Exhaust Tubing Diameter

Boxer 6 · 10-27-2005, 06:53 AM

I am seeking some "expert" advice on the proper diameter tubing for a custom exhaust system that I am having fabricated for me. Let me paint the picture accurately first. The car has a stock 1987 3.2 liter engine. I am planing on using MSDS 1 5/8 inch headers into two independent Raceflow muffs coming out side by side just under the license plate. What size tubing should I be using after the header collectors? Also, I was told that a "crossover" pipe is not necessary for these engines. I have attached a picture to show what I was thinking of. Thanks in advance!

Mark

mb911 · mb911's Garage

Muffler inlets are typically 2 inch but I suppose you could go as high as 2.5 but I don't believe you would see much low end torque with that

Boxer 6 · 10-27-2005, 11:36 AM

Thanks Ben! I was also told that I could lose some low end torque. I guess I should try to keep it to 2 inch.

Mark

randywebb · 10-27-2005, 12:11 PM

bigger means less clearance under the car; and 'larger' bends

so I'd try to figure out what the adv. would be to larger tubes -- you can use empirical data from dyno runs -- or try to calculate it from flow theory -- best is always a combination

JeremyD · JeremyD's Garage

I think for a stock car you will get as much from a set of SSI's and a sport muffler. Probably the best bang for the buck in a stock 3.2 is a steve wong chip and a euro premuffler. My impression is that unless you change the cam, you will not benefit from the better breathing of 1 5/8 headers.

That being said, and if you are hell bent on gettin a custom exhaust - I'd try and keep the collectors around 2"...

Steve@Rennsport · 10-27-2005, 02:20 PM

Quote:

Originally posted by Boxer 6
I am seeking some "expert" advice on the proper diameter tubing for a custom exhaust system that I am having fabricated for me. Let me paint the picture accurately first. The car has a stock 1987 3.2 liter engine. I am planing on using MSDS 1 5/8 inch headers into two independent Raceflow muffs coming out side by side just under the license plate. What size tubing should I be using after the header collectors? Also, I was told that a "crossover" pipe is not necessary for these engines. I have attached a picture to show what I was thinking of. Thanks in advance!

Mark

Just for the record, the pictured exhaust was designed & built here in our shop and the poster should denote the source,......

JeremyD · JeremyD's Garage

Nice looking pipes Steve!

randywebb · 10-27-2005, 08:45 PM

Well in that case, the answers are pretty easy.
1. the correct tubing size is whatever they tell you - just be sure to describe your intended use accurately.
2. If they tell you you don't need an Xover pipe, then you don't.

You are paying for a highly expert shop... I guess if you were having surgery you'd want a 2nd opinion even tho the 1st is an expert, but be sure the 2nd one is also expert if you are doing a X check or something... i.e. don't compare Steve or other - ah - Gamrother's (Gamrothians?) opinions to those of Joe Blow on the Internet.

Steve@Rennsport · 10-27-2005, 11:17 PM

Quote:

Originally posted by JeremyD
Nice looking pipes Steve!

LOL,....Thanks Jeremy,.....my wife says the very same things,...

Boxer 6 · 10-28-2005, 04:57 AM

Sorry Steve I apologize for not giving credit where credit is well deserved. I knew I got that picture from "someone" who does really nice work!

Steve. Do you mind sharing some of the details of this car and exhaust system. What diameter exhaust tubing did you use after the header collectors?

Thanks!

Mark

Steve@Rennsport · 10-28-2005, 09:08 AM

Quote:

Originally posted by Boxer 6
Sorry Steve I apologize for not giving credit where credit is well deserved. I knew I got that picture from "someone" who does really nice work!

Steve. Do you mind sharing some of the details of this car and exhaust system. What diameter exhaust tubing did you use after the header collectors?

Thanks!

Mark

Hi Mark:

Accepted,....

The pipes are 2.5" from the collectors to the mufflers. The crossover is 2". Headers are 1 5/8".

This car has a 290 HP 2.7 in it.

Bill Verburg · Bill Verburg's Garage

What Steve isn' t tellling you is that they used some nice smooth gentle transitions

The pipes are extensions of the collectors, you want to avoid sudden increases or decreases in the pipe size.

Superman · 10-28-2005, 12:53 PM

Mark, that exhaust system is more difficult to fab than most people would assume. Wouldn't you agree, Steve?

Oh and I'd bet that folks who have just been passed by that car will be able to hear it just fine.

Emission · Emission's Garage

That exhaust is beautiful.

Steve@Rennsport · 08:48 PM

Quote:

Originally posted by Superman
Mark, that exhaust system is more difficult to fab than most people would assume. Wouldn't you agree, Steve?

Oh and I'd bet that folks who have just been passed by that car will be able to hear it just fine.

LOL,....These were quite labor intensive to build, yes,....

Indeed, anyone being passed by a car so equipped couldn't miss it,..........

For me, this was THE best sounding exhaust I've ever heard and the performance benefits were more than satisfactory as it was designed & intended for racing, not street use.

randywebb · 10-28-2005, 07:17 PM

Gamrother's (Gamrothians?)

- Inquiring minds want to know....

Also, re-read Bill V's comment above -- here is your mnemonic:
"fluids don't like to turn corners"