Just curious, has anyone ever swapped mufflers and picked up E.T.? If so how much, what mufflers, what size exhaust and whats your approximate horsepower? I've seen dyno claims that say there is power to be gained by getting rid of my Flowmasters but I'm not sure I buy it, at least in my application. Thoughts?

i have the same questions

I saw .84 ET and 8.5 MPH differences between a set of the old 2.5 inch in and out turbo muffs with a very short(less than 36 inches) set of 2.5 inch exhaust pipes when compared to removing them to run open headers I put a set of Dynomax Bullet 14x 3.5 race mufflers on the car later that same day after getting beat in the brackets and it slowed down right at .12 ET and 1.2 MPH My last street and strip car with a three inch system with a set of 14x7 oval x 3 inch in and out Magnaflows changed .04 ET and .2 MPH in the eight mile removing the complete exhaust system The muffs on that car where mounted behind the rear end at the rear bumper so the weight may have been the basic difference for the change and maybe not the back pressure Flow masters are not the best muffs out there

I think it really depends on the motor. For example, my car runs almost the same with or without the exhaust...just a couple hundredths slower with the exhaust on, and that it probably due to the added weight (about 25 lbs or so). My exhaust exits just before the rear tire, and I pull it off the car from time to time, not much different in ET, just louder....my exhaust consists of 3" flowmasters with 3" pipes.

Try measuring back pressure, or drop the exhaust and make a pass, see if it picks up. Every car will want something a little different.

Dropping the dual 3" w/ 2 chamber flows gained 0.1 sec on my Belv, running mid 11's

The car in the article above is now in the low 11's, with the same exhaust as when this article was written.

There are so many variables on this. You won't know what your combo likes until you try a thing or two. Certainly the more flow out of the engine, the more critical the exhaust becomes.

Personally, I run electric cut-outs on all my cars. That way, I can have my quiet and my noise with no compromise on performance. And they are a blast at shows and cruises.

I've posted it before, but on my IHRA Stocker with a 360, I picked up at least .05 going from open TTI headers with collectors to their 3" X-pipe ending with Dynomax UltraFlo mufflers at the rear end housing. I'm convinced that the X-pipe helped and the mufflers didn't hurt! Your results may vary and may require minor jetting changes for optimim results.

My sons mid 11 Dart picks up 2 tenths when he spaces the headers with washers over the Flow Masters. As for my car I run the 3" TTI x-pipe out to the rear bumper and I use Ultra-Flow muffles. I dont know if it makes any difference as I run through the pipes and have never uncapped it. But I dont think it would pick up much if I uncap it. Ron

I run a 3" exhaust that reduces to 2.5" after the mufflers and out the back. I took off flowmasters and replaced them with magnaflows and picked up 1-2mph right off. It also shined some light on some fuel delivery problems I was having as it went waayyy rich when i swapped the mufflers. I have since taken some fuel out and still need to take more and the car has picked up considerably. It was obviously constipated with the flowmasters on there.

This is on a 450-500HP 360. The car is also a lot quieter and it sounds better IMO.

i have a demon with a 440 . i run pro parts headers an H pipe and 3" flows dumped at the axle. my car has tons of torque and bottom end . i droped the exaust and jetted up 4 sizes went to the track didnt get to make any changes but the car lost all bottom end it was very lazy . im going to run exaust next time i go but the car felt slower to me maybe i jetted up to much i dont know?

Like said before, there's a lot of variables. There's no question a straight through style muffler flows better than a flowmaster, but will making the switch make your car run faster? Maybe, maybe not.

One of my old 440s w/ a 509 cam and ported 915s ran 11.40s at 117 mph in my cuda through 3" exhaust and 2 chamber flowmasters. It ran no better w/ open headers...and yes I tried to tune for the difference.
My last 440 ran 10.40 at 129 mph through 4" exhaust w/ 2 chamber flowmasters. Open headers made no difference. I don't think it would have needed a 4" system if I had better flowing mufflers to run that. I just happen to like the sound of Flowmasters.

Having said that, I have seen guys change from flowmasters to a straight through style muffler (Dynomax Ultraflow, Magnaflow, or Hooker Max Flow) and have the car run faster.

My current hemi combo loses a little over a tenth and about 1.5-2 mph (compared to open headers) when I run it w/ the 4" H pipe system w/ a pair of one chamber flowmasters....but the system is heavy and hemis hate mufflers (generally).

My demon has TTI headers and a 3" x pipe and mufflers at the rear axle, switched from a 2 chamber Flow Master to Dynomax ultra flows same day at the track, probably an hour apart. no noticable difference in et or MPH, it's quieter with the ultraflows though.

Like said above, lots of varibles.

When I was back in the lab we tested multiple style
and manufactures of muffs... we did it on the dyno
for a comparison.. we took a few extra readings besides
the HP.. we took back pressure, DB, and did a cost..
this was about 10 years ago... back then we were trying
to get more power, quieter exhaust and low weight
along with cost savings.... dont ask what the numbers
were.. I dont recall... they were just numbers to
me that had to be compiled to submit... all I remembered
was the flowmax was on the bottom of the list for
multiple reasons and HP was one

my 605 hemi was almost a tenth faster through the muffs. 4 inch straight pipes into borla XR1, turned down in front of rear ladder bar crossmember.

my dragster picked up .05 when changing from 2" upswept to 2" downswept with Borla collector muffler.

bob_spelic