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Magnaflow muffler for V-8 / cross-pipe

Discussion in 'Technical Q&A' started by snj5, Mar 15, 2004.

  1. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
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    Russ Turner
    Ok
    The guy at Magnaflow said that I would get a very low deep tone by going with design 'A' below as well as taking advantage of the X-pipe effect to promote scavaging from negative pressure waves as well as cancelling out unwanted sound roughness as opposed to 'B' using separate mufflers.
    He recommended an 18" packed muffler length using either plan.
    The lenths of pipe from both header connections to the muffler will be approximately equal.

    Ideas? Experience?

    many thanks
     
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  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    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"?
     
  4. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Steve
    Thanks for the reply.
    I made a big effort explaining it was a flat crank V-8 like 2 X 4-cylinder engines. He seemed familiar and was even familiar with the tubi I have now.
    In 'A', the 'X' pipe occurs IN the muffler packing in the middle of the muffler.

    I was just reading last night that the pressure wave and the flow wave are not neccesarily the same. Intuitively I would pick 'B', but he was quite confident 'A' was the better choice. Actually 'A' would be much cheaper and easier to do, which also makes me think it is not as good as 'B'. :)
     
  5. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,893
    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.
     
  6. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
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    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
     
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  8. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    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 ;)
     
  9. M.James

    M.James F1 Rookie

    Jun 6, 2003
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    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?
     
  10. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Russ Turner
    Thanks everyone for the great posts!
    Steve - could you rephrase that a bit to ensure I understand, please? I hoping for something much more smooth, sonorous, melodious and deeper pitched than the tubi that is not as loud.

    The twin mufflers are about $100 each, with the single being about $130.
    Stebro is custom making some of their tips with removable resonator to fit (most expensive part). The twin set-up 'B' is just a bit heavier and more complicated requiring two offset inlet mufflers.

    Thanks again everyone.
     
  11. thomas_b

    thomas_b Formula Junior

    Sep 15, 2003
    765
    “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.
     
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  13. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Thomas
    Thanks for the explanation. There will not be any cats down stream, and the length of tubing between the headers and the box will be approxinately the same. Attached is a schematic of plan 'A'

    again, many thanks
     
  14. cavallo_nero

    cavallo_nero Formula 3

    Nov 3, 2003
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    Giovanni Pasquale
    #11 cavallo_nero, Mar 16, 2004
    Last edited by a moderator: Sep 7, 2017
    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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  15. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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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?
     
  16. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Steve and C Nero - many thanks as usual for the great help - John, do you have a sound file?.

    This is how the US single cat 3.2 is set up; Euros aft headers are the opposite.

    The muffler box(es) are 5X8 ovals, 18 inches long, the maximum volume I can fit between the US hangars. Had considered going two mufflers fore-aft, but it starts getting heavy and the mounting gets complicated. Will call Magnaflow again today about tone and volume. I know many people who spend more on a couple of shots of Scotch than on this muffler, so may just give it a try.

    And yes, the moon would be fine. :) And could I get a graphic equalizer with the little horsey like on on boxers... :)
     
  17. Dandy_Don

    Dandy_Don Karting

    Dec 8, 2003
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    Don McCormick
    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
     
  18. cavallo_nero

    cavallo_nero Formula 3

    Nov 3, 2003
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    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
     
  19. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Different day, different tech, different advice. These guys ought to be doctors.

    Talked to a new guy at Magnaflow today that says the crossflow option 'A' would work, but not well - certainly not as well as 2 separates.
    So, am back to the dual system idea.

    John - which mufflers (round, oval, length?) did you install and how do they compare to stock and tubi?

    Don - will keep you informed.

    Many thanks
     
  20. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    We are now at design 'C' using two center/offset Magnaflows (or whatever) utilizing 18' long 5X8 ovals; Will entail putting a hanger at the inlet. Have tried to eliminate number of bends in the system.
    Alternatively, could use an Ansa unit from a Toyota they (Ansa) are clearing out for $50 per side.

    Ideas?
     
  21. cavallo_nero

    cavallo_nero Formula 3

    Nov 3, 2003
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    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.
     
  22. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
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    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
     
  23. EspritSE

    EspritSE Formula Junior

    Dec 1, 2003
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  24. snj5

    snj5 F1 World Champ

    Feb 22, 2003
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    Got back from the tubing welding shop. The US spec rear headers exiting on the starboard side are a problem to get a 180 degree turn off and still have room to have a real twin exhaust. There is room for the boxes, but the tubing bending is not looking good.
    Mind you, this is not an issue for non-single cat cars as those headers exit on the port side. I'm not as keen on replacing the rear headers at this point without doing both sides and removing the air injection nozzles. So any of you pondering one of these systems with those cars would have an easy time of it.
    I've also been advised it might not be a bad idea to leave the system where I could put the cat back on if needed.
    So, I'm back to the original plan of a hybrid Tubi/Stebro system unless I have a flash of brilliance or someone else knows a good answer.

    The Burns products do look great - aircraft quality.
     
  25. chrismorse

    chrismorse Formula 3

    Feb 16, 2004
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    chris morse
    #22 chrismorse, Mar 16, 2004
    Last edited by a moderator: Sep 7, 2017
    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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