Ok guys so i got a Aem with everything for it and i got the car on the dyno to get a base line on the car. Well the base line was ok i guess after spending so much money in parts but i never got the car tuned since i put the catback and dropin filter so i put on a crap load of mods since. So we put in the AEM in the car we had many problems trying to get it to work right map sen. wasnt working so i got a new one fixed then the software wasnt loading right after a few calls to AEM fixed. So after everything was in and running ok we started to do the dyno pulls. My sponser shop got over 40 pounds of tq more out the car he set the time 10 deg. under the stock trim. When he started to add timeing the car was losing power and he was like wtf so they ran a compression test on the car and what you know piston #4 was at 50 psi and the other 3 where at 150 psi where they should be at so we stop the tuning there. I drove the car around for 3 days one night i couldnt go pass 20mph and i knew right off the bat my piston was gone and sure enough it was. Now you as what causes low compression your rings after a while they start to go out or in my case i was running so many mods not tuned right this what caused this problem. So i got the money to fix the motor new pistons and rods. But once we pulled the motor apart the piston was chiped and the metal piece was bounceing from the head to the piston so i had to get a new head cause i didnt want to get mine re done well not yet so i got a used head from a local shop and send it out to get cleaned up and reworked so i can just drop it in with the new setup. Now once i asked why this happen and the shop told me this is a common problem that happends to evo because of the way the piston is made by mitsu if the car was stock this would never had happen but once you start to mod the car and not have it tuned right this happens a hole or chip in the piston so for the many out there you have a check engine light on find out what it is and get it fixed or retuned for that part that turned it on and this wont happen to you. Here is some of the pics of whats going on.



its kinda hard to read but the numbers are
322whp
258tq this is with stock ecu no tune what so ever on pump gas

 

here a better dyno copy

 

I've driven around for over a month with a full Buschur Stg. 4 setup on my car on a stock ECU untuned... waiting for Al to fly local to me. Didn't damage anything... but sorry to hear 'bout your bad luck. =[

 

Another example of why tuning is so important. Good luck.

 

stock ECU is very conservative. It shouldn't be like that unless you surpass the limit of your injectors or fuel pumps. and it is odd that 4th cylinder was detonated. faulty injector on 4th may be?

 

That looks like somthing was bouncing around in there, I do not think that has anything to do with a tune.Did you change the plugs before the tune ??

 

The problem you are seeing is caused by either poor tuning or a failure of one the fuel system components. To me looks like you detonated and the cylinder pressure spiked too high and something had to give. People often mod these cars never looking at the most crucial engine parameters: timing, fuel pressure, duty cycle and air/fuel ratio. I wouldnt be surpised guys running only minor mods are already at 90% duty cycle on their injectors. 80% is the maximum safe reliable duty cycle for injectors.

 

Out of curiousity, why would you drive the car if one chamber was showing 50psi?

 

Oh yeah lets not forget knock level. Thats going to have an effect on timing and fuel trims also.

 

I've never heard of this being a common problem on the Evo. Maybe among people who run around with untuned vehicles, but not people who get a good tune.

 

Well once the engine is that screwed, whats the difference if you drive it anymore. One of my friends has a dsm with 100 psi in 3 cylinders and still drives it with 155,000 miles

 

Looks like a piece of the piston top broke off and was bouncing around

 

You were detonating! Simple as that. Thats what caused a piece of your piston to break off and thats what caused you to lose compression and probably burn oil.

 

Ok guys most of you are talking about the injecotrs going bad thats not the case i put in 850's before i go the aem in. Another thing is i been driveing the car around with 50 psi on the 4th piston for over 8 months and for the first reply ive been stage for the past 9 months the check engine light has been on since jan of 05. And that peice of piston that broke of was because of the rings where going out i didnt take close up pics of the rings but at certin points of the rings they where worn down. The person that told me this was a common problem was someone that use to work at AMS he has seen this happen to over 60 evos and also when i called a few shops they all said the same thing its a common problem with modded evos its just due to the fact that the piston rings are so close to the top of the piston so they are most likely to give at any point if the car where to stay stock this would not have happend. Point being the car was running in safe mode with stock ecu which explanes the reason why i would run other evos that where lightly moded and i would have a hard time keeping up i always thought it was the tune but i was worng it was the piston the whole time. The injectors that i put in the car are new so there is no way the are faulty if they where bad the data logger in the AEM would have showen that injector was bad or not running right. The reason i drove the car with a half *** tune was becasue this is the only car i have an i need it to work im on the road all day long so i need a car i cant be down for a long time this right now with this new build and soild tune im dieing to get my car back i hate being a taxi useing somones elses car.

 

^^you Were Detonating! Any Questions?