3in exhaust on jrsc?

[SSBP]

If you are going to do the exhaust right, it has to begin with the header.

Since you have fat pockets, this is what I would do.

1) Buy the Hi-Tech SC Header with a 3" collector
2) Full custom exhaust from a 3" cat to a 3" mandrel bent exhaust with a resonator and a Dynomax UltraFlow muffler.

I believe there is at least 20 H.P. and 15 Torque with this setup.

If you add a header to your system (DC RSR, etc) it still goes into a 1.75 inlet on the cat and a 1.75 outlet. Then from there adding a exhaust does really nothing. If you are cheap, just replace the factory muffler. That is the only restrictive part of the Integra Exhaust system because they want to control the noise. If you want the stealth look, get the Type R exhaust. 2.25 with a high flow factory muffler.

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00 Naples Gold 3.2TL

[gsr98]

crom is a idiot, always and forever.
SSBP is right about it being nice to have the biggest collector u can, but on a turbo car people still see gains using 3in pipping when there down pipe doesn't equal that length. i think the 3in exhaust would work well on a SC'ed car, im sure real gains would be seen when running higher boost, but every little bit counts. a bigger exhaust always helps when ur engine is compressing more air, whether turbo, SC, nos, or a built all motor car. good luck

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www.importpo.com

[MADDracer]

right now i'm running the rsr header i want to go with a straight pipe but i dont kno how to ground my second o2 sensor(obd2). i know its gonna be loud but i dont care as long as i'll gain power. anyone kno a 3in muffler? i wanted the 5zigen fireball but they only make 2.5

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99 white gsr
18x7.5 te37
oem front lip
tein type na
greddy exhaust,rsr 421,iceman, JG tb, aem pulleys,
JRSC
no stickers, no body kits, no bull sh*t

[lundgren]

Given a pipe with two ends, each have a cross section of areas A1 and A2.

If we watch the fliud at one end for a short time, say dT, a fluid particle will move a small distance V1dt and a volume of dV or fluid, given by:
<CENTER>dV = A1v1dt = A2v2dt</CENTER>

We can write, for any point along the tube of flow: R = Av = a constant,
in which R, whose SI unites are meters^3 per second, is the volume flow rate. If we multiply R by the (constant) density of the fluid (or air), we get a quantity Avp, the mass flow rate measured in kilograms per second, which also remains constant.

We call R = Av = a constant the equastion of continuity. It tells us that, in the narrower parts of a tube of flow, where the streamlines are closer together, the flow will be faster. It is an expression of the law of conservation, which eventually lead to Bernoulli's Equation. But it is also helpful in the study of fluid mechanics.

Now the fun part:

If we have a 3 inch exhaust section of pipe, with the same volume of air moving as a 2.5 inch section of pipe we have:

[Where the 3 inch pipe is (1) and the 2.5 inch is (2)]

dV1 = dV2, and dV1 = A1v1dt, and dV2 = A2v2dt, or A1v1dt = A2v2dt. Since dt is the same, then the only difference is the change in velocity, such that A1/A2*v1 = v2.

What this means is that a smaller section of exhaust will move exhaust gases faster through the pipe, than the larger section. If the volume of gas goes up, then in order to maintain the same velocity (which is important for exhaust excavation), we need to increase the diameter of the pipe. Period.

The only other factor is what happends if you have a smaller collector that is 2.5 inches on a 3 inch pipe. Well air will move quickly through those areas, but once it passes out, it will slow down again. We shouldn't forget that the exhaust gas will cool off as it moves back. As the density chnages, and the gas compresses, it won't require as much pipe diameter to maintain the same volicity.

Also, we don't know what the effect of having the gas speed up near the entrance to the cat, or the exit. Maybe this is good.

In short, larger is better where ever it is found, to a point, where the diameter of the pipe reduces the speed of the air moving through it. This includes headers, cat and exhaust, where for larger boost levels, or FI at all, the pipe should be larger, and it's more important up front, at the header.

Sorry to take you back to physics class again.

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http://www.netbsi-kc.com/integra/
http://www.netbsi-kc.com/aa/
http://www.groupbuycenter.com/

[SSBP]

Lundgren,
I realize you are smart but can you post it in lay mans terms?

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00 Naples Gold 3.2TL

[CROM]

I figured I would add on this.

Why get a 3" exhaust when the largest collector on any header is going to be 2 1/4". The DC collector is even smaller I believe. I think 2 1/4 is fine for our applications, 3" is overkill. Remember, the smallest part of the whole exhaust system is the weakest link and determines the flow of the entire system. So if you have a 12" exhaust, and a 2 1/4 inch collector at the header, you are still only going to be flowing as much as that header can flow. Many dont agree, but I have a lot of musclecar tuners who do.

[lundgren]

Basically, large pipe is good for FI motors to a point, even if it's only part of the way. More critical up front that in back.

[Zeus]

Thank you Lund...I was a mathmatical washout, but I knew what I ment...

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1998' 4dr GSR, 8psi JRSC w/hand ported plenum, Walbro HP fuel pump, valves set to .005i/.006e, MSD BTM, B&M CommandFlo regulator(working it out), stock intake w/resinator cut off at fenderwell for "cool air", Greddy sp exhaust, Tokico Illumina 5-ways, Neuspeed springs(sux!), Skunkworks 22mm rear swaybar, ES motor mounts and front swaybar bushings, Yokohama AVS 205/50/15's, Metal Master brake pads(KVR Carbon Fibre pads sitting on work bench) ,B&M fuel pressure gauge, Autometer sport comp A/F gauge in dimmer location...

YLW 00' ITR #00-1011 with AEM CAI and 143db triple air horns

Honest officer, I had no idea how fast I was going...the speedometer only gos to 150...

[This message has been edited by Zeus (edited July 01, 2000).]

[CROM]

Thanks GSR98, I love you to!!