Long story...I was leaving a light. I was WOT at about 6000rpm and the car fell on its face and i looked at my afr gauge and it was at 17:1. I babied it home and got my computer, went out and did a light pull to about 6-6500rpm to get a datalog (ran fine out of boost). Looked over the datalog and found the engine knocked 33 times on cylinder 2. I ended up doing a compression test and found all cylinders at 240psi. Found i was having trouble getting the car started, i would have to cycle the key over and over to get it to start. I got a fuel pressure tester and found when keying on it would go to ~42psi then drop to zero a second after the pump primed. Didnt see any fuel leaks so i pulled the fuel pump and found the rubber hose between the pump and hanger split open. I replaced the hose and went out to get another datalog. Car ran alot better than before but was still getting knock on cylinder 2 and i could feel the car hesitating to accel only under boost. I replaced plugs and still knocked on cyl 2. I tried swapping coils, and injectors and still knocked on cyl 2. Did a compression test and found all cyl at 240psi. Did a leakdown test with the engine hot and found cyl 1 at 34%, cyl 2 at 35%, cyl 3 at 32% and cyl 4 at 37%. I could hear air coming from the oil fill from all 4 cylinders. I used a boreascope and looked at the tops of the pistons. On cylinder 4 i thought i saw what i thought, was a melted piston. I sent some datalogs over to LJ at fullblown (tuned the car) and he said he didnt see anything wrong from the datalogs. I pulled the head and did a visual insp. All valves spring a sitting at the same height. All valve sealing surfaces look clean/no pitting. Very little wiggle from valve guides. Cylinder walls dont have any scoring. No signs of headgasket issues. Piston tops look good, no pitting. Sent pictures over to LJ, he said the burn marks on the pistons look good. No signs of cylinder, retainer cracking. Im planning on taking the head to get inspected by a machinist.

I was going to replace piston rings but I have been doing research on ring replacement and alot of people say special machines and shop that know how to work on these engines is required. Im in omaha, NE and there arent any locate shops that work on these cars.

So my questions are:
Has anybody else experienced this problem?
Any other ideas of what could be wrong?
Is replacing rings and rod bearings without honing the cylinders a bad idea?


Car and mods
2006 S2k with 39k miles
Boosted to 8k miles
Stock engine, arp head studs, oem gaskets
ILP stage 2 turbo kit with pte6262bb turbo
ID1000 injectors
Aeromotive 340 pump
Tuned on e85 with flashpro
Aem electronic boost controller
Aem wideband
Stock fuel lines, fpr and fuel rail
410whp on 9.5psi
Tuned by LJ at FBM

 

 

I recently did the same. cracked an oem wrist pin changed out bearings wrist pins and in rings. My cylinder still looked good. so installed everything back without honing and everything is fine. no smoke and compression is about 240 in each cylinder. Had crank micro polished also.

 

are those leak downs bad?

pressure sounds good.

Running it with bad pressure might have just screwed the pump up (maybe burned it out or something) I think the flow keeps fuel pump motor cool. I dont know if I would of torn it apart quite yet at that point. But because of the extreme knock you had; it might have altered the ignition or fuel maps and so after you fixed leak it was thrown off. From what I have been told you want to tune the map for no knock so the ecu doesnt dumb it down or go into complete save my life mode cause if it does start knocking the Knock software will start changing your tuned map.

Also read running more then a 255 in a returnless fuel system is a no-go?

Looking at the NEW POWER CHART --Im not to savvy with fuels and power figures but 410 @ 9.5lbs sounds like the advantage of using E85 and more timing was deffly exploited. Im just saying more boost and less timing might have been another route even if using E; another note Increasing timing no matter what fuel will also increase maximum cylinder pressures finding a sweet spot for what the max is with these setups is probably very intuitive and should be researched, also knock or not. just turns it from TNT 2 Atomic.
I am in no way a tuner or guru, Heck I'm having my own problems, I know they all have there trade offs tho.
It takes 30% more fuel on E to make the same power on pump gas but with the higher knock resistance of E you get head room up top for more timing and also able to make power outside of pumps (safe limits)
ex. a car on the chart on 91 Oct. roughly same power figure added more lbs with still head room (safe limits) on pump but probably lost more timing then you but still made 10hp more. End of rant and last point You probably have a very solid tune but running lean because of another issue is still running lean count it up to bad luck karma what ever and try again. Pay attention to detail and inspect things very good that could make your car go boom!