I keep reading that Flowmaster catbacks are "mistakes", "poor flowing", etc...due to their supposed poor performance on LS1 cars...IMHO, most everything else (except true duals) has a overly loud, raspy, sounding like you're going faster than you really are, effect...

Does anyone have any actual back to back hardcore muffler testing evidence of this? Whether it be dyno results or track results...anybody???

Reason I ask is that IMHO the Flowmaster sounds better than most every other single pipe into dual outlet muffler exhaust out there...How much "worse" (alledgedly) for performance is this setup?

Does anybody really know, or is it just hearsay/bandwagon opinion? I'm really curious about this because I have personally built/owned a 500+rwhp car that ran no differently with Flowmasters than it did with supposed much better "flowing" mufflers...

Can anyone elaborate with facts?

Not everyone wants loud and obnoxious, which is why I ask the question.

 

Yes there is Dyno Proof...

https://ls1tech.com/forums/generation-iii-external-engine/583067-dyno-tells-flowmasters-true-flow.html

 

in that thread though, that was a comparision from a muffler, to absolutely no muffler, wasnt the OP wanting facts between flowmaster and another muffler?

 

Alot of people have the flowmaster cat-back with a QTP exhaust cut-out activated by a wide open throttle switch...

I honestly love the flowmaster sound more then anything in the world and wouldnt trade it for nothing.

 

The flowmaster catback being a power robber is one of those internet legends that everyone spreads around with no proof.

One guy comes in claiming he gained 20+ rwhp through an open cutout.

Someone else then will come in saying "I used to believe that, until I dynoed with mine and only gained 2 rwhp through the open cutout."

I've seen it both ways. I've seen flowmaster provide horrible results backed up by a dyno, and I've seen it provide great results backed up by a dyno.

Then, because a few people gained a lot of rwhp through an open cutout, we have the legions of people spreading the idea that everything flowmaster makes flows poorly, even though that saying is ONLY limited to the 80 series catback, limited to f-bodys ONLY. You have people coming in saying "flowmaster = chokemaster" or "flowstopper" or something completely untrue.

In short, it doesn't matter what catback you buy. Buy your catback based on sound ONLY, then add a cutout. ANY catback can accommodate a cutout, so who cares how well it flows? Want to be stock quiet? Add an electric cutout and go from silent to wide open in seconds. Want to run a flowmaster? Add a cutout for when the performance is necessary. Catback flow is irrelevant.

 

It is dyno proven but if you like them get them its your car.

By the way, there are other mufflers that arent loud like bullets

 

but if you put a cut out on any muffler, won't you get better gains? isn't that why people run cut outs to begin with?

 

Manny Z28's dyno comprison was a B&B exaust vs. Flowmaster 80...not a cutout.

 

i run the 80 series flowmaster and i'm going to install a cutout to see what gains i get from that

 

The problem with most flowmasters' is they have 2 or 3 chambers, so instead of straight though exhaust it has to bounce back and forth, thus the loss of power over other cat backs. A single chamber flowmaster will flow just as good as the others because there is no bouncing back and forth. The reason it is so much quieter is for the same reason. Straight though catbacks have almost no restriction. If you want performance and no rasp get a straight through exhaust with a resonator.

Travis

 

I totaly agree
This is the reason I never went with the regular F-body catback I am running the Flowmaster Single On The Left [SOTL] set up that was offered on the LT1 cars. it uses a 2 chamber 3'' inlet/outlet muffler. This system is similar to Mufflexes SOTL sytem but obviously has smaller 3'' tubing. I'ts also proven fact that a single out system is more efficient than a muffler the turns the exhaust flow around 180 degrees.
I also Dynoed it last year on a Dynapack it made 300 RWHP. Mods are similar to MannyZ28's in the link above, but I had 109K miles and was still on the original clutch.

 

this ones been around for a while. even tho its on a Mustang, the results would still be typical IMO.

"This test was performed by 5.0 Mustang & Super Fords Magazine, December 2002 issue (page 55) on a '90 Mustang LX coupe with 370hp and 11 second potential. 66 pulls were made for this comparison:

Muffler Flow Testing

All tests via an independent lab
All tests @ 15” wc

2 “ Straight Pipe 283 CFM
2 ¼ “ Straight Pipe 365 CFM
2 ½ “ Straight Pipe 521 CFM

2 ¼” Typical Bent tailpipe 268 CFM
2 ½” Typical Bent Tailpipe 417 CFM

2 ¼” Inlet/Outlet_ Glass Pack Tips- No Louvers- Smooth 274 CFM
2 ¼” Inlet/Outlet- Glass Pack Tips-Louvered 133 CFM
Same as above set for reverse flow 141 CFM
2 ¼” Cherry Bomb 239 CFM
2 ½” Cherry Bomb 294 CFM

2 ½” Inlet/Outlet Dynomax Super Turbo 278 CFM
2 ½” Inlet/Outlet Ultraflow Bullet 512 CFM
2 ½” Inlet/Outlet Gibson Superflow 267 CFM
2 ½” Inlet/Outlet Flowmaster ( 2 Chamber) 249 CFM
2 ½” Inlet Outlet Flowmaster ( 3 Chamber) 229 CFM
2 ¼” Inlet/Outlet Thrush CVX 260 CFM
2 ½” Inlet/Outlet Maremount Cherry Bomb 298 CFM
2 ½” Inlet/Outlet Hooker Aero Chamber 324 CFM
2 ½” Inlet/Outlet Hooker Max Flow 521 CFM
2 ½” Inlet/Outlet Borla Turbo 373 CFM
2 1/2" Inlet/Outlet Magnaflow 284 CFM

Standard OEM 2 ¼” Inlet/Outlet 138-152 CFM
Standard OEM 2 ½” Inlet/Outlet 161-197 CFM


The results in HP order:
1.Flowtech Warlock (open) 374.2 hp/ 333.1 tq
2.Bassani Real Street 373.7 hp/ 333.8 tq
3.Hooker Maxflow 373.5 hp/ 333 tq
4.Borla XS 373.3 hp/ 332.6 tq
5.Magnaflow 372.8 / 332.5 tq
6.MAC 372.3 hp / 331.5 tq
7.Flowtech Afterburner 372.3 hp/ 330.1 tq
8.Hooker Aerochamber 372.1 hp/ 330.4 tq
9.Bassani 372 hp/ 333.5 tq
10.Spintech 371.6 hp/ 332.2 tq
11.Edelbrock Performer RPM 370.9 hp / 331.3 tq
12.Borla XR1 370 hp/ 334 tq
13.Flowtech Terminator 369.5 hp / 331.3 tq
14.Dynomax Ultra Flo 369.4 / 333.2 tq
15.Flowmaster 369.4 hp / 331.8 tq
16.Flowtech Warlock 366.3 hp / 325.3 tq
17.No muffs 365.2 hp / 330.1 tq

Sound Off in Quietest to Loudest (Decibels):
1.Borla XS, 80db at idle, 90db at 2,000 rpm, 110db at WOT.
2.Hooker Maxflow, 80db at idle, 90db at 2,000 rpm, 120db at WOT.
3.Magnaflow, 82db at idle, 91 at 2,000 rpm, 114db at WOT.
4.Flowmaster, 82db at idle, 93 at 2,000 rpm, 115db at WOT.
5.Flowtech Warlock, 83db at idle, 92 at 2,000 rpm, 112db at WOT.
6.Dynomax UltraFlo, 83db at idle, 94 at 2,000 rpm, 113db at WOT.
7.Borla XR1, 83db at idle, 96db at 2,000 rpm, 118db at WOT.
8.Bassani Street, 83db at idle, 96db at 2,000 rpm, 120db at WOT.
9.Edelbrock RPM, 84db at idle, 93db at 2,000 rpm, 118db at WOT.
10.Bassani Real Street, 84db at idle, 96db at 2,000 rpm, MAX. (120+db).
11.Flowtech Afterburner, 86db at idle, 94db at 2,000 rpm, 115db at WOT.
12.Flowtech Terminator, 86db at idle, 94db at 2,000 rpm, 119db at WOT.
13.Hooker Aerochamber, 87db at idle, 94db at 2,000 rpm, 114db at WOT.
14.SpinTech, 87db at idle, 97db at 2,000 rpm, 116db at WOT.
15.MAC, 87db at idle, 98db at 2,000 rpm, 119db at WOT.
16.No Muffler, 91db at idle, 103db at 2,000 rpm, MAX. (120+db)."

 

The American Thunder cat-back available for us has not only proven to be less flow efficient, but its not stainless steel. Just knowing that it will rust eventually should be enough to keep you away from it.

It sounds great, yes, but my Borla sounds pretty damn good if you ask me.

 

Lots of good answers guys...I appreciate it.

I have a Borla adjustable setup on my car, which is why I posted the question.

I wonder if anyone has cut the Borla muffler out of the Borla exhaust, and replaced it with something that still flows well, but isn't a gurgle-ey? That way the exhaust would still be stainless, but a bit quieter and much less annoying to my old ears...

The guy I got the setup from had an electric cutout on the right tailpipe and I had thought about doing the same thing if I kept this setup.

Any thoughts?

 

i doubt you would find guys chopping up the 800$ catbacks.. at least not me..

I had considered this exhaust setup on my 99 trans am...

Had loudmouth, got longtubes and ory, wanted to keep resonator and add flowmaster super 40s in each of the tailpipe sections 2 1/2 in. one in one out. about 6in. away from the tips.

 

I guess I shall be the first...lol.

 

wow for some reason the borla xr-1's dyoned with a little bit more torque than all other mufflers, cant wait to get my borla mouth installed

i have a flowmaster catback that came with my car and i hate it, looks like **** sounds like **** and its holding me back on a few extra ponies. Its for sale if anyone wants one.

 

GMmexican....how much are you asking?
Do you have a pic?

 

I have a Borla with a QTP cut out in the bypass pipe, I love it.

 

Electric one?

I am seriously thinking of doing that myself. I put in the block-off plate this afternoon and it isn't bad at all like that...then flip the switch on cut-out when you need/want to...

Is that what you do?