conversation w/ Dynomax about Sc's and they said..

j rick kirby

Registered User
that 2 1/4 downtubes,2 1/2 intermediate pipe and 2 1/4 tails is perfect even on a modified SC like mine.The intermediate cross section is less than the downs or tails and that's ok.Any larger mid pipe would likely cause a decrease in low/mid torque which is where our cars run best.A 3" mid pipe probably would give slightly higher hp at the extreme top end but at the expense of losing the bottom which is where an SC is designed to run anyhow.Heads and cam are not top end hardware.So anyhow,I'm sure this will really stir things up but this is what Dynomax said.
 
It will tend to lose some bottom end torque but you can't use all of it now. Why not lose some of what you aren't using to gain some of what you can?
 
No, you won't stir up much trouble. Most of the SC's are are making respectable HP numbers have large exhausts, either 3" midsection or 2.5" duals. However, one of the top HP SC's has (I believe) a 2.5" mid section Flowmaster system. He's making over 300rwhp.

I would say that exhaust is way over analyzed on these boards. Get something that flows ok and sounds decent and don't worry about it. I don't think it makes a hill of beans difference on a supercharged motor.
 
Well...that is nice Dynomax atleast has an opinion. I can say though that is basically what the "old" MN12 Performance exhaust system was and what I have on my 92. That car has a CMRE Stage 1.5 (Stage 1 heads on a Stage 2 short block), S Model with 10% OD, 75mm TB, Shortie headers (old SCCoA version), double IC, ZR Intake and I peg the boost guage at 2500 RPM due to the excessive back pressure at WOT.

My experience is the stated size is too small for what I have in the 92.
 
I think that what Dynomax said is basically the same thing spouted for any car with the same level of horsepower.

But with our car we have plenty of low end torque to burn (unless your hobby is using up a pair of rear tires in one evening of fun) and at HIGH rpm we have high boost. It helps to flow that exhaust. And while a 3" center section is a little large. It certainly is a nice standard size where 2.5" would just be too small.

Now of course, you are dealing with 2.25" down tubes. Well, yes, 2.5" center section with 2.25" down tubes should be o.k. It's when you get into the headers with 2.5" down tubes that the 3" center section makes a whole lot more sense.
 
Duffy, your MN12Performance exhaust is still holding together? Mine rotted off the car this past spring. The Dynomax's fell right apart, the pipes are rusting at the outside of every bend, and the resonator is developing a crack in the seam where the rear is attached to the body.

It's not very old either, 3 years or so. It was one of the last sets Rich sold, he stopped advertising the exhaust a week after I bought it. BIG waste of $1k if you ask me.
 
Andy,

The system seems to be holding up alright. I had the rear section off when I did the diff replacement last month. There is some rust on the pipes but so far so good. The previous owner of my 92 installed the system not me. I am saving for a replacement SS custome exhust now. Probably will go 2.5" to 3" to 2.5" as I have Georges old Borla 14" mufflers already. Perhaps Banzani custom resonator and high flow cats as well.
 
I had the Dynomax cat-back on my SC a few years ago ... I experienced the mufflers corroding away at the inlet pipe ... but that was after two Toronto winters. Sounded nice on the car, don't think it made any difference to the performance though.


cheers
Ed Nicholson
SCCoO
 
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