I just stuck a superchipped ecu and what i have been told is a -31 actuator on my series 2 rst.It is boosting to 22-25 psi and then the engine is shutting down with a couple of bangs (sounds like a shotgun goin off).I have lengthened the actuator rod 3 turns and its still doin it.it even boosts when you lift off the throttle.I just passed a field full of horses and when i got the double bang they freaked and started a stampede.Why so much boost and what can i do to reduce it even more fellas?thanks.

 

Come on guys.someone must know what this is.I cant drive it and its peeing me off.I cant be the first one to experience this.

 

Keep on loosening the rod. You could try bypassing the amal valve, just in case that's faulty. Just whip it up and connect the hose to the actuator direct to the turbo. That should give you a max of about 7psi. Which should allow you to prove if it's the actuator or amal.

 

It's maybe a -34 and giving you far too much boost,just keep lenghtening the rod till itgets to about 16 psi.

 

Cheers fellas.I tried a different amal valve and it was still the same I then closed loop the system.put the hose off the compressor housing straight to the actuator and hey presto i now got a max of 11 psi.The wiring to the amal valve must be knackered.I assume it goes to the ecu?

 

Yep, the amal goes straight back to the ecu, the ecu does PWM to flick the amal valve open and closed about 10 times a second to modulate the boost. Initially the ecu keeps the amal shut so the actuator doesn't see the boost, this lets you overboost. Then the ecu starts doing the PWM to bleed off some of the boost so that the actuator only sees some of it, by altering the amount of PWM done the ecu can limit the amount of boost you get. Finally if the ecu thinks the boost is going OTT then it opens the amal wide and lets the actuator control the boost on its own limiting you to whatever the static spring loading is set at. In your case, with your rod length that's 11psi.

 

What the chuffin hell is that?

 

Pulse Width Modulation.

Think about turning a light switch on and off very quickly, if you could do it quickly enough the light would only dim slightly, if you go a bit slower the light would be dimmer and if you went slower still you'd start to notice that the light was more off than it was on.

Basically it allows the ecu to control how much boost is bled off before the actuator sees it.