Boost solinoid duty

[m1tch]

Hey everyone, just a quick question about this as its vexxing moi lol

Basically I have a new OEM wastegate actuator on my stock turbo, I know that this can fail as at higher boost the wastegate is powered open from the exhaust flow even when it wants to be closed, I know this, but that isn\'t the issue.

I have set my boost controller (Apexi AVC-R) to 0.8 bar, its mapped to 0.9, but need to check the telemetry from the e-manage on duty cycle on the injectors.

Anyhow, I have set the duty quite high, at around 65-70%, I boosted and it came back saying it went to 90% solinoid duty and only boosted to 0.66 bar, which sucks lol

Then I pulled back the boost solinoid duty to 60, I then boosted and the car was noticeably faster, but on a lower duty cycle

Can anyone explain why this is? the higher solinoid duty holds the wastegate closed for longer, im getting instant spool

Can anyone help?

[Prof]

Depends on how it\'s plumbed in and what the duty waveform does to the solenoid valve - ie, is it opening the valve or closing it.
 
With a lot of these aftermarket controllers, the signal fed to the boost control solenoid is a fairly fast 25Hz signal that \'chatters\' the valve.  Depending on the duty cycle, you are effectively creating a proportinal valve - the higher the duty the more the valve is open.  Because it switches so fast it gives the effect of a controllable valve.
 
What the boost controller should do, is to keep the wastegate shut until some inital stage just before the desired boost (that\'s important, otherwise you just get overshoot which will lead to a boost spike), then begin to open it as it gets to the desired boost point.  As boost pressure increases, the valve allows more boost air to hit the actuator and open the wastegate - bleeding it back off again.
 
With the controller you have, you can adjust the profile of the actuator for different gears - so you can avoid what normally happens which is higher boost in higher gears.
 
There is one thing that may be happening - if the valve can\'t open and close quickly enough - it\'s response at really high or low duty values may be unexpected - either not opening at all or staying open - so effectively it\'s not controlling as it should.
 
Best way to test this would be to use the valve to control a known pressure source of air into a boost gauge, and ramp the duty up in steps to check the relationship of air flowing to duty.