RST_mark

I'm going to order a new -31 actuator tomorrow as i've noticed a boost drop recently on my S2 turbo with stage 2 t3.

The car currently has an adjustable bleed valve fitted in the pipe from the turbo compressor housing to the actuator, can i just remove this and fit a new pipe then adjust the boost on the actuator rod? Is it better to adjust the boost at the actuator this way?

Also am i correct in thinking that i need to shorten the actuator rod to raise the boost and lengthen it to decrease the boost?

Many thanks

Rick

Hi mate.

It's debatable what's better. By adjusting it on the actuator only, and having no bleed valve, you get a flatter boost response. Ie, it won't spike or drop as much as if u have a bleed valve. It's better like this in terms of power, as the ignition doesn't have to be retarded for the spike. But, the bleed valve makes adjusting it much much easier.
You can have best of both worlds by taking the boost feed to the actuator from the inlet or crossover - this tends to eliminate any spike or drop.

Shorten to increase boost. Remeber, the longets u can have the rod is half a hole preload. And don't shorten it massively, as u'll get boost creep.

RST_mark

Hi mate, that advice is great thanks. Just one question, what do you mean by boost creep?

Rick

Ok, when u shorten the actuator rod, it means the wastegate opens later, and obviously - it can't open as much as the rod is shorter and it runs out of travel.

What can then happen, is that as the revs rise, the wastegate opens, but not enough to let exhaust gas go through to keep the boost at it's set level. The left over gas is forced through the turbo instead, spining it up more, and the boost rises with rpm.

It's a slow process, so u only notice it in 4th and 5th, as the other gears are over too quickly.

RST_mark

Ok mate, many thanks for your advice. Just another one for you, i've fitted the new actuator now and still don't seem to be having much luck, i've road tested it, then shortened the rod and repeated this a few times now, the boost is increasing each time i shorten the rod but is now at about 12psi and there is only a few threads left to adjust, shall i adjust it further and see if it will reach 14psi like it was previously running?

And just to check it is a -31 actuator i need for 14psi isn't it?

Thanks, Mark

reality

What chip is the car running?

RST_mark

Hi the car is running a superchip i think, from when it was set up.

When i fitted the new actuator i got rid of the bleed valve that was previously fitted in the pipe between the compressor housing and actuator, and tried to adjust the boost at the actuator but ran out of adjustment to get the desired 14psi of boost, could only reach 12psi with a couple of threads left.

Starting to get a bit concerned so tonight i thought i'd refit the bleed valve, took the car out with the valve wound all the way in and was still 12psi as thought, stopped and wound it out a turn and it's now boosting at 15psi, dropping back to about 12psi. So i'm very pleased.

I'm thinking of slackening off the actuator as there is a lot of tension on the wastgate at the moment and adjusting the bleed valve a little more, would this be the best idea?

Also thinking of taking the feed to the actuator from the inlet plenum to see if i can achieve less boost drop, would this work?

Many thanks to rick and others for your advice.

Rick

Hey Mark - what u done is spot on

The -31 gives around 14 psi when used with the std amal valve. Without a bleed valve, you will have to shorten it quite a lot. Putting a bleed valve in as you have is fine, and pretty much needed if you aren't using the amal. I would keep the tension on the wastegate - it gives better response - just double check that you're not getting creep as i mentioned before.

Take the feed to the actuator closer to the throttle body will help with boost drop, especially if you are using a twin pass intercooler. You may not eliminate it totally - u'd need a stiffer actuator like a -34.

Boost spikes can be quite useful - they just don't work too well on std management due to the ignition system.

RST_mark

Thanks Rick, learning a lot here

Just gonna run past you what i'm gonna do now, to check that it is right and will work.

I'm gonna take the feed to the actuator from the inlet plenum which is after the throttle body, run this to the actuator with the bleed valve in this pipe. Then because i am running mfi and i will have an air leak from the bleed valve when open, run a pipe from the bleed off outlet to the metering head (where the amal valve is/use to be connected into it).

Is the the correct way to plumb it in?

My car still has the amal valve bolted to the gearbox and the pipe which goes to the metering head and wire's connected but has always been just left like this not connected up and using a bleed valve instead, didn't realise these could still be used on modified engines running more boost.

Cheers, Mark

Rick

Bang on mate

My amal valve is exactly as u have described, has just been sat there chilling for the past 7 years....

You can run amal's with more boost no problem. There are a million ways of acheiving the same result.

In the future, once u have an idea of how it all works, u can try replacing the bleed valve with amal - then wire the amal to a switch inside the car, and have a high/low boost switch

RST_mark

Rick your an absolute star!

RST_mark

Hey, hoping Rick might be around to answer another question

Just connected everything back up with the feed from the actuator taken from the inlet manifold and using the bleed valve, leaving the bleed valve done up tight at the moment so it's not bleeding any air and gonna take it out in a moment to set the boost.

The bleed valve is connected back into the metering head as the amal would normally be. I noticed while the engine is idling when i open the bleed valve the rpm rises as i thought it might do, once i've set the boost as i want it can i just adjust the rpm to it's normal level and all will be ok. Or will having it plumbed in this way affect the mixture while driving the car and have any more implications?

Cheers mate, just wanna check.

Rick

Just set the idle as required. It won't affect the mixture, as the air is being metered