Exhaust formula?

[Jolly Roger]

Does anyone have a good genaric formula for exhaust? Something simple? Or mabey even horse power and torque at a rpm range? Or mabey even somthing for volume and volosity?

Once opon a time i had a table that had ci, hp, tq, rpm, and it would give a pipe size to start with. That seamed pritty acurate.

Not tryin 2 start anouther war. Just thought if there was somithing easy to use most can get a decent ansewer on there own. However it is easyer to ask over and over again.

 

[Jolly Roger]

How about some of you experienced drag racers? Before every one had a pc with a desk top dyno. Or when dynos were hard to come by and high dollor at that. And you had to figure out every thing on paper if you wanted to know before the race with out just making that run down the street.

 

[Hahnsb2]

There's some basic guidelines for your "average" engine. 2-2.25" single for 4 cylinders. 2.5" single or dual 2" for V6s. And 3" single or dual 2.25-2.5" for V8s. You can find charts on the internet that have similar guidelines but that's what I stick to.

 

[BlueChariot]

I always like rules-of-thumb more than formulas. If you were building a 100K dollar machine for just track use, yeah I'd break out an abacus and work out exactly what was best for that engine, but in the real world the "rule of thumb" sizes will do just fine.

I would still be interested to see one of those charts you were talking about. It sounded very specific. I'm still an information whore at heart.

 

[Hahnsb2]

 

[Jolly Roger]

Thanks guys. I argee with rule of thumb too. Some times its just nice to glance at a chart or use a fourmula and know your doing whats best. It might clear up alot of repeted questions as well.

I dont remember who put together the chart i had. When i got it i was working at an automotive machine shop and some one left a few on the countor. I lent it to a buddy to make a copy and never seen it again.

My 2.3l is stock with a turbo muffler and needs new pipes anyway. I want to go 2.25" cat back with a turbo muffler for a little more top end. I was gona go with 2.5" but cant afford to loose the low end i dont have mutch of. Looks like 2.5" is just to big anyway.