New Exhaust System Advice

[kervinridgley@earthlink.net (Kervin)]

There are variable intake runners in BMW's 745.  VW did kinda the same
thing with their 16v engines.  US models had narrower runners to move
the peak power down the rpm range.

Alan Stamper wrote:
> 
> 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
> >
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> 
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-- 
Kervin
86 Scirocco 2.0 8v 4K+80% and lots of other numbers and letters
88 Gti 1.8 16v Not done and now it's winter :(
00 tt600