Instead of one large single exhaust tip on your muffler, how would dual small trea tips work, if you got the total area of the openings the same as the muffler's outlet? But from what Beandip says, smaller openings may be of an advantage.

Data:

2" muffler outlet = 12.6 sq. in. (pi x radius squared, pi = 3.14)

2 1/4" muffler outlet = 15.9 sq. in.

2 1/2" mufler outlet = 19.6 sq. in.

dual 1" tips = 6.3 sq. in.

dual 1 1/4" tips = 9.8 sq. in.

dual 1 1/2" tips = 14.1 sq. in.

As you can see, the dual 1 1/2 inch tips have about the same cross-sectional area as the 2 1/4 inch muffler outlet.

Either that or how about a Y feeding into dual glasspacks with single tips each? I've never seen glasspacks with small outlets like 1 or 1 1/4" diameter.

Either way, it must be correctly done- not riced!

What kind of crack are you smoking? Area = pi x radius squared.

Sorry, I don't smoke.

If the area is the same, so is the restriction - or lack there of. I can't see where this would have any noticeable effect at all.

I bumped the exhaust on my GTO replica from a single to a quad using similar logic-and to look right...

Will

You can get the 2 1/4" glasspacks easily, but the tips and the Y would be harder to locate. I think that if anything would effect the backpressure, it would be the resonance holes in the tips, or any baffles in the tips.

BTW, when I replaced the whole exhaust a couple years ago, the muffler guy tried a glasspack in for the 'pre-muffler' both normally and backward, and the sound was the same. He claimed it would still be quiet (glasspack on backward) and the flow would still go well. I have no problems with it or the sound.

  Arne said:

If the area is the same, so is the restriction - or lack there of. I can't see where this would have any noticeable effect at all.

The area is not the same. Simple proof: draw a 2" diameter circle. then draw two 1" diameter circles inside the 2" circle. See all that extra space? That's the area that you're losing running 2 smaller pipes.

My autoshop teacher drove this lesson home for me. He was telling us why the drain at the school was always backed up. They had 2 options when building the drain. One 24" pipe or three 8" pipes. Even after drawing the aforementioned picture on a chalkboard he was overruled and the end result is that the smaller pipes can't flow enough and it causes flooding just about every year.

Nothing like making your mind up and staying with it even when you have been proven wrong. I work for the City of Missoula. That type of stuff happens all the time. One word for that, ego. The unfortunenant side effect is the legacy that the ego leaves behind.

  jmortensen said:

The area is not the same. Simple proof: draw a 2" diameter circle. then draw two 1" diameter circles inside the 2" circle. See all that extra space? That's the area that you're losing running 2 smaller pipes.

Smaller pipes (or tips) yes, but if you notice from my initial post, two 1 1/2 inch pipes are about the same as one 2 1/4 pipe. I'm not sure if there are any effects ofthe gas going through that need you to adjust the dual pipes any, but since it's not liquid that's flowing, I'd just go with the mathematical equivalent on the areas. Beandip suggests that just a little backpressure will help the engine, so that means if need to err on the diameters, you can go slightly on the smaller side.

  TomoHawk said:

Smaller pipes (or tips) yes, but if you notice from my initial post, two 1 1/2 inch pipes are about the same as one 2 1/4 pipe. I'm not sure if there are any effects ofthe gas going through that need you to adjust the dual pipes any, but since it's not liquid that's flowing, I'd just go with the mathematical equivalent on the areas. Beandip suggests that just a little backpressure will help the engine, so that means if need to err on the diameters, you can go slightly on the smaller side.

Air/gases ARE modelled as fluids. Areas are only part of the system. Adding two pipes instead of one will also increase the perimeter of the pipes, thus creating more friction. But for tips of an exhaust, doesn't really matter that much...

I used this

1 pipe at 3" has approximately 7.01 Square inches of area

4 pipes at X have approximately 7.01 square inches of area

1 of the four will have approximately 1.75 square inches of area meaning the diameter will be approximately 1.5"

Will

More tubing = more weight = slower autoX times.

That's my reasoning.