osunick

iTrader: (8)

Hopefully some guru on here can help me figure this out-

My car-
Apex'i Power intake
Buschur catback
stock cat and dp
stock boost control
dynoflash (boost controlling rev)

Based on Al's advice I replaced my boost solenoid as it looked like I wasn't making enough boost (18-15 taper) with the boost controlling flash. With the new solenoid, I know that things are different as now the boost is limited on a cold start to 10 psi and I get 20.5 psi at around 3500 rpm. This tapers to 17 at around 5000 and then down to 16 at redline. I've tightened all my IC piping clamps and the clamps on the factory DV.

I don't think this is a boost leak issue, as I consistently get 20.5 psi at around 3500, but if I'm flooring it from 4500, I'll get 17 psi max and it holds there until it drops again towards redline. If I had a leak, wouldn't it spike to 20.5 then level back to 17?

I should also mention that I reinstalled the FBC after uninstalling an MBC, the lack of a failsafe mode on an MBC scared me off. So there's a chance that I have the lines to the turbo nipple and wastegate actuator wrong, but I don't think so. I have the turbo nipple going straight through the tee to the solenoid. The right angle of the tee goes to the wastegate actuator. That way there's a straight path for boost pressure to go through the solenoid instead of the wastegate. Then of course the lines hook to the forward nipple and the line back to the intake tract is on the rear nipple.

I'm wondering if there's enough inherent backpressure in the vacuum line/boost pill/solenoid assembly that there's no way to avoid taper even if the solenoid is completely open?

Where else should I look?

superz

iTrader: (7)

SO you're saying that with the MBC your car held boost better? If so then its obvious the problem lies with the boost solenoid. YOu can check every clamp and every hose to make sure everything is ok and tight. I would personally go with a MBC. I have yet to hear of any Evo that has blown up with a MBC as the cause. THey run pretty accurately and are far more quiker in response as compared to a EBC or factory solenoids.

osunick

iTrader: (8)

I haven't had an MBC in a while so honestly I don't know if it would hold better in my car's current state. I might throw one back on to see if I'm holding boost.