Re: fenders, and...

[trnsfrma@ix.netcom.com (Shawn C. Meze)]

At 08:39 AM 3/14/97 -0700, you wrote:

>What'll he do with the header?  How do you know the gains of a larger
>exhaust are minimal?  Curious.  Maybe I'm wrong.  When I looked into it, I
>determined that for sheer horsepower, 2.75" would be arguably the best -
>but gas velocity started to suffer drastically after that.  


I think your determination of Sheer HP is what your goal was, but there is 
more power to be had by the 2" systems. My research indicated that the 
difference in power from the 2" to the 2-1/4" was only in top end ONLY and 
the larger lost some low end. So, overall, yes, more power but still, you 
loose some in the low end. Since not many of us spend alot of time on the 
top end of things, the 2" is a fine system, as long as its Mandrel bent. 
 Its that game of give and take again, thats all.  


>See, velocity
>and backpressure are two different things - an exhaust can be free flowing,
>but have slow velocity/no backpressure.  Better exhaust gas velocity
>(smaller pipe) will somewhat enhance torque.  I went for power in mine.  


Oh, see, I needed to read mre before going into my own tangent, you did it 
for me....
With our small displacement motors, IMHO Velocity IS everything. Torque is 
everything. HP is secondary but still important. 


>Go
>to your local college (there's a big one 5 minutes from here, and I have to
>go to it;), the enginerd library should have books all about this - I waded
>through them a while ago and then again recently, it seems that in terms of
>horsepower, bigger is better, when you put space for the pipe into the
>equation.  How much better?  I don't know, that's why I am asking you - how
>minimal are the gains?

Im not sure of that anwser. I remember recently reading an exhaust size -VS- 
engine deplacement and aspiration. Basically, it listed the 2"-2-14" for 
anything at 2.0L and under, non turbo/supercharger. The 2.0L with the t
urbo/supercharger said that 3" to 3-1/2" worked well. I wish I could 
remember which mag it was in. It was pretty interesting and actually well 
written. 
Id like to see a 3" system on a VW. Well, not really, it would be gawdy. Id 
like to see it done right, is all. I dont think one will fit. 




Shawn

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