I thought I saw some dyno charts some where that showed the differences
between some of the performance exhausts... specifically the dual vs. single.
I believe that Roger Williams "how to improve" book also discusses the
subject. I seem to remember that the big bore single pipe systems ultimately
developed about 8 more horsepower on highly tuned engines than the dual
system. However the extra horsepower was only seen at the top end of the rev
range, near redline. Important for race cars but negligible difference for
street car tht rarely spends extended periods of time at higher RPM's. So the
difference between single vs. dual to most street cars boils down to sound and
looks with both being fairly equal in the performance category for street
performace.
If my memory is failing plese let me know.
Shawn J. Loseke
1972 TR6
Fort Collins, CO
>===== Original Message From "Navarrette, Vance" <vance.navarrette@intel.com>
=====
> Don:
>
> I believe Kas makes that assertion based on cross sectional area
>of the pipes:
>
> For a dual 1.75" system, area = 4.8 in^2
> For a single 2.5" system, area = 4.9 in^2
>
> So the improvement is tiny, about 2%, for a single 2.5" pipe
>over a dual 1.75" pipe.
>I believe that the stock system is 1.75"x2 on the later cars, correct?
>The early cars had
>1.75"x1, so they were poor in terms of exhaust flow. The factory went to
>the dual European
>system on the later US cars as the emissions requirements began to choke
>all the power
>out of the engine. The factory had to start putting in the better parts
>to make up for
>the loss.
> In general the muffler is the main restriction, not the pipe. So
>going to
>a true dual exhaust with two mufflers, even if the pipes are 1.75",
>would probably
>way out perform a single 2.5" system with one muffler.
> Evaluating the system on the basis of pipe diameter is a way to
>get hard numbers,
>but far better is to get a rated flow for the muffler at say, 18" of
>water pressure drop.
>None of the exhaust system manufacturers are talking about that though.
>You need to go to
>someone's book to get comparisons. I have only ever seen David Vizard
>compare the flow
>numbers for the various mufflers.
> Just looking at the pipe diameter is looking at only 20% of the
>picture, when you need to
>look at the muffler to get the remaining 80%. Some of the aftermarket
>mufflers are
>surprisingly weak in terms of flow.
> Enough babbling.
>
> Cheers,
>
> Vance
>
>
>-----Original Message-----
>From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
>Behalf Of Don Malling
>Sent: Wednesday, April 21, 2004 2:18 PM
>To: Lizirbydavis@cs.com
>Cc: 6pack@autox.team.net
>Subject: Re: ANSA vs Monza for TR250/TR6
>
>Hi Joe,
>
>According to Kas and others a single 2.5 inch pipe is better than two
>pipes. I'm not sure why. I also think the Falcon is 2.25" rather than
>2.5" so I'm not sure of the implication of that. Exhaust systems and
>Headers are black magic to me. I'm just doing what I read and what folks
>
>tell me :-)
>
>Don
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