Resonator / Exhaust Flow - Pipe Size

[Slip_Angle]

I'm getting my midpipe done on Monday and am pondering what to do... I've been reading about exhaust flow and the importance of it's design and wonder if a combo setup would work well.

Here are some options.

1. A 2.25" midpipe tapered down to a 2.0" closer to the muffler. I don't think this would work that well because the flow would slow down only to hit a smaller diameter pipe near the muffler.

2. A 2.0" midpipe tapered up to a 2.25" closer to the muffler.. This may make more sense as the flow waves would keep moving better in the smaller diameter pipe, then it would hit the 2.25" and dissipate quickly through the muffler..

See this thread for more information: http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

...hmmm what to do...

Feedback appreciated!

[Slip_Angle]

bump

[TrippZ]

are you really gonna pay for tapering just for a few (if that) more horsepower? I'd say just get a 2.25 man and save the trouble :-P

[chunky]

well, I'm having a custom exhaust made with variable pipe diameters. I'll let you know how it goes.

[Slip_Angle]

TrippZ: Good point, however my neighbour owns an exhaust business, so it's not going to cost me much :)

It's really just curiosity that's got me thinking about it.. Why not try something different if there's no additional cost..

...

[Slip_Angle]

Ok so, if I went with option #2 --> A 2.0" midpipe tapered up to a 2.25" closer to the muffler.. (This may make more sense as the flow waves would keep moving better in the smaller diameter pipe, then it would hit the 2.25" and dissipate quickly through the muffler..)

Where should I start the 2.25 inch section of pipe?

Am I wasting my time here? People? Hello? Man, if I suddenly find 15WHP on this experiment, I'm not telling anyone!!!

[chunky]

Originally posted by CDN-SiR-02
Ok so, if I went with option #2 --> A 2.0" midpipe tapered up to a 2.25" closer to the muffler.. (This may make more sense as the flow waves would keep moving better in the smaller diameter pipe, then it would hit the 2.25" and dissipate quickly through the muffler..)

Where should I start the 2.25 inch section of pipe?

Am I wasting my time here? People? Hello? Man, if I suddenly find 15WHP on this experiment, I'm not telling anyone!!!

well, I'll give you the following advice

pipe diameter heavily influences exhaust gas velocity. If a certain pipe diameter yields a particular exhaust velocity, increasing the pipe diameter will decrease the exhaust velocity. Decreasing the pipe diameter will increase the exhaust velocity. However, if you increase the exhaust volume, then you can increase exhaust pipe size w/o adversely affecting exhaust gas velocity.

as for changing pipe diameter at various points in the exhaust path - the common logic is to keep the pipe diameter the same, or make it slightly larger as it vents to atmosphere. The smoother the transition from high pressure to atmospheric pressure, the better the exhaust will perform.

[Slip_Angle]

Chunky: Thanks for the advise! Since my only other engine mod is a SRI, I think I'm going to go with a 2.0" crush bend and remove the resonator. I know most people haven't done this but considering the stock midpipe is mostly 1.66" crush bend, tapering down to 1.5" in places, I think the increase to 2.0" will be good. It should hold the torque and possibly gain in mid range HP..

What about the resonator? Some posts say it is a bottle neck and other say it is not.. can you answer that Chunky?

Thanks again.