Hi I cannot get my head round this am messing with my boost on my s2 on cosworth management. I want to take off my bleed valve to stop it spiking so when that's off I can not get anymore than 15psi so got a stronger spring for my actuator 18psi rated put it in and still only 15psi. So I bought a new actuator one good for holding 22-24psi put it on last night and still only 15 psi when I have bleed valve I can bleed it to 21 but it spikes to 26 and kicking boost limiter in anyone have any ideas why I cannot get it over 15 with no bleed valve

 

You know the amount of pre tension on the actuator influences your boost? Is the "arm" screwed all the way in?

 

I have done it half a turn at a time till it just boost flat out guessing that's the spring bottomed out

 

That is not how it's designed to work, you need some form of boost control in addition to the actuator, either a decent manual controller like this http://shop.motorsport-developments....alve-294-p.asp or an electronic controller.

 

I have run a bleed valve but it give me a 5-6 psi spike that I don't want to have

 

Can you not use a AMAL valve if your on cossie management, with it jetted to suit your requirements?

 

Not all bleed valves are equal mate, what do you have?
Also what turbo do you have, what intercooler, manifolds etc?
This is also a good idea if your management is setup correctly for it.

 

What is your experience on manual boostcontrollers? A mate got one cheap on eBay, but with a benchtest i wasn't a hudge fan of that one...

 

To be honest mate, and with all due respect, you are potentially going to kill the turbo if you keep haphazardly guessing at it like this.

The first thing to do is get the whole inlet pressure tested to 30 psi as this fault sounds like an air leak developing at about 15psi. The most common cause is the dump valve, especially if it's a Bailey one, we take those of all the time for leaking at about 12psi.

With an air leak, the turbo will spin faster to overcome it, but it is trying to pressurise the whole universe so it will die trying.

Bleed valves are fine fitted properly and allied to an actuator that has the balls to maintain the bulk of the pressure. IE: bleeding a 5psi spring up to 30psi is pointless. Your fighting turbine inlet pressure too so you need a spring ,an enough to offset that first. For manual bleed vales I recommend the turbo smart one we sell, I've fitted them to tens of cars and they work very well. Even a normal brass 3 port valve will work fine if it's set up right.

As an aside. To quickly see what the turbo itself is capable of, just pull the pipe off the actuator and block it then take the car for a gentle full throttle run in 3rd. It will now run whatever it can do until turbine inlet pressure overcomes the spring as it has no pressure assistance above the diaphragm. Sometimes the wastegate has problems or a big air leak is hindering you. This will quickly help to prove this is the case.

 

Mate am not new at all this am not just turning things up not knowing what am doing I have just spent over Ł4000 on engine work and parts so it's got everything that it will ever need to make the boost there are no boost leaks I have pressure tested to 30 psi. I have got rid of the bleed valve and now running my old amel valve but still getting 5 psi spike so I will just get an electronic boost controller

 

Also it's a brandnew Collins actuator with there strongest spring to rule that out

 

It's got grs front mount and Okc efi inlet manifold

 

So what's wrong with having a spike? The peak and hold boost is quite normal on Cosworth management and is rarely seen as a problem.

 

Because I am wanting to run 24 psi but my boost limiter is set at 26 and my spike is making it hit the limiter all the time

 

As Stu says above, if they are setup correctly there's no problem, just make sure it is lockable.
Without proper boost control you will struggle to hit 24 and not spike over 26 mate, what turbo it is?

 

So you need to jet the Amal valve correctly. Increasing the C port jet will reduce the spike, decreasing the R port size will increase the boost. By adjusting these you should be able to get very close to a spike free boost.

Be careful winding up the preload on the turbo as you can bend the actuator arm. A few turns of preload should be all you need.

 

Ok good stuff I will try doing that with the amel valve how about electronic boost controllers will they stop spike or will I just be in the same boat

 

If the chip you are using is designed to work with an Amal valve then the
fuelling may not be correct if you force it to hold 24psi at high revs.

The Amal valve design gives the chip author the ability to control the boost
to a limited extent allowing them to reduce the boost at high revs.
An electronic controller will remove this safeguard.

Only the designer of the chip will be able to tell you this is safe. Even if the pump
and injectors can supply enough fuel for 24psi at 6000 rpm does the chip have
those load sites mapped correctly? It might not have if the author was using Amal
valve control to limit boost to 18psi for example as he would simply think that those
load sites would not be accessed.

 

Ok well I will get a wide band lambda on the car to make sure the fueling is ok to play on and it didn't have an amel valve on just a manual bleed valve before

 

TBH mate it might be worth taking it to someone who can set it up correctly, making any adjustments to the ECU if needed, even if you get your target boost without the spike and your WBO2 shows the fuelling is good what about the spark advance, detonation? It may all be fine of course but just a thought fella.

 

Ok thanks mate just a struggle getting someone to do it near me am in North Yorkshire

 

I'd head across to MSD in Blackpool, Stu will look after you.

 

Yes think that's what I will be doing about 3 hours from me

 

5 PSI spike? Christ I was wincing over my car having a 2PSi spike! It is running around 18-20PSI though depending on the day . I really need to plumb in a chargecooler pump...