Installed Dual Stage Boost, But It Creeps, Why?

[Turbz RB-25]

Fellas,

I had installed yesterday a dual stage boost controller. One side of the switch is off (So theoretically, should be running what ever the wastegate spring is set to - which is roughly 12PSI), and the on side of the switch my car runs 25PSI.

Now, when the boost switch is on, car runs a smooth 25 PSI the whole was, no drama what so ever.

However, when the switch is off, the boost controller starts making this funny rattling sound. Also, as I accelarate (while the switch is off), the boost spikes to 15PSI, goes down to about 11PSI, stays there until about 4,500 rpm, and then slowly creeps up to like 23 PSI.

Does anyone know why this may be?

I have an external wastegate tial 38mm. I've checked all the hoses, there are no leaks.

I remember before I had my Autronic SM4 unit (when I had the PFC), the car would run fine at 12PSI without a boost controller, not sure what's happening.

any help would be greatly appreciated.

CHeers

[NSNPWR]

In all likeliness that 38mm gate is too small to pass all the exhaust gas of your 35/40....what exhaust manifold are you using? Where is the gate merged?

[Turbz RB-25]

It worked fine with the PFC, I don't see why it wouldn't with the SM4? The exhaust manifold is a GCG CTR highmount one, and the gate is plumbed back about 30cm after the dump connects to the turbo.

[Harey]

Thats strange that it worked fine with the PFC. It does sound like the wastegate cant flow enough to keep the boost down. Have you changed anything else since the move from PFC to SM4?

[R31Nismoid]

In all likeliness that 38mm gate is too small to pass all the exhaust gas of your 35/40....what exhaust manifold are you using? Where is the gate merged?

Well given he didn't have an issue with 12psi off the gate before...

I remember before I had my Autronic SM4 unit (when I had the PFC), the car would run fine at 12PSI without a boost controller

In all likeliness it has nothing to do with the gate.

People here have run 38mm gates with GT35's before without a problem. This instance shouldn't be any different.

What it does have to do with is the installation/type of "dual" stage controller being used as a good (and obvious) starting point.

So to just make sure I've read it right you've changed the following only:

1 - ECU

2 - Boost Controller installation

3 - Previously running off the gate the setup was completely fine

Thats correct yes?

If so i have some more questions.

1. How long as the VAC lines and so on?

2. What brand is the boost controller setup?

3. The "rattling" sound, do you also hear this when the boost controller is "ON"?

"rattling" that some people describe is when they can hear the solenoid actually working... so perhaps its not going totally "OFF".

Few AVC-R solenoids over the years i've been able to hear "rattling" when mounted close to the firewall/passenger side. Nothing wrong with them and working fine

4. Have you removed the entire boost controller setup just for testings sake?

5. Is it 2nd hand? It could be fault product even... same thing applies if it's new as well of course