Exhaust comments/Stebro & 2small pipes vs. 1 large

[Ben Swann]

Just wanted to comment on this.

Sometime back I had heard this from an Engineer familiar with fluid
dynamics and its application to exhaust dynamics.

He said that GM had done some testing and found that one large pipe was
better than two smaller pipes that provided comparable area particularly
for forced induction applications(aka supercharger in the V6 -
Cylcone/Typhoon).  The reasoning behind this was largely due to the
increased friction of the surface area inside two pipes was greater than
one large pipe.

Don't know how we ended up talking about 2 pipes vs. one though, unless we
are referring to what is inside the muffler.  The Stebro system for the
5ktq is one 2.5" pipe with no crimps and a large can where the resonators
were on the stock system.  The stock system is around 2.35" in the widest
spots with several places that are significantly smaller restrictions due
to crimping and placement of the stock resonators.

I measured the stock cat as just under 2" and the Stebro slightly less than
2.5"(id) in and just over 2.5 out to match the 2.5 exhaust flange.  A
larger donut washer is provided to match thing up.  This is off the top of
my head again, so this may not be exact.

Ben

[> > Dual 3" is some serious exh, I can't ever imagine needing that on an
Audi, esp. a 5 cylinder...no, single 3" is what I'm referring to.
>
> Ok, cool.  So, the stock exhaust is 2.125" dia pipes (x2) right?

no...

>  The Stebro is
> 2.5" dia (x2) pipes.  So total areas:
>
> Stock: (2.125/2)^2 x 3.14 = 3.55  error: x 2 = 7.1 sq.in.
> Stebro: (2.5/2)^2 x 3.14 = 4.91   error: x 2  = 9.82 sq.in.
> 3":     (3.0/2)^2 x 3.14 = 7.1 sq.in
>
> So the single 3" system is on par with the stock system, as far as total
area
> goes.  If I did my math right, and there is no guarantees there.

why did the 2.125 and 2.5" systems get doubled?? what 5 cyl Audi has
dual exhausts?

What you've shown, is that the 3" pipe is double the area of stock, if
stock is 2.125".

--
Huw Powell]