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http://bdc.cyberosity.com/v/Tuning/Ohio_June06/
This link shows pictures and a couple videos of Luke's car from a tuning trip I just got back from a few days ago up in central Ohio. I did a few cars there; Luke's being the heaviest-load one. Today, he called me and told me it had popped while driving a relative of his around the neighbourhood. He had done a 12/13psi run (low boost setting for pump gas) here and there and then went up to the high boost setting (18.5psi). He said it stuttered once then sounded like a Harley at the top of 2nd gear in the 7k-8krpm range. Here's the specs: - Half-bridgeport motor I built two years ago. Pictures of the assembly and porting work for reference can be found here http://bdc.cyberosity.com/v/Assembly/LukeWeber/ and here http://bdc.cyberosity.com/v/Porting/LukeWeber/ -- Series 5 motor w/ the smaller rear dowel pin land, 9.0:1 rotors, Rotary Aviation apex seals (2mm), etc. - HKS TO4R w/ a custom divided manifold, twin Tial 38mm WG's, 3.5" exhaust, 1.32 A/R P-Trim turbine housing - Plugs used were BUR9EQ's all around but am unsure if they were platinums or not Luke's car is very well built considering the time and effort he has taken into constructing it. Good parts were used and there were no short-cuts taken. We had the same kind of stuttering occur on the dyno at both low and high loads. On low loads, I had him setup to run about 12-13psi on 93octane pump gas and nothing higher. On higher loads, the sky was pretty much the limit as I knew the next limiting factor would be the fuel pump. As was found, we were in the 18psi range when his duty cycles are edging towards 90% on 720's and 1680's with a base pressure of 40psi. Everything else working correctly. The fuel pump is a Supra pump and the EFI system is a Haltech E6X. The stutter was intermittent yet, when it was consistent, would only happen at high RPM's, say right at 7krpm and above. The stutter was usually a fairly nasty jolt which felt identical to what would happen when running too hot of a spark plug for the given heavier loads. While we were on the dyno, it occurred three, perhaps four times and was enough to have me concerned. We were pretty much wrapping up by the time I was concerned enough to stop things as he was beginning to run out of pump. On the way back to his house (a good 20-30min drive), it didn't stutter or pop a single time. I had figured that perhaps there was an issue with a hot plug causing a misfire with the car being on the dyno and concluded that since it was on the dyno compared to being on the road that overall the vehicle would be hotter -- hotter water temps, air temps, oil temps, that kind of thing that's not experienced as much while on the road in normal driving conditions. Today that same stutter came back and as best as I know it only happened once. It was a hard enough knock to deflect the rear rotor housing and resultantly crack the upper rear iron dowel land, sending oil all over the engine bay, emptying the system out in about 10-15 seconds of running. I have seen this one other time before and it was on another Turbo II about three years ago under much lesser loads. The vehicle was being tach'd out in 2nd gear at higher RPM's, similar to Luke's, when it encountered one, single, hard stutter, then it cracked the same dowel land, dumping the oil out. Other than that, I've only encountered odd misfires three times and I believe all three of them were plug related where the leadings still had 7's in them instead of 9's (being the stock plug configuration). I've spoken to GMON about it some today and he's mentioned the possibility of problems w/ the plug wires that are in use. As best as I can tell from the pictures I've taken of Luke's engine bay, he's using some high quality MSD wires but am not sure exactly what kind. Any thoughts? B |
A couple of things I forgot to mention:
The race fuel he was using was 110 Leaded and was barely diluted with any pump fuel. The amount of spark advance I had him setup to run on this was 16* advance on the leadings with a 6* trail-split past about 15psi of boost. It was left on the conservative end purposefully. I also took 13 datalogs of the car on the dyno and not once did I ever see any indication of a trigger problem in terms of not having smooth, sequential RPM's going up and down. B |
I've been told you can actually SEE arcing on the outside of MSD wires. This was on my car, but I wasn't there at the time. Whether that would cause a motor problem other than poor running I don't know.
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crossfire maybe? spark 180 degrees out on the trailings might be bad....
um ive seen the e11 do stuff like that, but not the e6 anything. i'm not sure what else would be intermittant like that..... |
Originally Posted by TYSON' post='827144' date='Jul 6 2006, 08:23 PM
I've been told you can actually SEE arcing on the outside of MSD wires. This was on my car, but I wasn't there at the time. Whether that would cause a motor problem other than poor running I don't know. one of the cars on the dyno would have the msd wire arc onto the IC pipe. |
Originally Posted by kahren' post='827209' date='Jul 6 2006, 10:11 PM
one of the cars on the dyno would have the msd wire arc onto the IC pipe. There were a few people watching us dyno but they were a good 6-10 feet away. The engine bay was also facing the sun at that time of day so I am not sure if they would've seen a spark at the end of the plug wire or not. In any event, I know I didn't because I was in the car tuning. Anybody else have any information about these MSD wires? Is this something bonafiable that others have experienced or is it more a heresay kinda thing? The problem here on Luke's car is definitely in the world of ignition to the tune of a random misfire causing seriously advanced pre-ignition. B |
Very interested to hear ohms per foot on those wires as well as what plugs he was running.
I was on the dyno last friday and heard 3 nasty bangs. Scared me shitless, turned down the boost and all was good. Couldnt imagine how nervous Id be with that kinda power. On two of my buddies cars I can hold the home key down on at 6k and watch the map change from 10k to 0k maps all while the engine runs relatively well. Both are E6X's and both have been turned upside down trying to find the problem. We have made it better but arround 6k it still happens. I personally think the X has issues with reluctor type pickup. Id love to hear from others what they find while doing the above experiment. Do it in vac of course https://www.nopistons.com/forums/pub...IR#>/smile.png |
if you are usign msd wires, make sure the trailings dont run next to each other, ive seen a lot of peopel zip tie the trailing and leading plugs together. this is a no no, esp with the msd wires or whichever other ones that may arc. i like to use only stock wires, as it seems they work best against arching.
it seems that when runing way conservative timing you can also start detonating, or burning of the fuel is not as smooth when the spark goes off too late, preignition can occur even with high octane and low boost, this is almost the same thing as having the spark ignite too late, and having detonation, both of these can feel similar. ive also noticed that varing split timing can reduce the chance of this happening, too little split and the engine doesnt run smooth too much split and not smooth again. NAs seem to be happy with around 5-8 deg and turbo 8-15. |
Originally Posted by BDC' post='827210' date='Jul 6 2006, 11:37 PM
Anybody else have any information about these MSD wires? Is this something bonafiable that others have experienced or is it more a heresay kinda thing? The problem here on Luke's car is definitely in the world of ignition to the tune of a random misfire causing seriously advanced pre-ignition. B i had a 1st gen years ago, with racing beat wires. it was kinda so/so uptop, and it would burn up coils, i checked literally everything on the motor, and it was all fine. what fixed it was a set of $6 kragen wires, i hadnt checked the RB wires, cause they are RB wires. i'd have a hard look at the wires..... |
Ok B, Thanks for posting this up. The wires that I'm using are the MSD 8.5 Super Conductor Wires.
They are a very nice quality wire, and I was very impressed by them when I received them in the mail. They came with a sleeve over the wire to help with conducting the spark directly to the plug (to prevent arcing) and to help insulate against the heat. I have a picture of them somewhere, and I'll have to find it and post it up. My wires are zip tied together...so maybe that was the problem? I am very disappointed that this happened, but i've been trying to keep a positive attitude about it, and have my motor come back stronger and better than ever. I do still need to figure out what caused this in the first place... I definitely think that we have it narrowed to ignition, whether it was the wires or the plugs, or maybe a combination of both... |
Originally Posted by Comitatus' post='827496' date='Jul 8 2006, 09:28 PM
Ok B, Thanks for posting this up. The wires that I'm using are the MSD 8.5 Super Conductor Wires. They are a very nice quality wire, and I was very impressed by them when I received them in the mail. They came with a sleeve over the wire to help with conducting the spark directly to the plug (to prevent arcing) and to help insulate against the heat. I have a picture of them somewhere, and I'll have to find it and post it up. My wires are zip tied together...so maybe that was the problem? I am very disappointed that this happened, but i've been trying to keep a positive attitude about it, and have my motor come back stronger and better than ever. I do still need to figure out what caused this in the first place... I definitely think that we have it narrowed to ignition, whether it was the wires or the plugs, or maybe a combination of both... one of the only things somkey yunick is concrete about in his book is the importance of not having crossfire, small block chivvys fire 2 cylinders right next to each other right after one another, and guess which one rutinely fails? the wires should be (according to him) 3/4" apart from each other and everything else as much as possible. now of course you see wires ziptied together on all sorts of race cars with no apparent ill effects, but its an easy thing to do too |
A buddy of mine named Mario w/ a black T2's car is doing this. Our friend Eric told me that he took it out while I was out in Ohio at your place Luke and that it did the same kind of pop thing once in similar fashion -- high load, high RPM, randomly. He's running 9's all around but I'm unsure of his plug wires.
B |
Ok, so as of right now, to remedy this....I need to run 9's and 10.5's for plugs, or maybe 10.5's all around.
And I need to make sure that my plug wires are gapped and free from interference. What about the CAS wiring? Do you think think that might play into it, and maybe causes some noise on the plug wiring? |
Originally Posted by Comitatus' post='827514' date='Jul 9 2006, 12:22 AM
Ok, so as of right now, to remedy this....I need to run 9's and 10.5's for plugs, or maybe 10.5's all around. And I need to make sure that my plug wires are gapped and free from interference. What about the CAS wiring? Do you think think that might play into it, and maybe causes some noise on the plug wiring? Mind if I speculate a bit? I manged to break out the dowels at both ends of a NA 12A. Or more accurately, my driver ran two laps with the engine bucking like a mule, and would not take his foot out of it and return to the pits. It ran fine sitting still, but not under load. It was my first attempt to run a crank triggered system and I had run the pickup pairs inside the same dash 4 braided stainless hydraulic line. The triggers were mounted on both sides of the front cover and ran through the fire wall, so I thought that shielding them from the high voltage lines was the most important thing to do. To keep the trigger wires from inducing each other, I twisted the pairs in opposite directions. At anything over 4000 RPM the pickup pairs would induce each other and lite the opposite rotor housing 180 degrees too soon. It just lost the end irons. Everything else was fine. Early on when I was still using the exciter boxes on the sides of the distributor, I could not get a split timing situation going. No matter what I did, both leading and trailing would fire together when I reved it up. I asked a Mazda driver from NC about this and he didn't even blink. He just said throw those exciter boxes away. I did and never had another problem. Mazdas around the world had the same problem. So Mazda moved the boxes (just points eliminator SCRs) to the fender. No more problems. I separated the pickup wires. Ran both through dash 4 and grounded the stainless shielding and had no more problems. The wires from the CAS are antennas and need to be shielded from high voltage energy. The leading wires cross fireing has no effect at all. But a trailing wire picking up a leading hit from the other housing is the problem. Or inducing a CAS wire from one housing with a leading or trailing hit from the other is a killer. The inductive high voltage wires act to remove the peaks and noise off the the high voltage and extend the burn time of the arc. This you may notice is helpfull in not killing the radio and not having so much noise in it that AM radio is not usable. This (inductive reactance) also acts as an additional load so as to reduce unwanted arcing around the plug boots. It is probabe that boot arcing is an after the fact (after the plug gap is up and arcing) and does not cause a misfire until it has happened enough times to make a carbon path inside the boot, and is seldom a problem. (I only had this happen once) This is another good reason for .010" plug gaps. Until we bought the Drummond engines (well, the driver bought them) we never ran over 20 degrees of lead on both leading and trailing. Plenty of power and never any problems with heat or engine damage. The Drummonds came set up to run 25 or 27 degrees. And he wanted more octane than we had been using. So think about this. Why is one amount of lead a better choice than another, and what is the correct amount for any situation. The short answer is about 100 pages. But the bullets are: To arrive at the highest cylinder pressure at the ideal crank angle. Period. Nothing else to learn. So what are the other 99 pages about? All of the problems that will be generated while attempting to accomplish this feat. I don't like turbocharging. It is just like crack. Once you try it, you cannot get it out of your mind. And just like crack, a little crack is no good after a while, so you need way more crack just to stay even. So you see people that seem perfectly intelligent gutting a third gen engine compartment and adding $25,000.00 worth of very short lived equipment, so that the rush will be bigger the next time. And it can all go away in a split second. NA engines (piston or rotary) suffer reduced cylinder filling with increased RPM. Since the head space (compression volume) is not changing, the reduced cylinder filling is reducing the compression ratio with incrased RPM. Less fuel air mixture crammed into the same space, is the same as a larger head space, or a lower compression ratio. So unless the NA engine is lugged at a high throttle opening (same as way too much advance) or it cross fires (same as way too much advance) you just about cannot hurt it. I ran over 14:1 in my Fiat engines and never had a problem. Then I could buy 110 airplane fuel at the local airport. The rules had me running a little Weber DMSA-100 carb with a 23MM and a 27MM choke size. So as the revs came up the cylinder filling was so poor that the effective compression ratio dropped into the too low area and the 34 degrees of lead was just right. So the trick here is that the 14:1 is only the calculated compression ratio, and it vanishes as the RPMs come upoff of idle. In the turbo (or supercharged) engine, the compression ratio goes up with RPM. Think about that for a moment. The engine becomes more vulnerable to sudden death as you rev it up. The effect is that the engine gets bigger in displacement as you rev it up, but the head space stays the same. So the cylinder filling is getting better with RPM rather than worse, as in the NA engine. Easy to understand so far. So the one big killer of engines is ignition advance, and as the revs come up so comes the increased compression ratio and so the ignition advance must be reduced (retarded) with RPM so as to keep the maximum cylinder pressure right at (the same place as the NA engine) the ideal location in the cycle (about 20 degrees ATDC). I will continue this later. I have to run. But while I'm gone, think about this. The relationship of crankhaft degrees of advance in a piston engine and the 1/3 relationship of the cranckshaft degrees vice rotor face degrees in the rotary. How many degrees of rotation of usefull work in one vice the other. Lynn E. Hanover |
Originally Posted by Lynn E. Hanover' post='827526' date='Jul 9 2006, 06:14 AM
Mind if I speculate a bit? I manged to break out the dowels at both ends of a NA 12A. Or more accurately, my driver ran two laps with the engine bucking like a mule, and would not take his foot out of it and return to the pits. It ran fine sitting still, but not under load. It was my first attempt to run a crank triggered system and I had run the pickup pairs inside the same dash 4 braided stainless hydraulic line. The triggers were mounted on both sides of the front cover and ran through the fire wall, so I thought that shielding them from the high voltage lines was the most important thing to do. To keep the trigger wires from inducing each other, I twisted the pairs in opposite directions. At anything over 4000 RPM the pickup pairs would induce each other and lite the opposite rotor housing 180 degrees too soon. It just lost the end irons. Everything else was fine. Early on when I was still using the exciter boxes on the sides of the distributor, I could not get a split timing situation going. No matter what I did, both leading and trailing would fire together when I reved it up. I asked a Mazda driver from NC about this and he didn't even blink. He just said throw those exciter boxes away. I did and never had another problem. Mazdas around the world had the same problem. So Mazda moved the boxes (just points eliminator SCRs) to the fender. No more problems. I separated the pickup wires. Ran both through dash 4 and grounded the stainless shielding and had no more problems. The wires from the CAS are antennas and need to be shielded from high voltage energy. The leading wires cross fireing has no effect at all. But a trailing wire picking up a leading hit from the other housing is the problem. Or inducing a CAS wire from one housing with a leading or trailing hit from the other is a killer. The inductive high voltage wires act to remove the peaks and noise off the the high voltage and extend the burn time of the arc. This you may notice is helpfull in not killing the radio and not having so much noise in it that AM radio is not usable. This (inductive reactance) also acts as an additional load so as to reduce unwanted arcing around the plug boots. It is probabe that boot arcing is an after the fact (after the plug gap is up and arcing) and does not cause a misfire until it has happened enough times to make a carbon path inside the boot, and is seldom a problem. (I only had this happen once) This is another good reason for .010" plug gaps. Until we bought the Drummond engines (well, the driver bought them) we never ran over 20 degrees of lead on both leading and trailing. Plenty of power and never any problems with heat or engine damage. The Drummonds came set up to run 25 or 27 degrees. And he wanted more octane than we had been using. So think about this. Why is one amount of lead a better choice than another, and what is the correct amount for any situation. The short answer is about 100 pages. But the bullets are: To arrive at the highest cylinder pressure at the ideal crank angle. Period. Nothing else to learn. So what are the other 99 pages about? All of the problems that will be generated while attempting to accomplish this feat. I don't like turbocharging. It is just like crack. Once you try it, you cannot get it out of your mind. And just like crack, a little crack is no good after a while, so you need way more crack just to stay even. So you see people that seem perfectly intelligent gutting a third gen engine compartment and adding $25,000.00 worth of very short lived equipment, so that the rush will be bigger the next time. And it can all go away in a split second. NA engines (piston or rotary) suffer reduced cylinder filling with increased RPM. Since the head space (compression volume) is not changing, the reduced cylinder filling is reducing the compression ratio with incrased RPM. Less fuel air mixture crammed into the same space, is the same as a larger head space, or a lower compression ratio. So unless the NA engine is lugged at a high throttle opening (same as way too much advance) or it cross fires (same as way too much advance) you just about cannot hurt it. I ran over 14:1 in my Fiat engines and never had a problem. Then I could buy 110 airplane fuel at the local airport. The rules had me running a little Weber DMSA-100 carb with a 23MM and a 27MM choke size. So as the revs came up the cylinder filling was so poor that the effective compression ratio dropped into the too low area and the 34 degrees of lead was just right. So the trick here is that the 14:1 is only the calculated compression ratio, and it vanishes as the RPMs come upoff of idle. In the turbo (or supercharged) engine, the compression ratio goes up with RPM. Think about that for a moment. The engine becomes more vulnerable to sudden death as you rev it up. The effect is that the engine gets bigger in displacement as you rev it up, but the head space stays the same. So the cylinder filling is getting better with RPM rather than worse, as in the NA engine. Easy to understand so far. So the one big killer of engines is ignition advance, and as the revs come up so comes the increased compression ratio and so the ignition advance must be reduced (retarded) with RPM so as to keep the maximum cylinder pressure right at (the same place as the NA engine) the ideal location in the cycle (about 18-20 degrees ATDC in a piston engine and 40-50 degrees in a rotary). Read Paul Yaws tech articals. I will continue this later. I have to run. But while I'm gone, think about this. The relationship of crankhaft degrees of advance in a piston engine and the 1/3 relationship of the cranckshaft degrees vice rotor face degrees in the rotary. How many degrees of rotation of usefull work in one vice the other. Lynn E. Hanover So now you look at the rotor as though it is just a piston and cylinder rather than geared to a shaft. First notice that it is turning very slowly. Events involving time, such as burn rate will appear to accelerate. Burn rate is fixed depending on pressure, mixture, octane ect. When the boost is up and the oxygen molecules are very close to the fuel molecules the burn rate is very high, and very little ignition lead is required to get maximum pressure at 40-50 degrees ATDC. So suppose the degree wheel were mounted on the rotor to make it look more like a piston and cylinder without the devide by three of the crank gearing. The 16 degrees of advance at the crank seems modest enough, but the crank is turning three times faster than the rotor. The rotor is operating in slow motion, in a situation where the burn rate is very high and the pressure peak cannot help but be a tad early (before 40 degrees)? So when we say the advance is 20 or 16 or whatever, we are talking about a rotor that is by any description, at TDC. So the difference between engine and no engine might be between 10 degrees and 16 degrees of advance at the crank, and that difference at the rotor cannot be detected with the eye it is so small. (the rotor will have turned 3 degrees, one third of 6 degrees). Another interesting feature of ignition systems is that the higher the cylinder pressure the higher the resistance in the plug gap. That sounds backwards but it is true. Champion used to sell a gizmo to gas stations that had a supply of sand at the bottom and a window to look through to watch the plug gap. You would screw in the dirty plug and test is by turning on the high voltage supply and watching the arc while you let in air pressure up to whatever was available at the shop. Soon after the pressure started up, the arc would die and a shorting path would be visible along the porcelene. You would then use the cleaning feature and retest the plug. The arc would be maintained up to maximum shop air pressure. What else would affect the arc? The gap distance. There are pluses and minuses to haveing the ground electrodes shielding the the plug center to maintain heat and keep off dirt. You see both that type and conventional looking plug tips used in rotaries. I use the Mazda comp NGKR6725-115 fine wire electrode plugs. Gapped at .010" Note that systems used for supercharged drag racing engines operate at much higher voltages than are available in the MSDs we use in racing. (MSD-6AL) The colder the plug, the shorter the path across the porcelene, so they will foul quickly without a CD style ignition system. When a plug does not fire due to high resistance where does that energy go? It is made available as radio energy, and you have all of those antenna laying around the engine compartment waiting to cross fire the engine. Where detonation cracks corner seals and folds over side seals and if it persists fractures apex seals, a crossfire at high boost shears off dowels and breaks cast irons. So, shielding of primary triggering circuits and running them well away from secondary wires, is a good idea. Ground the shielding to the chassis. Running minimal plug gaps to eliminate missfires. Reduce advance until it affects power a measurable amount, and return only a nominal amount of that value. Just speculation. Lynn E. Hanover |
Originally Posted by Lynn E. Hanover' post='827701' date='Jul 9 2006, 09:35 PM
Note that systems used for supercharged drag racing engines operate at much higher voltages than are available in the MSDs we use in racing. (MSD-6AL) Also note that every such dragster I have seen, including our own, has the plug wires just sort of zip-tied together in a fat bundle instead of spacing them out. This being on engines with absurd ignition requirements, such as alcohol engines running 60psi boost. It takes a lot of juice to light a super high pressure wet fog! If your plug wires are arcing, then they need replaced. I have never seen new MSD wires arc. If they do, that means they are faulty. |
Originally Posted by heretic' post='827725' date='Jul 10 2006, 03:13 AM
Also note that every such dragster I have seen, including our own, has the plug wires just sort of zip-tied together in a fat bundle instead of spacing them out. This being on engines with absurd ignition requirements, such as alcohol engines running 60psi boost. It takes a lot of juice to light a super high pressure wet fog! If your plug wires are arcing, then they need replaced. I have never seen new MSD wires arc. If they do, that means they are faulty. The inductive wires are less prone to induce enough energy in adjacent wires to fire a plug. But Smokey has never been wrong, and bundling high voltage wires may not kill the engine but may damage the electronics in the ignition box. Good practice is to keep wires well apart, and shield primary wires. Run magnetic pickup wires around the exhaust side of the engine and in a shielded tube. Note that aluminum is the ideal shielding as it will not pass a magnetic flux field. Run pickup wires in separate tubes. They will crossfire each other when run together. And ground the shielding. Trust me on this. Plus the track owner gets mad when genius driver drives the damaged engine a lap dumping the 2 1/2 gallons of oil on the line. Also the oil fire was a bit unhandy. Lynn E. Hanover |
yeah, putting oil from turn 1 to turn 6, is only good if you want EVERYBODY at the track to comment on your racing line.....
|
Originally Posted by Lynn E. Hanover' post='827526' date='Jul 9 2006, 06:14 AM
Mind if I speculate a bit? I manged to break out the dowels at both ends of a NA 12A. Or more accurately, my driver ran two laps with the engine bucking like a mule, and would not take his foot out of it and return to the pits. It ran fine sitting still, but not under load. It was my first attempt to run a crank triggered system and I had run the pickup pairs inside the same dash 4 braided stainless hydraulic line. The triggers were mounted on both sides of the front cover and ran through the fire wall, so I thought that shielding them from the high voltage lines was the most important thing to do. To keep the trigger wires from inducing each other, I twisted the pairs in opposite directions. At anything over 4000 RPM the pickup pairs would induce each other and lite the opposite rotor housing 180 degrees too soon. It just lost the end irons. Everything else was fine. Early on when I was still using the exciter boxes on the sides of the distributor, I could not get a split timing situation going. No matter what I did, both leading and trailing would fire together when I reved it up. I asked a Mazda driver from NC about this and he didn't even blink. He just said throw those exciter boxes away. I did and never had another problem. Mazdas around the world had the same problem. So Mazda moved the boxes (just points eliminator SCRs) to the fender. No more problems. I separated the pickup wires. Ran both through dash 4 and grounded the stainless shielding and had no more problems. The wires from the CAS are antennas and need to be shielded from high voltage energy. The leading wires cross fireing has no effect at all. But a trailing wire picking up a leading hit from the other housing is the problem. Or inducing a CAS wire from one housing with a leading or trailing hit from the other is a killer. The inductive high voltage wires act to remove the peaks and noise off the the high voltage and extend the burn time of the arc. This you may notice is helpfull in not killing the radio and not having so much noise in it that AM radio is not usable. This (inductive reactance) also acts as an additional load so as to reduce unwanted arcing around the plug boots. It is probabe that boot arcing is an after the fact (after the plug gap is up and arcing) and does not cause a misfire until it has happened enough times to make a carbon path inside the boot, and is seldom a problem. (I only had this happen once) This is another good reason for .010" plug gaps. Until we bought the Drummond engines (well, the driver bought them) we never ran over 20 degrees of lead on both leading and trailing. Plenty of power and never any problems with heat or engine damage. The Drummonds came set up to run 25 or 27 degrees. And he wanted more octane than we had been using. So think about this. Why is one amount of lead a better choice than another, and what is the correct amount for any situation. The short answer is about 100 pages. But the bullets are: To arrive at the highest cylinder pressure at the ideal crank angle. Period. Nothing else to learn. So what are the other 99 pages about? All of the problems that will be generated while attempting to accomplish this feat. I don't like turbocharging. It is just like crack. Once you try it, you cannot get it out of your mind. And just like crack, a little crack is no good after a while, so you need way more crack just to stay even. So you see people that seem perfectly intelligent gutting a third gen engine compartment and adding $25,000.00 worth of very short lived equipment, so that the rush will be bigger the next time. And it can all go away in a split second. NA engines (piston or rotary) suffer reduced cylinder filling with increased RPM. Since the head space (compression volume) is not changing, the reduced cylinder filling is reducing the compression ratio with incrased RPM. Less fuel air mixture crammed into the same space, is the same as a larger head space, or a lower compression ratio. So unless the NA engine is lugged at a high throttle opening (same as way too much advance) or it cross fires (same as way too much advance) you just about cannot hurt it. I ran over 14:1 in my Fiat engines and never had a problem. Then I could buy 110 airplane fuel at the local airport. The rules had me running a little Weber DMSA-100 carb with a 23MM and a 27MM choke size. So as the revs came up the cylinder filling was so poor that the effective compression ratio dropped into the too low area and the 34 degrees of lead was just right. So the trick here is that the 14:1 is only the calculated compression ratio, and it vanishes as the RPMs come upoff of idle. In the turbo (or supercharged) engine, the compression ratio goes up with RPM. Think about that for a moment. The engine becomes more vulnerable to sudden death as you rev it up. The effect is that the engine gets bigger in displacement as you rev it up, but the head space stays the same. So the cylinder filling is getting better with RPM rather than worse, as in the NA engine. Easy to understand so far. So the one big killer of engines is ignition advance, and as the revs come up so comes the increased compression ratio and so the ignition advance must be reduced (retarded) with RPM so as to keep the maximum cylinder pressure right at (the same place as the NA engine) the ideal location in the cycle (about 20 degrees ATDC). I will continue this later. I have to run. But while I'm gone, think about this. The relationship of crankhaft degrees of advance in a piston engine and the 1/3 relationship of the cranckshaft degrees vice rotor face degrees in the rotary. How many degrees of rotation of usefull work in one vice the other. Lynn E. Hanover Sorry, but ideal maximum cylinder pressure for a piston engine is 18-22 degrees ATDC. For a rotary it is 40-50 degrees. And 2 is one third of 6 not 3. But cut the advance way back in any case. Ken Weller uses a 100 horse nitrus shot in his rotary powered sea plane to get it up on the step (planing) during nitrus injection he shuts off the trailing ignition to avoid detonation. Isn't that interesting? Lynn E. Hanover |
Definitely have learned a lot throught this reading. Some seriously interesting stuff, here.
With all this said, what steps should I take to remedy this situation in my motor? Shielding the appropriate wires, colder plugs, different plug wires? At this point, I feel myself already hesitant to want to go above 7k rpms when the motor is running again...I just don't want this to happen again. I have put way too much time and research into this setup, to start poppin motors left and right. |
that is a huge problem, the factory had different goals, but who knows how many engines they blew up tuning for the stock t2/fd/rx8?
they spent 5 years developing the racing turbo engines 81-86, and they ran 1 race and bonneville they have more time, more money, more everything, how do you compete with that? well for one, you can copy them.... we know the intake air temps, we know the turbos, the porting, egt's, compression etc etc |
Is the motor apart yet?, put the apex seals face to face, if they are sunk in the middle, there is the source of your pre ignition.. Hold them up to the light.. Stock mazda seals are bowed outward, in the centre, when they are not worn out. Every aftermarket seal I have see so far is sunk inward in the middle even when new and unused, but it becomes substantially worse after a little mileage and boost . Check the seals for colour difference, if the centre is different from the outer corners, thats combustion leakage between chambers..Been there done that...
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Originally Posted by Maxt' post='828137' date='Jul 12 2006, 03:10 AM
Is the motor apart yet?, put the apex seals face to face, if they are sunk in the middle, there is the source of your pre ignition.. Hold them up to the light.. Stock mazda seals are bowed outward, in the centre, when they are not worn out. Every aftermarket seal I have see so far is sunk inward in the middle even when new and unused, but it becomes substantially worse after a little mileage and boost . Check the seals for colour difference, if the centre is different from the outer corners, thats combustion leakage between chambers..Been there done that... What's the link between inwardly bowed apex seal centres and pre-ignition? B |
Originally Posted by BDC' post='828186' date='Jul 12 2006, 11:19 AM
What's the link between inwardly bowed apex seal centres and pre-ignition? B hot gasses from one chamber can go into the other and heat up the charge.... |
spent an interesting afternoon with our reps cx7, two engineers from japan, looking for better response under 2500rpms. we talked about it, drew a bunch of graphs, they plugged their stuff into the car, made and datalogged some changes, and we'll see, maybe they will have a TG reflash for it.
the hopeful thing is that they didnt have too much in the way of datalogging, their 2 boxes plugged into the car and added 1 sensor. |
Originally Posted by j9fd3s' post='828211' date='Jul 12 2006, 01:53 PM
hot gasses from one chamber can go into the other and heat up the charge.... Yeah, that's true. I guess I'll know when I tear it apart. I still don't think that's what caused it, however. I still think it's ignition-related as in something abnormal going on per the symptoms and how it felt. B |
Originally Posted by Comitatus' post='828105' date='Jul 11 2006, 09:28 PM
Definitely have learned a lot throught this reading. Some seriously interesting stuff, here. With all this said, what steps should I take to remedy this situation in my motor? Shielding the appropriate wires, colder plugs, different plug wires? At this point, I feel myself already hesitant to want to go above 7k rpms when the motor is running again...I just don't want this to happen again. I have put way too much time and research into this setup, to start poppin motors left and right. I know so little about turbocharging anything, that I would get hold of the factory manuals for the twin turbo engine and see what ignition advance those things use at high boost, then run a little less than that. Make sure the controller is actually pulling out advance for each lambda hit. Find out what mechanism is used to determin that, and apply it. I would run about 10% glychol and a dose of Redline Water-Wetter or a teaspoonfull of dish washing detergent, and the rest distilled water for coolant. Bring up the fans with boost no matter the coolant temp. Add water spray onto the intercooler and radiator with high boost. Maybe even some intake spray at high boost. You might consider tuning for just 450 HP peak and hang on to the engine for much longer. Add an intake air temp gage. Add a datalogger. Tune a bit richer than ideal for any boost. I remember when Electromotive was trying to get a full lap out of the Nissan V-6 twin turbo GTP car. They ended up with (among other things) an engine that was tuned so rich under boost it looked like a diesel truck. But it stayed together. Lynn E. Hanover |
Originally Posted by Lynn E. Hanover' post='828272' date='Jul 12 2006, 08:40 PM
I know so little about turbocharging anything, that I would get hold of the factory manuals for the twin turbo engine and see what ignition advance those things use at high boost, then run a little less than that. Make sure the controller is actually pulling out advance for each lambda hit. Find out what mechanism is used to determin that, and apply it. I would run about 10% glychol and a dose of Redline Water-Wetter or a teaspoonfull of dish washing detergent, and the rest distilled water for coolant. Bring up the fans with boost no matter the coolant temp. Add water spray onto the intercooler and radiator with high boost. Maybe even some intake spray at high boost. You might consider tuning for just 450 HP peak and hang on to the engine for much longer. Add an intake air temp gage. Add a datalogger. Tune a bit richer than ideal for any boost. I remember when Electromotive was trying to get a full lap out of the Nissan V-6 twin turbo GTP car. They ended up with (among other things) an engine that was tuned so rich under boost it looked like a diesel truck. But it stayed together. Lynn E. Hanover well we played with the cx7 today, and even doing something dumb, like trying to get the turbo spooled quciker, was hard, if you advance the timing, it maybe make pinging sound. if you retard the timing, turbo might spool quicker, but long term it might be bad, and then it also raises air temps, and also make pinging sound. we talked about loosening the converter on the transmission, which they can do with the laptop, but they gas mileage goes down. tons of tradeoffs road racing is different than a street car too, street car doesnt have to have the cooling, as full throttle is a much shorter time period.... |
Provided it's not too dang hot to work tomorrow (it's supposed to be 104* degrees!), I'm tearing down Luke's motor to get a peek at the damage. I'll get some photos and get back to this thread with them.
B |
Originally Posted by BDC' post='829248' date='Jul 19 2006, 08:18 PM
Provided it's not too dang hot to work tomorrow (it's supposed to be 104* degrees!), I'm tearing down Luke's motor to get a peek at the damage. I'll get some photos and get back to this thread with them. B i'm building a miata engine, its supposed to be 107! here! |
2 Attachment(s)
Got the engine torn down. Yep, big nasty set of cracks on the dowel land of the rear iron housing. Turns out its an older S5 w/ the thinner casting, same with the front iron. Hopefully we can find a newer S5 rear w/ the thicker casting. The front rotor had one collaped corner seal only. Rear rotor had one apex seal that was smashed in the groove but otherwise the seal and the groove are fine. I suspect only the springs were flattened so those will have to be replaced. Both rotor housings fine and smelled like leaded race gas. https://www.nopistons.com/forums/pub...IR#>/smile.png
Here's the pictures, guys: https://i114.photobucket.com/albums/...r/IMG_4475.jpg Attachment 20610 Attachment 20611 B |
Overall, That is good news to hear, B. I was preparing myself for the worst!
Since we have to replace the springs...I think I'll go with the OEM Mazdas. I've heard a that the RA springs were subject to some debate when comparing to OEM. So I'm thinking Replacing all Corner Seals with Solid Atkins, and going with Stock Springs...Hows that sound? P.S. - Seeing these pics still makes me feel sick, and I want to cry i think https://www.nopistons.com/forums/pub...O_DIR#>/11.gif |
Any more pixs of the rotor grooves/seals etc? Any data on oil/water/air/exhaust temps etc? I have some speculations, but some more data would help.
I would also like to add that we use MSD wires on a lot of cars in the shop, not prefabbed ones, but we've never seen them fail. |
Originally Posted by Comitatus' post='829368' date='Jul 20 2006, 09:30 PM
Overall, That is good news to hear, B. I was preparing myself for the worst! Since we have to replace the springs...I think I'll go with the OEM Mazdas. I've heard a that the RA springs were subject to some debate when comparing to OEM. So I'm thinking Replacing all Corner Seals with Solid Atkins, and going with Stock Springs...Hows that sound? P.S. - Seeing these pics still makes me feel sick, and I want to cry i think https://www.nopistons.com/forums/pub...O_DIR#>/11.gif Ok, scratch that...I already have Solid Atkins Corner Seals... https://www.nopistons.com/forums/pub...1047683664.gif But, Mazda OEM seal springs for sure. |
So, any new ideas? My gut still says there's something going on w/ the plug wires but a part of me doesn't sit well with that since they're a high-dollar, aftermarket brand...
B |
Originally Posted by BDC' post='830244' date='Jul 27 2006, 10:26 AM
So, any new ideas? My gut still says there's something going on w/ the plug wires but a part of me doesn't sit well with that since they're a high-dollar, aftermarket brand... B I think a combination of timing & the plugs is the cause, but more the plugs. I'm not sure about the wires. I was about to buy a set of those from summit racing last week, but couldn't get enough info on it and didn't know of anyone else running that wire on a fd so chickened out. I mapped a car before that had similar issues and it ended up being the ht leads, funnily enough they were brand new ht leads. Put stock ones on and they were fine. P.S Post an update on your alky kit, is it all fitted? have you started tuning yet? |
Originally Posted by BNA_ELLIS' post='830344' date='Jul 28 2006, 06:49 AM
I think a combination of timing & the plugs is the cause, but more the plugs. I'm not sure about the wires. I was about to buy a set of those from summit racing last week, but couldn't get enough info on it and didn't know of anyone else running that wire on a fd so chickened out. I mapped a car before that had similar issues and it ended up being the ht leads, funnily enough they were brand new ht leads. Put stock ones on and they were fine. P.S Post an update on your alky kit, is it all fitted? have you started tuning yet? Hey BNA_ELLIS, I still don't think it's either (timing or plugs) because I've got a good chunk of prior history that convinces me of the reliability of both under the same and heavier-load circumstances. Even though I like to think that every motor I build is "special" (taking pride in what I do kinda thing), as far as his porting scheme and build, it's not really different internally than many of the other half-bridgeports I've done that I've tuned that ran with the same plugs and timing. Infact, on one car, I was running 20* at 20psi of boost with a 5* split. Luke's I had parked at 17* at 18.5psi with a 6* split from what I recall; same plugs. Both running leaded race gas. My gut still says it's something related to spark, either be it plugs, some weird grounding thing, or something else screwbally that I am unfamiliar with. I've seen this happen on a handful of Rx7's (all 2nd gens now that I think about it) but am not sure what's causing it. I've got a local buddy here w/ a motor and haltech that I built and installed and tuned to lower boost that's got the same intermittent hiccup; same as Luke's at high RPM, very randomly. His power level is still in the mid 300rwhp range and isn't at the point yet of challenging pump gas let alone being too hot for the all 9's he's got plug-wise. I talked to him yesterday about it and he told me that one time when he had his intercooler piping touching his throttle body (underneath the connecting coupler) that it was misfiring badly. He's got that GReddy front mount w/ the intercooler outlet piping that travels right next to the leading coil and leading wires so perhaps there's something there. /shrug B |
hey b, my ports look real good thanks! but anyways, i understand that there was most likely a problem with ignition. but besides that fact, could there have been a tension rod issues causing vibrations and rendering the iron to crack? i also know the fact that, usually a tension rod wich is thinner than cast iron side housings would snap before cracking iron. but its deffinatly a possiblilty to take into consideration.
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Originally Posted by BDC' post='830719' date='Jul 31 2006, 11:51 AM
I talked to him yesterday about it and he told me that one time when he had his intercooler piping touching his throttle body (underneath the connecting coupler) that it was misfiring badly. B the 20b vert ive been working on did the same thing, the ic pipe was touching the #3 L wire, and was arcing, its not something you would have seen with only 1 person either, it took him cranking it and me looking for something else to see it |
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I've uploaded a few pictures of Luke's engine bay for reference for anyone who may be interested in playing detective. As it stands right now, I'm at a loss as I've got nothing concrete to blame this failure on.
After checking the pictures out, I noticed the alternator power harness is nearby the plugs and plug wires - Suspect? B Attachment 20577 Attachment 20578 Attachment 20579 Attachment 20580 |
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