SlowPokeEg

So I made a post stating how low my compression was in #1 and #2. Thought it was most likely the rings. Keep in mind my Vitara/FJ bottom end has 300miles on it.

So first we decided we'd pull the head to make sure it wasn't the headgasket. Headgasket looked fine, but the turbo had oil getting past the seals. Great. Brand new Precision 5431 with blown seals?! Fantastic. Will be giving them a call Monday.

Then we decided to pull the pistons. Removed the rod caps and popped the pistons through. Piston #1 was CRACKED between the upper and middle piston rings. A chunk of piston actually broke off. How is this even possible with only 300 miles and only making 272whp!?!?!?!?

Pulled the #2 piston, only to find the EXACT same crack, only this one had not yet broke a chunk off yet.

Pistons #3 and 4 looked perfect...except it seemed like #4 was not wiping some moisture off the piston wall.

FML.

Guess I'll see what Precision and FJ have to say and see where I go from there. I'm sure Precision will just tell me to send the turbo in and they'll look at it. FJ will likely say tough luck because I can't prove why/how the piston broke.

HiProfile

Oil burns much hotter and slower than gasoline. This was CP's verdict when all their pistons started melting. I presume there may have been some detonation or even light pre-ignition due to the oil heat. Light pre-ignition in a ~8:1 motor is more likely to crack the ringlands than blow a hole through the piston.

Another thing I've been wondering about is injectors. I've been doing lots of research, and there's 2 big things I've found. 1) there are actually china knock-offs of certain injectors now, and 2) certain injector designs (like GM Multec, same type as Precision) can't open past ~56psi of fuel pressure. That's 14psi of boost.

Speaking about injectors & detonation, did your tuner ever "read" you plugs? It's possible an injector or two is clogged and those cylinders are lean while the others are overly rich. The wideband still reads that as perfect AFR's.

TheShodan

iTrader: (14)

Please verify if you can. For I do know that the "Precision" injector is actually a Delphi in-house injector, that can do over 56psi of fuel pressure without issue.

HiProfile

Multec is a Delphi product.

http://www.youtube.com/user/rbanner1...13/02iMnBRpyQs

One thing to note is that test is more of a base pressure problem. Meaning 63.5psi fuel with 20psi boost is still 43.5psi differential fuel pressure, so they'd still open. Regardless it implies a weak coil.

They did lead many moons ago with their larger injectors being ball seat instead of pintle design. The big change in newer injectors (post-90's) is their ability to take high base pressures (Deka, EV6, etc) while still being a ball design. Ball > Disc > Pintle in every way, shape, and form.