I have a Stebro stainless exhaust and muffler.  When I temporarily
installed a stock muffler I noticed a drop in power starting at about
4K RPM.  Stebro muffler is essentially a huge glasspack so it flows
very well and that of course has the greatest benefit at high RPM.
The stock muffler has a built-in inlet restrictor/diffuse.  While for
me 70 mph is 3850 RPM (gps verified) many with stock tires can benefit
from this power increase even more due to higher RPM.

A custom designed exhaust should yield even better results, to a
point. You can also tweak the AFM for a slightly richer mixture to
work with the higher flow exhaust.  Anyone up to make a custom intake
manifold?

The WBX may be an ancient design, but it has much goodness to offer.

2010/2/13, Kim Springer <kimspringer@astound.net>:
> Hey listers,
>
>
>
> Has anyone ever measured up a stock exhaust system to see where it's
> designed to make HP. I assume VW did this a long time ago.
>
>
>
> I guess another way to ask this question is: Did the folks making SS exhaust
> systems in a 4-2-1 or 4-1 design improve on what VW designed?
>
>
>
> I have a book that helps to design 4-Stroke intake and exhaust system
> lengths, inner pipe diameters, etc.
>
>
>
> All this talk about hollow cats makes me wonder about the secondary pipe
> length. Not that anyone is going to gain 10 HP out of this.just wondering.
>
>
>
> Kim
>
> 88 Tristar #7 (it's either going to get painted or sold in the next year)
>

-- 
Wysłane z mojego urządzenia przenośnego

Chris S.
Disclaimer: "Death and serious injury may occur"