4-rotor anyone
07-06-2006, 01:50 PM
#71
Senior Member
Join Date: Nov 2001
Posts: 2,284
Originally Posted by Danomite' post='827031' date='Jul 6 2006, 06:49 AM
He uses a stock front weight and makes the rear weight, but the shaft still needs to be balanced, which he can do as long as you have accurate rotor weights, or you will have to balance the assy here. Its up to you whether you send him the irons and gears or have him supply them. Keep in mind the exchange rate (avg-1us/1.58nz) which helps quite a bit. He figured shipping to be about 1k for the parts you listed, including the irons and gears. So figure about 300 to ship two irons and gears to him.
Dano
He's got several '83-'85 cores to tear apart. I'll try to find a set of four rotors within one letter of each other if not the same letter. How to I find accurate rotor weights?
We'll be using two GSL-SE intemediate plates for the mounting studs at the bottom sides. I don't feel confident in the front cover mount. $300 or so sounds ok to me. I'll let him know when he gets back. Thanks.
07-06-2006, 02:50 PM
#72
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Join Date: Nov 2001
Posts: 2,284
Z, I think I remember you. You were the only one on a bike, and you went with us on the poker run. I was in my friend's orange 1st gen with the orange and black 13B 4 port and the 5" SC. He's the guy who wants to do this 4 rotor.
He actually wanted to do a 20B at first, but since I had already done one and he had so many 12A cores sitting around, it just seemed like the logical choice. A 3 rotor 12A would have been cool, but there is enough room in the engine bay for a 4 rotor, so why not?
A peripheral port with Weber carbs is easy enough. Move the tranny back a little, and get rid of the radiator frame to mount a bigger rad further forward, and viola! We won't even need to remove or relocate the front sway bar, as is necessary in a 20B swap into an FC.
There will be an extra 128lbs of engine weight, but the Webers weigh less than Nikkis and a light aftermarket flywheel with an FC waterpump will keep the weight from kreeping up much beyond that. A four pipe header shouldn't weigh too much more than a two pipe or a stock cast iron manifold. Relocating the 40lbs battery to a storage bin should help the front corner a bit. Wasn't the GSL-SE the heaviest 1st gen they made anyway? Meh.
The ignitors will probably be GM HEI units since they're cheap and we've had good luck with them before. Yeah, it'll have four ignition modules and four coils. The dizzy will have the leading pickup in the stock position and the trailing pickup wil be relocated to 135° or 225° depending on which direction is easier/more secure. The leading pickup will be for L1 and L2 as they are still phased 180° like any 2 rotor. Likewise the relocated pickup will trigger L3 and L4. Since the dizzy spins at half engine speed, the 135 or 225 degrees away from the leading pickup is necessary to get a trigger event every 90° of engine rotation from the 4 tipped reluctor. That is to say, the reluctor will provide a trigger event to one of the pickups every 180° of dizzy shaft rotation. For comparison, the stock trailing pickup is about 185° after the leading pickup and since the reluctor tips are one every 90° of dizzy shaft or 180° of eccentric shaft rotation, it translates to a trailing spark 10° after the leading spark. If I move the trailing pickup 45° + or - (135 or 225) from its stock position, it'll encounter a reluctor tip 45° after (or before—doesn't matter) of dizzy shaft rotation, or 90° eccentric shaft rotation which is appropriate for a 4 rotor. The late leading sparks allow the use of one pickup to trigger two ignitors/coils/spark plugs every 180° on a set of rotors phased 180° thus keeping the whole ignition system actually quite simple.
If I didn't want late leading for whatever reason (I can't think of one) It would have required four pickups, which would be impossible to fit in that small space, and two tips shaved from the reluctor. This would be necessary for trailing, but since it'll be NA, trailing won't add noticeable HP or help with combustion and emissions aren't even a consideration. That late leading spark is capable of igniting the unburned AF mixture in the trailing edge of the rotor actually pretty well.
The 20B dizzy mod had late leading sparks as well, but it required three pickups in that small space at 120°. They barely fit. The reluctor was stock with four tips although I could have shaved two tips off since each pickup went to one ignitor and then to one coil. Trailing could be done this way on a 20B dizzy placed above the leading set of pickups. I actually did have a double decker with six pickups and two reluctors (one stock for leading, the other with two tips shaved for trailing) but I couldn't justify the expense in running three more ignitors and coils for the miniscule power they would have added. It was NA too so there you go. Now with the MegaSquirt, it still is NA and still has late leading, still sounds excellent and I may go turbo in the future, so who knows.
Rear end bracing. I'm sure that's something he would consider. We would just need to know what to do and where to place it. He actually broke several rearends in the MG Midget back when he was the owner. I got it from him in '96 and have tinkered with it off and on. Part of the problem was that the shop installed a '71-'73 engine with its heavy 30lbs stock flywheel. Racing Beat didn't offer an aftermarklet light flywheel for it because of those engines' "characteristcally poor low RPM torque". Something about carbon apex seals and low RPM... Well, I installed my REPU engine complete with its stock heavy flywheel and could chirp them at just above idle. We're talking a 2kRPM burnout. 2nd gear scoots were like nothing. This prompted me to try at least a light steel flywheel. Oh man, it was a major improvement. It accelerated extremely nicely after that with less danger to the rear end. It's geared with the taller 3.7 so I suspected aluminum may not be as fun. Then again, the car is so frightingly light. Anyway, the light steel is going back in since it appeared to be the perfect middle ground, and it was already sitting here. I'm also swapping to an FC clutch master and slave cylinder since the stocker is too small for the 1st gen slave it's currently using. It's advice from RX-Midget. The pedal is just way too stiff even with a stock 215mm pressure plate at the moment. I may take it to the BBQ if it's done in time. I doubt the 4 rotor will be done by then, but you guys could talk about it if he can make it there this year.
He actually wanted to do a 20B at first, but since I had already done one and he had so many 12A cores sitting around, it just seemed like the logical choice. A 3 rotor 12A would have been cool, but there is enough room in the engine bay for a 4 rotor, so why not?
A peripheral port with Weber carbs is easy enough. Move the tranny back a little, and get rid of the radiator frame to mount a bigger rad further forward, and viola! We won't even need to remove or relocate the front sway bar, as is necessary in a 20B swap into an FC.
There will be an extra 128lbs of engine weight, but the Webers weigh less than Nikkis and a light aftermarket flywheel with an FC waterpump will keep the weight from kreeping up much beyond that. A four pipe header shouldn't weigh too much more than a two pipe or a stock cast iron manifold. Relocating the 40lbs battery to a storage bin should help the front corner a bit. Wasn't the GSL-SE the heaviest 1st gen they made anyway? Meh.
The ignitors will probably be GM HEI units since they're cheap and we've had good luck with them before. Yeah, it'll have four ignition modules and four coils. The dizzy will have the leading pickup in the stock position and the trailing pickup wil be relocated to 135° or 225° depending on which direction is easier/more secure. The leading pickup will be for L1 and L2 as they are still phased 180° like any 2 rotor. Likewise the relocated pickup will trigger L3 and L4. Since the dizzy spins at half engine speed, the 135 or 225 degrees away from the leading pickup is necessary to get a trigger event every 90° of engine rotation from the 4 tipped reluctor. That is to say, the reluctor will provide a trigger event to one of the pickups every 180° of dizzy shaft rotation. For comparison, the stock trailing pickup is about 185° after the leading pickup and since the reluctor tips are one every 90° of dizzy shaft or 180° of eccentric shaft rotation, it translates to a trailing spark 10° after the leading spark. If I move the trailing pickup 45° + or - (135 or 225) from its stock position, it'll encounter a reluctor tip 45° after (or before—doesn't matter) of dizzy shaft rotation, or 90° eccentric shaft rotation which is appropriate for a 4 rotor. The late leading sparks allow the use of one pickup to trigger two ignitors/coils/spark plugs every 180° on a set of rotors phased 180° thus keeping the whole ignition system actually quite simple.
If I didn't want late leading for whatever reason (I can't think of one) It would have required four pickups, which would be impossible to fit in that small space, and two tips shaved from the reluctor. This would be necessary for trailing, but since it'll be NA, trailing won't add noticeable HP or help with combustion and emissions aren't even a consideration. That late leading spark is capable of igniting the unburned AF mixture in the trailing edge of the rotor actually pretty well.
The 20B dizzy mod had late leading sparks as well, but it required three pickups in that small space at 120°. They barely fit. The reluctor was stock with four tips although I could have shaved two tips off since each pickup went to one ignitor and then to one coil. Trailing could be done this way on a 20B dizzy placed above the leading set of pickups. I actually did have a double decker with six pickups and two reluctors (one stock for leading, the other with two tips shaved for trailing) but I couldn't justify the expense in running three more ignitors and coils for the miniscule power they would have added. It was NA too so there you go. Now with the MegaSquirt, it still is NA and still has late leading, still sounds excellent and I may go turbo in the future, so who knows.
Rear end bracing. I'm sure that's something he would consider. We would just need to know what to do and where to place it. He actually broke several rearends in the MG Midget back when he was the owner. I got it from him in '96 and have tinkered with it off and on. Part of the problem was that the shop installed a '71-'73 engine with its heavy 30lbs stock flywheel. Racing Beat didn't offer an aftermarklet light flywheel for it because of those engines' "characteristcally poor low RPM torque". Something about carbon apex seals and low RPM... Well, I installed my REPU engine complete with its stock heavy flywheel and could chirp them at just above idle. We're talking a 2kRPM burnout.
07-06-2006, 02:59 PM
#73
Senior Member
Join Date: Feb 2003
Location: Iowa Baby....Oh-Yea
Posts: 212
Originally Posted by z-beater' post='827072' date='Jul 6 2006, 10:01 AM
WOW, I thought that shipping would be worse that 300. Let us know what the exact amount is going to be. Are you planning on using stock ignitors? Since you are on a budget I would assume so. I will have to take a look at your dizzy mod on the 20b. I actually have not read through that thread. I love project threads.
$296.43 Global Express Guaranteed® Document Service through USPS from Iowa to Auckland.
07-06-2006, 03:09 PM
#76
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Join Date: Feb 2003
Location: Iowa Baby....Oh-Yea
Posts: 212
Originally Posted by Jeff20B' post='827104' date='Jul 6 2006, 12:00 PM
Can FedEx ship to NZ? I can get a discount.
I tried to do a quote online and it was being a biatch, so I just went to USPS. My quote was also valued @ $1.00
07-06-2006, 04:56 PM
#78
Senior Member
Join Date: Jan 2006
Posts: 1,114
Great information in there Jeff. I can now see how you plan on running the ignition...
That was me. I was the only fool that was on a bike, too bad it was not a rotary. Eventhough one rotary can be headache enough...
I do remember your friend. I talked with him for probably about 15mins last year. I kind of picked his brain because I had yet to see his car. I like to see things that don't come around. I liked his car...the SC was even painted And IIRC was kind of like a orange bumble bee...
That was me. I was the only fool that was on a bike, too bad it was not a rotary. Eventhough one rotary can be headache enough...
I do remember your friend. I talked with him for probably about 15mins last year. I kind of picked his brain because I had yet to see his car. I like to see things that don't come around. I liked his car...the SC was even painted
07-06-2006, 08:49 PM
#79
Senior Member
Join Date: Feb 2003
Location: Iowa Baby....Oh-Yea
Posts: 212
Originally Posted by Jeff20B' post='827116' date='Jul 6 2006, 01:13 PM
I see. Used plates = low value.
My work has a fedex account and I've noticed that the invoices are always more than the shipping reciepts, Ill have to look closer and see where the extra charges are coming from
07-06-2006, 09:32 PM
#80
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Join Date: Feb 2003
Location: Iowa Baby....Oh-Yea
Posts: 212
Originally Posted by Jeff20B' post='827092' date='Jul 6 2006, 10:50 AM
He's got several '83-'85 cores to tear apart. I'll try to find a set of four rotors within one letter of each other if not the same letter. How to I find accurate rotor weights?
I have not asked how accurate the figures need to be, or even what unit of measure. I would assume all he needs is a dead weight. I just planned on sending all four of mine out to be spin-balanced and weighed just to be sure, that is once I get all of them. I have annother month or so to figure it out though