Magnaflow versus Flowmaster ~ Showdown on the Dyno

Yeah, so the URD is a sizable increase in internal diameter compared to the double walled. Also I wrapped the cross over pipe in header wrap due to it sitting right below the transmission pan to control some of the heat.

The collector location is identical, but the URD looks to be better flowing, with the two incoming pipes parallel to each other and not forced into each other as in the stock design.

If money was no object I would have cut off the collector from the URD, and ran dual piping into a dual in/out muffler. Like the design on 3 series bmws. Adding an H pipe or an X pipe would be good too. It would probably help the sound as well. 1grs sound like crap. Sounds like a 3 cylinder... You 4 banger vid sounds so much better IMO.

And although the modern cats are really free flowing, they do add restriction. Gains aren't that noticeable on trucks. But for my previous rotary and turbo cars, they freed up a lot of power. I'll keep the front two for my 4 legged passengers in the truck bed, though.

 

So the basics of air flow haha when going from small diameter to a large diameter (depending of how the sever the change in size happens) there is a thing called flow disturbance. In the below picture it's circled in red, what that is, is the air filling the gap, it's basically air flow going backwards to fill the gap. It's an exaggeration of what happens, but it does. So it slows down the flow



A normal flow through a pipe looks parabolic, because the edges are experiencing friction due to the surface of the pipe, so the flow in the smaller pipe looks like a normal parabolic shape, but as it hits that opening it really slows down the edges and impedes the flow as seen below



And then finally as the air flow hits those hundreds of little holes, more disturbance happens. As seen below circled in red, the air flow actually reverses and creates an obstruction of the flow.



So all in all, a cat is definitely mess with the flow haha BUT this is why keeping the stock y-pipes created back pressure, which helps low end torque like someone else stated, so opening up the pipes with smooth piping and no obstructions allows way better air flow and high rpm response/power but you lose that back pressure for the low end torque

Little lesson

 

I feel ya haha Subaru to tacoma are two totally different set ups! But yeah the two pipes into a duel in/out muffler would be ideal, or a better collector design. Or even run true duels the whole way, no collection or ypipe at all

 

Sorry. Port and Polish is where the intake and exhaust ports on an engine head are rounded and smoothed to allow better airflow. Ramp and throat is similar...it is what a gunsmith does to allow the cartridge to feed smoother and reduce jamming.

 

Thanks, man.

That's interesting to know. It makes sense why the flow area for the cats expands to such a large cross section that's way larger than the exhaust pipe diameter. They need to compensate for the extra turbulence created by the grids.

It's dyno day tomorrow...

Greg

 

Exactly, all the engineering that goes into cars, minuscule details in a cat, which people don't even find a big part of a car haha gotta love it!

I'm excited to see these results, im completely curious

 

You were doing quite well in your description,,, until you mentioned back pressure. Given your knowledge, you should know better . Backpressure is an overused term that ends up being meaningless. Reality is larger free-er flowing pipes slow down the exhaust gas velocity at low rpms, which reduces the scavenging affect of the exhaust flow out of the cylinders, which reduces low end torque.

 

SHHH i was close enough

same size pipes but no cats = higher velocity
larger pipes no cats = slower velocity

right? i mean logic says if the pipes from the headers are the same size as the y-pipe, you have 3 pipes of the same size now moving through 1 pipe, then you have 2 pipes (one from each side) from the y-pipe going to 1 pipe the exhaust, wouldn't that reduction in number of pipes at the same size create a higher velocity?

i mean essentially you're going from 6 pipes to 2 pipes to 1 pipe, or am i completely off? and that reduction in number of pipes and the disturbance caused by the cat is what produces the scavenging effect?

 

Here's the results of the muffler dyno shootout...

Magnaflow: BLUE
Flowmaster: RED

Just wanted to get this posted to let you know as soon as possible.
More later...

 

Hmm, not much difference but the Flowmaster definitely made more torque throughout. I'm not surprised by the increased torque at low rpms but I am surprised it made more torque up top also.

 

I feel pretty vindicated. As I suspected there is little to no noticeable power difference between the two products. Yes there is a little mote torque and hp on the lower end from the flowmaster, but overall it's all within 3 hp and 2 ft/lbs of torque. So buy whichever makes the sound you want, and don't let one guy or another tell you "don't buy the chokemaster!"

On a side note, check out the hike in the A/F ratio . That engine is finding a lot more air with the Flowmaster on there, any other changes between runs?

 

Good to know I won't be loosing power when I dump my raspy farty Aero Turbine for a Flowmaster!!!

Still curious why you chose a center in/offset out muffler instead of a center in/out muffler.

 

I assume you're referring to me, which I never said there would be much of a difference at all and I don't believe anyone really has in this thread. I agree buy what makes you happy, cat back exhausts just don't do much and I think most people understand this. I was also surprised the A/F was even worse with the Flowmaster, I figured it would be the reverse if anything.

 

wow i wonder what the v6 numbers look like with more airflow. now im second guessing taking out my flowmaster

 

It is significant that the Flowmaster performed consistently and measurably better at pretty much every RPM on every run. At best, there was about a 5% gain. That's good for a simple, bolt-on mod!

And, it sounded great! Oh, yeah, Greg let me show up for the runs so I was able to hear it live and in person. Thanks Greg. And thanks for spending the time and money to do this showdown. I'm sure all appreciate it!

 

Wildcat I feel vindicated from the 90% plus of threads on here that are pro magnaflow and anti flowmaster. When I bought mine I even questioned it due to the astoundingly negative comments against flowmaster. Finally here's a thread that says "Hey, they are pretty much the same", which was always my feeling on the matter.

Yeah, that A/F ratio is scary. I'm wondering if this is why I don't have fat A/F ratio issues with my mods while some other similar trucks do...

 

I agree, most people refer to the flowmaster as chokemasters, well now that's defiantly not true. So all the magnaflow die hards have no ground to stand on. And I'm not bragging or putting anyone down, but it's finally nice to see numbers to prove the myth wrong

 

And a big thanks to Tooter for this!

 

Alright no problem then, I don't have either so I have no side. I'm surprised by the results, but knew there wouldn't be a big difference either way.

 

Nice work Greg!

Could the results be skewed at all by different weather between runs? Were ambient temps and pressures the same? Especially since the margin is only a small number of hp i feel the weather could be at play here, either for or against the flowmaster, pic your side