My friends Mustang is getting repoed due to his cosigner filing bankruptcy so we cut the pair of Flowmaster 40's off of it the other night. This along with putting the stock air box on it made the car gain a TON of power. Those mufflers were seriously bottlnecking that car. He had dual 2.5 inlet 40 series on his car which're the higher flowing ones. This is just to verify what several members have said on here, Flowmasters are NOT very high flowing mufflers. I had tried before to talk him into running a set of flow through mufflers but that's a moot point now.

 

After working at an exaust shop I will try to stay away from flowmasters for all exaust builds since they flow like crap!

 

How did you verify that it "made the car gain a ton of power"?

 

loud=fast


dont you know that!!!!!!!!!

 

Exactly, track times or dyno numbers would be great. THAT would really let us know how "bad" they flow and give us some actual hard evidence.

 

And the "40" is 1 in a line of about 10 or so different mufflers...

 

I've been racing for years now and have a feel for what power is so don't patronize me and act like I'm an idiot. We had been running the snot out of the car all weekend and when we took the mufflers off low and behold it picked up bottom end torque and ran to the red line quicker. To top it off it will now rip tires going into second and chirp third consistantly. Oh but that must've been my ears deceiving me... because I'm some 16 year old tool. When you can NOTICE the car gained power by the butt dyno and see it in the tach and speedo, you're not fooling yourself into thinking the car is faster. The car gained ALOT of power throughout the power band. I guess i should've taken the car to the dyno and given you all scientific evidence instead of just verifying what alot of members already know about these mufflers, well even then people would probably come on here and argue that I was wrong.

 

Without solid numbers, it could be argued that this is a classic example of the placebo effect. You anticipated picking up significant horsepower going into the "expiriment" which heavily biases the outcome. A couple simple 0-60 runs could have provided some tangible evidence.

I've personally seen some pretty decent dyno numbers using a 3" flowmaster exhaust system, enough so that I'm fairly confident that there would be less than 10 Hp to be gained going to straight pipes.

 

^ Very true. I know someone with a 10 second fbody that runs dual 40 series. When he took them off and went to no mufflers, he gained NO mph in the 1/4 mile at all. So we all can say different things. I myself won't go around saying 40 series flow as well as having no mufflers, because everyone has their own experiences. Not to mention all the different 40 series out there.

 

We didn't take the mufflers off expecting a gain, we took them off because the car is unfortunately going back to the bank. It's a very basic 4.6, non PI heads, PI intake, and a CAI. The rest of the exhaust was dual 2 1/4 pipe ran to an X pipe and dual 2.5's out to the twin 40 series with dumps. The car gained power; if he was going to have it long enough I'de take it and see if it would run a better time, hell if I had a G tech I'de even use that but the car's going back Friday. I would say that it just changed the torque peak higher but the car revs faster throughout the RPM band. Maybe it's just this combo but I've heard on these boards more than once that Flowmasters don't flow that well, this seems to back that up; take it for what it's worth.