Compression numbers....damn it

[s14unimog]

"well there's your problem..."


http://img.photobucket.com/albums/v721/s14unimog/CompressionResults-03-10-11001.jpg

What's the best procedure for a leak down test? Can't I add oil to the cylinder to verify if the ring seal improve? What's the best way to differentiate ring problems from something head/valve related? Right now the symptoms are heavy oil flow to the catch can and what looks like oil residue on the #1 piston. Sure would be nice to just have to pull the head, but watch it be rings...

Here are the plugs. In the order 4-3-2-1 from left to right.

http://img.photobucket.com/albums/v721/s14unimog/CompressionResults-03-10-11002.jpg

[roboticnissan]

By the looks of the plugs my guess is head over the rings. I have like 60 psi on my miata on cylinder one and my plug is more oily than fat ppls belly rolls

[s14unimog]

^ okay... so how do you relate that to the head?

Edit:
Ya know what, screw it I just need to assemble a leak down tester, pop the valve cover and check the valve guides or if its coming from the case. That would be nice if its just something like that.

[97nismo]

nooooooooooo how did this happen?? I remember riding in this car really quick.

sux man

[s14unimog]

I'm not exactly sure how this happened yet. It still is fast actually, just dumps an obnoxious amount of oil into my catch can. Once I do the leak down I'll know for sure where the problem is. Once I know that I'll decide. Stay SR or do something else. I'm getting tired of the lack in tq.

[s14unimog]

And here is the problem...

http://img.photobucket.com/albums/v721/s14unimog/BreakDown04-22-11016.jpg

I guess almost 500hp is too much for stock pistons.

[camaro379ss]

that puppy is toast!

[boost addict]

glad to see thats the problem, i have the same thing going on right now and im about to pull the motor

[s14unimog]

^^ tell me about... Looks like I've got another ash tray...

^I tell ya though, I would much rather have had some issue with the head, haha.

[codyace]

Yuck! Detonation is a bitch. Imaginary +1 rep for 'that mother fucker' hahaha.

[s14unimog]

I'm not sure yet if it was detonation. The guys at the machine shop seem to suggest the erosion was from the blow-by gases and likely happened after the ring lands failed. It had been running strong for over a year & half now. I'm planning to send the injectors in just too verify there wasn't a problem but I still haven't got the other pistons out, so we'll see how bad they look.

[DinoMan]

Hopefully its just one bad one to replace.

[singlecamslam]

Good time to invest in some better internals.

[usmcgetsome]

how are the cylinder walls? what about the bearings?

[codyace]

Chipped ring lands and 'lunar surface' stuff on the piston are signs of lack of fuel or pinging. Erosion of blowby? Never heard of such crazy talk. I've had friends with POS engines that burn through oil like none other, that have perfectly fine pistons.

Even the slightest bit of detonation at WOT can do that.

[s14unimog]

Hopefully its just one bad one to replace.

yeah it's just this one that is messed up but I doubt I'll rebuild on stock pistons

Good time to invest in some better internals.

I heard that.

how are the cylinder walls? what about the bearings?

Luckily virgin, there is absolutely no scaring. Oddly enough the bearings have some damage to them as well. I've got some patches missing from the number 1 and number number 3 upper rod end bearing. What's disturbing is that they have only been in there for about 10k miles and the motor saw a very gentle 500 mile break-in.

Chipped ring lands and 'lunar surface' stuff on the piston are signs of lack of fuel or pinging. Erosion of blowby? Never heard of such crazy talk. I've had friends with POS engines that burn through oil like none other, that have perfectly fine pistons. Even the slightest bit of detonation at WOT can do that.

And that might be the case. I plan to send off the injectors to double check their condition and inspect the wiring to them as well, I noticed the other night some of the injector wiring had pulled out from under its heat shrink. I'm not suggesting you're wrong on this. I've been messing with motors for about 7 years now and I'm still learning; especially on the high load failures. The only reason I suggested that might be what cased that erosion look is b/c that's what the guys at the machine shop said. What I should have done was completely stop driving it as soon as it happened so that I might see more accurate damage. Unfortunately I have no trailer and needed to get the car over to my work for leak down testing when pops had my compressor.

What likely caused the lean out condition might have been these winter months. My 20G is difficult to control and likes to creep under WOT in 4th. I know I exceeded 20psi a couple times and may have leaned out in the top end. I need to work on my proficiency with the Nistune so I can adjust my map for the seasons.