New Exhaust System Advice

[scirocco-al@insight.rr.com (Alan Stamper)]

All this backpressure talk has me thinking.  I know that headers need to be
tuned to get maximum scavenging from the cylinders.  Some come with long
primary tube and some come with short primary tubes.  I think the theory is
that the length dictates what engine RPM it's best efficiency is at.  This
probably has more to do with matching exhaust pulse frequencies than it does
backpressure.  As for the argument that the best backpressure is zero,
evidently Ferrari doesn't think so, as at least one of their production
cars, maybe 2 come with variable length exhausts.  There is a flapper
mechanism that reroutes the exhaust at different backpressure loads.
Evidently at slow speeds the exhaust travels through the whole system and at
higher engine speed the flap moves and the exhaust travels a shorter
distance for less back pressure.  BMW is doing something similar on the
intake side with a new variable length intake.  I forget what car it is,
maybe the new 7 series.  I read about it in one of my automotive design and
engineering magazines at work.  All of it cool stuff

Alan

----- Original Message -----
From: <Captnbr@aol.com>
To: <Scirocco-L@scirocco.org>
Sent: Sunday, March 23, 2003 9:39 PM
Subject: Re: New Exhaust System Advice


> I wonder if the venturi effect has ever been tested in exhusts systems.
You have a somthing like a large 3 inch pipe, reduce it down to like 2
inches and then back to 3 inches, this will create a venture effect which
will speed up the exhaust gases as they leave acting like a vacum pulling
the exhaust gasses out of the engine.
>
> Brian 86 16v
> 98 Jetta Vr6
>
> _______________________________________________
> Scirocco-l mailing list
> Scirocco-l@scirocco.org
> http://neubayern.net/mailman/listinfo/scirocco-l