muffler flow comparison data

[Budnicks]

...have you ever flow tested any of the exhaust systems or mufflers on an actual flow bench ??

After reading the posts on moparts, that's exactly how the chart in the first post was compiled. This guy Tom Hand took a whole bunch of different exhausts and blew air through them flowbench style, comparing them to straight pipe. The sound measurements are from attaching them to his wagon.

I'm not saying that the Dynomax isn't the best muffler or not, I personally don't know for a fact... I guess I'm just in denial...LOL... It sounds like a decent comparison, I don't know that guy from anywere though, I too read the posts at the other forum, I don't care for that forum much either... I just see some stuff I personally don't 100% agree with, not that it isn't true either... That isn't what I'm saying at all... I was around a bunch of the guys first using/testing the Flowamsters many years ago late 70's at Sacramento, Fremont & Sears Point raceways {were they originated from} along with many in the winged sprint car series, out in Calif., when nobody was making performance mufflers except Super Traps & they were highly suspect, the loudness & droning effect of the mufflers {Santa Rosa Based company Flowmasters} was the biggest complaint that most people had, but the increase in performance was "hands down, much better" than anything that was available at the time... I have never experienced the supposed big power losses or droning in my personal use, except on big tube headers, big inch motors & large pipes, dumping at the axles, which I completely expected... I also have seen "in person" non-biased comparisons, side by side on many of the mufflers vs open headers on a friends flow bench at his shop in Sacramento, the Flowmasters outflowed all of them at the time, maybe the past few years there has been BIG improvement in a couple of brands, for sure 1 being Dynomax... But also some are making some kind of unrealistic claims, that I never saw in our private tests, with several different size & lengths of pipes 2.5"-3.5" with the bench at a constant 28" of flow {if I remember correctly} threw a 9" tube {I think it was} going to the head to simulate an intake, both  fully professionally ported & Non-ported Brand X BBC Brodix head bolted to a custom set of my headers from one of my personal Brand X race car, stepped 2" & 2-1/4" 34" custom tuned headers 3.5" 4-2-1 collectors, we/he used a air flow meter from an EFI set-up & a computer to measure flow differences "after the mufflers" & after the H-pipe, {a bunch of stuff I knew nothing about & can't completely explane}, but we actually saw a scavenging effect with the 3" Flowmasters Delta Flow Racing Mufflers, that we didn't see with any of the others, straight threw or not, {but any type of straight threw exhaust can logically flow better to a certain point}... We also saw a drop in flow the farther back the mufflers were mounted away fromthe collectors after like 20"'s or so {I think it was}, I was doing this for a reason, I was was going to Super Chevy Race in Phoenix were we wanted to be the fastest street car, with license plate, street tires & mufflers, 8.98et @ 156 mph, 2790lb full Chassis 67 Camaro 468ci BBC Brodix Head, full roller, PG, 4.56:1 9" Ford rear etc. & crappy MT 18"x33" Pro-sportmans {no Drag Radials allowed at the time}, we left with the trophy & a pretty messed up race car too {that's a different story for a different time}... I don't think anyone is lying or anything like that at all, but I have seen some different results, grant you they are old & antiquated by now... Opinions may vary & I'm sure they will... Especially you guy knowing I also have raced the Brand X stuff, in my past...LOL... SORRY FOR WRITING A BOOK

[c00nhunterjoe]

Freeflow of the muffler IS important. I cannot argue that. But there is much, much more to exhaust then slapping a set of mufflers on your car when it comes to horsepower. There are tons of articles available online that you can read about properly setting up your exhaust. Tuning the resonance, harnessing the exhaust pulses. Style, type and placement of mufflers with pipe and header combos all has to be taken into account.

Buying and installing exhaust on your car is exactly like buying and tuning a carb for your engine- out of the box may run. But change the jets, accelerator pump, squirters, cams.etc...etc. and th same carb will make lots more power.

[Dave Cleveland]

Several years ago there was a member here trying to make his car go faster. He had a 493 with E-heads, 2in TTI headers using 4ft of straight 3in pipe into a set of Flowmasters....pretty much the most unrestrictive extension pipe arrangement possible. I remember sending him a message to try dropping the exhaust on his next track day.

Low and behold, he drops the pipes/mufflers and picks up 7 tenths and 6 mph....the car went from high 11.60's (11.68) to low 11's (11.04) and picked up a bunch of speed at the big end.   In case you were wondering....the ex pipes were 3in to 3in Flowmasters with dumps at the rear axle. No compression bends, tailpipes or anything that would hinder exhaust gases. It was all in the mufflers.  

Flowmaster is the only muffler company that I have NOT seen argue flow charts to sell their product.

There's a reason for that....if you had a poorly flowing design, the last thing you would want to do is compare it with something superior.   Flowmasters are marketed on their sound which is unique and mostly annoying to some. Granted, on some builds that aren't making enough power the use of a restrictive muffler won't hurt performance but on high HP stuff those mufflers will slow your car down....that is a given.  


Ron

Don't take this wrong please... I'm not going to say there aren't better mufflers than Flowmasters, there probably are... I don't doubt your ability at all either, You seem to give great advice to many people, have you ever flow tested any of the exhaust systems or mufflers on an actual flow bench ??, but Were the guys muffler installed backwards or something ??, was the carb way too fat with the exhaust on it ??, was it properly tuned ??, did uncapping it just make it run LEAN & mean ??, was that the only change from the exhaust to uncapping in the tune ??, also there is a weight difference between the exhaust & no exhaust, but it wouldn't make anywere near that big of a difference... That seems like "way too much difference too me" on a properly tuned combo, even with Flowmasters & full exhaust... I have run 9.77et @ 135mph w/479-w/6bbl & 8.81et @ 152mph same car & bottom end & exhaust system, bigger roller camshaft, better {lighter} Ported Aluminum heads {50+ lbs weight savings off the front end}, 500rpm higher stall speed converter 4300rpm, 1050cfm trick Dominator, capped up full exhaust out the rear & when running threw 3" Flowmaster's old 50 Delta Flow Race series w/mandrel tubing on a prepped track, fully prepped 3520lb plus the 250lbs for me, in my old 68 RR about 3-1/2 or so years ago now, uncapped exhaust removed & installed 20"x 3.5" header extensions same 479ci w/1050cfm Dominator combo 8.58et @ 156mph Sacramento Raceway 95*-100*+ day on 315 Drag Radials, CalTracs, 3.73:1 gears, corrected altitude of 1200-1500ft depending on the day, all runs were made on all the above 8.81et & 8.58et combos with a Top Gun System 300hp total N20 activated at the 60' mark 100hp, then 200hp at 330ft then progressing to the full 300hp at 660ft, only difference was the 90-100+lbs removed exhaust weight & header extensions... Is that enough HP, N20 or not, that isn't a real HP killer too me 8.81 capped to 8.58 open & only the loss of 0.23 sec.s & 4mph... Explain that one....  I know others that have had similar results... Results may vary... That is the "long winded point" I'm trying to make... Sorry for such a long post

It's resurection day. Lets clear something up for those who do searches for this kind of info and hope they read this far. After taking off the full length ehaust he did not mention re-tuning carb.  With headder extensions only it's going to change the a/f ratio at different RPM's. Did he have an a/f gauge and wide band he was looking at for differences on the 2 runs? I have one. And changing exhaust that dramatically WILL harm performance if it is designed to max performance WITH the exhaust.  Dial that a/f ratio back in through out the range and see what happens. And do the tests on a dyno where conditions are 100% the same each run. 
To answer his questions, yes the mufflers have been flow tested.  Flow testing don't account for scavenging. But you can make the pipes scavenge just as much as the muffler. A proper X pipe can have great scavenging effects. Why have a giant flow muffler? Because you want the muffler to be invisible to the motor. All the flow should be governed by the headder extention and X pipe, after that the exhaust needs to flow as much or more then the prior. So making it big, or extra big ensures that. Bends need to be made with pipe at least 1/4 inch larger then the straight pipe size to maintain the same CFM, even mandrel bends too. 2.5 inch pipe flows 521 cfm.  most mufflers even flow masters flow less the 400cfm with there 2.5 inch mufflers, while some get to 400 cfm, only a couple straight through, no s curve, mufflers actually flow over 500 cfm with there 2.5 inch muffler. Hooker max flow, and thrush glass pack.  CHerry bombs, glass packs with louvers suck, borls fairs ok high 300"s flow, magna flow 385 sux I had those.  If you want a muffler that flows the same as the pipe that feeds it your options are very limited. So if you go 1-2 sized bigger you can get more choices that meet your flow needs. just buy 3 or 3.5" mufflers for your 2.5" system.  All the info I have stated can be searched and found...

[BSB67]

Several years ago there was a member here trying to make his car go faster. He had a 493 with E-heads, 2in TTI headers using 4ft of straight 3in pipe into a set of Flowmasters....pretty much the most unrestrictive extension pipe arrangement possible. I remember sending him a message to try dropping the exhaust on his next track day.

Low and behold, he drops the pipes/mufflers and picks up 7 tenths and 6 mph....the car went from high 11.60's (11.68) to low 11's (11.04) and picked up a bunch of speed at the big end.   In case you were wondering....the ex pipes were 3in to 3in Flowmasters with dumps at the rear axle. No compression bends, tailpipes or anything that would hinder exhaust gases. It was all in the mufflers.  

Flowmaster is the only muffler company that I have NOT seen argue flow charts to sell their product.

There's a reason for that....if you had a poorly flowing design, the last thing you would want to do is compare it with something superior.   Flowmasters are marketed on their sound which is unique and mostly annoying to some. Granted, on some builds that aren't making enough power the use of a restrictive muffler won't hurt performance but on high HP stuff those mufflers will slow your car down....that is a given.  


Ron

Don't take this wrong please... I'm not going to say there aren't better mufflers than Flowmasters, there probably are... I don't doubt your ability at all either, You seem to give great advice to many people, have you ever flow tested any of the exhaust systems or mufflers on an actual flow bench ??, but Were the guys muffler installed backwards or something ??, was the carb way too fat with the exhaust on it ??, was it properly tuned ??, did uncapping it just make it run LEAN & mean ??, was that the only change from the exhaust to uncapping in the tune ??, also there is a weight difference between the exhaust & no exhaust, but it wouldn't make anywere near that big of a difference... That seems like "way too much difference too me" on a properly tuned combo, even with Flowmasters & full exhaust... I have run 9.77et @ 135mph w/479-w/6bbl & 8.81et @ 152mph same car & bottom end & exhaust system, bigger roller camshaft, better {lighter} Ported Aluminum heads {50+ lbs weight savings off the front end}, 500rpm higher stall speed converter 4300rpm, 1050cfm trick Dominator, capped up full exhaust out the rear & when running threw 3" Flowmaster's old 50 Delta Flow Race series w/mandrel tubing on a prepped track, fully prepped 3520lb plus the 250lbs for me, in my old 68 RR about 3-1/2 or so years ago now, uncapped exhaust removed & installed 20"x 3.5" header extensions same 479ci w/1050cfm Dominator combo 8.58et @ 156mph Sacramento Raceway 95*-100*+ day on 315 Drag Radials, CalTracs, 3.73:1 gears, corrected altitude of 1200-1500ft depending on the day, all runs were made on all the above 8.81et & 8.58et combos with a Top Gun System 300hp total N20 activated at the 60' mark 100hp, then 200hp at 330ft then progressing to the full 300hp at 660ft, only difference was the 90-100+lbs removed exhaust weight & header extensions... Is that enough HP, N20 or not, that isn't a real HP killer too me 8.81 capped to 8.58 open & only the loss of 0.23 sec.s & 4mph... Explain that one....  I know others that have had similar results... Results may vary... That is the "long winded point" I'm trying to make... Sorry for such a long post

It's resurection day. Lets clear something up for those who do searches for this kind of info and hope they read this far. After taking off the full length ehaust he did not mention re-tuning carb.  With headder extensions only it's going to change the a/f ratio at different RPM's. Did he have an a/f gauge and wide band he was looking at for differences on the 2 runs? I have one. And changing exhaust that dramatically WILL harm performance if it is designed to max performance WITH the exhaust.  Dial that a/f ratio back in through out the range and see what happens. And do the tests on a dyno where conditions are 100% the same each run. 
To answer his questions, yes the mufflers have been flow tested.  Flow testing don't account for scavenging. But you can make the pipes scavenge just as much as the muffler. A proper X pipe can have great scavenging effects. Why have a giant flow muffler? Because you want the muffler to be invisible to the motor. All the flow should be governed by the headder extention and X pipe, after that the exhaust needs to flow as much or more then the prior. So making it big, or extra big ensures that. Bends need to be made with pipe at least 1/4 inch larger then the straight pipe size to maintain the same CFM, even mandrel bends too. 2.5 inch pipe flows 521 cfm.  most mufflers even flow masters flow less the 400cfm with there 2.5 inch mufflers, while some get to 400 cfm, only a couple straight through, no s curve, mufflers actually flow over 500 cfm with there 2.5 inch muffler. Hooker max flow, and thrush glass pack.  CHerry bombs, glass packs with louvers suck, borls fairs ok high 300"s flow, magna flow 385 sux I had those.  If you want a muffler that flows the same as the pipe that feeds it your options are very limited. So if you go 1-2 sized bigger you can get more choices that meet your flow needs. just buy 3 or 3.5" mufflers for your 2.5" system.  All the info I have stated can be searched and found...

Do you have any personal test data, or just stuff you have read?  Please share you personal experiance and track results.  To suggest that flow is the the only measure to determine what is best or appropriate is a bit of an over simplification.