RE: 5kCSTQ boost Q

[Phil@sievers.com (Phil Payne)]

In message <841939167.1195.0@omdc.gso.uri.edu> "Sheffield Corey" writes:

> 	Well, I guess I'm not a very accomplished hose inspector. After putting
> the car up on the lift today to inspect the turbo to IC hose and finding it
> soft but unholed my mechanic lowered the car to remove the same hose I'd pulled
> last weekend to clean and inspect( what I call the "bellows" hose from the top
> of the IC to the intake manifold(plenum)). This fellow was a bit "rougher" on
> the hose than I was  and his finger easily slid into a 24mm crack under the
> center reinforcing ring.

OK - this is the source of my confusion.  The only "bellows" hose on my car 
runs from the filter/injector assembly to the turbo inlet.  It's wire-
reinforced because the air pressure inside gets a bit low sometimes and it 
would otherwise collapse.

> I'd cleaned the thing inside and out; flexed it all over the place, but 
> never looked carefully under the rings figuring it would blow-out in one of 
> the wide inter-ring areas where oil had collected...WRONG

All this is foreign to me - the hose from my intercooler to inlet manifold 
is large diameter heavy-duty _smooth_ rubber.  It's slightly C-shaped to 
accomodate the movement you describe.  No rings, no metal fitments of any kind.

> ... same hoses with a built-in dump valve available. Scott, of PDQSHIP 
> fame, said this was a dangerous set-up, but never explained why vented 
> pressurized air at that point was dangerous to the engine.

It's not.  It's the turbo.  Think of the exhaust manifold.  Large quantities of 
hot gases are appearing and want to go home.  There are two routes - wastegate 
against spring pressure, or turbo against vane back pressure.  Allowing for 
some minor diameter issues, vane back pressure on the exhaust side is the same 
as vane forward pressure on the inlet side.  Releasing the inlet back pressure 
allows the compressor side of the turbo to spin up against no resistance.  This 
suddenly diverts the entire exhaust flow through the turbo.

There are two sources of danger - one is that the turbo can reach _much_ higher 
speeds than in normal use, and another is that the loading on it is very light, 
shifting the wear pattern in the bearing.

--
 Phil Payne
 
 Phone: +44 385302803  Fax: +44 1536723021  CIS: 100012,1660