[s-cars] Exhaust dyno results...

[calvinlc at earthlink.net]

Dave,

I will have to respectfully disagree that a dual 2" exhaust is capable of
supporting 680 HP.  I guess myabe I shouldn't say it that way...the dual 2"
is not ideal for 680 HP.

I have long been a critic of exhaust systems and the sales pitch the
manufacturers do.  I think that they are mostly a lot of hype.  However,
there are many sound principles and tried and true methodologies.  Having
built many many large displacement hi-po engines there is not a doubt in my
mind that 2" duals will limit a 600+ HP engine.  I can give you empirical
evidence from timeslips showing a 0.3 to 0.5 second drop in ETs at the
dragstrip for going from 2.25" exhuast to 3" headpipes/2.5" tailpipe duals
and keeping the same mufflers and headers on a 450ish HP machine.

You can force 100 gpm of water flow through a soda straw but it takes a lot
more effort than pushing it through a 1.5" PVC pipe....so I am sure that
dual 2" will "support 680HP" but it certainly is not optimal.

Your test simply proves what has been known in the drag-racing community for
a long time, it is possible to put too open of an exhaust on any engine
combination.  Not only does this have to do with the pulsing action as
somebody had mentioned before, but in the extreme it can make your
combustion temperature drop too much.

I am sure the stock S-4 exhaust is good up to 300-350 HP...the aftermarkets
probably make a little difference, a cat bypass would probably make even
more.  Uncorking the whole thing though is going to be too much for our
little 2.2 liter to handle.

The only experience I have with Audis is on my '89 200 equipped with a K-26
where a cat bypass pipe loweres the boost threshold by about 400-500 rpm.
Maybe there is something I am misunderstanding about these little T-charged
engines....but as far as the bigger normally aspirated engines go I would
guess that dual 2" would knock about 50-70 HP off of dual 3" on a 680HP
engine.

--Calvin


-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com]On Behalf Of Djdawson2 at aol.com
Sent: Tuesday, September 14, 2004 1:09 PM
To: nick at newtsplace.com; s-car-list at audifans.com
Subject: Re: [s-cars] Exhaust dyno results...


In a message dated 9/14/2004 12:03:02 PM Mountain Daylight Time,
nick at newtsplace.com writes:

> I agree, I think there is a happy medium somewhere in between, because
> some exahaust systems do obviously add horsepower over others.

Ah... but where are the dyno results to prove this?  Remember, a dual 2" is
capable of flowing up to 680hp.  What would make anyone suspect that this is
a
limiting factor in our 300-400hp cars?
Dave
_______________________________________________
S-CAR-List mailing list
S-CAR-List at audifans.com
http://www.audifans.com/mailman/listinfo/s-car-list