SC muffler: 2 pipes or not 2 pipes? That is....

s2per · s2per's Garage

Sorry about the pseudo-Shakespeare. As my SC becomes more of a track car, I trying to decide if I should add a second 3" outlet to my muffler. Florida has no exhaust checks and I already have '74 heat exchangers with an early 2 in/1 out muffler, which I've changed to a 3" pipe.

I'm thinking of adding the second outlet for lower restriction, but still keeping it street legal. I know I'll have more noise (or is that music?), but will I appreciate any increase in power? BTW, no worries about cutting the rear valance, since it's already in storage.

Thanks and Happy New Year.

avi8torny · 01-02-2003, 07:29 AM

I can't imagine that it will give you anything but more noise.

masraum · 01-02-2003, 07:30 AM

Well, I don't know if it would help, but I can tell you that if the volume of air that is passed has anything to do with the size of the pipe then your one three inch pipe is already passing more volume than 2 2 inch pipes. Some of the guys who know more about flow should be able to tell us definitively, but I would think you should have low restriction covered at this point.

AirCooledExcellence · AirCooledExcellence's Garage

I'm thinking of doing this as well, purely for looks/noise, has anyone done this before? any tips?

Cheers,

Tim.

rdane · rdane's Garage

The gentleman at SSI says less back pressure won't do a thing but add noise from all the results they have over the years. Don't really care about the noise within reason, but cutting up the car I did care about and the added time/expense. I went with a single outlet Monte and am happy with the results on my SC.

dd74 · 01-02-2003, 11:20 AM

During the SoCal/TRE/New Year's run in Malibu Wednesday, I talked to a guy who has a dual-out exhaust on his car. He bought it only for track use, and at that, not for a power increase, but more for a noise increase so that he could hear his shift points via the exhaust pipe noise. Hence, when racing, he was surrounded by so many 911s with megaphones, he couldn't hear his own engine to find the correct powerband. So he went with a twin pipe outlet.

As for power, a dual-out system realizes "incremental at best" power (maybe 2hp) which comes only at the topmost edge of the powerband. If at all, as I've heard it, a driver won't even feel the increase. The other more important advantage to the dual-outs is allowing the RPMs to drop less than with a single out. In short, RPMs on a dual-out drop about 200 RPMs (read "not 2,000 RPMS) less than with a single out.

So it seems aside from noise increase, the pipes don't give a huge hp advantage. One interesting note, however, is their bang for buck value (depending on the model of exhaust you choose) is very good. I've seem some dual-outs going for a reasonable amount of money. Plus, they're great looking to boot!

autobonrun · autobonrun's Garage

When I changed from stock to dual in/dual out, I performed some noise measurements using a meter. The big difference is that the noise level doesn't drop off as quickly with the dual outs as you get further from the car. Notice the difference in noise levels at 3' and 10' in this thread I posted earlier:

Performance Test done - SSI vs Stock SC

79SC

dean · 01-02-2003, 03:35 PM

I added a second outlet to my SC muffler. It added a little more noise at idle. I liked it and would do it again.

masraum · 01-02-2003, 03:59 PM

The secret is to just get rid of the muffler!

That's what I did, the cat does enough muffling for me.

s2per · s2per's Garage

Thanks for the input, guys! I really liked autobonrun's link with the db meter readings.

With my record of 4 stops and 2 tickets last year (ouch!), I really shouldn't draw any more attention to myself, especially when gearing around. I think I'll probably leave it with the one big outlet.