Wastegate VSV and Actuator

[merckx]

I've been trying to figure out the reasons for putting a bleed valve in to increase the boost a little.

 

I want to increase it from 1.0 bar which I'm getting now with my full decat to 1.2 bar.

 

Am I correct in thinking that a sensor measures the boost pressure and a pre-determined level 12v is applied to the wategate VSV which then opens.

 

This allows boost pressure which is already present at the actuator to then pass through it and so open it up.

 

So if I put a bleed valve in the location marked by the cross.

 

The VSV will still open at the set boost pressure but even if you bleed a little air off , the actuator will still start to operate even if the pressure acing on it may be less.

 

So in effect the acuator would still operate at a much lower pressure if the VSV was open.

 

By fitting a bleed valve you're not delaying the actuator from opening at all but reducing the pressure acting on it a little.

 

 

[img]http://i4.photobucket.com/albums/y122/rexmerckx/Vacuum.jpg[/img]

[Pete]

I want to increase it from 1.0 bar which I'm getting now with my full decat to 1.2 bar.

You only get a max of 1.0? No restricter ring? Isn't that a bit odd?

[Steviekid]

Am I correct in thinking that a sensor measures the boost pressure and a pre-determined level 12v is applied to the wategate VSV which then opens.

 

This allows boost pressure which is already present at the actuator to then pass through it and so open it up.

 

The wastegate VSV is normally open and actually closes to open the wastegate (pressure "backs up" to the actuator).

 

The wastegate spring keeps the wastegate closed until the actuator sees around 12psi and isn't completely open until around 18psi. Putting a bleed valve between the boost source and the actuator allows you to cause the actuator to effectively receive less pressure than what you're getting into the engine. The ball and spring boost controllers are better and don't let the wastegate actuator see any pressure at all until you want it to.

[merckx]

You only get a max of 1.0? No restricter ring? Isn't that a bit odd?

I've got a restrictor ring fitted, the pressure dropped to 1.0 bar after sitting a new SMIC.

 

I would rather have something I can adjust instead of opening up the restrictor ring.

[merckx]

The wastegate VSV is normally open and actually closes to open the wastegate (pressure "backs up" to the actuator).

 

The wastegate spring keeps the wastegate closed until the actuator sees around 12psi and isn't completely open until around 18psi. Putting a bleed valve between the boost source and the actuator allows you to cause the actuator to effectively receive less pressure than what you're getting into the engine.

 

Thanks for that Steve, it makes sense now!

 

If I did fit the bleed valve then it shouldn't matter which hose on the acuator I make the connection to?

 

The ball and spring boost controllers are better and don't let the wastegate actuator see any pressure at all until you want it to.

I'm confused as to why quite a few members prefer the bleed valve, Chris Wilson does and he's got a fair bit of knowledge.

 

If I fitted a ball and spring boost controller and for some reason it didn't open then the wastegate wouldn't open at all.

 

 

Everyone appears to have different opinions on which is best.

[Steviekid]

If I did fit the bleed valve then it shouldn't matter which hose on the acuator I make the connection to?

 

Yeah, you could put it in the hose you've marked X, or between the actuator and the VSV.

 

I think people prefer the ball and spring MBC's because they're easier to set more accurately. I suppose the potential is there for the spring to seize and the car to overboost although probably highly unlikely. Just get a nice shiny electronic one

[merckx]

Just get a nice shiny electronic one

A little short of money!

 

Thanks Steve , nice to know how the wastegate operates.

[ardasaliah]

Bleed valve works fine.

[merckx]

So

 

Bleed Valve can be fitted at point A or B

 

Manual Boost Controller fitted at B

 

 

[JohnA]

EBCs ask you to block off A so they can control boost by manipulating the flow through B

 

MBCs can be set up either way (A blocked or not)

 

Blocking off A obviously disables the VSV for boost control purposes.

[merckx]

B

 

MBCs can be set up either way (A blocked or not)

 

But if you did block off A

 

and

 

Is a MBC just a one way valve which you can adjust?

 

Then any pressurised air going past it would just keep the wastegate open permanently as the air acting on the actuator has got nowhere to go to if you effectively disable the venting through the VSV by blocking it.

 

Or doesn't a MBC work like this?

[JohnA]

In my post 'MBC' stands for Manual Boost Controller and I mean the ball&spring variety.

Operation is like I said on the other thread.

[merckx]

Okay, so the MBC can bleed a little air off to atmosohere to release the actuator.

[JohnA]

The MBC resists the air buildup up to a specific (adjustable) point. It then opens up and air flows.

Whether the actuators will be pulsed open or closed by the ECU, that depends on revs, load etc.

 

If you want to totally forgo ECU control then just block off A and let pressurisation happen through B.

That's what EBCs do.

[merckx]

I was reading up about the MBC's, I didn't realise they also let a little of the pressurised air to leak out. Without this it would act as a check valve.

 

All is clear now.

[JohnA]

It's pretty straightforward as long as you get the right end of the stick.

Many people confuse MBCs for bleed valves, because they see the tiny hole they have on the body.

That is *not* a bleed, it is there to relieve the pressure behind the ball so it can move quickly back in place when the pressure changes.