I got a MINES ECU and installed it on one of my evos. (evo4)
and on the first run at 7500 rpm limit and getting 150 kmh i stopped. Did not over done it.after a while i opened the hood to check the engine and there was oil leakage from the oil cap. only 2 cm around it
my mechanic opened the engine after some research and we found an overheated piston. #4 to be accurate.
I dont mind about the problem that occured but how the hell this happened "so easily" and its a good question for all evo guys.
Here is my engine.
ALL STOCK (K&N racing sunction kit and half of the exhaust is 3" ss with APEXI muffler)
Luckily, no cylinder walls damaged and im installing new evo6 pistons in polished cylinders. IM NOT GOING FOR FORGED INTERNALS.
I havent heard any detonation although i know that happens without hearing it.
Any guys having ideas if anything else happened or im totally unlucky

 

It definitely sounds like a lean condition on that cylinder.. BTW, I think the Oil leakage was due to excessive pressure in the crankcase, not necessarily due to damage though in your case it probably was. Is your fuel system upgraded? I saw in another post someone had made a good point about some engine damage and the possibility that the stock fuel rail may not provide enough fuel to the #4 cylinder even though the overall engine is running at a normal Air Fuel Ratio.. I don't know enough about the Mines ECU to really know how aggressive the timing or fuel curves are, so I can't really give you an opinion on that.

You definitely should go through the whole motor though.. there can be all sorts of little things that can go wrong if you don't at least check/clean/rebuild it..

 

FWIW, its possible that piston damage was done some time ago.. not just on your one run.. it might have finally shown itself on that run.. Unfortunately it happens to all of us eventually..

 

hmmm thats 2 motors down in #4
i think its time to move the regualtor to the center and tap the other side of the rail and make it dual entry.
what you think malibu?

 

I was actually thinking the same thing.. though at the stock levels this really shouldn't be an issue.. Though my modified setup will likely use a larger aftermarket fuel log at the least..

 

Thanks Guys and your answers are very appreciated.
Im not new in cars and drag since i was racing a Lancer GSR 1.8 90' model at 10.8"
This ****ed my day wondering why and im trying to find the reason since:
1. I have an evo 5 which was detonating (could be heard from outside) and drove it couple of days(stupidity), and nothing happened.
2. Another Evo6 from a friend of mine, the same until he modified the car.

Was my problem possible due to electricity from coil? (too much?) but this is standard i think and i didnt feel anything which i think is impossible and i can think of anything that happened.

MalibuJack, i think you are right and projekzero the same. Does it have to do with injectors which are a bit smaller on evo 4? Are we raising a #4 piston weakness? Good questions
The only sure is that got too much heat in cylinder
I didnt expect this from an evo engine to be honest on 14-15psi.

 

What should i do (your opinion) in order to use that ECU safely again?

 

I would say you probably should look into an aftermarket fuel rail, higher volume fuel pump, and slightly larger injectors (stock EVO VII injectors possibly) . My guess is the Mines ECU is running pretty lean with aggressive timing. Given you really can't adjust that, you could drop the boost a little. I wish I could offer more insight, but we only got the evolution in the past year so most of my ideas are based on information I've gathered from helping friends with their Eclipses (had basically the same drivetrain as the earlier Evo's)

 

i will post pictures of the piston as well
Take care

 

the Mines Ecu is in fact very aggressive. for the E7 it is in this order, Mines>Tomei>Ralliart>Stock
is your fuel as good as japan.

 

im using 98 octane superunleaded

 

I live in Puerto Rico, my #4 piston also was damage and know other 3 persons that had the same problem with their motors. I had 785 cc injectors, walbro 255, fuel rail and greedy e-manage at that time. The other cars were also upgraded. None of the four cars had forge piston at the damage time. It happened with the stock pistons.