Flowmaster Axle-back

M1Rifle

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May 23, 2004
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I a re-posting this into this forum (it's on another well known site as well).
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Well, after leaving my car with Flowmaster for a few days, I got it back.

WARNING, the results here are NOT what they are going to be offering as a kit!

Background: I contacted Flowmaster and they were interested in building an "American Thunder" system for this car, and wanted to use my car for R&D. "American Thunder" systems are fairly loud, but not obnoxiously so.

They tried many, MANY of their existing mufflers in order to try and get their sound. They tried the Super40 (too quiet, even though it's a very free-flowing muffler), and various Delta40's, and none of them got the right sound. The Delta's tended to drone too much in the interior of the car. The dynamics of the long tubes from cat-back, and the short tips (no tail pipe to speak of) made tuning the sound a completely new ball of wax.

The status on the R&D of their exhaust system KIT is that they are going to probably build an entirely new muffler (new part number) in order to get their "American Thunder" sound and sell it as a kit.

The system they left me with was axle-back (they didn't have time to do the pipes, they were too busy trying mufflers) Super40 system. Joe at Flowmaster said that if they decide to market a "Force II" exhaust system (one notch quieter than American Thunder), then this is the likely setup.

Mufflers: Flowmaster Super40 part# 952548
Tips: Flowmaster part# 15365

The tips are similar to the Magnaflow system seen here and elsewhere, with "Flowmaster" stamped into the body of the tip (sorry, it's out of focus):

IMG_0205_800.jpg


View from the rear:
IMG_0206_800.jpg


Larger photo, of the tip and muffler from underneath
http://www.squadengine.com/~bill/2005/flow...G_0208_1024.jpg

Here is the back, where it connects to the pipes:
http://www.squadengine.com/~bill/2005/flow...G_0209_1024.jpg

And finally the whole package from the rear, underneath:
http://www.squadengine.com/~bill/2005/flow...G_0212_1024.jpg

The Sound: This system moves the sound at idle down a couple of octaves, it now has that classic V8 rumble. It's a bit louder at most speeds, but is VERY liveable for those of you who, like me, are past the headers and glasspacks part of your life. In fact, if you want "Thunder", this isn't it. But it's got a growl that is deeper and in my opinion nicer than stock. There are only a couple of cases where you get some resonance in the cockpit, like flooring it WOT at 1900rpm in 5th gear (like 45-55 mph). But you should be downshifting it anyhow, and it's not bad, just a bit boomier than stock in that one situation.

Flowmaster mentioned that the stock exhaust ROCKS, it really flows well. So nobody sweat it if you are keeping it stock!


Dyno runs, before and after, available as soon as they forward them to me! :nice:
 
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Zero gains from this off-the-shelf muffler over the stock RPM range. Flowmaster is going to develop a new muffler from the ground up to get the sound they want (more agressive) while getting a measurable gain in performance.

When I get independent dyno work done, I'll try to validate their measurements.
 
Ah, sorry, I meant to say "Flowmaster emailed me back, and said that the dyno runs showed no measurable difference". Not that I don't trust them, but I haven't seen the runs. If there were any areas where the Flowmasters produced a small DECREASE in horsepower, they wouldn't want to tell anyone.

So I will trust them, but verify later.
 
I wouldn't know how the Magnaflow sounds, I don't think too many people have heard them side by side. As for sound clips, unless you are taking the sound clip with the same microphone and recording system in both cases, it's pretty useless.... the microphones on most digital cameras people are using are complete crud.
 
I got my car back from an independent dyno shop today, and the Flowmasters actually COST me 5 horsepower across the board.

Not to knock Flowmaster. This is NOT a package they are selling for the Mustang. They WILL come out with a muffler specifically for the Mustang, later.

My car is now back to STOCK exhaust.

Dyno details will be posted tomorrow (I don't have the electronic copies of anything yet).
 
I have Flows installed - removed them and went with the cat-back Magnapacks. I also felt the torquq loss with the Flows. Once I installed the Magnapacks, I regained that loss and added a bit more :)

You can get more info/pics/sound clip from my link below in my sig
 
I have a hard time "feeling" 5hp. I suspected a loss considering that Flowmaster wasn't readily giving me the dyno charts. Can't blame them really, I mean, this wasn't a kit advertised for use in the Mustang, they aren't done with R&D, so they shouldn't advertise a failed attempt.

I should have hard dyno charts from my shop today.
 
M1Rifle said:
I have a hard time "feeling" 5hp. I suspected a loss considering that Flowmaster wasn't readily giving me the dyno charts. Can't blame them really, I mean, this wasn't a kit advertised for use in the Mustang, they aren't done with R&D, so they shouldn't advertise a failed attempt.

I should have hard dyno charts from my shop today.
When will Borla have an axle back system? I tend to like the unique sound the Borla delivers.
 
M1Rifle said:
I got my car back from an independent dyno shop today, and the Flowmasters actually COST me 5 horsepower across the board.

Not to knock Flowmaster. This is NOT a package they are selling for the Mustang. They WILL come out with a muffler specifically for the Mustang, later.

My car is now back to STOCK exhaust.

Dyno details will be posted tomorrow (I don't have the electronic copies of anything yet).

Try a pair of Spin Tech mufflers if you love that chambered rumble. I used to be a die-hard fan of Flows for years until I tried the Sportsmans ... now Flowmaster will never get another penny out of me. These things are built like a tank and really roar when you get on it compared to Flows ... I love mine. :nice: