Hi everyone, im currently tuning my car and my tuner opened my eyes on something, check out this boost curve



look at the dip after initial boost. sometimes i can feel it on partial throttle as well (like 8 psi or so). car has stock motor stock turbo stock cams, bolt ons only, and a Grimmspeed EBCS. did a boost leak test, fixed them all, tested the wastegate actuator with a bicycle pump, it "Started" opening at ~14PSI opens fully at like 15 or 16 psi.

any suggestion or ideas?
your help is much appreciated.

 

261 Views and no response, come in guys i need some help.

 

It all depends on the tune. If boost correction is turned on and the car sees a spike, it will do what you are seeing. It all depends on your boost targets and the car. Also, the taper is normal on a stock turbo Evo X.

 

Yeah after 5000 rpm is fine i understand that this is what the stock turbo like, but that dip is concerning me since my tuner is asking me about it, is there somthing mechanically i could check? As far as i can tell the WGDC correction when i log is always 0.

 

Totally normal for stock turbo and stock wga.

 

yeah, watched my boost spike to 28psi on my MR when i mash that gas then dip for a sec due to correction then clime again before the normal taper.....

 

Yeah but the correction are 0 with me, so its not it i guess.

 

what are you AFRs during the dip?

 

Around ~11.4, it does not get richer during the dip if thats what u mean.

 

HMMM have you tested you BOV yet?

 

I didn't exactly test the bov itself, just a normal boost leak test, but i did swap it with hks ssqv4, and the same thing happens.

Also i did notice today when i hold the RPM on 5k on forth gear then go WOT it does the same dip, goes down to 22 then 25 then tapers 21 at 7k. I really don't think this is normal behavior.

 

I can show you 50+ datalogs of 50+ different evos with the same behavior.

 

Please show me one, it will help alot.

 

Here you go




and another:




and another:

 

the first one seem normal, but the one in the middle looks exactly like mine. can you share the log files as well, i also attached mine for information.