Re: stock dual downpipe vs. TT dual downpipe

[Kevin <aventari@cts.com>]

I have personal experience w/ this. :) In 81 the dual outlet manifold has
the o2 sensor in the manifold between the two outlets. The sensor connects
the 2 'pipes' together, reading exhaust from all 4 cyls, as opposed to the
sensor just reading 2 cylinders in the downpipe. You can get the deisel or
early gas manifold w/o the o2 in the manifold, but put it in the downpipe.
	Advantage of the 81 manifold are that it reads the air/fuel ratio of all 4
cylinders together which is marginally better than reading just 2 cyls..
VERY marginally.
	The disadvantage of this style is that it connects the 2 flow paths
together _very_ early in the exhaust path. This will make it a prime
candidate for overscavening the cylinder in my opinion. Also it cannot
possibly promote a good exhaust flow, which means more back pressure which
means: BAD. But on our mildly tuned (relatively) street machines it might
not make a any difference. 

At 10:19 AM 12/22/98 -0500, you wrote:
>I have an opportunity to get a dual exhaust manifold and a dual downpipe
from a 1981 scirocco.  I know that TT claims that their downpipe is better
than the stock one, but does anyone have any practical experience w/ the TT
downpipe vs. the stock dual downpipe?  For around $100, the TT one sounds
reasonable, and I can get it w/ the O2 hole....don't know if the '81
sciroccos had 02 sensors.
>
>BTW I have an 84 8v w/ the crappy 4-1 exhaust manifold.
>
>Thanks
>
>Victor J. Farren
>Research & Reference Services
>PPC/CDIE/DIO/RRS
>Tel: (202) 661-5842
>Fax: (202) 661-5891
>E-mail: vfarren@rrs.cdie.org 
>
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>

Kevin Fry roccin '81 S 1.8 
"You are what you drive- BMW 7-series: I'm still not important, but I've
perfected the art of living beyond my means."

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