If a straight pipe makes less power than the cat (suggested many times on
> this list), then you, my friend, are a monkeys uncle :)
Only in situations were backpressure is required to increase exhaust velocity.
What you are trying to do is evacuate the exhaust gases out of the combustion
chamber as fast as possible. True, if you have too much volume were the exhaust
exits, it will just have a tendency to 'sit around' instead of rush out. This
is were smaller piping works to 'rush' out the exhaust and increase exhaust
velocity. Then again if you rush the gases out too fast you will not get enough
of a difference in internal vs. external temperature in the exhaust chamber to
make power. Its kind of a weird balance.
Sometimes tuning is also set up to be optimized to use a cat by running a
specefic air to uel mixture. But I don't beleive this is the case for V-8 Daks
of any year.
Once you add in all the losses associated with the length of pipe that goes to
a muffler and all the bends that it takes to get the gases to an exhasut pipe i
would tend to think that the freeist flowing muffler made would be in your best
interest. Even with the lower compression in our trucks, the horsepower level
that --I-- would like to generate warrants the use of larger pipe, freer
flowing mufflers and cats,basilcally the least restrictive designs I can find.
On our trucks I would suggest at least a 3" cat back and the freeist flowing
mufflers possible. If I didn't have OBD2 I would ALSO eliminate my cat. Put it
on a dyno and I'll bet that an open pipe will almost ALWAYS make more power
than a muffler or cat if you stick with anything under 3". The only times I've
seen an open pipe make less power is when you are running open headers or the
knock sensor is retarding the timing because of all the noise and extra
vibration.
IMHO it is in our best interest to free up the exhaust the most possible in our
trucks. Specially if you are keeping stock diameter pipes. In this instance I
don;t think you could lose any low end torque. Now if you shorten up the pipes
or dramatically increase pipe diameter THEN you may lose some low end torque.
Otherwise I'd go for the freeist flowing design. In my experiance it makes NO
sense to restrict the exhaust with an inferior muffler on stock pipes or even
3" pipe.
-- George Hernandez Tocquigny Advertising + Design 512.329.8065 ext.135 Fax: 512.328.5645
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