Recently I have had my Evo 8 with UTEC professionally tuned at TurboXS. The latest issue that I have had is that when downshifting from say 5th to 4th and getting on it the boost spikes very high ~ 24psi and there is what sounds to be a backfire followed by a sudden decrease in acceleration.

Can anyone provide me with some ideas of what is happening? Is this boost cut?

Mods are as follows:
3"TBE w/high flow CAT
Helix lower and upper piping
MR BOV
K/N Filter panel
255 walbro
650cc FIC injectors
264+ comp cams

Put down ~ 300hp and ~300 tq. on a dynapack at 22psi

 

Its probably some sort of boost cut (or MAF cut) It is something you can set in the UTEC if you have the MAP sensor installed..

 

Thanks Jack. Next quesiton, since the boost cut is put there as a safety feature. How should I go about adjusting the tune so that this instance does not repeat itself? Yes, there is a MAP sensor installed.

How dangerous is this?

 

yes, that is boost cut...i experienced that multiple times when i had an XEDE. I had to get a base flash to get rid of it...not sure if the UTEC has another option.

Oops...i see Jack already mentioned that it can be adjusted using UTEC

 

If you're getting a boost spike to 24 psi on pump gas (91 or 93 oct), I would leave the MAP fuel cut where it is to protect your motor and fix the problem with the boost spike. If it's your MAF fuel cut you may need to increase that to above 2000 Hz to accomodate the increased airflow from your tune.

24 psi is way too high for pump gas. I was having the same problem until I moved my MBC pressure source from the turbo compressor fitting (had that plugged) to a tee off the line to the BOV. Alfred at Tuning Technologies recommended this and it seems to have worked.

 

Drag yourself back there and have them look at it. I have had nothing but good experiences with Jermaine and Nathan. They will take care of you.

 

that power u put down seems really low. when i got my first utec tune i put down 306/308 with tbe, mbc, utec. No cams, just the three mods. something is wrong with ur car/ tune. go back and see whats up with that.