Flowmaster Mufflers on Turbocharged Engines.....

DaveP

DaveP

Active member
There has been a dearth of technical content on the forum lately. This is an attempt to jump-start some participation in technical subjects by knowledgeable people again.

Over the years I've seen posts here stating: "Flowmaster mufflers are not good on turbo engines" time and again. I saw this again this morning in another thread. OK, fine. Why not?

I found this article by David Vizard. Evidently Mr. Vizard was responsible for developing the concept muffler that became the Walker Super Turbo that was on SyTy as OEM equipment. This article was written regarding exhaust on N/A racing engines with tubular, collected, exhaust systems.

I gleaned from the above article that the Flowmaster muffler 'appears' to the the pulses as the end of a round pipe, such as a header collector and there fore can be used to "tune" collector length for torque. I understand this. A turbo smooths out the pulses. Turbo engines are sensitive to back pressure downstream the turbine. A straight-through design is favored. The DynoMax is not a straight-through muffler, but is acceptable? Comparing the designs of Flowmasters and DynoMax seems to me that the Flowmaster is freer flowing than the Dynomax. What am I missing?

I spent about an hour looking for a direct "Flowmasters cause power-loss when installed on a turbocharged engine" but never found anything online. Can anyone point me to a definitive explanation supporting this statement, rather than it just being "something I read on the internet?"

Thanks, and Merry Christmas
 
2

2kwik4u

Resident slow guy
Re: Flowmaster Mufflers on Turbocharged Engines.....

You're on the right track I think. While I can't offer any definitive proof, I can offer the semester I just spent in Thermodynamics studying turbines, compressors, and nozzles (among other subjects). The big picture concept is that your turbine operates on a thermal energy difference between the "hot side" and the "cold" side. Increasing this difference by either increasing heat on the hot side, or decreasing heat on the "cold" side will increase the available work to be done by that turbine. Pressure is analogous to heat in a system operating as an ideal gas, such as air (or exhaust gas). Therefore, decreasing pressure on the "cold" side (exhuast side) will allow more work to be done on the turbine blades.

NOW... transferring that to exhaust flow technology under the truck.....The faster you get the exhaust gas away from the turbine, the more available work there is to create boost in the compressor side. This leads me to think that the straighter, and larger the pipe is behind the compressor wheel the higher the available work. Assuming no change in input (same boost, and fuel levels), you should see an increase in efficiency if my math is done right.

I have no empirical data to back that up in terms of real world testing. I do have some anecdotal evidence though, that mufflers like the Magnaflow design (Straight through, non-chambered) perform better (and sounds better IMO) than the chambered designs, such as the Flowmasters. I'm not sure I've ever seen anyone do a before/after test on these trucks with various mufflers. Since they are so finicky, without a "side-by-side" comparison, I'm afraid all we have is conjecture.

Does that help? I can post the turbine, compressor, and nozzle effeciency equations if you like, as well as hand work some equations if I can get some data in terms of temperature and pressure on either side of the turbine blade. Does that data exist?
 
GEMELLI

GEMELLI

The Best of Both Worlds
Re: Flowmaster Mufflers on Turbocharged Engines.....

Other than the fact that I have a Flowmaster(s) on every vehicle I own because I love the sound, I don't have anything technical to add to this thread. What I do have to add is that the amount of tech info on this site is astounding, and I too want more. When I can, I will add to the technical side of things. Thank you Dave, for always keeping tech on the forefront of your mind.

What I'm really trying to say is... Subscribing. :)
 
Icarus-54

Icarus-54

Donating Old Member
Re: Flowmaster Mufflers on Turbocharged Engines.....

Gee,it's nice to see a post on the trucks again.Great post Dave,this should stimulate some good discussion.Personally I prefer the Borla muffler,straight thru,great sound.
 
jeepruby04

jeepruby04

New member
Re: Flowmaster Mufflers on Turbocharged Engines.....

NA engines or forced induction operate on the same principals. Engines are simple air pumps, the more air you move through them, the more power they make (assuming you can add sufficient fuel and spark).
The problem with our trucks concerning free flowing exhaust systems is the wastegate port being too small. A well known example is the removal of the catalytic converter causing extreme overboost.
I would assume that a 40 series Flowmaster compared to the stock muffler might have enough flow increase to cause some overboost or boost spikes.
 
G

GM TURBO

Sell Out
Re: Flowmaster Mufflers on Turbocharged Engines.....

Many of us have run straight pipe from the cat back without issue. I too was puzzled by the 'no flowmaster on a turbo engine' comment.
 
qbnkiller

qbnkiller

Conflaguration Specialist
Re: Flowmaster Mufflers on Turbocharged Engines.....

flowmaster mufflers (or any chambered muffler for that matter) present added backpressure by adding deflections inside the muffler. In any turbocharged application, back pressure post turbine is unwanted (as it applies to maximum power). You can add back pressure in moderation to help reduce lag, but once the engine starts breathing deeply, back pressure chokes the turbine wheel.
 
gaugeprower

gaugeprower

Doghouse Member
Re: Flowmaster Mufflers on Turbocharged Engines.....

Ok nothing technical, just a sound question. I have the pitbull exhaust.. i believe catback, im not sure. The sound is ok, but who's heard this exhaust vs others specifically on syty's I always liked Corsa's tight growl but I know they dont have a syty application. Someone mentioned Borla.. what's the "best" sounding exhaust for these trucks?
 
warmpancakes

warmpancakes

New member
Re: Flowmaster Mufflers on Turbocharged Engines.....

Can't get more technical than wifes truck had boost control issues (10-15-10-15 like a wave form)and ran like poop, did nothing to it other than replace flowmaster with straight pipe and boost was stable and truck ran better also flowmasters get hot real hot it actually cooked the paint off the floor of wifes truck and melted the carpet

DSC00220_zpsc7a7bdd5.jpg


http://www.theturboforums.com/threads/339072-Why-Flowmaster-and-Turbo-dont-mix


from above thread

I made 666/572 through #335408 flowmasters with a 350 @19psi. TH400 and 33" tires

the switch to dynomax bullets definately freed it up and I had to add fuel.
havent dynoed it since, its a street car and too fast like it is.
 
Last edited:
Throws

Throws

Active member
Re: Flowmaster Mufflers on Turbocharged Engines.....

Damian said:
Here are some pictures that show the inside setup of a Flowmaster muffler: http://www.google.com/search?q=insi...8KRiQK19YHYAg&ved=0CAoQ_AUoAA&biw=981&bih=425

I use a Dynomax TurboXS muffler on mine and love it. http://www.google.com/search?q=insi...3984f92babfdc1f&bpcl=40096503&biw=905&bih=426

You can clearly see the difference between the two and see why I chose Dynomax over Flowmaster.
Click to expand...

I'll raise you, and see you a Magnaflow. :D

magnaflow-muffler-schematic.jpg


This, 3" catback, no cat, and a ported Waller 20G. ;)
 
NJSERRANO

NJSERRANO

New member
Re: Flowmaster Mufflers on Turbocharged Engines.....

Would the pulses revert back to the turbo and essentially counteract the desired rotation of the turbine wheel?
 
midnightbluS10

midnightbluS10

Banned
Re: Flowmaster Mufflers on Turbocharged Engines.....

I did find a before and after flowmaster dyno comparison. It wasn't a Dyomax Super Turbo that replaced it, though. It was a Dynomax Ultra Flo. Guy picked up 17 peak rwhp and 31 peak rwtq and alot under the curve. But he replaced the stock tailpipe with an upgraded piece, as well.

http://www.theturboforums.com/content/177-The-Great-Muffler-Swap

On October 1st 2002, I took my car in to have the exhaust that was on the car when I bought it removed for some 2.5" Dynomax Ultraflows and tailpipes. The current exhaust consisted of some really, really old 2.5" Flowmasters circa 1991. Apparently that is all that was installed because it looks like the tailpipes are still stock 2.25" units.





I knew for sure this crappy setup was holding me back normally aspirated and I could only imagine the backpressure it was creating for the turbo. Turbos do not like backpressure and they do not get along at all with chambered style mufflers like Flowmasters.

The hot setup these days is the Dynomax Ultra Flow aka the Ultra Flow "welded". These things flow a ton and they are also very quiet. Unfortunately it is a pain in the ass to get the wlk-17394 cat back at a decent price because when you order it from Summit you have to pay a $60-75 truck freight charge, not to mention it is always on back order. So this is what I did. I ordered the two Dynomax Ultra Flow mufflers (Part number: wlk-17222) at about $60 each. Then I ordered the Summit 2.5" catback (PN: SUM-680793). This catback comes with 2 Summit super turbo mufflers and a set of 2.5" mandrel bent tailpipes and it is only $180. So I got two extra mufflers and still came out at least $80 cheaper, then I was able to sell the super turbo mufflers for $40.


Update: 4-17-04, a reader notified me that Full Line Exhaust offers Dynomax products with FREE shipping. They are not in any way tied to this site but if you order from them please mention you saw it here.

I took the car Keith at Street Flight who dyno'd the car several times with the flowmasters at 10 psi of boost. Then he cut off the old cat back and welded on the new mufflers and tailpipes. Afterwards we re-dyno'd the car without touching anything else. The results you see below show the best of the Flowmaster dyno runs and two dyno runs with the Dynomax Ultraflows made back to back. As the power curve shows not only did I pick up horsepower and torque throughout the RPM band I also picked up better spool time. Look how much faster the power comes on now. This was with the car making 10 psi up to about 4000rpm then the boost was falling off to 5 psi because of some intercooler piping and wastegate problems (I have since fixed this problem for the most part).

The car is also very, very quiet, to see a video demonstrating this, save this video to your hard drive by right clicking and choosing "save as" Video. The car sounded damn near the same when I had the Flowmasters on too, the turbo really quiets everything down. If you want your car to be louder but still have high flowing mufflers you can try the Dynomax Bullets.

Click to expand...
 
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Flyin Ryan

Flyin Ryan

hated cuz he drives fords
Re: Flowmaster Mufflers on Turbocharged Engines.....

Turbos HATE backpressure as we all know. You want the highest flowing exhaust system you can fit without causing issues with over boost. I know this isn't a Mustang forum and no one likes them here but since the Flowmaster muffler was the most popular with these cars it was more common to see Mustangs with these mufflers with a turbo involved and hear how owners liked or disliked the use of a flowmaster or chambered muffler with there cars especially since dyno tuning is huge in this crowd. It wasn't uncommon to see people post that they had 20hp difference or a little less when making the swap to a straight thru type muffler in the mustang community.

Most vehicles like mustangs that have been converted to turbo don't have to worry about undersized wastegates so they get to benefit from going as large as possible. Race Bullets are very common on turbo mustangs because they are completely straight through design, no restriction.The larger the better and it's not uncommon to find turbomustangs running a 3" downpipe which would u out to two 2.5" catback setup and straight through style mufflers that's good for 700hp. My mustang had a 3" downpipe to a single 3" race bullet and a turn down.

I remember a local member on here, Can't remember who it was but it was never posted on the forum. He had his ty dyno tuned through his 3" catback setup then through his exhaust cutout and on the dyno he saw a 37hp difference to the wheels with the exhaust dump open. Now the truck wasn't stock turbo/dp/injector wise but that's a huge difference.

I had originally posted on this subject back in 08
http://www.syty.net/forums/showthread.php?t=57508&highlight=flowmaster
 
Icarus-54

Icarus-54

Donating Old Member
Re: Flowmaster Mufflers on Turbocharged Engines.....

I know when I swiitched to the borla muffler the turbo seemed to spool quicker.It had stock mufflers but with a 3" set up runing into a fabricated Y into the 2 2 1/2" stock mufflers.The borla being straight thru made quite a difference.
 
Smkur50

Smkur50

SYTY Fleet owner
Re: Flowmaster Mufflers on Turbocharged Engines.....

I would think the baffling would cause pulsing in the exhaust backpressure, causing the turbo to not spool smoothly. just my :2cents:
 
warmpancakes

warmpancakes

New member
Re: Flowmaster Mufflers on Turbocharged Engines.....

Smkur50 said:
I would think the baffling would cause pulsing in the exhaust backpressure, causing the turbo to not spool smoothly. just my :2cents:
Click to expand...


it does, thats what was happening on wifes truck at WOT you could watch the boost fluctuate

10-15-10-15
 
Don W.

Don W.

Stab it and steer it
Re: Flowmaster Mufflers on Turbocharged Engines.....

I'd have to look at the brand but I have a 3" straight through, gutted cat, and ported, but stock otherwise, hot section. Except a spike at the hit boost control is solid. Originally I had 3" from the miffler back to the rear of the truck. Almost couldn't hear it, very quiet. Removed the tail pipe and it sounds very nice. Although obviously not, it almost has a V8 sound. I like it.

Now in the big truck end where turbos are the norm those mufflers are commonly 5" straight through. (Except new ones which have all kinds of smog stuff on them.) My strictly unscientific opinion is any kind of baffled muffler on a turbo is not going to work as well as a straight through. Quite a few independent truckers will run straight pipes but they are loud.

As an aside Flow Masters were developed here in Santa Rosa. One day a few years ago I ended up on a flight from here with a couple of Flow Master guys. Chatted with them a bit and asked if they had a "straight through" model for turbo charged motors and they didn't even want to go there. They were stuck on their "our baffles help pull the exhaust out of the motor" mantra. It was almost as if they never heard of a turbo. Flow Masters sound great on a NA motor though.

Off to read Dave's posted article....
 
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