Magnaflow - a closer look

[Paul Workman]

Yesterday Bob G and I together took a close look at my new "3 inch" Magnaflow system and together we noted some...er..."discrepancies"??

In short, I don't think either of us would call it a pure 3" system, towit:

• The 3-bolt flange on the passenger side - the flange ID is smaller than 3", and thus an approx 2-1/2" dia. X approx. 2-1/2" long "choke" point exists. (That's one)
• The X pipe appears to be a 2-1/2 or 2-3/4 ID, as does the inlet to the resonator - another choke point. (That's two)
• Inside the resonator, on closer look, the (narrower than 3") X pipe outlets funnel out to morph with what appears to be a short single section of 3" tubing - maybe 8" long - essentially another "X" pipe...sorta...another choke point...before splitting to form what appears to be a 2-3/4" (not a 3") outlet junction onto the 3" tail pipes. (I wouldn't count this as a choke point as the ID is simply morphing from the narrow(er) resonator output to slightly wider 3" tubing.)
• Then at the muffler input, the 3" tubing is again sharply choked down to what might be no more than 2-1/2" dia. inlet - definitely a choke point (more on that).
• The muffler inlet is internally split into a pair of perforated tubes, approx 2" in dia that appeared (to me) to funnel out to about 2-1/4 to 2-1/2" each before morphing into more or less a pair of 3" outlets. (Note: Two 2" tubes has less cross-sectional area than a single 3" tube, FWIW)

Physics, being a discipline of mine in a previous life, lends me enough knowledge about fluid dynamics to be really dangerous. So, when Bob and I were examining the system up close, the choke points I mentioned raised some questions about overall impedance of the system as compared to a true (nothing less than) a 3" system. In particular, there were some abrupt changes in ID that are much more concern than gradual transitions; especially the X pipe and the second "Y" inside the resonator, and the muffler inputs.

I don't know to what extent these choke points are significant, but they certainly are not going to enhance flow dynamics. And, if a 3" system is baseline for a big displacement LT5, I would prolly keep looking or perhaps get cozy with a good exhaust man and do some modifications.

All that said, the Magnaflow system is beautifully made and sounds great (on Dom's car). I'm going to install it for now, but I'll be revisiting it later, after I get the rest of my "stuff" done. In the mean time, the "best exhausts" topic never gets old (to me - it's that physics thing, yaknow)).

P.

[XfireZ51]

Paul,

Excellent analysis! I hope you or anyone else do not feel that they were
misled by my enthusiasm for this system. At the end of day,
It comes down to how it runs and sounds. In actual use,
I can state that the system does a great job in providing
A sweet exhaust note and no resonance at cruise.
Performance wise, I dyno'd the same HP as with the
B+B system. On the track, I picked up another 1.5mph
than my best trap speed with the B+B. And I believe there's
more available with additional tuning now that I've installed
my WB O2. Marc H. has often said that he found virtually
no power dropoff with the 2.5" Corsa system.
I'm looking forward to your impressions once your ZR is
up and running. I guess the ZR exhaust system quest continues!

[Aurora40]

Doesn't sound much worse than the "3 inch" B&B system, except it sounds like it is much more livable.

Thanks for the in-depth scoop. Got any pictures to accompany it?

[HIZNHRZ]

I sold my B&B system because of resonance not performance but what I seem to remember about the system was:

- no choke point from the collector to the resonator.
- there was a reduction into the resonator.
- there was a reduction into the mufflers.
- there was a reduction into the tailpipes.

I'll apologize in advance if my memory of the system is wrong.

I replaced the B&B with a Corsa system and I am very pleased with performance, tone, and resonance. If I could change anything it would be the fake tailpipe outlet on each Corsa muffler. I also spoke with Marc Haibeck about the Corsa vs the B&B and what I remember him saying is he has found no difference between the two with his top end package and factory displacement engines but has seen differences with stroker engines and Corsa systems. After reading Pauls analysis (and others) it would appear B&B and Corsa have nothing on the Magnaflow system in the way of quality, resonance, and tone and it remains to be seen whether the Magnaflow system proves to be better than Corsa and no worse than B&B.

The only other thing is I still want to see is whether the tailpipes visually compliment the ZR1s big fat butt! Until proven otherwise, this is still where B&B has them all beat.

[jonszr1]

have dominic send you a pic of his car with the magnaflow system it looks way cool

[XfireZ51]

Originally Posted by HIZNHRZ

I sold my B&B system because of resonance not performance but what I seem to remember about the system was:

- no choke point from the collector to the resonator.
- there was a reduction into the resonator.
- there was a reduction into the mufflers.
- there was a reduction into the tailpipes

...After reading Pauls analysis (and others) it would appear B&B and Corsa have nothing on the Magnaflow system in the way of quality, resonance, and tone and it remains to be seen whether the Magnaflow system proves to be better than Corsa and no worse than B&B.

The only other thing is I still want to see is whether the tailpipes visually compliment the ZR1s big fat butt! Until proven otherwise, this is still where B&B has them all beat.

HIZNHRZ,

I had a B+B as well. The resonance could get a bit rough but I was able to mellow it out with some tuning. It was better at cruise with the tune on the "lean" side. However, I really wanted to put on an Xpipe but didn't want to exacerbate the noise issue by removing the resonator. I liked the idea of a resonator mit Xpipe but couldn't find one other than the Dynomax, I believe. Then I heard about the Magnaflow which included the Xpipe. When I spoke with Marc H. , he told me the B+B resonator would neck down to 1 5/8" and the B+B did drop to 2.25" as it entered the resonator and coming out. The Magnaflow seemed to have more consistent ID than the B+B. They advertise a consistent 3" O.D.
As for the Magnaflow resonator, when I looked at mine it was 2 flow paths
through it, not merging into a single pipe. That was in August so maybe my eyes were playing tricks on me.
If the MF system had the B+B tips, it would be perfect IMO.

[Paul Workman]

Well, there's no doubt the SW/Magnaflow is going to be a huge improvement in what I have now; stock manifolds n cats, 2-1/2" Borla with some serious resonator inlet narrowing! I like everything about the looks and sound (yours has).

Anywayz...it was interesting to see "how it was done". I've got just a few parts and some gaskets to round up an I can begin the long road to 400 rwhp and mebby some lowish 12s at the track!?

Oh! BTW, I had a nice chat with Bob G about rear gears. As result, I'm prolly going to push that 4.11 (4.10?) rear end change up on the priority list, I recon! A P&P top end, SW headers n no cats, "3 inch" exhaust, a tune, and I suspect she will drive like a totally different BEAST!

Have a Merry Christmas, Dom (and Z gang!).

P.

[jonszr1]

[quote=Paul Workman;50583]Well, there's no doubt the SW/Magnaflow is going to be a huge improvement in what I have now; stock manifolds n cats, 2-1/2" Borla with some serious resonator inlet narrowing! I like everything about the looks and sound (yours has).

Anywayz...it was interesting to see "how it was done". I've got just a few parts and some gaskets to round up an I can begin the long road to 400 rwhp and mebby some lowish 12s at the track!?

Oh! BTW, I had a nice chat with Bob G about rear gears. As result, I'm prolly going to push that 4.11 (4.10?) rear end change up on the priority list, I recon! A P&P top end, SW headers n no cats, "3 inch" exhaust, a tune, and I suspect she will drive like a totally different BEAST!

Have a Merry Christmas, Dom (and Z gang!).paul you will love the car after those mods . they are the same mods as on my blk car except for a different exhaust(spin tec with dr gas xpipe) and fidanza fly wheel. depending on tires you should get very low 12s and maybe a high 11 sec time out of her . this look will always be on your face