Frank,

Forget that trip to the Moon-wer'e going to Mars!!

I have been experimenting myself with exhaust configurations however without 
the advantage of a state of the art laboratory!

I have arrived at similar conclusions with regard to muffler, pipe, 
suspension and length. Here is a chronology:

1995-first muffler:
The vehicle, a 1982 Vanagon Westfalia diesel converted to gasoline 91 Jetta 
engine. The exhaust manifold, Diesel-the muffler-Diesel. �

The results-loud, and the expensive muffler mounts broke. It was decided that 
the pipe diameter was to small for the larger displacement gas engine. Before 
changing the exhaust manifold to the 88-92 Jetta one, I replaced the muffler 
with a high volume and loud flowmaster, and 2 1/2 "downpipe.

The results: the muffler got so hot it melted a hole in the Diesel oil filler 
pipe, stranding me on the freeway. At the time I didn't realize that the 
engine was experiencing a false air or unmeasured air condition.had to be 
towed home, (three days later I discovered the melted hole that prevent the 
engine from starting) 
Replacing the tube and improving the heat shielding for the tube and the 
engine ran again. 

The second arrangement was to use a 88-92 G-J exhaust manifold and a smaller 
2" downpipe was settled for. I got rid of the flowmaster and replaced it with 
a cheap 20 dollar muffler. The results? noise is inexpensive!

I got rid of that muffler, and added a cat, and used a Walker oval muffler. 
It was quieter, but not between 55-65 mph. Over 70 mph, it became quieter. 
resonance was worst right where average speeds were driven. So then I tried 
using two mufflers end to end-it quieted down, still, there was not enough 
length of pipe to cool the exhaust gases. 
I am now ready to finish the system-it's take 5 years. In the I-4 scratch 
conversion, the Tiico, and others, the muffler gets the least attention. 
the Tiico gives you short pipe and a muffler-and it is loud. 
What I have now is real funny, but it shoed me something-long pipe is good. 
I have a custom made Jetta or Golf dual down pipe-it starts at the exhaust 
manifold as two pipes the collect four feet down into one. This is routed 
directly under my oil pan diagonally to the right rear where it makes a bend 
to the left a goes into a stock 2.1 vanagon muffler in the stock location. 
Since there is only one muffler and no cat, it is not as quiet as with the 
two mufflers-but the resonance is gone. There was a power and mpg increase, 
and it sounds a little racy. I know a shop in a county who will finish my 
system like you have described. 
I will use the 1993 G-J manifold with dual down pipes that are run rearward 
about three feet. Will connect with a muffler that has inlet/outlet on the 
same end, and then return back on the right side to the rear and into the 
second muffler in the stock location. Six feet of pipe, dual downpipes too 
cool the exhaust, and two mufflers to scrub the noise. All without 
sacrificing flow, but increasing the backpressure some and helping to retain 
low end torque are the other benefits. 
Now to deal with sound deadening the body from road noise. 

Robert K 1982 Westfalia 2.0 Golf lll powered
Seattle

[text/html]