Magnaflow versus Flowmaster ~ Showdown on the Dyno

You won't lose anything.

I duplicated the exact CI/OO position of the stock muffler with the Magnaflow because then I was still using the stock tailpipe. And so got the CI/OO configured Flowmaster since the mandrel bent tailpipe had already been fabricated when the Magnaflow was on it.


Greg

 

It sure felt like the Flowmaster pulled better off idle, but I had chalked that up to its neato sound. Now the dyno shows that it actually does do a little better at very low rpms.


Greg

 

Seems like there was more HP at key rpms. Would definitely go with a flowmasters

 

Well, that was my intention to finally put a stake through the heart of that stupid lie that Flowmasters don't flow as good as Magnaflows.

Check out the dyno runs, with the stock muffler, the Magnaflow, and the Flowmaster. All three are actually pretty close...

No, the muffler was the only change. In normal closed loop driving the A/F is normal. Right now I'm checking out the Split Second MAF calibrators.


Greg

 

The dyno runs are SAE corrected for temp and pressure.
Even though they were corrected, the conditions for each day were very similar.

Greg

 

Another intersting tidbit...



The Magnaflow hit its torque peak at 2,900 rpms...

...but notice that the Flowmaster meets and surpasses the Magnaflow torque peak at 2,800 rpms.

This is a torque peak an even 1,000 rpms below the stock peak of 3,800 rpms.


Greg

 

Been lookin forward to this today.
A little cornfused about the a/f ratios and open loop?

Thanks for posting Greg!

 

I'd go with Flowmaster just for the sound... but I am glad that it also flows better. I'm especially pleased like that it hits a higher torque peak at lower rpms (2,800).

Greg

 

In normal partial throttle driving, your O2 sensors feedback signals to the ECU which is constantly adjusting the air fuel ratio. That's closed loop because it is constantly self correcting the air fuel mixture.

However, in a wide open throttle situation, the ECU ignores the sensors and reverts to a factory preset fuel map which was designed to work on a stock engine... which mine is no longer stock.


Greg

 

All of the A/F ratios indicate pretty much the same lean condition. The preset factory open loop fuel map at wide open throttle can't handle the increased flow capabilities of the engine.


Greg

 

Just from what I've read, your wide open throttle factory preset open loop 4.0 fuel map is reported to be on the rich side. Just that difference alone makes difficult to extrapolate results between the two engines.

They're so close, I'd just go for whatever sound you like the best. That's what I did.


Greg

 

Thanks for coming to witness the process, Dan... it was a pleasure meeting you.
It's so much fun exploring stuff like this, and coming up with definitive informative results that everyone can use.

Greg

 

So the combination of all 4 of your mods is what causes it to lean out at WOT?
I'm wondering if the header alone "with stock intake and exhaust" would run lean in open loop or WOT?

Lowering the torque peak 1000 rpm is impressive, I'm really hoping that will have a positive effect on mpg's.

 

I'm pretty sure that each one of them individually increases the flow at open loop wide open throttle. And since the open loop fuel map is fixed, it can't handle the increased flow.

I wouldn't be surprised if it did, Bob...
After all, the header produced the biggest torque peak drop (650 rpms). All the mufflers flow pretty close together. The stock intake might help some.

And remember, I'm running an undersized 2.25" tailpipe and the engine still flows like crazy. Man, I'm sure glad I didn't open up the exhaust! It would have killed off the torque.

It is. My engine achieves a higher torque peak than stock at 25% less rpms. I can really feel that added pull because my work truck is always fully loaded down. It just makes my truck even more fun to drive.

That has a lot to do with driving style. The lower the torque peak, the easier you can short shift the engine without lugging it down. I drive under really crappy conditions with lots of first gear crawling, and no 5th gear freeway driving, and am still averaging better than 23 mpg. I'd love to take it on a long trip to see how good the mileage could get.


Greg

 

A little concerned about adding the header with the A/F thing?
Oh and driving style, I drive like an old man, hardly ever break 2,500 RPM with an auto, guess thats why I'm gettin 27 to 29+ mpg.
Dam, I am an old man,,

The way I drive it may not effect the A/F much anyway, I'll keep following this thread it may be a while before I can get a header anyway.

I really appreciate what your doing.

 

So the conclusion here is that a Flowmaster will produce down low torque better and sooner than a Magnaflow? Would you say this is due to the chambered design creating some back pressure that our trucks really depend on? Also you have a 4 banger, would this apply to the 4.0 V6? Do you known which FM is the quietest? 70 series perhaps? Or the larger version of the 50 series? I'm currently running 24" magnaflow and hopefully FM has something similar! Good job on this experiment!

 

Thanks, Bob.
That's really good mileage. If I did freeway driving, I'm pretty sure my average would be a lot better than it is. I'm not in any big hurry to do anything about the lean condition because I hardly ever put the pedal to the floor. The most times it's ever been floored are on the dyno. I'm an old man driver, too.

Greg

 

That's what the dyno chart shows...




It's a modest difference, but it's definitive and consistent.

Note how the leading edge of each rising Flowmaster line precedes each rising Magnaflow line? That shows the Flowmaster torque coming on just a little bit sooner. The 100 rpm difference between the two peaks quantifies that difference.

Rather than backpressure itself, I think it's more a matter of retaining exhaust gas velocity. Something is going on inside the Flowmaster that isn't going on inside the Magnaflow, because each one has a completely different design and operates on different physical principles. The Flowmaster just does it a little bit better.

While that's an excellent question, I don't know the answer. 4.0's flow 50% more exhaust than 2.7's at equal rpms.

So much performance testing has been done on the 4.0. In contrast there has been almost none on the 2.7.

Here's a chart of most of their models...




Their website has more detailed information on each model...

http://www.flowmastermufflers.com/?page_id=10995


Greg

 

+1 for doin this!