In a different thread somebody mentioned about flowmaster 40's being restrictive!!!!.........Well having spent a bunch of money on a recent 2.5" exhaust with flowmaster 40's, I set out to disprove them.....Found a website that compared a bunch of high end exhaust and guess what????
some of the borlas and magnaflows got 1000+ scfm......flowmaster 40's with 2.5".......352 scfm???????...............that means that a pair won't get rid of the exhaust gases from a 750cfm fed motor at full throttle....................any comments??? sort of a bummer for me
They sure sound nice though

 

I've read that before too, but I'd like to see some before/after dyno or drag strip tests.
Heck if someone can prove to me that my flowmasters are costing me horsepower I'll change them out this week, but I just need some real world data.

 

I've heard the same thing, not sure how accurate the info was though. I'm planning on going to Dynomax ultraflow's, after I put the finishing touches on my 383 install, just to be sure. I'll be interested to see some more replies

 

What was the website?

 

The best way to compare Flowmasters to other mufflers is with a dyno on a running engine. The baffles are designed to use the sound pulse wave to pull the gasses thru it.

 

Hes right, I did my home work before purchasing a set of magnaflows, the info is out there on the net. And also the mustang magazine 5.0 had an excellent comparison on all performance mufflers, and dynomax, and magnas came out if not the first, pretty close. I am recalling this from memory, but I also was very surprise of the lack of performance from flowmaster. I guess people look for the sound more than performance. Go on the web sites, I'm pretty sure that you can find links to Articles from various magazines. Its a jungle, theres a lot of info, It took a lot of time for me to choose a good compromise for performance and price.

 

 

If they aren't loud they are restrictive, it is simple physics and they haven't figured out how to make a quiet muffler that also flows well, everything is a tradeoff, my MagnaFlows flow good and I know it because they will blast your eardrums at WOT.

There's the tradeoff, it is a little too loud for me after a quite a few years. I am going to install a 3 in. system and I have come up with something that works for me, I will go with quieter mufflers but I am installing electric cutouts for the times I want a little more performance ( and noise )

 

Well, the Flowmaster 40 IS loud, which should equate to less restrictive flow, BUT, louvered glasspacks are loud AND restrictive, too...

 

http://home.earthlink.net/~tmahon281/image.html

 

It's not like the information I read had the stamp of approval from the federal gov. or nothing....I assumed it to be somewhat accurate because of posting of flownumbers and that they didn't seem to "talk up" one muffler or the other.............in other words it "seemed" to be an independent test.......If anyone can offer any information to the contrary I would be glad to hear it.......I still like my super 40's, just supreised to read the info!!!!....

 

This isn't scientific at all but it is my experience....

I have a 502ci / 500 hp engine and when I bought the car, it had 2" exhaust on it. It would choke above 3000rpm at the drag strip. When I ran it just by unhooking the exhaust from the header and pulled it back 2-3 inches, it would really wake it up and BOY was it loud. I had 3" exhaust with an H pipe and Flowmaster 40's put on it and went back to the drag strip and had identical times with when I was running the headers only. Take it at face value, I ran the same times with Flowmaster 40's as I did with open headers.

 

As mentioned..it all depends.

I ran some 40's with 2.5" pipes on my 427 for a long time. At the track it made almost no difference whether it was capped or uncapped. They weren't huring anything at that HP level. It was making 423 RWHP and ran 11.20's@123 capped up.

After I installed the 540, I ran the same 2.5" pipes for a little while. it would pull decent of course, but I knew it HAD to be killing it. I later installed 3" pipes with 40's and it was slightly better, but nothing fantastic. Later, I was working out the tune on the chassis dyno and decided to uncap it and see what happened. It literally picked up over 50 RWHP!! That is incredible!

So it all depends on how much air you have flowing through them. You have to remember that a 383/406 at high rpm can move a lot of air too!

I'm running the 3" pipes with Dynomax Race Bullets now. A little loud, but it really isn't too bad. But it depends on whats in front of them too. When I had a slightly larger cam in it on a tighter LSA, it was a completely different sound and it was awful loud in the lower rpm "cam thumping" ranges. It's a lot different with a wider LSA now. Cams make a lot of difference on noise.

All that said, I believe the Ultraflows (the straight through ones) with the large case are the best compromise between sound and power. Borlas work great....but they get pretty noisy too. Ever heard a nasty C-5 with Borlas? Jeez..........



JIM

 

I read a test posted here year before last that had the same results....Flowmasters at the bottom. That's why I went with the Dynomax Race Bullets. They're loud but I know they aren't costing me any HP.

Brett

 

I had the same experiences as Jim with my 40 series 3" in my 69 with a 500 rwhp 454. The car went 11.54 at 124; all capped up on street tires.

 

I never said you can't have loud and restrictive, pretty much defeats any purpose of a muffler though, I guess Thrush comes to mind too

 

Good point about the dyno.That way you analyze the entire system related to your horsepower etc.

 

Electric cutouts huh? Cool idea... Are you thinking of having electric motors that open/close plates to divert exhaust to not flow through your mufflers?

 

You are correct sir !

 

OEM..................................... ........................................ ...225
Gibson SuperFlow 788200.................................. ............311
TTS Bullet Cat Converter............................... ..................324
Flowmaster 40 series 42540................................... .......352
Flowmaster 50 Series.................................. ...................362
Flowmaster 40 series 43040................................... .......392
Dynomax Super Turbo................................... .................410
Flowmaster 62631................................... .......................435
Carsound Cat Converter............................... ..................436
FLP Cat Converter............................... ............................440
Edelbrock Victor 5535.................................... ..................562
Flowmaster 40 series 435409.................................. ........576
Edelbrock RPM series 5511.................................... ..........579
Flowmaster Delta Force Racing 54040-10........................634
Edelbrock 304 series 5560.................................... ...........640
Edelbrock Gen App 5505.................................... ..............708
Dynomax Race Magnum Welded 17216...........................711
Borla XR-1 40600................................... ..........................836
Borla XR-1 40615................................... ..........................854
Dynomax UltraFlow SS 17263................................... .......1000
Dynomax Race Magnum Welded 17218...........................1000
Borla XR-1 40575................................... ..........................1100
Dynomax UltraFlow............................... ...........................1133
Edelbrock Victor 5537.................................... ..................1400
Borla XR-1 40450................................... ..........................1400
Borla XR-1 40741................................... ..........................1450
Dynomax UltraFlow SS 17296, 17268..............................2200
Dynomax Race Magnum Welded 17220, 17224...............2200
Dynomax Race Magnum Welded 17225...........................2600

The formula for required exhaust flow is: horsepower times 2.2. Pretty simple eh?

So if your car makes 400 hp, you will need a total of 880 cfm muffler capacity for an unrestrictive exhaust system. So for dual exhaust, you would need mufflers that flow 440 cfm.

For reference, a 2.5 inch diameter pipe flows ~500 cfm. Adding non-mandrel bends will lessen that amount.