When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
RS got the motor apart. piston #4 heated and causing knock against cylinder, slapping the wall. only on cylinder 4. block is scored on that wall, shavings from it in the oil.
not sure yet on cause, but piston 4 issues are usually oiling issues
It should just be standard in any logging systems people are running (Does AIM have analog inputs to log?) that oil pressure is watched. It doesn't tell the whole story but it tells most of it.
The piston top on #4 looks cleaner than the others. I wonder if it was running extra rich (with E85) and there was a bore wash problem? Maybe flow test the injectors?
Any plans to do anything differently in the oil pressure department? Accusump? Dry sump?
The piston top on #4 looks cleaner than the others. I wonder if it was running extra rich (with E85) and there was a bore wash problem? Maybe flow test the injectors?
Any plans to do anything differently in the oil pressure department? Accusump? Dry sump?
Was probably from the oil coming past the rings and cleaning the piston top. My one piston was cleaner than the others when I had the oil burning issue.
RS got the motor apart. piston #4 heated and causing knock against cylinder, slapping the wall. only on cylinder 4. block is scored on that wall, shavings from it in the oil.
not sure yet on cause, but piston 4 issues are usually oiling issues
Sorry, dude. Get er fixed and back on track, asap!!
That is 110% not an oiling issue. The scoring you see is perpendicular to the wrist pin so it's not from the pin.
What you're seeing is the result of that cylinder running a decent amount hotter than the rest. The piston is cleaner than the rest because detonation cleaned it off, small amounts of detonation will do that and it's evident by the small pock marks in the crown of the piston.
Another sign that tells me it's an overheating issue is the scoring is deeper at the top of the bore and gets less severe as it travels down the bore. Most bores have a small amount of taper from the factory and they're tightest at the top. If your piston to wall clearance closes up because the piston overheated and expanded you'll see evidence of it at the top of the cylinder first, which is exactly what your picture shows.
Lastly, the scoring pictured is on the major thrust face of the cylinder wall. Again, if PTW closes, that is where you'll see it first because the piston is pushed hardest into the major thrust surface during the power stroke.
Cylinder 4 runs the leanest because it receives the most air which could be a contributor but I'd be looking into the tune first. Who tuned the car?
The noise you were hearing in your video wasn't the pin knocking against the wall, it was the piston rocking back and forth slapping the wall.
Last edited by Ayoustin; Jun 16, 2021 at 10:49 PM.
That is 110% not an oiling issue. The scoring you see is perpendicular to the wrist pin so it's not from the pin.
What you're seeing is the result of that cylinder running a decent amount hotter than the rest. The piston is cleaner than the rest because detonation cleaned it off, small amounts of detonation will do that and it's evident by the small pock marks in the crown of the piston.
Another sign that tells me it's an overheating issue is the scoring is deeper at the top of the bore and gets less severe as it travels down the bore. Most bores have a small amount of taper from the factory and they're tightest at the top. If your piston to wall clearance closes up because the piston overheated and expanded you'll see evidence of it at the top of the cylinder first, which is exactly what your picture shows.
Lastly, the scoring pictured is on the major thrust face of the cylinder wall. Again, if PTW closes, that is where you'll see it first because the piston is pushed hardest into the major thrust surface during the power stroke.
Cylinder 4 runs the leanest because it receives the most air which could be a contributor but I'd be looking into the tune first. Who tuned the car?
The noise you were hearing in your video wasn't the pin knocking against the wall, it was the piston rocking back and forth slapping the wall.
very interesting. tuner is the one who built the car, but i didnt think that could necessarily be a problem given e85 (my thought, not anyone else's).
also - how do you tune for one cylinder (i.e., in general i look at afr's, but afrs are from all 4 cylinders). do you just make the whole thing a little richer?
could it also have been from - bad gas, failing injector (unlikely, running well for about 8mo, run 93 through every once in a while)
i didnt think that could necessarily be a problem given e85 (my thought, not anyone else's).
This is unfortunately a common misconception with E85. It can absolutely detonate!
What kind of AFR and timing was the car running on track?
I run all track cars on E85 richer than I would on the street to help with cooling. I run my personal Evo 10 at mid 11's on my track map with logged E79-E80.
This is unfortunately a common misconception with E85. It can absolutely detonate!
What kind of AFR and timing was the car running on track?
I run all track cars on E85 richer than I would on the street to help with cooling. I run my personal Evo 10 at mid 11's on my track map with logged E79-E80.
yea again, that was my own thought (ie not the tuner's)
it looks like it was running around low 11's on the track when it happened, not sure on timing.
Ask for pictures of the plug and combustion chamber.
Just because you're on E85 doesn't mean the engine can't get damaged with improper timing.
I'd also get your injectors flow tested. If you look at your piston crowns you can see strong evidence of fuel spray on #4 which isn't apparent on the other pistons. This is usually a sign of a poor spray pattern, which can massively decrease your threshold for detonation.
Ask for pictures of the plug and combustion chamber.
Just because you're on E85 doesn't mean the engine can't get damaged with improper timing.
I'd also get your injectors flow tested. If you look at your piston crowns you can see strong evidence of fuel spray on #4 which isn't apparent on the other pistons. This is usually a sign of a poor spray pattern, which can massively decrease your threshold for detonation.
Jun 16, 2021 | 10:12 AM
