Air Shrouded Injectors (and low boost)

[auditude at cox.net]

Hi Mike,

I put some commens within your quoted text below.

Mike_Buckham at ptk.pioneer.co.uk wrote:
>
> Thanks for your reply, Ken.
>
> If the air ends up in the cylinders then I definitely shouldn't be losing
> any boost through the injector air supply tube. My wastegate spring seems
> fine. Though I don't have another spring to compare it with, it is not
> broken and seems to apply a plentiful pressure against the wastegate shaft.
> There is plenty of easy free movement in the wastegate shaft and the
> diaphragm is not leaking.
>
> The rushing air noise I can hear is exactly the same and seems to be coming
> from the same place (though quieter) as when I suddenly release the
> accelerator and there is a rush of air from the wastegate.

I don't know why you'd hear a rush of air from the wastegate when you let up on the gas.  Bypass valve maybe, but not wastegate.  I could be wrong on this tho'.  I just don't think the wastegate makes all that much noise, altho' I've heard others here refer to wastegate noise, so I guess it does make some.

I just tried to think it through (it's early), and I don't see why the wastegate would do anything related to the throttle closing.  It runs off of intake manifold pressure, which means it only opens when there is pressure in the intake.  So, if you close the throttle, the wastegate remains closed.  However on the other "outside" of the throttle, boost is being "stacked up" with nowhere to go.

I just think you are leaking boost somewhere between your turbo and your throttle body.

> I have checked
> the "michelin man" hose and it is fine. I have also checked the hose from
> the turbo to the intercooler, though not the intercooler itself. I am
> fairly sure that the rushing air is from the wastegate or somewhere close
> to the wastegate due to the noise that I can hear. I don't have an analog
> boost gauge. I have been relying on the digital gauge in the dash, but in
> this case it seems adequate.

Do you have a bypass valve?  Are you running higher than stock boost?  Is your intercooler strapped?  If no, yes, no, then perhaps you've blown a seal on the intercooler.

> Is it possible to be losing boost through the wastegate even if the shaft
> is not stuck open and the spring is working fine? Is there an adjustment
> which could be made to the wastegate shaft somehow which might be stopping
> the wastegate from closing properly? Perhaps my wastegate is never closed
> for some reason.
>
> Cheers, Mike.

In my opinion, if you hear air rushing sounds, boost is being created and then lost.  In a non-turbo car where there's no boost, there's not exactly anything that is going to create an air rushing sound.  So, if you are hearing noises, I don't know what else they'd be.

What do you think?

Hth,

Ken

<auditude at cox.net>
>
> 1.  Into the cylinders and then burned and finally out the tailpipe.
>
> ...
>
> I'd be curious to know the condition of your wastegate spring.  Perhaps
> it's weak or broken, or the shaft is bent and it is stuck open somehow.
> You should be getting unlimited boost otherwise.
>
> But then again, if you actually hear the sound of rushing air, I think that
> is likely to be boost that is being created and then is being leaked out
> somewhere.  Have you removed your "michelin man" hose (from the intercooler
> to the throttle body) and closely inspected it for leaks?  Hold it between
> your hands and compress it to see if it holds pressure?
>
> Perhaps there is a leak somewhere else.  I would think the sound of a leak
> would be leaking boost, not exhaust rushing past the leaking wastegate.  Do
> you have an analog boost gauge?  Where is it hooked up and what does it
> read when this happens?
>
> Good luck,
>
> Ken
>
>
>
>