so i bought a MBC yesterday (greddy giant robot head looking tvvc).

88 10th ann is my car, stock turbine.

wastegate is activated directly by the pressure on the turbine, but it will not boost past 5 psi. none. even if i disconnect the vacume and run no vacume to the wastegate, it still wont boost past 5psi. does this make any sense to anyone?

logic:

no pressure to wastegate diaphram = infinate boost?
wastegate automaticall opens at 5psi. why?

h

 

What ECU are you using? IIRC stock does a fuel cut at 5psi or somesuch?

 

hmm. stock ecu 88 10th ann,
but the issue is that it mechniacall will not boost more. my mechanical boost guage hooked up direct to manifold is the boost guage im watching. fuel cut shouldnt have anything to mechanically do with boost

h

 

blerf.

helps!

 

What modifications do you have to get the boost higher eg intake, exhaust?

 

check the linkage (actuator rod) for your wastegate... it it's not hooked up, you need to rehook it.

Josh

 

I've had similar problems for the last few months, and recently came to this conclusion. The stock actuator has a 5psi spring. As a result, anything higher than 5psi will blow the wastegate door open. If you've ported the wastegate, it sucks even more, because you won't be able to even creep past 5. My solution was actually really simple. I went to a hardware store and bought a spring. I hooked one end around the lever that the actuator rod attaches to and the "other" end to something in the engine bay in front of the turbo.

Here's the cool part. The closer you attach the "other" end to the wastegate door, the lower baseline boost you have. The further you attach the "other" end from the wastegate door, the higher baseline boost you have. I used the small bracket that's attached to the heater return line. Combined with the spring i bought, that gave me 8psi with no boost controller. I then attached a boost controller (hks EVC IV) which is able to at maximum, double the boost that your configuration is capable of without the controller. I've got it set to 12psi and it seems to be working quite well!!

Exhaust config, HKS 3" DP to HKS DUAL 2.5", empty cat.
Intake config, 4" inlet.
FMIC
2 additional injectors
FPR