I posted this on preludeonline, thought I'd post this here also to get some more input...

I finally got around to tearing my motor down this afternoon. For those that don't know I've got an '01 Prelude SH with an fmax setup, minus the mf2, with 720's controlled by and AEM computer, and a built bottom end. Well to make a long story short I lost compression in #4 while on the dyno and suspected that it was due to excessive piston slap after pulling the head and seeing the scarring on my previously pristine GE sleeves. I waited a while to finish tearing it down both due to being pretty pissed and the fact that I'm still recovering financially from a period of unemployment last year (f*&$ing Lucent ) Just wanted to get your opinions, here are the pics:





The block was bored with only one piston (#1...go figure. )...not my choice, I didn't know until I got home and found 3 pistons still in their original packaging from JE. They must have done a hell of a job balancing too with the plastic still on everything...but I digress, I was pissed enough at how long they took I was in no mood to take the stuff back. Surprisingly enough the bearings look pretty good despite the amount of "glitter" in the pan...doesn't look like any damage was done aside from the obvious. Now that I have confirmation I'll be overboring (haven't decided between 88 or 89mm) and replacing the JE's with Wiseco's. Hopefully with the new pistons, some new bearings and some other odds and ends I'll be back in business soon.

--Ian

 

The motor ran lean...its called black death. Need to get a tuner. GLTY

 

you're Piston to Wall clearance was too tight.

 

Wow!

 

Uhh...it was on a wideband...actually 2 of them, the dyno's and my techedge setup. Never went leaner than 12.7:1

--Ian

 

Definately Piston to Wall clearance, things heated up, and your pistons started rubbing, i'd go to your machine shop and have a little talk. general piston to wall clearances on high silicone pistons are .035 -.45 somewhere in there.

 

dang......

 

On a better note, you are breaking in your engines properly.

 

Yeah, that was the general consensus for those that I've spoken with. The motor was broken in with no boost, stock injectors, and a stock ecu. There has been a wideband on it since the EMS went in and save for a brief period of being pig rich when the 720's were installed it was at 12-12.5 under boost at all times. I have a feeling that #1 was smaller than the others explaining the fact that it has no wear. Nos. 2 &3 have some scarring but #4 by far is the worst. BTW the rings are welded into place...

--Ian

 

Seized... That sucks man, your machine shop did you in on that one. i'd go to someone else for your problems.

it's quite possible they only bored one cylinder! You may want to get a nice set of calipers and measure an unscored part of all of your cylinder to check the clearances.

(probably at the very bottom is your best bet)

 

Heh...yeah won't be going back there. They have been having alot of issues as of late, it's a local machine shop that used to have a pretty good reputation. AFAIK they've fallen into the same old "we've gotten too big for our britches" mentality.

Nah, they were unbored GE sleeves when the block went to the shop so all of them were bored. I'm ahead on the checking, I've got a call into a buddy to borrow his calipers to investigate. Let this be a lesson to all...doublecheck everything even if a "reputable" machine shop did the work. Believe you me, I won't be that naive again.

--Ian

 

i trust my machinist. He gave me a (personal) garuntee. if they mess up, they'll pay to fix it.

they do DAMN good work here. being the owners friend does have it's benefits

 

Definitely black death...new pistons, rings bore and hone time. Make sure the shop knows the proper piston to wall to bore with. This problem could very well have be caused by improper tuning rather than improper piston to wall.
BTW, JE pistons come balanced from the factory within a gram or two which is close enough. They should all be the exact same diameter and probably were but your shop should have at least checked them. When you balance the straight 4 cyl, you only need to do the crank. That's what most shops do.
IMO, if you rebuild with the same tune-up, the same thing will happen again.
You may want to consider skirt coating on the pistons.

 

Hmm...yeah, I just find it hard to believe that it was running lean when it was on a wideband for most of its short life with nary a lean reading and the tuner that I was working with is pretty good, I've seen him make plenty of power before without these disastrous results.

That's the only reason I didn't take everything back after finding three pistons untouched...I figured that they were balanced from JE and that should be sufficient. The thing that pissed me off was that they didn't check them...live and learn I guess.

--Ian

 

Looks like the motor got hot which probably was a lean situation. Running a 12.7-1 is pretty lean on a turbo car. I think he should have had it more around 12-1 12.2-1 . Id tell him to shoot for those numbers next time because something went pretty wrong. Also you might want to get those injectors flowed to make sure they really are 720cc.

Did you ever check the water level? maybe it ran dry as well? I know plenty of machine shops that only use one piston to bore if the piston is of a JE quality. They are into good enough spec to not have your motor look like that. Its either your tuner or a fuel issue which is kinda the tuners issue as well.


[Modified by ninesecrx, 6:45 AM 11/17/2002]

 

i doubt he overheated it. and at low boost 12.7 is'nt too lean on forged pistons.

 

They were new RC's...I've got the spec sheet on them. We were aiming for 12-12.5...the 12.7 was an outlier in the logs. Regardless I'll be adding fuel when the motor goes back in if not just for a little peace of mind from all this.

--Ian

 

Funny you should mention that...it had sufficient coolant at that time (one of the things I checked while diagnosing post mortem) but I did have a headgasket issue prior to installing the ARP headstuds/cometic gasket. Not long after the breakin was completed I lifted the head under boost...heated up a bit (read 3/4 on the temp...not _too_ high) but cooled as soon as I got out of it. The car wasn't run after that until the studs/gasket went in...this was maybe 500miles prior to this last run on the dyno. This session had been to do any final fuel/ignition tweaks and then up the boost. It was running 15psi when it failed. You think that when I blew the gasket it may have triggered this?? It was blown between 3&4 and from both 2&3 into the cooling jacket. Could it have made enough heat to do that much damage on one pull despite the relatively small change in the reading on the guage?

--Ian

 

i've seen that before also. too much timing in boost can cause that also.

 

We had a problem with a local machine shop not installing the sleeves correctly and this happened. It seems that it was easier to just bore the block bigger so the sleeve would go in easier rather than having to press it in. This resulted in the sleeves distorting and grabbing the piston just like this. Since you have golden eagle sleeves I don't think this is the problem. If your a/f ratio was good (12.7 a little lean) then it was probably the result of too much timing. How much timing were you running under boost?

 

Hey Lazerus...ever see what happens to a motor when it overheats? Im guessing not since you seem to have 10 posts on this board with no useful info to him. I think you need to read up a little on things.

Black death can also happen little by little over time as well. It might not have been an isolated incedent. Since your rc's are brand new and they are 720's the fuel should be fine in the car since you only had 15 pounds of boost in it. What happened has a dircet coralation with overheating. Like Tony said as well, pull out a little timming in it. Do you know what you guys set it at? I think you should bring the af down like I said before. Theres no reason to have it that high...you can make the power on raising the boost, not leaning the car out.

 

And it is this exact reason that I will be checking my pistons and cylinders personally! That seriously sucks! Good luck with fixing the problem, let us know what you find out.

 

22 degrees at 15psi.

--Ian

 

Another thing to look at:
Even though you are running off a wide band, the adjustments that it makes do not happen as fast as the tune-up needs to change. This can give you momentary periods of the wrong settings. Most race cars run open loop and set the air fuel on the dyno to where they want it rather than trusting it to the constantly changing readings of an O2 sensor.

 

Err...it was open loop. The wbo2 was for monitoring only, not for any on the fly adjustments.

--Ian