Magnaflow muffler for V-8 / cross-pipe

Are you sure the guy at Magnaflow realizes that you have an alternate-bank-firing V8 (i.e., a flat crank in a 90 deg V block)? "Unwanted sound roughness" is more of an issue on the "B" set-up with a non-alternate-bank-firing V8 (i.e., a 90 deg crank in a 90 deg V block) IMO.

Where is the actual muffler(s) in "A" -- before the "X", after the "X", it is the "X"?

 

The potential problem with the A design is that positive pressure waves that enter the header as the exhaust valve opens will pass from one bank to the other. Depending upon all the lengths of the hose, this can augment or disrupt the header harmonics. For example, at one RPM, an opening exhaust valve will allow a pressure wave to trvel down the header, accross the mufler back up the other header and arrive with both the intake and exhaust valves open. At this point, the positive pressure wave blows the current misture back up the intake, and fills the intake 'velocity stack' with exhaust residuals (which don't burn well the second time). This leaves a big hole in the TQ curve at the RPMs where this happens.

Proceed with caution.

 

Russ
As you may know, John Asselta (sp?) has "B" and has dynoed it with good results, likes the sound etc.

I believe the factory muffler (and I am guessing the Tubi too) looks more like B inside the muffler can than A (actually I think one side does a "C" pattern, the other the mirror image). Didn't someone cut one open recently?
Philip

 

Well, you've always got the problem that the vendor might not be as objective as you are in the decision

I'm a little surprised that he talks about only one version promoting "scavenging from negative pressure waves" sort of implying that the other version doesn't have any scavenging effect at all.

My take is that "B" is a simplier (single) flow path, and its best scavenging will be stronger (higher-Q) than "A" when "B" is at its maximum;however,

"A" may have multiple/lower-Q scavenging resonances, which won't have as large a single maximum resonance as "B", but may provide a better overall response (i.e., more power than "B" when not operating near "best" scavenging).

Acoustically, I'd go the same way -- "B" having a very strong fundamental tonal quality, while "A" would be less "singular" (i.e., more fundamental + other harmonics).

JMOs -- please don't take too seriously.

Regardless, you are going to have the best sounding 3.2 on the planet just from the intake noise

 

I had heard from another post that with Magnaflows, the best setup was with two units in a True Dual Exhaust configuration. This config used Cat Bypass Pipes to seperate the two headers, routing the exhaust of each cylinder bank seperately to its own muffler. Was this not sound? Or just more expensive than the single muffler with dual intake and quad output?

 

“A” is actually the better design if the merge box is designed right, i.e. flow is not disrupted

reasons are:

- each pipe 1-4 and 5-8 sees actually two output pipes -> reduced backpressure

- the exhaust pulse in pipe 1-4 can expand into pipe 5-8 backward and vice versa –> reduced backpressure

- pulses in pipe 1-4 and 5-8 can cancel each other out -> reduced popping; harsh noise

What actually happens is that the crossover levels out the exhaust pulses between the two cylinder banks.

I am skeptical about the claimed scavenging effect of opposite banks if the merge box is that far downstream of the headers and with cats in-between.

The Stebro competition exhaust http://www.stebro.net/fr36rc.gif is a good example for a merge box.

 

HI folks, good topic here, i almost went with the A configuration using a flowmaster and i am glad i did not, i too think there would be too much interference on that setup. And actually, we could not get the crossflow flowmaster or magnaflow to fit under the 308 backend. my dual magnaflows sound great, look great,and i felt a significant power increase, i am still trying to jet the carbs to this configuration. magnaflow mufflers use a special perforation in the chamber that do not protrude into the exhaust flow, thus a more freeflowing setup - a lot like a crotch rocket motorcycle design - for higher rpms. when i get my 34mm choke venturies, i will go to the dyno with my bag-o-jets. here is another pic. has anyone cut open a stock or stebro (god forbid a tubi) to see the internal structure???????
john asselta
78 308 GTS euro
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Well why not just ask for the MOON! -- how about auto volume control with equalizer? . Seriously, any header+nothing+performance muffler system is going to be on the loud side IMO. Your comment about "deeper" makes me think you should try to maximize the size of the muffler chamber more like the old steel 308 ANSA silencers (effectively using the chamfer as a low-pass pressure filter) -- but I'd still characterize that set-up as "loud". "A" would be better in this respect compared to "B" (if it's got more internal open volume than the "B" silencer).

With regard to the tonal quality of "A" vs "B", my point was that in "B" you have a singular, well-organized exhaust pulse occuring at one tailpipe; while in "A" you have two half pulses occuring at two tailpipes. While mathematically this works out as equivalent to an observer, in a real system the half-pulses don't remain perfectly coherent so when recombined in your ear this adds more "stuff" to the acoustic spectrum -- not saying that one is more pleasing or better than the other just that they may have a slightly different "chords".

PS -- Doesn't the 1/4 header exit in the other direction than shown in your sketch?

 

Russ

I am interested in this thread as I am in the market for a free flowing exhaust as well. If there is any advantage to be gained by ordering more than one then please let me know. Don

 

HI Russ
I do not have a sound file, wish i did tho. the sound is quite throaty, not too loud, but it has a healthy growl at 7000 rpm. i get complimemts from the vintage F1 race guys all the time at the track, maybe its my webers. but all the other ferraris out there have the tubi setup.
john

 

HI Russ
I used the round muffler, i think 4 inches round, and of course mine are transverse mounted. i think they are 18 inches long. i am surprised that you can get those two mufflers under the 308 in the configuration you have above. i also had my mufler guy make a set of 2 cats with tips to replace the magnaflows in case i need them for emissions purposes, but in colorado, since my car is 25 years old, i no longer need a e-test..... i think the oval mufflers you have pictured above will be quieter than what i have on my car.
john
i will see if i can track the model of magnaflow i have on my car.
good luck, either way, you are smart to go with 2 mufflers.

 

Russ
I too am surprised you can mount the mufflers longitudinally - must be that the Mondial is quite a bit longer than the B, S behind the engine??
Following your progress with interest
Philip

 

No offense, but, Magnaflow welds look like bird s**t. Have a look at Burns.
http://www.burnsstainless.com/UltraliteMuffler/ultralitemuffler.html

fwiw...

 

Hey Russ,

I really liked your developement series on the 3.2 carb engine.

Take a look at some of the earlier ,(old) posts on flowmaster 308 systems. Ben Millermon tried it and I have been unable to contact him on his thoughts about it. If I am successfull, you will see a picture below.

My two week old 77 GTB is about to loose the 100 lb thermo - ansa.

I have ordered a series 80 flowmaster and will get it installed Friday by a great muffler tec that I have had do two prior flowmaster systems on other vehicles, with good results. He has tried "type A" and "Type B" systems on two other 308s and indicated that the type B seperate dual systems had a sharp snap to the exhausts that the owners did not care for and that the type A systems worked out better.

He did not indicate whether he had tried to tune the soud with resonator tips. I will try it without for a couple of days and report back.
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