RE: Performance difference w/o a cat?

[Chris Coracini <Coracin@usdl.com>]

>
>
>"New 2" Racing Dual Downpipe for Scirocco 16v
>Same as above except with 2" primary pipes. This
> downpipe was designed for modified engines. Adds
> approximately 11hp."
>
>I don't claim that it adds 11hp Chris, TT does.

yeah, i know.  i have the catalogue too.

>  It may be less, it may be more,
>but my main point was (and still is) that consistent pipe diameter throughout
>the
>sytsem will provide more torque and hp than a big ole cat chamber just 1 1/2
>feet
>downstream from the header (read: turbulence=bad).

i understand that.  i never said there is NO difference.  BUT, notice
the comment about "designed for modified engines".  take a cat off a
stock 1.8 16V and you won't get 11hp.  no way.  the racing downpipe is
also bigger in diameter, so we are talking about not only removing the
cat, but also increasing the inside diameter of the downpipes.  this
will help an engine with a p&p job, hot cams that is being restricted by
the stock exhaust.  but the stock 1.8 16V is not that restricted, and
removing that cat *without doing anything else* will not add 11hp.  that
was/is my point.

>  The Scirocco cat is one of
>the best out there, but still is no match for a non-cat dual downpipe, even
>if
>the one i've described is for modded engines.  Get one=go faster.

again i agree, but the question is "how much faster".  the answer is:
stock engine, not much faster, *a little*, but not much.  modified
engine, yes, you may see up to 11hp, but only if the engine flows
enough.

i don't remember if it was you or someone else, but there was a comment
made on how rich mixtures don't overheat a cat.  this is not true, rich
mixtures DO overheat cats, sometimes even to the point of
melting/catching fire.  in europe when they sold the scirocco, leaded
gas was still readily available.  maybe some of you yurpeens could help
out with facts here, but my theory is that the difference between the
129 and 139 hp figures is that the catless 139hp engine used leaded
fuel, which allowed it to used more ignition advance (K-jet), and
perhaps a slightly richer mixture too.

chris
86 16V scirocco

>
>jim
>
>
>
>Chris Coracini wrote:
>
>> >
>> >I agree.   Precious exhaust gas velocity is severly hindered when the
>> >downpipe opens
>> >up into the cat, then must be re-funneled into the rest of the system.
>>Not
>> >exactly a
>> >device designed with performance in mind, although it is a highly
>>efficient
>> >unit, as
>> >far as cats go.  Going with a catless downpipe like the new TT offer
>>greater
>> >torque,
>> >throttle response, and hp (I think TT claims 11 peak).
>>
>> hold on, 11hp?!?!  hmmmm...  i seriously doubt that, VERY seriously.
>> maybe comparing the single outlet manifold/downpipe w/cat to a dual
>> outlet manifold/dual long downpipe, then MAYbe it would be close to
>> 11hp.  but not comparing the 16V dual downpipe with or without a cat, no
>> way...
>>
>> chris
>> 86 16V scirocco
>> >
>
>--
>Jim Buck
>1990 Passat Wagon 2.0 16v
>1987 Scirocco 16v "lil 109"
>1982 Rabbit Convertible **FOR SALE** http://www.mixi.net/~vwpride/cabbie.htm
>
>Got Wheels? Visit anyway!
>
>http://www.mixi.net/~vwpride/
>
>
>

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