L1+L2 0°
L3+L4 90°
L1+L2 180°
L3+L4 270°
We're still sparking at the same timing intervals, but instead of sparking each plug individually, we're sparking the two that are phased 180°. Then 90° later, the other set. Simple, elegant, very easy to fit and diagnose.
The above can be accomplished with a dizzy or a CAS. I've already described how to do it with a simple mod to the dizzy and a couple of GM HEI ignitors. The other way is with a CAS. The CAS will send a signal to the ECU, and the ECU will output a trigger signal to the stock ignitor in the base of each coil. This solution is more elegant and high-tech but requires a middle man (ECU) while the dizzy solution is perfect for carbs. Either way, it's far easier to deal with than a 20B.
So for right now since you plan on doing an NA setup first, I'd go with the two 2nd gen leading coils and not worry about trailing. The dual leading sparks will cover for the loss of trailing and add more than if you had single leading sparks with or without trailing (believe me, the difference trailing makes is not noticeable, but dual leading vs single leading is noticeable). Dyno tests have proven trailing does nothing for power. Numerous tests by 1st gen and early rotary owners (who upgraded from points or a hacked-in electronic dizzy from a 1st gen) have really fallen in love with the extra power and smoothness/driveability of my leading direct fire ignition upgrade. I wouldn't be caught dead doing anything less on my rotaries. I guess that's where my true passions are.
Again you need to do more research on rotors. I don't know of anyone who fills rotors to change the compression. 20B rotors are the same as S5 T2 9.0:1. I'll run my 20B NA because I don't know how to tune and it's an early engine. If it was a B series or later, I could get away with a large single. It's ok though since it's going into a 1st gen. I always have the option to turbo it in the future, but I'll keep it small because too much power will make it untractable. You need to examine just how much power you can get away with in an FD.
You should start with S5 T2 rotors and leave them at 9:1 compression. Don't bother with the NA rotors at 9.7 or whatever they are because you'll lose the ability to turbo it in the future. Besides, the early rotaries were 9.2 compression until the GSL-SE which went to 9.4 compression. I'd say 9.0 isn't much of an issue. The actual power loss or gain from different compression dish depths is actually quite minimal in NA form. I wouldn't lose sleep over it. Just go with S5 T2.
As for getting them lightened, it's costly and entirely up to you. We were going to use the lightest stock 12A rotor ever made; the '83-'85 which weigh about the same as S5 rotors if I remember correctly. And we were going to compensate for the extra rotating weight by using the lightest flywheel we can find that will fit our tranny. The car currently has a 1st gen tranny so we're stuck with no larger than 225mm. But that's not a bad thing because it is a smaller diameter than 240mm (T2) and therefore has less interia between shifts. I'm thinking a puck style clutch should hold the power and not weigh too much. This model appears more streetable than ACT and fits '83-'92 NA. http://cgi.ebay.com/ebaymotors/XTD-STAGE-3...1QQcmdZViewItem
What I think about exhaust is in order to make it streetable it will need a lot of muffling, which will kill power but is a necessary evil, unless an alternative could be found which would allow for quiet street driving but also provide the free flow that a peripheral port needs. Nothing like that exists. Either you can have small ports and lots of muffling, which might work, or large ports and almost no muffling but forget about driving it on the street. You can't have it both ways.
So I started looking for alternatives. I came up with an exhaust cutout with an electric valve. Either wire it up to a switch or maybe even the gas pedal so when it's mashed, the valve opens and the unmuffled (or maybe lightly muffled depending on where it's located in the system) is free to make as much noise as it wants. If we weren't going with MFR housings and their large ports, I don't think the exhaust cutout would be necessary because the power peak would be below 8 grand, but the owner insists on them so I had to come up with a solution that would allow it to be driven on the street but also flow well enough for the higher RPM these housings are capable of. Of course they will kill the low end but we figured having four of them will compensate for the loss down low, and the 1st gens are so light that even a street ported 12A has some get up and go down low.
If the thing idles below 2 grand, I'll be surprised. It's his project and his money. If I had my druthers I'd have gone with smaller ports that cost less than the MFR housings, and the 48mm IDA carbs, again for a lower cost than the 51mm, and stock apex seals since he has one or two sets of new Mazda seals already instead of buying 12 new carbon seals, and we'd need to keep the RPM below 8400, thus smaller ports would be necessary to hopefully peak at around 7k or so. The idle quality and street driveability would be much better as well with the total power output reduced a noticeable amount. It would probably feel faster since the torque would be lower in the RPM range and used more often. But then again, he's the type of person that actually enjoys driving a jungle cat. A smooth torquy low end isn't as important as high end power to him. He's from the old school of street ports, RB Holley carbs and a loud header exhaust. Low end torque and rotaries don't coexist in his mind. I'm the opposite where I'd prefer stock or near stock ports, a stock carb for the low end driveability and major ignition improvements with a well built, quiet but adequately flowing exhaust. I'll soon put my money where my mouth is when I get some of my projects going around here.
I suppose I could delve into the exhaust design we're working with. Racing Beat sells a long primary dual pipe exhaust system that consists of a short header that connects to a dual pipe center section which contains one presilencer per pipe, that then connects to a primaflow muffler which has a Y adaptor which funnels the pipes into a single 2.5" pipe before it enters the muffler. This system is very nice for a ported 12A or 13B whether NA or superchargerd. My owner also has a 5" Camden on a streetported 13B in an '81 GSL and it has enough torque to break the rear tires loose in gear on dry road. Perfectly adequate flow for that much power. He's never dynoed it so we don't know how much power it actually has, but he and Dave Atkins worked it out to around 195HP or so. So what happens if you double the HP? Of course the torque curve of a large periport will look different but it still crosses over at 5252RPM and with MFR ports, the power will keep building up probably to 10k or something like that. Scary to think about.
Wait a minute. What does the RB dual pipe system have to do with a 4 rotor project? He purchased the center section and two dissassembled header kits (the same 'road race' header that comes with the dual pipe system, only you weld it for custom applications) and two unflanged collector assemblies (Y adaptors). Each 180° rotor pair will collect into a Y adaptor and go down one pipe of the dual pipe center section. So the car will essentially have two single pipe center sections with a presilencer on each rotor pair. The nice part about this is since the rotor pairs will join together sooner, as per RB's short primary header instructions suggesting 10 to 18 inches as opposed to their long primary of 89 to 94 inches, it should allow enough room to fit it all under the hood and be quiet. RB also recommends 1.9 to 2.0" inner diameter. Their pipes are actually closer to 1.8, but such a small difference probably won't be a big deal, especially if we uncork it with the exhaust cutout.
Exhaust manifolds are the quietest. Short primary headers are louder and long primaries are the loudest. Think of a speaker box with two woofers. What happens when one is hooked out of phase? The bass disappears. They are phased 180° apart and cancel each other out. The same can be said for an exhaust manifold where the ports join very close to the engine. The further away they join, the louder the exhaust will be. Also, since only one port is flowing at any one time, it's ok to funnel two 2" OD pipes into a single 2" OD pipe as long as the angle at which they join is smooth at 30° to 40°.
The difference in exhaust noise between an RB dual pipe system and a single pipe system is quite appearant. The dual pipe system is quite a bit louder. Now imagine how my 4 rotor project will sound where each 180° pair of rotors flows into just one pipe of the dual pipe center section. Each pair will flow through one presilencer and come out quieter than if it had a 2 rotor engine. Well, maybe not quieter but certainly no louder. I've heard an RB dual pipe system without the muffler and it's dangerously loud. I've also heard the single pipe system without a muffler and it wasn't nearly as loud.
It's a question of acousticlly balancing with noise cancellation rather than that of impedance to flow, like what stock systems do. It's ingenious and elegant, kinda like my ignition idea, I think.
It's well known the Primaflow mufflers are somewhat restrictive in order to quiet the rotary enough to pass noise ordinances and sound good. That kind of restriction worries me. If the 4 rotor had smaller ports with power limited to around 300HP, it would be ok. However since the owner wants to use MFR housings, I have to install a cutout. Chances are the only place it will fit is within the single 2.5" pipe where it goes over the rear end, maybe. I'd rather not install two (one on each of the center section pipes) because it just adds complication and would cost twice as much, plus I'd lose the awesome 4 rotor sound and it would end up sounding more like two 12As reving together. No thanks. I want it to be loud and obnoxious, but quiet and streetable too. An exhaust cutout with an electric valve should give me what I want.
I'd say this email had a little more A material in it than I though. I don't think Ihave any more in me. I'm also not sure how much of it you'll find useful.
If you have no idea what I just talked about, I can give you some links to the RB exhaust components so you can get a visual. Maybe it'll help you design an exhaust sytem for your FD. Turbo rules don't apply to an NA unless you're going to turbo it some day. Then again, a turbo can quiet an exhaust some 50% but it also acts like an ugly cork in the system. My 20B could rev much faster than the PAC Performance RX-3 because mine was NA with a light steel flywheel and no clutch on it at the time (I was test firing it to check on ignition). I bet if it had an aluminum flywheel with a clutch and pressure plate, it would rev about the same. The Pac RX-3 had a large turbo and an automatic torque convertor. Both had very loud exhausts and sounded raspy and generally pretty awesome. I want something similar for the 4 rotor. Check here for the RX-3 http://www.geocities.com/cd23c/
I can send you the audio clip of my 20B if you want.
Anyway, here are the RB exhaust parts.
Disassembled Road Race Header Kit 74-85 (12A) (we got two)
http://www.racingbeat.com/resultset....rtNumber=16211
Street Port Center Section 79-85 RX-7
http://www.racingbeat.com/resultset....rtNumber=16398
Unflanged Collector Assembly (we got two)
http://www.racingbeat.com/resultset....rtNumber=16004
We still need to get this muffler.
http://www.racingbeat.com/resultset....rtNumber=16433
Hmm, reading the specs on that muffler, I sure am glad I have the option of adding a cutout.
Pports are the simplest.
Jeff Bruce can do any intermediate plate you want; with or without fuel injector holes.
Hmm, maybe you could buy us some MFR rotor housings with your discount.
Well, I think I've used up all my A meterial. You really should consider getting on the forum. There is a lot more to it than I can cover. Much of what I talk about is due to my assumption that the other person already has an idea of what I'm talking about. Several people on the forum could help fill in the gaps better than I could. Especially if it is FD-specific and powerFC/EFI specific and what not.
By the way, I posted our correspondence on the forum because it's filled with a ton of useful info. Perhaps others will read through it and fill in the gaps that I missed.
