missfires and E85 = bad news
Mar 19, 2010, 03:37 PM
#31
The ignition on the car is stock. But early stock ignition is far stronger than evo 8 coils. I make 570tq on my other early car with stock coils. That car has never had spark issues. this car with 150-200tq less has issues.
Its always easy to point fingers and say poor tuning is the cause. I still feel pre-ignition is the cause here. Rods just dont bend this easy. If you excede MBT you are simply making making less than maximum MBT. But it is being done when the rod is closer to being straight up and down (0 degrees) on the crank pin. The rod is in its strongest position. Rods simply do not bend when they are at or near TDC. If they did rods would bend with detonation on a regular basis. Normal cylinder pressures are in the 1600-2600psi range. with proper timing this max MBT will occur at 14 degress after TDC. This is when the crank pin is at perfect angle to do maximum work on turning the crank. when detonation occurs it happens at TDC . cylinder pressures are instant 4000+ psi.. You will lift head, break ring lands, flatten rod bearings, etc. But never will you bend a rod.
I rest my case here. it is easy to bend a rod when you twist it from both ends. This only happens with pre-ignition. We could bench race till we are blue in the face on this subject. but in the end I dont really car if you buy my diagnosis or not. I am sure it is the correct one.
I have tried both E85 and meth injection. There is no question i like the simpler approach to things. My favorite quote right now is "if the solution is simple God is answering" E85 is wonderful fuel to make power. No question about it. but it is not without drawbacks. It is still too much like race fuel by definition of availability. For me 93/alky is far more practical. I hate that it is more complex. But it does work well. Very well in my experience.
Its always easy to point fingers and say poor tuning is the cause. I still feel pre-ignition is the cause here. Rods just dont bend this easy. If you excede MBT you are simply making making less than maximum MBT. But it is being done when the rod is closer to being straight up and down (0 degrees) on the crank pin. The rod is in its strongest position. Rods simply do not bend when they are at or near TDC. If they did rods would bend with detonation on a regular basis. Normal cylinder pressures are in the 1600-2600psi range. with proper timing this max MBT will occur at 14 degress after TDC. This is when the crank pin is at perfect angle to do maximum work on turning the crank. when detonation occurs it happens at TDC . cylinder pressures are instant 4000+ psi.. You will lift head, break ring lands, flatten rod bearings, etc. But never will you bend a rod.
I rest my case here. it is easy to bend a rod when you twist it from both ends. This only happens with pre-ignition. We could bench race till we are blue in the face on this subject. but in the end I dont really car if you buy my diagnosis or not. I am sure it is the correct one.
I have tried both E85 and meth injection. There is no question i like the simpler approach to things. My favorite quote right now is "if the solution is simple God is answering" E85 is wonderful fuel to make power. No question about it. but it is not without drawbacks. It is still too much like race fuel by definition of availability. For me 93/alky is far more practical. I hate that it is more complex. But it does work well. Very well in my experience.
Mar 19, 2010, 03:45 PM
#32
Isn't the waste spark firing at the same crank angle as the event spark? What about the exhaust side or intake side valves being open during the waste spark, not allowing sufficient cylinder pressure to build? I'm not saying your diagnosis is wrong...I just can't visualize what you're saying is happening as being the case.
I do agree that preignition on the compression stroke can definitely bend a rod or ignition that's way too early (why ppl were asking for your timing numbers), but you were saying that you thought the mixture was igniting on the waste spark.
I'm just as curious as you are, as I'm sure others are as well. But I think we would like to find the true root cause.
I do agree that preignition on the compression stroke can definitely bend a rod or ignition that's way too early (why ppl were asking for your timing numbers), but you were saying that you thought the mixture was igniting on the waste spark.
I'm just as curious as you are, as I'm sure others are as well. But I think we would like to find the true root cause.
Mar 20, 2010, 11:32 PM
#36
Just tuning into this thread. It looks like in the first post, waste spark during final phase of the exhaust stroke is the blame, but then later on, pre-ignition is the blame?
Waste spark - During waste spark on the exhaust stroke, it seems that either the intake or the exhaust valves or both sets of valves are both likely to be open, so that would stop any pressure spike. The mixture ought to be very low density at this point as well.
Preignition - If you are referring to the classic preignition scenario where something like the ground strap gets too hot and ignites the mixture prior to the spark event, how could this happen if EGTs are as low as you say for your setup? What heat range spark plugs were you running?
Waste spark - During waste spark on the exhaust stroke, it seems that either the intake or the exhaust valves or both sets of valves are both likely to be open, so that would stop any pressure spike. The mixture ought to be very low density at this point as well.
Preignition - If you are referring to the classic preignition scenario where something like the ground strap gets too hot and ignites the mixture prior to the spark event, how could this happen if EGTs are as low as you say for your setup? What heat range spark plugs were you running?
Mar 31, 2010, 01:09 PM
#38
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I spent last saturday setting up a dsm with the evo 8 ecu. We did about 35 pulls till we got boost, fuel, timing, and SD setup. He is misfiring badly either due to the origional coil packs or 8 year old plug wires. You could feel it bad and did it multiple times per gear. This car has been on e85 for over a year now. Anyways no ldamage, no bent rods, stock billion mile 1990 bottom end, oil pan never off. It has gone 10's and will go 10's again soon enough.
Many of you guys are running WAY too much timing with E85 and hurting motors, bending rods, etc.. It is the tune, not the fuel. I have the logs if anybody doesn't believe me.
On my personal car I slammed the spark cut rev limiter a couple times for 1-2 seconds when I broke traction in second and third. Again stock rods/pistons and NO damage.
Many of you guys are running WAY too much timing with E85 and hurting motors, bending rods, etc.. It is the tune, not the fuel. I have the logs if anybody doesn't believe me.
On my personal car I slammed the spark cut rev limiter a couple times for 1-2 seconds when I broke traction in second and third. Again stock rods/pistons and NO damage.
Mar 31, 2010, 01:12 PM
#39
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Indeed. I bounce off the rev limiter daily in my personal Evo 8 with E85.
I've also had misfires on multiple occassions from spark cut out.
7Xk still going strong
- Bryan
I've also had misfires on multiple occassions from spark cut out.
7Xk still going strong
- Bryan
Mar 31, 2010, 02:08 PM
#40
He is misfiring badly either due to the origional coil packs or 8 year old plug wires. You could feel it bad and did it multiple times per gear. This car has been on e85 for over a year now. Anyways no ldamage, no bent rods, stock billion mile 1990 bottom end, oil pan never off. It has gone 10's and will go 10's again soon enough.
Many of you guys are running WAY too much timing with E85 and hurting motors, bending rods, etc.. It is the tune, not the fuel. I have the logs if anybody doesn't believe me.
On my personal car I slammed the spark cut rev limiter a couple times for 1-2 seconds when I broke traction in second and third. Again stock rods/pistons and NO damage.
Many of you guys are running WAY too much timing with E85 and hurting motors, bending rods, etc.. It is the tune, not the fuel. I have the logs if anybody doesn't believe me.
On my personal car I slammed the spark cut rev limiter a couple times for 1-2 seconds when I broke traction in second and third. Again stock rods/pistons and NO damage.
Mar 31, 2010, 02:40 PM
#41
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This is good to see (read). I remember a quote from the last guy that did my tuning and it went something like, "You can run globs of timing with E85. You are going to love it." A week after my tune... BAM! I threw a rod. Lesson certainly learned and that is to enjoy the added benefit of E85 but not at the expense of trying to squeeze every single whp out of it.
MBT is actually fairly easy to see on a repeatable consistant dyno. Some people chose to stay right at MBT, some like to get to it, then dial back a little.
http://en.wikipedia.org/wiki/Maximum_brake_torque
- Bryan
Mar 31, 2010, 02:55 PM
#42
Yes, it is very easy to go beyond MBT with E85. This creates exponential cylinder pressure. Easily enough to bend a rod or vent the block.
MBT is actually fairly easy to see on a repeatable consistant dyno. Some people chose to stay right at MBT, some like to get to it, then dial back a little.
http://en.wikipedia.org/wiki/Maximum_brake_torque
- Bryan
MBT is actually fairly easy to see on a repeatable consistant dyno. Some people chose to stay right at MBT, some like to get to it, then dial back a little.
http://en.wikipedia.org/wiki/Maximum_brake_torque
- Bryan
And no, JMS wasn't who did my initial tuning.
Apr 1, 2010, 12:22 PM
#45
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One thing people tend to forget is the oil. IMO the very first time you switch a gasoline powered car to E85 the oil needs to be changed immediately. Probably within 25 miles and the second one again after a few hundres miles. You need to be sure all the carbon build up that is cleaned up by the e85 is flushed out of the engine.
Then go and worry about the tunes...
Then go and worry about the tunes...