Re: your opinion on dual exhaust

Posted by Texasmark1 on February 27, 2012 at 05:36:06 from (67.142.164.25):

In Reply to: your opinion on dual exhaust posted by Justin SE IOWA on February 26, 2012 at 17:58:35:

Engine is an air pump. Air in, air out. restrict either, you restrict
performance.

1. I have seen GM and Ram P/U trucks at least back to '05,
maybe as far back as '98 on the Ram that have separate exhaust
systems initially on each side of their V8 engines. Those
systems each contain a cat. conv. Then they join and exit one
tail pipe and muffler.

2. On velocity of air out, obviously rpm of the engine for a given
set of conditions has it's limitations.

3. Type of flow has it's effects, i.e. laminar vs turbulent.
Laminar is straight line and has the least contact with the walls
of the pipe hence the least resistance, hence breathing of the
engine is best. Turbulent on the other hand puts the air to
circulating and it moves down the pipe, slowing it down and
scrubbing the sides over and over; both limiting flow.

4. Used to be (mid 70's for a benchmark) 1 7/8 tail pipes were
what you got with your small block V8. Dual exhausts helped
that by doubling the area of the outlet.

5. I think Ram started it but doesn't matter, especially with
diesel trucks. Check out the size of the exhaust in today's
trucks and there is a marked difference in size between these
and yesteryear....yes part of it is hp increase, but that's only part
of it.

6. On 1 pipe vs 2, other than just to get your brain rattled by the
noise, area of the pipe is 22/7 (pi) x radius squared. So the
diameter of a single pipe doesn't have to go up all that much to
equal the area of a pair of smaller pipes. Additionally, the flow
in that single pipe is much less restricted due to the reduction of
the surface area of the pipe that the air has to pass by, and
hence be slowed by.

7. Now I will give you the fact that a flow through muffler
(glass/steel pack) will offer less resistance to flow, that normally
are used with after market dual exhausts, than a poorly
designed conventional muffler, but there are those out there that
are quiet and minimally restrictive.

Lots of reference books out there to support what I said. Not my
words, words of mathematicians, physicists, propulsion
engineers, and equipment designers.

My 2c,
Mark

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