Well, I finially broke my STI motor. ;) ;)

Summary:

I'm trying to diagnose the cause of my EJ207 (JDM STI 02) engine failure. Here is a synopsis. Ran the car at the track, during 2nd session out I mis-shifted from 5 to 4th instead of 6th at redline, engine poped up to about 10kRPM. After pulling into the pits at the end of the run, car seems ok, except for a bit of what sounded like rod knock (knocking sound even at idle, near #1 piston).

Got home, checked compression, 70psi in #1 piston. Pulled engine out of car. Removed heads.. Heads and valves look fine. #1 piston sleve is scared and pulling #1 piston out reveals that the side skirts are heavly scared, almost as if there was no oil. Most scaring is on the larger skirt sides ( 90 degrees from the wrist pin). It looks almost like the piston was either way to tight tolerance, or somehow rocked side to side. The block will certainly need an overbore to fix, and of course new pistons. The question is, what happened. Is this failure related to the overrev? There didn't appear to be any "knock" damage of any kind.. I pulled the block apart, all crank bearings look a good as new.. Rods seemed ok too, although I havn't measured them yet.

Even the rings on the bad piston look ok, minus the scratching. EGTS while on the track never exceeded 1520F, and spark plugs looked great after the session. I was running race fuel as well. The other three pistons/cylinders look shiny and brand new.

Any ideas?

I have heard about this happening to at least two other STi motors (though both were version 6) bot were over revved one during a dyno run and the other at a track day. Same deal it was like the piston has moved from side to side. THe explanation was that the tolerances are real tight in the STi motors (do not know whether this applies to just the STi or all EJ motors) and that if you over rev them they will stick a piston. Like I wrote this is what I have heard but it seems to fit with your criteria.

Jeff. Sorry to hear about the Failure man. But, thanks for posting about it.

I have two theorys.

1. The rod stretched due to the super RPM and no load causing side load on the piston.

2. Forged pistons run lose when cold and run tight when hot. You could have EGT's in that piston might have been very high (Det) causing expansion and a tight fit to the bore.


I was kinda hoping that the EJ207 would be a bullet proof little motor but it looks like its not from your story. All good things come to an end as in the case of my EJ20.. Its making top power and compression is great but its doing a magic trick with a Q of oil for a tank of gas. Pooof its gone...

CT


Originally posted by sponaugle
Well, I finially broke my STI motor. ;) ;)

Summary:

I'm trying to diagnose the cause of my EJ207 (JDM STI 02) engine failure. Here is a synopsis. Ran the car at the track, during 2nd session out I mis-shifted from 5 to 4th instead of 6th at redline, engine poped up to about 10kRPM. After pulling into the pits at the end of the run, car seems ok, except for a bit of what sounded like rod knock (knocking sound even at idle, near #1 piston).

Got home, checked compression, 70psi in #1 piston. Pulled engine out of car. Removed heads.. Heads and valves look fine. #1 piston sleve is scared and pulling #1 piston out reveals that the side skirts are heavly scared, almost as if there was no oil. Most scaring is on the larger skirt sides ( 90 degrees from the wrist pin). It looks almost like the piston was either way to tight tolerance, or somehow rocked side to side. The block will certainly need an overbore to fix, and of course new pistons. The question is, what happened. Is this failure related to the overrev? There didn't appear to be any "knock" damage of any kind.. I pulled the block apart, all crank bearings look a good as new.. Rods seemed ok too, although I havn't measured them yet.

Even the rings on the bad piston look ok, minus the scratching. EGTS while on the track never exceeded 1520F, and spark plugs looked great after the session. I was running race fuel as well. The other three pistons/cylinders look shiny and brand new.

Any ideas?

Oh man that sucks. And just as I was convincing myself to buy a JDm motor. Keep us posted please.

Pete

Oh my....10k??? what did that sound like? Anyway, looks like a good time to stroke it, overbore it, knife edge the crank, HPC coat the combustion chambers, lap the valves, etc.....

Just out of curiosity, does the STI have floating wrist pins, or press in pins in the con rods.

I have heard or wrist pins binding up under high load/rpm it can put enough side load on a piston to break the side skirts 90 deg from the wrist pin.

I'm guessing there wasn't enough oil, or possibly clearence on the wrist pin and it wouldn't let the piston follow the cylinder wall (tried to **** in the bore due to this friction side load)

Take a careful look at that wrist pin, check to see if its bent, and the bushings and piston for signs of gauling in the wrist pin bushing and piston bores.

Also carefully check the con rods for bend and twist. Usually you can see it by putting two conrods on the same wrist pin and seeing if they lay flat on each other. If one is bent the big ends won't match up properly.

If thats the case may want to improve the oiling to the wrist pin next time around.

Larry

Here's some good diagnostic info:

http://www.babcox.com/editorial/ar/ar80125.htm

http://www.hastingsmfg.com/Service%20Tips/piston_cylinder_scuffing.htm

By the way are the stock STI pistons antifricition coated ?

http://www.federal-mogul.com/sealedpower/piston_fitting_sealed_power.html

http://www.federal-mogul.com/sealedpower/piston_trouble_shooting_sealed_power.html

Originally posted by mr2guru
Oh my....10k??? what did that sound like? Anyway, looks like a good time to stroke it, overbore it, knife edge the crank, HPC coat the combustion chambers, lap the valves, etc.....

dude youre crazy

sorry to hear that. its time to build it now i guess

my friend did the same thing in a Type R, and some of the valves were bent..

Man - so sorry to hear !

Did you get those big injectors in ??

BTW - My sti engine has been 100% fine - in daily driving use after dynoing at 500 wheel hp with nos

I remember on "another" site thread after thread after thread about people wanting to rev up to 10,000k. Look kiddies, here's you answer.

It sucks you had to find out this way man. Good luck on your rebuild. My prayers.

-scu

How fast was the car running before it broke?

~v6

what set up are you running, besides the sti motor.

Sorry to hear about the unfortunate incident, I did the same thing to my 200sx twice in one month due to a bent shift linkage. Luckily I only had mior damage to the valves both times.

ah...you misshifted your car

be glad you dont own a celica or a camaro

youd bend a pushrod or make the oil pump explode doing that on any other performance car....im surprised it ran at all afterwards.


the famous misshift BOOM.

ever seen the video of the RSX doing it?

it happens even to good drivers sometimes. that is the downside of a 6 speed. ive heard of vette and ls1 owners doing it rsx owners..basically any 6 speed will do it. its not hte motor...it just wasnt built to go to 10k rpm.

Good luck with the rebuild.
Wish I had an sti engine to play with.

Cheers,
Jim

I'm running the standard EJ20, but have made similar mistakes on track. So far three times have I shifted from third to second at or near red-line. Thankfully the car still runs! I have learned that one good reason for a good harness/race seat is that it keeps your body upright around right-hand turns. With the stock belts I am being pulled towards the door, so the normal "straight back" shift from three to four ends up three to two.

I am really pushing my luck as I continue to track the car, but when I have the money, a harness is going in. Problem is I want a roll bar, and seats to go with them :).