You know, I get tired of hearing people bash flowmasters. I run them and I think they are just fine. LET'S SEE SOME ACTUAL TRACK TIMES - THEN YOU CAN BASH! I don't give a damn about flow numbers; I'm not an engineer so I'd like to see a time slip from the track! I haven't seen a nickel's worth of difference at the 1/8 mile or 1/4 mile to tell me that flowmaster flows so bad you shouldn't run it. I have not seen anyone ditch a flowmaster and then gain a half a second by running hooker, borla, or anything else. I understand that some people don't like the sound or the fact that they are popular. That's fine. What's that got to do with performance? So? No flow numbers, I want real track testing to prove that flowmaster sucks. Anybody got any REAL proof?

To clarify, since I'm not an engineer, I think flow numbers are a tad misleading. When I first heard about flowmasters, I learned that by the design they are supposed to help scavenge exhaust due to the internal layout.

Doesn't that help, not hurt?

Wouldn't that design show less numbers on a forced air flow test instead of showing real world gains in HP vs stock and other aftermarket mufflers?

That's the main reason I don't trust the flow numbers as much as someone's time slip.

The reason that this is grating on me is two fold; 1.) because I like the way they sound and I hate to think I am choking the engine performance, and 2.) I have read lots of tech articles in Car Craft and Custom Rodder, etc.., that show the HP gains of the mufflers.

I'm not trying to start a flame-fest; I really want to see someone's track test to see if they are good or not, that's all.

Honestly.

I run 40 series flowmasters on my iroc, and I love them. I used to run thrush turbo mufflers and they don't have the sound or the build quality of the flowmasters. But then again they were only 20 dollars a piece. I think that people bash them because it's kinda like how people pick car brands. I love my camaro's and all of gm, but if there is a car out there that outperforms them we will find every reason to bash them because we loyalty to our brand and our cars. There is no way I will ever give up my camaro for a mustang or any other car. It's brand loyalty mostly. The other half is sound looks and performance. Not everybody is brand loyal and others have a bad experience and change there brand.

Absolutely nothing, and they sound great. Most of the fastest cars I know of run them, they're the most popular muffler because of that muscular sound they produce.

They're fine. Sound is over-done though and they don't flow as well as other mufflers. And flow numbers matter.

Think AFR heads and smogger heads have similar numbers?

http://www.andersonfordmotorsport.com/media/rumble.htm

Lowest power were open headers, Warlock (closed), Flowmaster/Dynomax (tie). All of the mufflers made more power than open headers.

Best combo for power & quiet was Borla XS (I can't seem to find a source for those - I see Pro XS, but not XS).

I think the article listed above said it best. "Any of the tested mufflers are better than stock, and all produced more power than open headers, so just pick out a pair that sound good to you and bolt em' on." If we were talkin about hundred thousand dollar competition cars, then it might be different. For street cars, I think you should have what sounds good to you.



Max

You're thinking along the right path. STEADY STATE airflow, like a flow bench, means NOTHING as far as a muffler is concerned. The exhaust system never sees steady state flow. The pressure and velocity is constantly, and rapidly, rising and falling, going from positive to negative pressure. Dyno testing is the only way to accurately rate the effectiveness of a muffler.

The muffler test in the link shows some interesting info that isn't spoken about in the test. The car made the least power with open exhaust-whether it was with no muffler or the Warlock opened up. For a test of that type to really be valid the motor would have to be tuned for max power with each combination with a wideband O2-at least. It would be interesting to know if the car went lean with open exhaust. Also notice that there was only 5hp difference between the best and the worst.

Years ago I built an 11 second 427 Biscayne. I used 2 big "race" Flowmasters (forgot which series) mounted 18" back of the collectors-close enough for the mufflers to really be effective. (more on that later) Once the car was really dialed in it was faster WITH the mufflers than without-it would go rich when the mufflers were removed indicating that the exhaust flow was greater with them on. If the mufflers were a restriction it would have gone lean without them. It also ended up working better with 24" long pipes after the muffler.

Every time an exhaust valve opens it sends a "bung" of hot, high pressure gas down the pipe which leaves a low pressure area behind it after the valve closes. On race applications the length of the header primary tubes are tuned to make use of this in a particular rpm range, and it's always a compromise. The objective is to time each low pressure wave to be in the collector ahead of the next high pressure pulse. This is one way that normally aspirated engines can achieve greater that 1:1 volumetric efficiency. The Flowmaster design is intended to "trap" the high pressure pulse from going backwards and thus maintain the low pressure pulse behind it to help draw the next high pressure pulse more effectively. As you get farther away from the exhaust port the gasses cool and the velocity of the high pressure pulse goes down. The purpose of header wrap is to maintain the velocity by retaining the heat- cooler under hood temps is really a side benefit.

How does this relate to our cars? The problem is that these cars just don't have enough room under them for a really effective exhaust system. Every exhaust system is a compromise but the options are more limited on a 3rd gen than on many other cars. The muffler is usually 4'-5' away from the collectors where the gasses have cooled significantly, and for the most part the pipe volume that will fit under our cars is too little. I think it's entirely possible that a Flowmaster muffler may not offer any significant gain over any other decent performing muffler on our cars-but it certainly won't be a restriction. The key to getting the most power out of a conventional "turbo" style muffler is to get the most case volume that you can to allow the high pressure wave to expand as much as possible. For the most part Flowmasters do have a lot of case volume. Another thing that is a common problem on our cars is that most people want two tailpipes, one on each side of the car, and that really compromises the effectiveness of any muffler that will fit in the stock location. A single 3" tailpipe allows for a better flowing muffler. In the end, any exhaust system that fits under the car is not going to be ideal, so get the one you like the sound of, and make the exhaust system towards the front of the car as good as possible.

The test car had what we call "long tube" headers. The "open exhaust" test was with the exhaust removed from the collectors. Look again at the Warlock - they made one pull with them corked, and one with them open - the open Warlock produced the best power of any test, while the corked was one of the worst. That squares with my experience with Warlocks. The reason they "work" uncorked is they act as a torque tube. Headers open at the collectors is rarely the best power configuration. However, an open Warlock in the stock 3rd gen position is going to make noise, not much else.

Being that it was a closed-loop mass air EFI system, it would compensate for that. Wideband might be able to split the hairs a little better, but not likely to make a significant difference in power.

Thanks for all of the replies, guys. These are the answers that I was looking for. I wanted to make sure that there was no reason not to run a flowmaster - and there isn't.

Again, thanks!

I missed that about the uncorked Warlocks making more power, and that the open baseline was at the collectors. Makes sense-most everything running open headers needs a collector extension. I was assuming that the car was speed/density and not very adaptive. My knowledge of FI is very basic. Too bad there isn't room under our cars to put 2 normal mufflers under the back seat.

I had the Warlocks on the '57. About 12" of pipe from the collector to the muffler, then another 16" or so of the muffler when uncorked. It was slowest corked, then open collector, then open Warlock.

I've since made other changes, including mufflers, and back-to-back uncorked headers and exhaust attached was always faster and quicker exhaust attached. Funny thing is with the headers uncorked, it "seemed" faster - the time slips showed otherwise.

For a 3rd gen, if a cut-out "helps" you, you need a different muffler. By the time the exhaust gets there (most of them installed where the cat was, or before the cat), any torque tube effect is long over.

Another part of the tale involves cross-flow mufflers. Typically, they are more restrictive that single outlet, or dual-on-same-side mufflers. Doing 180's takes energy.

Another part of the tale involves cross-flow mufflers. Typically, they are more restrictive that single outlet, or dual-on-same-side mufflers. Doing 180's takes energy.[/quote]i agree with u on the this one

Not to thread jack, or change to subject. But has anyone had any experience with the Dynomax Ultra Flo-X mufflers? The two in/ two out muffler with the X-pipe inside? Just curious.


Max

My iroc has two 40 series flowmasters under the rear seats. I had to beat the floorpans a little but I was the first in my area with true duals on a thirdgen. I kinda like it. The stock exhaust probably flows a little better since it is kind of pinched to clear the crossmember but I wanted it for the looks anyway. And the flowmasters for sound. Heres a pic.

wow 2 40 series' FM that thing must be purrdy loud..

it all depends on what you prefer, I can't stand the sound of flowmasters, not deep enough to make a real ballsy sound, but if it makes you happy you shouldn't listen to everyone else

The only comparison i had was my 80 series 3inch flowmaster to my now custom 3inch chambered tube. Both with cats

Not sure what the weather was the day i ran it at the track. but i can tell you this i lost alittle back pressure goin to the straight thru chambered tube over the flowmaster. The sound of the Flow was nice but the chambered tube is FAR better. I didnt really gain much at the track, maybe .3-.4 mph but that could be from the weather. i did lose alittle 1/8mile trap speed but ran near same times ET wise.

For some motor setups, the 80 series may choke the motor. Some setups like mild builds will handle that muffler. More serious combinations making more hp will want more flowing straight thru mufflers. Thats why some guys run open cutouts at the track and see gains.

Dude, a "ballsy" sound comes from a motor that has a set. A muffler will not give you're car a set of hangers. It's like the little dog with a big bark, all that noise don't make him any bigger. I have no issues with a FLOWMASTER on performance, the sound has just become tired to my ear. I personally don't want the "me too" sound. I would rather have a "voice" of my own. I agree with the earlier statement about cross-flow mufflers they sound horrible and its all because of the design. I would rather have a single tailpipe than a car that blatts and bubbles when you let of the throttle. But I'm opinionated and that's just my stinky opinion.

So if it has a big bark, doesn't that mean it still has a ballsy sound? You don't necessarily need that lope in the exhaust for a car to sound mean. A nearly stock L98 glasspacked car run with open headers sounds ballsy. It depends on what you consider a powerful or weak sound.

Just because it's loud doesn't mean it sounds good.

I didn't say that

Does the 80 series snap crackle and pop? I'm bone stock right now and thinking of going that route. I had a pair of FM's on an old Ranchero and I was stoked!

Again this is just my opinion. The "ballsy" sound STARTS @ 10.5:1 with 280+ degrees of duration. But that's just me talking. You can tell from the bark if the bite will really hurt or not.
But back to the real thread subject. Sound is in the ear of the beholder. I just don't like the FLOWMASTER sound. They perform just fine.

Good call.
Is there a deeper, more growly muffler in the same price range as an 80 series? I don't have a monster cam or anything yet, but you know how it goes--The exhaust is always the first thing to change
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Sorry to hijack this thread, BTW

You're thinking of a cam.

My L03 with long tubes and 3 inch duals sounds pretty rad but it still sounds lazy.

Had a much deeper tone with the Flowmaster 80, but it sounds better now I think. With my setup it needs a cam to really sound good, though.

flowmaster takes time to break in... i'm not sure how it works but it does, the flowmaster gets abit louder and less raspy the longer you run it. and it sounds best once it is very hot.

my car crackled alot the first month i had it on the car, but after that, the sound changed and continued to improve. Once i added headers tho, it was alot deeper and much less raspy/crackly. You need a good flowing system from headers to 80 series muffler to get rid of the crackling

Resurrecting old thread because I was trying to find quantitative data on flowmaster flow rates, and this compares many different brands against each other in a scientific way.

I would also like to add this about flow: You convert your cubic inches of your motor (a 350 is 350 cubic inches) and convert that directly into exhaust flow rate, such as a 350 ci motor will flow 350 cfm assuming 100% volumetric efficiency (in reality we're looking at 80% or so for most engines) meaning your muffler has to flow at least 350 cfm (assuming you're at 6000 rpm at WOT - less than 6k will flow less obviously) to be "unrestrictive" Going over this too greatly (such as some aftermarket mufflers advertising 800-1000 cfm flow rate) will drastically hurt low end torque and performance.

Bottom line about flow in mufflers: You can't go wrong. I've yet to see a muffler rated as "performace" flow less than 300 cfm, meaning they all will flow more than enough for you, which pretty much just says: Pick what sounds best as stated in a post above! Flowing too much WILL hurt your performance.

I vote sticky!

Too many people are making 400+ HP with Flowmaster mufflers for them to suck. I like the Flowmaster sound myself, and would put their system on my car if only they made it in stainless steel. Anyone know how long these aluminized systems last before rusting through?

So, far, I have never had a flowmaster rust all the way through...

I bought a used 80 series setup (don't know how old but it was rusted) and ran it for 5 years. It got a little louder, but never gave up.

I did have to repair the tailpipes and the mid pipe near the converter, though...

Hope this helps.

So, far, I have never had a flowmaster rust all the way through...

I bought a used 80 series setup (don't know how old but it was rusted) and ran it for 5 years. It got a little louder, but never gave up.

I did have to repair the tailpipes and the mid pipe near the converter, though...

Hope this helps.

How does an engine produce more power with more back pressure?

Try this: (More than you ever wanted to know about BACKPRESSURE...). It's been a while since I read it, so I don't remember if it has a direct answer to your question, but I'd say it's worth reading.

I'll paraphrase the article then:

It's not about backpressure being good so much asi t is about velocity being good. You have to balance flow with your engine. You want maximum velocity out the tailpipe to create the least backpressure and help suck exhaust pulses through the system. A system that is too large can't do that as well since the exhaust pulses are so weak compared to the flowrate the system can handle.

Flowmasters are like anything else in life, apples and oranges. One simple rule is that ANYTHING is better than stock.

I used a Flowmaster once and so did my friend on his fourthgen and it was perfectly fine. It didn't feel any less "ballsy" then another muffler. Honestly IMHO, the best "kick" I felt from any mufflers were plain good ol' Cherry Bombs but that's just me.

It's all about what makes YOU happy. My friend put a Flowmaster on his car because he was ONLY concerned about the sound but you could definitely feel it had a little more kick to it. I slapped one one because I picked it up for $5 at the junkyard. Bottom line is, do some research as to what's the best application for what you plan on doing ie. performance, sound, etc.

My flowmasters sound great. I think that's what I'm really after. As far as performance, I'm never satisfied lol...

Resistance creates velocity, an example is the venturi in a carburetor. It needs to be the right size and placement for the engine (tuned to the engine), but removing all backpressure makes an engine very weak, having the right amount in the right place can make it a giant-killer, and finding the right combination is pretty much experience + Trial-and-error, mostly the latter.

TA

Well I've had Flowmasters on many of my cars before I learned about building custom exhaust systems. Had the 80 on my Tahoe and the 2 chambers on my camaro and bmw. When changed it to a magnawflow mufflers I saw and felt a dif in towing and gas economy. With the Camaro, better take off and car was abit faster. The biggest improvement was to the bmw. In the quarter I gained over 1 mph and car pulls to 7000rpm with NO prblem. Also the one on the bmw had rusted at the back after four years so thats one of the reasons for going with the stainless mags.

You won't gain any hp if the mufflers you have meets the flow needs of your motor. You only gain if the motor needs more exhaust flow and you switch over to a higher flowing muffler. And tunning palys a big part in that too. All the cars were maf cars so that's why some guys gain and some don't.

You are describing something called scavenging. Similar to back pressure but not the same.

I'm trying to put it in simple terms so it can be better understood by the large number of people on this forum that don't understand that you can't eliminate backpressure and still have scavenging. The trick is to minimize backpressure while still retaining the right amount of velocity and wave reflective properties in the right places and timed to work with your powerband. Without some kind of restriction, or backpressure in the system, you loose velocity and any hope of wave reflection, and all your power disappears, and you post up like so many with "I put open long-tubes on and what happened to all my power?"

TA

Ah yes. Makes sense now. I wish I could find the article Hot Rod or one of those mags that talked about setting up a proper exhaust system. It was VERY well written and had a lot of good, never really discussed information in it.

Fact: 2.2cfm per horsepower of exhaust flow is required so as not to lose power due to a restrictve exhaust. For an exhaust to be truly effective (with or without mufflers) it must be tuned for length.
Flowmaster or otherwise, if there is significant back pressure, then power will be lost. That doesn't mean you can't make 400 or 500 horsepower with a crappy mufflers. It means you're not making all the power the engine is capable of producing.

I was reading the latest Hot Rod magazine last night, and Flowmaster had an ad for their 40 series mufflers, which are now offered in stainless steel. Hopefully this is the way the rest of the product line is going to go!

He is absolutely correct, but exhaust system design is not simply a matter of the right flow through a pipe, because as the exhaust cools, it contracts, and needs far less volume to maintain velocity towards the rear of a longer system (this is how stepped headers work). For this reason, everything happening within the first few feet of the exhaust port is critical, the further back you get, the less critical it is. Although it sounds kinda strange, if you put a more restrictive muffler substantially further back from the exhaust port, it becomes less restrictive and your power can go up a tad with exactly the same muffler, simply because the cooler gasses need less area to flow through.

This is OPPOSITE with catalysts, you need to keep cat converters as close to the hot exhaust as possible, because if the exhaust is allowed to cool before it hits the cats, the cats "re-light" the exhaust back to about 1500 degrees, and this results in an increase in pressure that effectively plugs your exhaust system. This is why most people think cats are restrictive, as our older cars have them too far back.

TA

I have a 3" Y-pipe into a 3" Flowmaster American Thunder "catback" (no cat...) and my car traps 119-120mph on motor through it. I have a cutout that dumps under the rear floorboard and the car only picks up 1-1.5mph with it open


...I'd say it flows pretty good

My only issue is the "Flowmaster" sound. I want to have an "engine" sound, not a muffler sound. Flowmaster is the only muffler that I can think of that you can pick out of a crowd. Now if your engine is bone stock, I can understand wanting a little more "sound". Fair enough. ...but if your engine has ANY grunt whatsoever, it'll probably sound good on it's own. Any aftermarket muffler will up the volume over stock muffler, but only the flowmaster changes the sound.

...but it's all about opinion. If you LIKE that sound, then that's cool.

The irony is that I have a built 383 running through true duals and Bassani mufflers. I lopes and surges and to me, sounds evil, especially at redline. I also have a beater bone-stock 5.0 Formula, with a Flowmaster on it, which is louder, MUCH slower and just silly to me (it was on there when I got the car).

I get 10 times more compliments on the "gnarly exhaust" and questions about "what have you done with the engine?" in the slow formula. Go figure.

TA

yeah yeah you are right about having an engine sound, and not a muffler sound. But on the other hand, I have heard old flatties that had no real power, but the sure "sounded" good.

you can go to youtube and watch and hear everything.

One of the reasons I own a vehicle with a v8 is because the sound darn nice! Not just because of inherent performance. Most people know that some of the cutting edge v6 engines will out do a stock 305, but I am not racing 99.99% or the time anyway.