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Re: Performance difference w/o a cat?



Chris Coracini wrote:

> 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.

Then we each had different points, and we both were right!

>  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.

Right.  The engine must be modded to increase flow for the larger pipes of that
particular item.  But I'm still maintaining that if you replace the cat/downpipe
of a 16v roc with a non-cat one of the same pipe diameter and routing as the
original, it will provide both more torque and hp.  I'm not sure on how much more,
just more.  Otherwise, IT and club racers would be scrambling to bolt up
cat/downpipes to their race cars, which would be nonsensical.  As a general rule,
cats interrupt flow to the detriment of performance, no matter how well designed.
As far as the Euro Rocco 16v goes, I think the 139hp comes from:
50mm intake runners
more radical intake cam
no cat
vacuum advance distributor

--
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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