Any ideas on why my car won't hold boost at high RPM's? I have a Dynoflash mod to kill the OEM boost taper, but that shouldn't matter bc I have an HKS EVC V so all of the factory boost control devices are bypassed.

I checked for vacuum leaks and I can't find any. It's weird though, the boost trails off pretty consistently no matter what gear I'm in. It'll make 21+ pounds without a problem from 4,500 - 5,500 but won't go over 19 pounds at 6,500+

I also have a stainless tubular manifold, stock turbo, 3" stainless exhaust (DP, HF Cat, Cat Back) and an HKS SSQV. Is it possible that the SSQV is bleeding off boost? Or is the stock wastegate just a piece of ****?

Any help would be greatly appreciated.

 

Solution: Hallman MBC...$90...

 

play with the offset function i have mine stable at 22psi till about 6500 rpm and then it tapers to 21psi.

had the same problem, till i adjusted the offest function. i would spike to 22 and drop to 19

 

I tried that, but when I called HKS they said to set it to 100. Where is yours set at, I tried everything from 30 to 170.

Sorry to bombard you with questions, but I would also like to know where you hooked up the small line on the EVC? Mine is tapped off of the line that goes to the BOV, but I also see one going to the fuel pressure regulator, is that a better choice?

Thanks for the help. Much appreciated.

 

DId you use new lines from teh turbo and wastegate to teh steeping motor or are u using the stock vaccum lines?

 

FPR is better place. I also have the EVC V and i get the boost taper, about 2 psi. I mean if you want to hold 21 stable, then just set it higher, to 23. That way it drops to 21. The reason is the stock internal wastegate.

 

I used the new lines that came with the EVC.


The stock wastegate is what I was afraid of, though some poeple seem to only have about 1 pound of taper, so I thought maybe I had a problem.

I cannot set it to 23 without getting excessive knocking and I imagine a bit of a lean situation as well. Right now I have it set to 21 and it tapers off to 19 when I set the offset to anything over 110, but for some reason there is no difference on any settings between 130 and 200, other than I have to increase the boost percentage to compensate for the offset. But I get about 2 ponds of taper no matter what ... guess I just need a new turbo / wastegate if I want stable boost. *shrugs*

 

Anyone know of any wastegate upgrades for a stock turbo?

 

you probably have a boost leak. I think Al uses that bc with no problems and I run the Blitz unit and it holds boost very nicely. Check your lines again, you shouldn't have to be shelling out for a wastegate.

 

The lines that came with the EVC are too wide. Try using smaller vaccum lines (4mm)

 

I second that^. I had to buy separate hoses with smaller diameter

 

Thanks for the tip, if you don't mind another question, are you tied into the BOV line for monitoring or the FPR line?

Well they seemed to fit rather snug, but I'll buy new silicon lines anyway, I really want to get this nailed down, and if I can keep the stock turbo, that would be great. Thanks for the help!

 

Stock turbo runs an internal wastgate. There is no way to replace or upgrade easily.

Most (if not all) aftermarket turbos run an external wastegate which can be swapped per application.


As for the EVC loosing boost, that is the stock wastegate. A dynoflash eliminates the stock soloniod from bleeding boost, but does not affect the EVC.

I run 22psi and finish a WOT pull at 19.9-20.1psi on the dyno.

 

mine does to. i try to set it at 21 but always spikes higher to about 23 and gradually works it way down to around 1.45 bars (21 psi).

 

Had the same problem. and after the offset mode was set, it holds steady and boost comes on stronger.