Air Shrouded Injectors (and low boost)

[auditude at cox.net]

Hi Mike,

I'll try to answer your questions, based on what I understand is going on.

1.  Into the cylinders and then burned and finally out the tailpipe.

2.  I think it's just a tube.  It would allow air to flow both ways, but since either the intake is under pressure or the cylinders are under vacuum, the air is sucked in instead of pushed out.  It's the same thing as the air in the rest of the intake manifold, it just gets to the ports along a different path.

3.  I think the tube can be plugged and no boost would be lost/prevented from building.

4.  My understanding is it would have poorer low speed atomization, which would hurt emissions.  Or it could be performance, but regardless it isn't a show-stopper.

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

Mike_Buckham at ptk.pioneer.co.uk wrote:

1. Where does the air which is forced into the head around the injectors
end up? Is there an exit port somewhere?

2. Is the restrictor in the tube from the intake manifold to the head a
one-way valve? If so, I presume it only allows air into the head?

3. How much boost would I lose if the restrictor was missing?

4. What effects would it have if I removed the air tube from the intake
manifold to the head and blocked up the intake manifold port? Would it
adversely affect the injectors?

One of the reasons for these questions is that I am not getting sufficient
boost at the moment and the air restrictor is currently missing. I have the
lower hose to the bottom of the wastegate diaphragm plugged, so the
wastegate should not be opening. As I drive along and I should be getting
lots of boost, I can actually hear quite a lot of air being forced out. It
sounds like it is coming from the wastegate (as it sounds close to the
bulkhead) but is this actually possible if that bottom hose is plugged? I
can't find any air leaks in any of the tubes.

Thanks for any help,
Mike.