Hi,I have an evo 5 and after one week I melted two pistons,and after the engine was opened up, it was found it had recently been rebored and fitted with 0.5mm oversized pistons,which tells me it had happened to the previous owner(without letting me know).Now the problem I have is I don't know what caused this in the first place, and I don't want it happening again.
If I drive the car without going over say 4500 rpm it will be fine but if I go beyond that I will need a rebore and a set of pistons.
Can anybody help me with this or give me a few pointers as to what it could be.
My local Mitsubishi dealer can't help me as they say evos never break down so they have never came across this problem(?).
I have been running it on 97ron fuel.
Your help would be very much appreciated.
Thanks in advance Stevie

 

what other kind of electronics are on the car and what all is done to it..... start there and then we can see what the problem is

 

The car is standard except for a blitz ss exhaust

 

Only the Blitz Exhaust?? Then how about the turbo and the compression rating? Were these in anyway modified? In any case, i believe that the pistons were sub standard quality ones. Try using forged pistons if you have not already done so. They can take more pressure. You mentioned you need to get a rebored set of pistons as well if going over 4500. What i would suggest is that you get yourself a set of forged ones and if the problem persists then you can contact some experts. I'll try to get you some contacts. Meanwhile you can check out this site for options for evo parts.

Cheers and hang in there!

www.SpeedXS.com - Center for Japanese Performance Cars

 

I don't know if the turbo was modified.The person I bought the car from told me it was standard apart from the exhaust and claimed he knew nothing about it melting pistons even though it had recently been bored out and fitted with the oversized pistons.So I have to assume he is lieing and it had happened to him,so he fixed it and sold it straight away or he never drove the car hard i.e over 4500rpm which I don't believe.The pistons where bought from Mitsubishi and as I mentioned it has happened twice,so what's the chances of both sets of pistons being sub-standard.

 

Burned pistons = lack of fuel.


I would check the base fuel pressure, if it is low you could have a fuel pump problem or the regulator itself. Even if your base fuel pressure is all right, if the fuel pump is old and tired it may not be able to keep up with fuel demand at high RPM / high load conditions. You should change out the fuel filter, and you may as well have the injectors flow bench tested to make sure they are not clogged.

Good luck,

Keith

 

I should have mentioned earlier,it only burns out one piston

 

Definitely check your injectors. Particularly the one on the bad cylinder. And also check your timing advance. Lots of advance will destroy pistons in short order. Try datalogging your car and see what sort of advance you are getting. If the base timing is adjustable, then check that. I doubt that it is, though.

 

Well everything seems to be pointing to either the injectors or timing so thanks for your help guys,and I will keep checking back to see if anybody can think of something new.
Thanks Stevie.