Hi Vance,
I believe that two pipes will flow less than 1 pipe when the cross
sectional area of the two is the same. Fluid flows faster at the center
of the pipe than at the edges. You can see this by watching water flow
down a river. It flows faster at the center than near the shore. It's
even more noticeable if the water is very deep in the center.
Calculating the flow through a pipe is one of the classic problems in
Differential Equations -- which kind'a sums up all I remember of
Diffy-Q. Other than the professor who had mercy on me :-). Exactly how
it applies to air in an exhaust system is quite beyond me.
In which of Vizard's books does he discuss Dyno-Max mufflers?
In Vizard's Tuning the A Series Engine he provides the following table.
Air flow in CFM @ 25 Inches water
Peco MO/2 121.8
Peco MO/4 80.4
T.I. AN 181 T 112.3
RC40 195
Metro Race Systems 170
Unipart 1275 84.5
Unipart Cooper 86.7
Cyclone Sonic Turbo 330
Maniflow System 209
Looks like Cyclone Sonic Turbo is a no brainer. He says APT sells them.
Anyone had any experience with them? I have not checked with APT yet.
Don Malling
Navarrette, Vance wrote:
> 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
|