What is the most common exhaust pipe diameter on enthusiasts cars?

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Kevin Jonker

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Is 2.5" the most common for V8's? What does a 4cyl/6cyl use these days? The reason I ask, is I have a patent pending exhaust modification and need to make sure I choose the most desirable/common diameter to start out with for tooling purposes and sales. then if it is deemed popular/profitable, then I can go on to other diameters to meet all needs.
 
For me, at least, the pipe size is HP dependent.
 
It's normally done for them without thought due to a few reasons like;

Advice
Copy cat
Kit form

If you wanted to get some insight to this "Properly size exhaust pipe" question, visit the exhaust companies web sites. Stick with the main stream companies. Reason being is some smaller companies that specialize in race systems only have a different way of looking at things and for a good reason.
 
I would guess 2.5" is very widely used.
 
On some early A bodies, you would be hard pressed to even get 2.5" pipes through the tight confines of the inners, torsion bars, crossmember, 90 degree oil filter adapter, power steering ladened path to the back!! So, it all depends on which model you're making up the pipes for IMO! Geof
 
I guess my thought is not to get scientific, just what does everyone think the most common size used is. I probably should just start a poll. If there isn't one already.
 
On my 273 commando, I used 2-inch all the way to the rear bumper, with the correct bends and angle cut at the tailpipe. I can't see me ever going over 2.5" because I don't think I'm realistically ever going to push that much out.

I'm "keeping it real". :D
 
Dual 2.5" here on my 5.9L mag motor. I'm aware 2" would have been fine, but I like the look and the sound :)
Summit / Jeggs offer full sets in 2.5" and 3"

Get that patent and post up some info!!!!
Let's hope it's not like the infamous "Power Pipe" for the slants :lol:
 
So if I were to design a new style exhaust cutout, 2.5" would probably be the first tooling, since it could cover the most applications. You could expand a smaller diameter pipe to 2.5" and then back down, without much if any loss to flow or pressure and a 2.75" or 3" could be necked down to 2.5" and brought back out to orig. diameter to the muffler(s)if the design worked well and proved to flow well. Thoughts?
 
I would say 2 1/2" intermediate pipes and 2 1/4 tail pipes are quite common. tmm
 
2.5 way common,on mild hot rod stuff,with good mufflers.2.0"/2 1/4" for the milder set. The bigger h.p. stuff(2.5",and bigger ) ,might prefer mandrel bends. For me personally,2.5" to about 425-450 h.p,3 " after that.
 
Kevin Jonker said:
Is 2.5" the most common for V8's? What does a 4cyl/6cyl use these days? The reason I ask, is I have a patent pending exhaust modification and need to make sure I choose the most desirable/common diameter to start out with for tooling purposes and sales. then if it is deemed popular/profitable, then I can go on to other diameters to meet all needs.
Click to expand...

duece and a quarter for v8
 
toolmanmike said:
I would say 2 1/2" intermediate pipes and 2 1/4 tail pipes are quite common. tmm
Click to expand...

Why anybody would design a system like this is beyond me. IMO, not that I know a whole lot, but, it seems stupid. But COMMON?!?!?!?!
LMAOROF !!!!!
Common like a long tail cat enjoying getting his tail stomped In a room full of kids in a rock the rocking chair contest! R U kidding me? Common? Really?
I've never seen that before.

Kevin Jonker said:
So if I were to design a new style exhaust cutout, 2.5" would probably be the first tooling, since it could cover the most applications. You could expand a smaller diameter pipe to 2.5" and then back down, without much if any loss to flow or pressure and a 2.75" or 3" could be necked down to 2.5" and brought back out to orig. diameter to the muffler(s)if the design worked well and proved to flow well. Thoughts?
Click to expand...

Crazy IMO, that's my thought.
 
Here is a little something I copied from "Flowmaster's" web site on exhaust sizing. They will straight up tell you that this chart is not a "Set in stone" listing but a guide line to (what is) probably the best set up for most applications. Of course a car/engine designed for racing only may very well be different. Things like the rules on the engine can change the exhaust requirements for the car and/or the type of racing going on.

Most street vehicles will fall under this chart.

Tubing Size ...... Dual Exhaust ... Single Exhaust
2.00” ............. up to 200 HP ...... up to 100 HP
2.25” ............. up to 325 HP ...... up to 160 HP
2.50” ............. up to 500 HP ....... up to 250 HP
3.00” ............. up to 600 HP ....... up to 300 HP

Alter from this guide lines at your own risk of less performance or mileage or both.
 
The way I understand the original question had zero to do with what size to use with what HP level, but simply what people used the MOST of.

Oh and the factory quite regularly used a smaller size tailpipe on HP cars with dual exhaust. It actually boosts bottom end torque.
 
I read it,as some one,trying to start a business That's how,I read it.
 
My main point to the question was to make sure I was thinking correctly that 2.5" exhaust was probably the most common size coming off headers/manifolds on V8's. It got a little off track, so I gave the reason why I asked for opinions. With tooling costs so high. decisions need to be right the first time. Thanks for the input!
 
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