So a local guy here bought a 2005 Evo 8 MR from the US and imported it to Canada. I guess it was running high PSI so he lowered it down to 21psi. Apparently this car doesnt have a tune.

Now i know that its recommended that when you want to up the boost you should tune your car...buuuut my question is, if he did it anyways and its still running rich on his wideband. Is it bad for the car? If so how?

Im curious cause there are people saying how if hes running rich its safe and his ECU will compensate for it, blah blah blah. I've always heard that when you increase PSI w/o a tune, your knock count increases, is that right?

 

theoretically he is safe if he is running 21 psi and his AFRs are below 11.5.

however, i am pretty sure he is still getting a lot of knock due to the aggressive timing evos run.

evo 8 MRs come stock running 21 psi not so? at least the JDM does.

 

my evo peaks at 21ish...sometimes even spikes out to 23-24 on the freeway. im not tuned either. im sure the car knocks but i've been too lazy to go under the airbox to turn down the boost.

 

turning down boost will only help so much.

the timing is too aggressive

 

bump...any more suggestions?

 

suggestions on?

 

well not really suggestions but more explanation/ is he harming his engine

 

yup he is knocking....

 

Hoose.

Your better off running less boost with a tune because the car will still make around the same power but will be more consistent due to less knock....

 

Running increased boost on the stock tune will likely cause degraded engine performance and at higher boost levels there could even be failure. As cylinder pressures increase, the window for proper combustion narrows, and the engine will be more prone to knock. The stock fuel and timing are actually both very conservative, but the ignition map has some nasty transitions that are likely to cause knock. Above about 21psi the stock map has negative ignition timing which will likely eliminate any gains from the increased boost levels.