missfires and E85 = bad news
Jun 13, 2010, 01:02 PM
#76
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For a comparison of fuels, on 93 I ran 3deg peak TQ and 13deg peak. This made 328/308tq on a dynojet at 23psi.
On E85 I ran 6deg peak TQ and 19 peak, making 375/378tq on a dynojet at 27psi.
On E85 I ran 6deg peak TQ and 19 peak, making 375/378tq on a dynojet at 27psi.
Last edited by drewdq; Jun 13, 2010 at 01:07 PM.
Jun 13, 2010, 01:08 PM
#77
Sorry for your motor, of course. But, again, I think your issue may have been your tune and not the misfire. I think the continued running at that agressive amount eventually caused the failure. But again, that's just my opinion and I could be wrong. In general, it seems like people are running too much timing at peak torque on E85. I think a safe approach would be to use your knock free pump gas peak torque timing numbers, then ramp up from there.
In either case, thanks for posting up your information. It definitely helps everyone when information is shared. Good luck in the future with your car and new motor (if you are sticking with the Evo, of course).
Last edited by l2r99gst; Jun 13, 2010 at 01:11 PM.
Jun 13, 2010, 01:19 PM
#78
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I was running ~6-7 deg at peak TQ because it was around this point that I didn't see any gains in power. I didn't think this was dangerous based on what I have seen, and I always imagined that MBT was higher than where I was. There's a good chance you're right, and I have been hitting MBT and eventually just threw a rod after long term stresses. I truly didn't think my tune was that aggressive - I've seen some nasty E85 maps on the forums and I'm surprised more motors aren't blowing.
I just found it interesting that my motor blew as soon as I started having misfire issues.
I definitely plan on sticking with the Evo!
I just found it interesting that my motor blew as soon as I started having misfire issues.
I definitely plan on sticking with the Evo!
Jun 13, 2010, 02:38 PM
#79
I was running ~6-7 deg at peak TQ because it was around this point that I didn't see any gains in power. I didn't think this was dangerous based on what I have seen, and I always imagined that MBT was higher than where I was. There's a good chance you're right, and I have been hitting MBT and eventually just threw a rod after long term stresses. I truly didn't think my tune was that aggressive - I've seen some nasty E85 maps on the forums and I'm surprised more motors aren't blowing.
I just found it interesting that my motor blew as soon as I started having misfire issues.
I definitely plan on sticking with the Evo!
I just found it interesting that my motor blew as soon as I started having misfire issues.
I definitely plan on sticking with the Evo!
with a built motor it still would have did what it did, but i think it would have taken much longer to happen with a built motor then it did with your stocker.
from experience my car keeps making power until about 19-20* uptop, i stopped at 14* on my latest tune because I wanted to do some other things before i pushed it further. What setup are you gonna go with? where in pa you live?
my timing maps posted on post #52 if you want to take a look.
Jun 13, 2010, 07:48 PM
#80
I made this thread because i felt pretty sure misfires caused me to loose two engines. Then some haters came in and suggested it was bad tuning. This made me think about it a little more. I took a hard look at my tune which in the end was not aggressive at all. But after more thought I am now 100% certain you cant bend a rod from going past MBT. heres how I got there.
in a normal good tune the flame front takes anywhere from ~15 to ~35 (power not cruise) crank degrees of rotation to reach MBT. this means at peak torque when your timing advance is set at 0 the fire takes 15 degrees of rotation to reach the ideal crank turning starting point of ~14-16 ATDC. at higher RPM the piston is moving faster so there needs to be more advance for there to be enough time for the fire to reach MBT at the same 15 ATDC. so at 8000rpm when you have 20 degrees timing advance the fire takes 35 degrees of crank rotation to reach MBT at 15 ATDC.
Are you with me so far? Now lets look at pressures all during the firing phase. If peak MBT arrives at 15ATDC then that is when cylinder pressures are highest and torque is at its peak. any degrees before that will be less. so lets look at a rough example. At 0 degrees advance there isnt much pressure at or near TDC. only the cranking compression magnified by RPM. cranking compression ~175-200. magnify that by some RPM and it like jumps to maybe 300 or so. When the spark ignites mixture the expansion begins. If the full expansion arrives at 15 degrees later. The PSI pressure will look something like this" 300 at 0, 900 at 5, 1500 at 10, and 2100psi at 15....This is a worst case scenario of pressure rise. Its more likely more exponential. like 300,600,1200, 2100. Its not likely at all the rod is bending at higher rpms. torque is lower so we all hopefully agree the rod is bending at lower RPM when torque is highest.
still with me? now what happens when you go past MBT? lets take 5 degrees past for an example. at 5 before TDC the starting pressure is gonna still be very close to that 300psi. the cranking compression or starting compression is gonna be lower because the piston hasnt reached TDC yet so that compression will be lower. Then the numbers will look something like this. 5BTDC= 300, TDC = 900, 5ATDC= 1500, and 10ATDC=2100psi.
I for the life of me cant figure how that type of psi change would be capable of bending a rod. Given the fact that detonation doesnt bend rods. detonation is an explosion of fire. it has instant pressure rise of over 4000psi . I have been playing with turbo cars for 30 years now. I have pushed dozens engines to detonation. many to the audible point. Never once have i bent a rod from detonation.
So if anyone is reading this who still disagrees please explain the physics of how you are getting there. I would really like to hear it.
in a normal good tune the flame front takes anywhere from ~15 to ~35 (power not cruise) crank degrees of rotation to reach MBT. this means at peak torque when your timing advance is set at 0 the fire takes 15 degrees of rotation to reach the ideal crank turning starting point of ~14-16 ATDC. at higher RPM the piston is moving faster so there needs to be more advance for there to be enough time for the fire to reach MBT at the same 15 ATDC. so at 8000rpm when you have 20 degrees timing advance the fire takes 35 degrees of crank rotation to reach MBT at 15 ATDC.
Are you with me so far? Now lets look at pressures all during the firing phase. If peak MBT arrives at 15ATDC then that is when cylinder pressures are highest and torque is at its peak. any degrees before that will be less. so lets look at a rough example. At 0 degrees advance there isnt much pressure at or near TDC. only the cranking compression magnified by RPM. cranking compression ~175-200. magnify that by some RPM and it like jumps to maybe 300 or so. When the spark ignites mixture the expansion begins. If the full expansion arrives at 15 degrees later. The PSI pressure will look something like this" 300 at 0, 900 at 5, 1500 at 10, and 2100psi at 15....This is a worst case scenario of pressure rise. Its more likely more exponential. like 300,600,1200, 2100. Its not likely at all the rod is bending at higher rpms. torque is lower so we all hopefully agree the rod is bending at lower RPM when torque is highest.
still with me? now what happens when you go past MBT? lets take 5 degrees past for an example. at 5 before TDC the starting pressure is gonna still be very close to that 300psi. the cranking compression or starting compression is gonna be lower because the piston hasnt reached TDC yet so that compression will be lower. Then the numbers will look something like this. 5BTDC= 300, TDC = 900, 5ATDC= 1500, and 10ATDC=2100psi.
I for the life of me cant figure how that type of psi change would be capable of bending a rod. Given the fact that detonation doesnt bend rods. detonation is an explosion of fire. it has instant pressure rise of over 4000psi . I have been playing with turbo cars for 30 years now. I have pushed dozens engines to detonation. many to the audible point. Never once have i bent a rod from detonation.
So if anyone is reading this who still disagrees please explain the physics of how you are getting there. I would really like to hear it.
Jun 13, 2010, 08:03 PM
#81
I made this thread because i felt pretty sure misfires caused me to loose two engines. Then some haters came in and suggested it was bad tuning. This made me think about it a little more. I took a hard look at my tune which in the end was not aggressive at all. But after more thought I am now 100% certain you cant bend a rod from going past MBT. heres how I got there.
in a normal good tune the flame front takes anywhere from ~15 to ~35 (power not cruise) crank degrees of rotation to reach MBT. this means at peak torque when your timing advance is set at 0 the fire takes 15 degrees of rotation to reach the ideal crank turning starting point of ~14-16 ATDC. at higher RPM the piston is moving faster so there needs to be more advance for there to be enough time for the fire to reach MBT at the same 15 ATDC. so at 8000rpm when you have 20 degrees timing advance the fire takes 35 degrees of crank rotation to reach MBT at 15 ATDC.
Are you with me so far? Now lets look at pressures all during the firing phase. If peak MBT arrives at 15ATDC then that is when cylinder pressures are highest and torque is at its peak. any degrees before that will be less. so lets look at a rough example. At 0 degrees advance there isnt much pressure at or near TDC. only the cranking compression magnified by RPM. cranking compression ~175-200. magnify that by some RPM and it like jumps to maybe 300 or so. When the spark ignites mixture the expansion begins. If the full expansion arrives at 15 degrees later. The PSI pressure will look something like this" 300 at 0, 900 at 5, 1500 at 10, and 2100psi at 15....This is a worst case scenario of pressure rise. Its more likely more exponential. like 300,600,1200, 2100. Its not likely at all the rod is bending at higher rpms. torque is lower so we all hopefully agree the rod is bending at lower RPM when torque is highest.
still with me? now what happens when you go past MBT? lets take 5 degrees past for an example. at 5 before TDC the starting pressure is gonna still be very close to that 300psi. the cranking compression or starting compression is gonna be lower because the piston hasnt reached TDC yet so that compression will be lower. Then the numbers will look something like this. 5BTDC= 300, TDC = 900, 5ATDC= 1500, and 10ATDC=2100psi.
I for the life of me cant figure how that type of psi change would be capable of bending a rod. Given the fact that detonation doesnt bend rods. detonation is an explosion of fire. it has instant pressure rise of over 4000psi . I have been playing with turbo cars for 30 years now. I have pushed dozens engines to detonation. many to the audible point. Never once have i bent a rod from detonation.
So if anyone is reading this who still disagrees please explain the physics of how you are getting there. I would really like to hear it.
in a normal good tune the flame front takes anywhere from ~15 to ~35 (power not cruise) crank degrees of rotation to reach MBT. this means at peak torque when your timing advance is set at 0 the fire takes 15 degrees of rotation to reach the ideal crank turning starting point of ~14-16 ATDC. at higher RPM the piston is moving faster so there needs to be more advance for there to be enough time for the fire to reach MBT at the same 15 ATDC. so at 8000rpm when you have 20 degrees timing advance the fire takes 35 degrees of crank rotation to reach MBT at 15 ATDC.
Are you with me so far? Now lets look at pressures all during the firing phase. If peak MBT arrives at 15ATDC then that is when cylinder pressures are highest and torque is at its peak. any degrees before that will be less. so lets look at a rough example. At 0 degrees advance there isnt much pressure at or near TDC. only the cranking compression magnified by RPM. cranking compression ~175-200. magnify that by some RPM and it like jumps to maybe 300 or so. When the spark ignites mixture the expansion begins. If the full expansion arrives at 15 degrees later. The PSI pressure will look something like this" 300 at 0, 900 at 5, 1500 at 10, and 2100psi at 15....This is a worst case scenario of pressure rise. Its more likely more exponential. like 300,600,1200, 2100. Its not likely at all the rod is bending at higher rpms. torque is lower so we all hopefully agree the rod is bending at lower RPM when torque is highest.
still with me? now what happens when you go past MBT? lets take 5 degrees past for an example. at 5 before TDC the starting pressure is gonna still be very close to that 300psi. the cranking compression or starting compression is gonna be lower because the piston hasnt reached TDC yet so that compression will be lower. Then the numbers will look something like this. 5BTDC= 300, TDC = 900, 5ATDC= 1500, and 10ATDC=2100psi.
I for the life of me cant figure how that type of psi change would be capable of bending a rod. Given the fact that detonation doesnt bend rods. detonation is an explosion of fire. it has instant pressure rise of over 4000psi . I have been playing with turbo cars for 30 years now. I have pushed dozens engines to detonation. many to the audible point. Never once have i bent a rod from detonation.
So if anyone is reading this who still disagrees please explain the physics of how you are getting there. I would really like to hear it.
Jun 13, 2010, 08:33 PM
#82
The eagle rod was clearly far stronger than the factory rod. It barely bent where factory rod bent like pretzel. This type of rod bending isnt really a good test of rods strength. Would have been nice to build a third motor with a better 700$ rod. But it was painful enough to loose the last built motor with less than 100miles on it. So i really needed to not risk breaking another engine. The new engine (2.3/scat/mahle)is in and running for about 2000 miles now. running it on 93/torco and not a single misfire. Not really sure the exact conditions that causes the rod bending misfires. maybe its both rich and misfire is bad. when lean and misfire is safe. maybe there are some other factors like cam duration or a whole host of other possible things.
Jun 13, 2010, 09:19 PM
#83
94AWD,
The only thing I ever disagreed with you was your theory about misfire causing ignition of the wasted spark throwing your rod. I gave my explanation for that and you never commented. The wasted spark will have valves open so essentially 0 pressure can build within the cylinder. How is that possibly going to throw a rod?
Preignition on the other hand is complete different and I totally agree that can blow pistons, bend rods, etc. What's preignition? It's basically running a timing WAY past MBT. How does that throw a rod? Because the entire pressure of the explosion is now going completely against the rod/piston with nowhere to escape (can't turn the crankshaft since the explosion is happening at an angle too early to perform work). So, something has to give.
My whole deal with running past MBT is simple geometry. Whether or not it's enough to bend the rod or crack a pistion, I don't know. There are too many variables involved to calculate it. But when peak pressure is attained before the angle where most work is performed on the crankshaft by the rod, the pressure axially along the rod is going to be higher. I would expect it to cause damage resulting in something like spun rod bearings. If you repeatedly stress a piece of metal, even below the point of plastic deformation, you can still have failure from fatigue. If you stress the metal beyond that point, you get plastic deformation (a bent rod for example). That's what you might see from preignition (way past MBT ignition).
So, maybe running past MBT damaged the bearing enough in the long run to cause enough play in the rod to eventually cause a rod bolt failure and then the rod being thrown? I don't know. I'm merely given suggestions and reasons why running past MBT is not a good idea. But, you just keep saying that it isn't a problem. I agree it may not be THE problem or YOUR problem, but you surely shouldn't suggest for people to keep running past MBT with no caution. It can and eventually will cause failure, just as detonation can and will cause failure. Metals don't heal themselves.
The only thing I ever disagreed with you was your theory about misfire causing ignition of the wasted spark throwing your rod. I gave my explanation for that and you never commented. The wasted spark will have valves open so essentially 0 pressure can build within the cylinder. How is that possibly going to throw a rod?
Preignition on the other hand is complete different and I totally agree that can blow pistons, bend rods, etc. What's preignition? It's basically running a timing WAY past MBT. How does that throw a rod? Because the entire pressure of the explosion is now going completely against the rod/piston with nowhere to escape (can't turn the crankshaft since the explosion is happening at an angle too early to perform work). So, something has to give.
My whole deal with running past MBT is simple geometry. Whether or not it's enough to bend the rod or crack a pistion, I don't know. There are too many variables involved to calculate it. But when peak pressure is attained before the angle where most work is performed on the crankshaft by the rod, the pressure axially along the rod is going to be higher. I would expect it to cause damage resulting in something like spun rod bearings. If you repeatedly stress a piece of metal, even below the point of plastic deformation, you can still have failure from fatigue. If you stress the metal beyond that point, you get plastic deformation (a bent rod for example). That's what you might see from preignition (way past MBT ignition).
So, maybe running past MBT damaged the bearing enough in the long run to cause enough play in the rod to eventually cause a rod bolt failure and then the rod being thrown? I don't know. I'm merely given suggestions and reasons why running past MBT is not a good idea. But, you just keep saying that it isn't a problem. I agree it may not be THE problem or YOUR problem, but you surely shouldn't suggest for people to keep running past MBT with no caution. It can and eventually will cause failure, just as detonation can and will cause failure. Metals don't heal themselves.
Last edited by l2r99gst; Jun 13, 2010 at 09:22 PM.
Jun 14, 2010, 12:55 AM
#84
94AWD,
The only thing I ever disagreed with you was your theory about misfire causing ignition of the wasted spark throwing your rod. I gave my explanation for that and you never commented. The wasted spark will have valves open so essentially 0 pressure can build within the cylinder. How is that possibly going to throw a rod?
Preignition on the other hand is complete different and I totally agree that can blow pistons, bend rods, etc. What's preignition? It's basically running a timing WAY past MBT. How does that throw a rod? Because the entire pressure of the explosion is now going completely against the rod/piston with nowhere to escape (can't turn the crankshaft since the explosion is happening at an angle too early to perform work). So, something has to give.
My whole deal with running past MBT is simple geometry. Whether or not it's enough to bend the rod or crack a pistion, I don't know. There are too many variables involved to calculate it. But when peak pressure is attained before the angle where most work is performed on the crankshaft by the rod, the pressure axially along the rod is going to be higher. I would expect it to cause damage resulting in something like spun rod bearings. If you repeatedly stress a piece of metal, even below the point of plastic deformation, you can still have failure from fatigue. If you stress the metal beyond that point, you get plastic deformation (a bent rod for example). That's what you might see from preignition (way past MBT ignition).
So, maybe running past MBT damaged the bearing enough in the long run to cause enough play in the rod to eventually cause a rod bolt failure and then the rod being thrown? I don't know. I'm merely given suggestions and reasons why running past MBT is not a good idea. But, you just keep saying that it isn't a problem. I agree it may not be THE problem or YOUR problem, but you surely shouldn't suggest for people to keep running past MBT with no caution. It can and eventually will cause failure, just as detonation can and will cause failure. Metals don't heal themselves.
The only thing I ever disagreed with you was your theory about misfire causing ignition of the wasted spark throwing your rod. I gave my explanation for that and you never commented. The wasted spark will have valves open so essentially 0 pressure can build within the cylinder. How is that possibly going to throw a rod?
Preignition on the other hand is complete different and I totally agree that can blow pistons, bend rods, etc. What's preignition? It's basically running a timing WAY past MBT. How does that throw a rod? Because the entire pressure of the explosion is now going completely against the rod/piston with nowhere to escape (can't turn the crankshaft since the explosion is happening at an angle too early to perform work). So, something has to give.
My whole deal with running past MBT is simple geometry. Whether or not it's enough to bend the rod or crack a pistion, I don't know. There are too many variables involved to calculate it. But when peak pressure is attained before the angle where most work is performed on the crankshaft by the rod, the pressure axially along the rod is going to be higher. I would expect it to cause damage resulting in something like spun rod bearings. If you repeatedly stress a piece of metal, even below the point of plastic deformation, you can still have failure from fatigue. If you stress the metal beyond that point, you get plastic deformation (a bent rod for example). That's what you might see from preignition (way past MBT ignition).
So, maybe running past MBT damaged the bearing enough in the long run to cause enough play in the rod to eventually cause a rod bolt failure and then the rod being thrown? I don't know. I'm merely given suggestions and reasons why running past MBT is not a good idea. But, you just keep saying that it isn't a problem. I agree it may not be THE problem or YOUR problem, but you surely shouldn't suggest for people to keep running past MBT with no caution. It can and eventually will cause failure, just as detonation can and will cause failure. Metals don't heal themselves.
You guys really need to be careful with MBT and E85. If there is no more power to be made as you're increasing ignition advance, congrats, you have just found MBT. Now, retard ignition timing 1-2 degs in that area and move on. Also, it's important to not tune too rich on E85 as well.
Jun 14, 2010, 04:10 AM
#85
http://www.dsmtuners.com/forums/tuni...ng-vs-afr.html
same bending as what you did.
http://www.google.com/search?hl=en&q...=&oq=&gs_rfai=
same bending as what you did.
http://www.google.com/search?hl=en&q...=&oq=&gs_rfai=
Jun 14, 2010, 01:13 PM
#86
I am not saying the points contrary to yours were right, but your resistance to them was obvious.
Jun 14, 2010, 01:32 PM
#87
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Still will stand by my stance that there was something else going on here. Either it was run too rich, past MBT for your setup, etc etc, or just bad luck.
I've tuned over 30 E85 4G63's at this point. A handful are used on track (the kind with turns) which is some of the most abusive use you can do to the car, all day long, with no issues.
We run E85 in our shop race car Subaru that competes in unlimited class in Redline Time Attack and makes 500 to 600whp depending on the mapping.
My personal Evo 8 has run E85 full-time for over almost two years now, currently at 412whp/401wtq on our mustang dyno, from 15F and 7500 ft altitude to 105F and sea level and it gets beat to crap all the time. I've run it with misfires from old plugs with no issues other then being annoying. Stock motor too.
You can call me a hater if you wish but the above cannot be ignored compared to your two bad experiences.
- Bryan
I've tuned over 30 E85 4G63's at this point. A handful are used on track (the kind with turns) which is some of the most abusive use you can do to the car, all day long, with no issues.
We run E85 in our shop race car Subaru that competes in unlimited class in Redline Time Attack and makes 500 to 600whp depending on the mapping.
My personal Evo 8 has run E85 full-time for over almost two years now, currently at 412whp/401wtq on our mustang dyno, from 15F and 7500 ft altitude to 105F and sea level and it gets beat to crap all the time. I've run it with misfires from old plugs with no issues other then being annoying. Stock motor too.
You can call me a hater if you wish but the above cannot be ignored compared to your two bad experiences.
- Bryan
Jun 14, 2010, 09:01 PM
#88
Bryan, i get that you have had great results tuning e-85 cars with no mist haps. I also get that it doesnt disprove my case at all. Just because you have experienced misfires without bending rods doesnt mean it cant happen with me or the others who are throwing rods out the block. Did you miss where drewdq just threw a rod and was experiencing misfires before it happen? Did you miss the part were I beat on my car too? I beat on it autocross style getting 8 miles to gallon for entire tank. in two hours. i ran 160 gallons of E85 through the stock engine at maxed out on 45lb min turbo. no issues with misfires and no thrown rods. You offer no engine running physics to support your case other than "it hasnt happen to my 30 cars" and "something else is happening " or the best one yet "bad luck"
wow thanks again for your input.
wow thanks again for your input.
Jun 14, 2010, 09:23 PM
#89
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Bryan, i get that you have had great results tuning e-85 cars with no mist haps. I also get that it doesnt disprove my case at all. Just because you have experienced misfires without bending rods doesnt mean it cant happen with me or the others who are throwing rods out the block. Did you miss where drewdq just threw a rod and was experiencing misfires before it happen? Did you miss the part were I beat on my car too? I beat on it autocross style getting 8 miles to gallon for entire tank. in two hours. i ran 160 gallons of E85 through the stock engine at maxed out on 45lb min turbo. no issues with misfires and no thrown rods. You offer no engine running physics to support your case other than "it hasnt happen to my 30 cars" and "something else is happening " or the best one yet "bad luck"
wow thanks again for your input.
wow thanks again for your input.
I am not trying to disprove your case. Just adding data points and other possible variations that could have caused your failures.
Alright, obviously nobody can post something other then your viewpoint without you taking offense so I wish you good luck in your future endeavors.
- Bryan
Last edited by GST Motorsports; Jun 14, 2010 at 09:29 PM.
Jun 19, 2010, 01:06 PM
#90
drewdq was obviously past MBT as outlined by his posts. Autox is childs play compare to open track as far as actual abuse on a motor. I've tuned a ton of local autoxers on E85 as well, a bunch of them class champions. I don't need to post engine physics equations to prove obscure points.
I am not trying to disprove your case. Just adding data points and other possible variations that could have caused your failures.
Alright, obviously nobody can post something other then your viewpoint without you taking offense so I wish you good luck in your future endeavors.
- Bryan
I am not trying to disprove your case. Just adding data points and other possible variations that could have caused your failures.
Alright, obviously nobody can post something other then your viewpoint without you taking offense so I wish you good luck in your future endeavors.
- Bryan