Frank,
Forget that trip to the Moon-wer'e going to Mars!!
I have been experimenting myself with exhaust configurations however wit=
hout the advantage of a state of the art laboratory!
I have arrived at similar conclusions with regard to muffler, pipe, susp=
ension and length. Here is a chronology:
1995-first muffler:
The vehicle, a 1982 Vanagon Westfalia diesel converted to gasoline 91 Je=
tta 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 f=
iller pipe, stranding me on the freeway. At the time I didn't realize that t=
he 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 sma=
ller 2" downpipe was settled for. I got rid of the flowmaster and replaced i=
t 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 muffl=
er. It was quieter, but not between 55-65 mph. Over 70 mph, it became quiete=
r. resonance was worst right where average speeds were driven. So then I tri=
ed using two mufflers end to end-it quieted down, still, there was not enoug=
h 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 scratc=
h 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 go=
od.
I have a custom made Jetta or Golf dual down pipe-it starts at the exhau=
st 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 ben=
d 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 t=
he two mufflers-but the resonance is gone. There was a power and mpg increas=
e, 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 rearw=
ard about three feet. Will connect with a muffler that has inlet/outlet on t=
he 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 sacrifici=
ng 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