ajenks144

Hey Everyone,

I have an F class 911(3.2 Carrera) that I currently run with B&B headers and no exhaust. Obviously the car is very loud. I wanted to get opinions on putting on an exhaust. Here are my questions:

Am I better off (performance wise) staying with an open exhaust?

Could the correct exhaust help low end torque by adding some back pressure?

If I choose to put on an exhaust, any recommendations on a brand that won't hurt performance or my wallet?

Thanks.

Tom W

If you call Rich at Jerry Woods, I think he'll be easily able to answer your questions. They are very familiar with tuning 911 engines and Rich races one (I think it's a 3.2, but it may be a 3.0).

My guesses at your questions: no, yes, Jerry Woods likes Phase 9 mufflers. Not a lot of "muffle" or weight, not pricey, but they accomplish the task.

earlyapex

Engines like some back pressure. You should be running at least a pair of racing pipes. Phase 9's are nice.

MJR911

Your car gains a SLIGHT bit on the top end with open pipes. I'd stick with what you have if you trailer the car and don't go to Lime Rock. Where do you live? The shop I use, Performance Automotive in Malvern, Pa once took apart one of the very pricey Fabspeed kits and figured out its nothing more than the flowmaster camero can with a few flanges. A lot cheaper and as effective as anything.

zffnhsn

OK. Here's my story.

I was running headers and straight pipes on my 3.4 MFI. It was so loud in the car I couldn't think. Most of the tracks I've been to have noise regulations. I'd never been busted but I'm sure the car was way over the desired decibel limit. I had a local guy mount a Flowmaster FLO-42583 dual 2 1/2 inlet-outlet muffler up under the bumper. (http://www.summitracing.com). He fitted pipes from the headers to the inlets as well as a 2 inch cross over pipe ahead of the muffler. I was pleased to discover the car is not only reasonably quiet but markedly more powerful, especially at mid to high rpms. I think the entire job cost less than $600. Let me know if you want a picture.

Peter H

944CS

the reason why the cars are more powerful WITH exhausts is because the engine tuning and camshafts are picked with the intention that the car will be running cat and muffler(USA) or two mufflers (ROW), which equates to backpressure in the exhaust. When you run straight pipes and stock or mild chip, the car is still going to run lean under full throttle because you are letting the exhaust escpape and allowing more fresh air to come into the cylinder, however due to the tuning you are not adding any fuel (full throttle has it's own fuel and ignition curves, ignoring the oxygen sensor) and the engine runs lean, reducing power. If you have a camshaft running more overlap, and tune the engine for the decrease in backpressure, then you can see significant gains running straight pipes.
turbocharged cars, or cars that are not kept in good shape, tend to gain a lot from cat removal because of a significant blockage in the catalyst itself, not to mention in an ideal world turbocharged cars would like the least amount of pressure possible.

ajenks144

Thanks everyone for the help! I think what I will try and do is get my hands on a set of Phase 9's and maybe a Flowmaster as well and head to the Dyno. A year or so ago I put the car on the Dyno with and without my B&B exhaust. The car had 12 more hp at the top end without the B&B exhaust can. I don't recall how the rest of the hp or torque curves were effected.

38D

I'd give up some top end for more area under the curve. You should look at the charts closely.

earlyapex

"Torque wins races. Horsepower sells cars."

Your exhaust and engine tuning should be dictated by what works best at the tracks that you are racing. Everything else being equal, I would opt for the combination that gets you off the corners with more speed.