RE: cat sucking engine...

["Rodney Moore" <m6bigdog@xxxxxxxx>]

There are many of the Bosch Motronics (mine are versions 1.0 basic and a
1.2) that cut off the engine fuel injectors in an operating region called
coast-off (throttle shut & RPMs >1500). Since the cylinders don't have a
fuel charge from the intake stroke this would cause a low pressure in the
cylinder when the exhaust valve opens.  Hence, an engine that is in
excellent condition will suck!!  I find the engine braking which is a
byproduct of this emissions related engine function very useful.    However,
in the final analysis there could also be some disadvantages. This condition
will also occur to a limited degree with all engines when they are turned
off.

Rod...




- ------------------original message---------------
Date: Mon, 14 May 2001 17:05:05 -0700
From: "HOTROD930" <HOTROD930@domain.elided>
Subject: cat sucking engine...
someone wrote:
If your engine is sucking stuff out of the cat, then you have a much
large issue than efficiency, or power. You should be shopping for a new
engine because yours is running backwards.
Nothing in the exhaust will ever be sucked anywhere, let alone upstream
to the engine. It would go out the tailpipe, away from the engine.
*********  This "absolute" struck me as odd, but I'm sure it's based on
experience/lack of.  Never say never.
The truly experienced know that they don't know everything.  How about a
backfire through the intake manifold *and* carburetor?  This is not the
correct "direction" for air/fuel travel, yet it can happen under some
circumstances....right?
I've only been interested in and working on cars for about 20 years, and own
a business related to automobiles, so I suspect there are many things I
haven't seen, and I know there are things I don't understand.  We all know
that exhaust flows out through the exhaust pipe.  We also know that there
are many different things at work. Outside of helping us to understanding
volumetric efficiency-the internal combustion engine is far more complex
than a simple air pump, to which it is sometimes compared.

My $.02
Rod Birch
- ---------------end-----------------------
- ---
Rodney Moore
BMW CCA #86830
Golden Gate Chapter
m6bigdog@domain.elided

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