So whats happening is once the turbo hits peak tuned, at 20 psi, say 3800rpm. By 4500 it drops to 15 and swings back up to 20, jerking the car. Originally I put in a Grimmspeed ebcs but since have switched to a Hallman. The Hallman holds boost a little better, around 20 psi also, yet drops about 2 psi, and swings back up. The best way to explain it is it feels like im hitting the brakes at peak boost, over and over. It does not boost smoothly to redline.

This is happening in the middle of WOT. Its not a taper, its literally hitting 20 and swing back n forth 2 psi. All while my bov is not going off. I went through and ziptied every vacuum line and replaced what looked worn. Also replaced spark plugs and checked timing. Last thing to check is the wastegate preload. Though even if it was opening it closing, it happens in milliseconds, doesnt make sense.

My UEGO is showing 10 afr under peak boost, so I know its not a fuel issue. Everything thing else about the car runs great. Idles fine, gets into boost fine. When I was adjusting the Hallman, 10 and 15 psi would run cleanly to redline. Its when its even above 15 psi by 1 it starts to cause this issue. Does not feel like misfire and there isnt any weird noises from the bay when its happening.

What do you think it could be?

FYI - This tune is a near stock tune on an E5 motor. Its running SD, 1200cc injectors on 91 octane and ecu boost is set to 20 psi.

 

Explain what near stock tune is? Not to mention you went from ebcs to manual bc without a retune.

 

Near stock means just that. It's tuned on SD with 1200cc injectors. Stock meaning low boost, as before it was tuned on E85 high boost. Also the timing and afr maps are set as if it's a stock Evo9.

Changing boost controllers shouldn't make a difference. For what's its worth, the Hallman is running better than the Grimmspeed. When the ebcs was installed, it would swing up to 5psi. Whereas the Hallman only does about 2.

 

have you logged when this happens?

 

Havent yet but will tonight. Stuck at work...

 

Almost sounds like the car is having an ignition problem and is breaking up .
Try a set of new plugs gapped at about 25

 

True, and I thought that too. When I switched the to the mbc, I replaced the plugs as well. Gapped to .24. A visual of the coilpacks looks good but we plan to test a set of newer coils from a Evo9.

 

Ok so here is the log. I think my tuner hasnt set my Omni 4Bar therefore the boost figures look off. I did test my gauge with wastegate pressure and turned it up from there. Seems pretty accurate thus far. With the Omni not possibly set, these logs almost seem useless..


2nd gear pull


3rd gear