Well been tuning the hotside for awhile now but the one thing I cannot seem to get rid of is a 23PSI boost spike right when I get into the throttle in any gear at any RPM below 4500.

It spikes to 23PSI then slowly falls to 20PSI to redline. Prior to the hotside upgrade I had almost rock solid 20 PSI till 6500 where it would start to fall a tad.

I know on my DSM this spike was caused by the restrictive O2 housing.....but looking at the EVO's I wouldn't call it even close to being a bottleneck.

I have an XEDE computer and have tied dropping the boost onset but even that doesn't seem to help unless I set it to 75% duty cycle until nearly 5k.

Any suggestions?

 

Is it nessasary to tune after installing the 10.5

 

Well....for some UNKNOWN reason....the O5's ran a more aggressive timing curve as well as a leaner AFR. In addition to those changes from the factory Vishnu has found that the 05s can get away with an even leaner tuned fuel curve.

It should run just fine with the 03/04 tune but your boost is gonna be off becaues mine was hella higher with the 10.5 hotside.

 

if you free up anything after the turbo, you will get the boost up. when I just installed catback, it spiked alot.

 

Do you still have the spike or have you found away to avoid it?