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Thread: I put Ferrari 599 mufflers on my 850 Ci

  1. #1
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    M73 850 Ci

    I put Ferrari 599 mufflers on my 850 Ci

    I merged both banks of the V12 into a single 3" diameter pipe and into a pair of OEM Ferrari 599 GTB Fiorano mufflers.


    This is what it sounds like: https://youtu.be/UeED_c2XvNc




    Now onto the explanation.


    I wanted an exhaust that brings out the character of the V12 with these requirements:
    1. Reduced (hopefully zero) low frequency 'deep rumble' / drone (below 120 Hz).
    2. High frequency, high pitched scream / wail at high rpm (above 1,200 Hz).
    3. Should produce at least two simultaneous high frequency notes (chord - like playing two keys on a piano).
    4. Should look stock to the casual observer, and not detract from the elegance of the E31.


    Exhaust pulse frequencies


    First we'll look at some examples of which sound frequencies are produced by different cars to try to understand why they reach the notes that give them their unique tonality. The vertical axis is frequency and the horizontal axis is time. The following spectrograms are under load at wide open throttle.



    This spectrogram shows the frequencies produced by a Mustang GT exhaust. It's a crossplane V8 with uneven pulses (LRLLRLRR). Most of its energy is concentrated below 500Hz, and strongly at ~100Hz (this is the deep rumble). Notice how the lines are muddled together - a 'dirty' sound. This is just a reference of what I am trying to avoid.



    This is a Ferrari F12 with a Capristo exhaust. Note the strongly defined parallel lines produced as a result of engine rpm and its harmonic series (fundamental frequency multipiled by two, three, four...). There is considerable energy above 1200Hz - this is the high pitched wail. There is very little energy below 150Hz because it lacks deep rumble.



    This is a stock Ferrari GTC4Lusso V12. The gearshift occurs at redline at at the black vertical line. We see strong harmonics that peak at 2,000 Hz. To see this more clearly we need spectrum plots at 2,900 rpm and 8,000 rpm.



    GTC4Lusso at 2,900 [2930] rpm. The fundamental frequency produced as a result of engine rpm is 293Hz, which is a D4 note. We find more peaks at its 2nd harmonic at 586Hz (D5), and 3rd harmonic (A5). There are undertones below D4. This could be a result of not having an x-pipe or if it does have one it does not fully merge pulses from left and right banks.



    GTC4Lusso at 8,000 [8080] rpm. The fundamental frequency is touching the sky at 808Hz and is very prominent, louder than its harmonics. However, the harmonics are still there. Undertones are present here as well. We can't reach this fundamental with an M73 - the most we can reach is 600Hz at redline.




    Merging into a single pipe (A very long x-pipe)
    To simplify we'll assume that the engine is running at 6,000 rpm, which is equivalent to 100 revs per second.
    One cylinder in a four stroke engine gives us one exhaust pulse every two revolutions. Each I6 bank gives us 3 pulses per crank revolution. At 100 revs per second we have a fundamental (base) frequency of 300Hz.


    Due to the firing order of the M73 V12 (1-7-5-11-3-9-6-12-2-8-4-10) the pulses on both cylinder banks alternate evenly. If we join/merge the exhaust from both banks (think a very long x-pipe, or into a single pipe) we can duplicate the sound frequency and we'd have a 600Hz fundamental at 100 revs per second. A V12 with a merged exhaust makes calculations easy for us because to get the fundamental frequency all we have to do is divide the engine rpm by 10. (3,140 rpm gives us a 314 Hz fundamental).


    All frequencies shift by 2x. Essentially the 2nd harmonic of an unmerged V12 becomes the new fundamental frequency of a merged V12. This helps solve requirements #1 and #2.


    For comparison, if we chose a different engine configuration to try to produce the same 600Hz fundamental as our merged V12 at its 6,000 rpm redline, we would need a merged flatplane V8 at 9,000 rpm or a straight six at 12,000 rpm to be able to generate exhaust pulses at this rate.


    This merging of both banks of the V12 into a single pipe is an idea that T.G. Sasaki executed masterfully in a Mercedes S600. https://jalopnik.com/how-to-make-a-u...nda-1611782156


    It was later replicated over at MBWorld by shooffnyc. https://mbworld.org/forums/s-class-w...ng-happen.html



    The exhaust by T.G. Sasaki for the most part produces a single note at the fundamental frequency we would expect for a single pipe V12 with very strong harmonics of that note. It even reaches sixth harmonics, which is impressive. A very clean soundwave produced by equal length headers (harmonics perfectly in sync) and unencumbered by catalytic converters or restrictions (almost no resonance at other frequencies other than those produced by engine rpm).




    OEM Ferrari 599 GTB Fiorano mufflers.
    The Ferrari 599 GTB rear mufflers seemed like a good candidate for the E31 due to their shape/size and pipe placement.


    Ferrari F140C (599) BMW M73
    Displacement 6L 5.4L
    V angle 65º 60º
    Valves per cylinder 4 2


    They were designed/tuned for a naturally aspirated V12. There are some important differences from our BMW V12 which will influence the sound, but the basic principle still holds.





    I got Ferrari part numbers 220193 and 220194 even though at this point proper fitment was just a guess.
    https://www.ricambiamerica.com/car-d...tml?mode=split





    It particularly caught my attention that the input pipe into the muffler box has a smaller pipe at 90º that also goes into the muffler box. Two different diameter input pipes are fed into the muffler, and the exhaust tips have two different output pipe diameters as well.
    The muffler has a vaccuum operated valve on the inner exhaust tip which I left permanently open.





    Although I can't see inside the muffler and don't know what exactly is going on in there, I am speculating that the two different diameter inputs and outputs are directed though separate chambers with different resonance characteristics. The tip with the valve might be a straight passthrough, while the smaller diameter pipes might be 'S' shaped inside the muffler. Each output is tuned to produce a different frequency. If this is true, it would solve requirement #3.


    The tips are staggered, aren't oversized, and styled in a way that they could pass for a stock CSi exhaust to the casual observer, solving requirement #4.


    Fitting it all together





    I discussed this diagram with a custom exhaust fabricator. He understood the idea of what I was trying to do and took on the project.


    The length of the 3" pipe although likely has an effect on the sound couldn't be changed much because it mostly depends on the geometry of the car and how the pipes can be routed. I left this decision up to the fabricator.


    A single 3" diameter pipe should be enough to displace sufficient air to not be restrictive for ~350hp, so the M73 should be fine.


    This is what it looks like.










    The 1-2 split after the center pipe.





    The 2-1 merge into the center pipe.


    Aesthetics














    Results
    These recordings were made on a stationary Sony RX100M4. I need to attach a microphone to the rear of the car to capture a better quality recording, but this will do for now.





    Notice how all the frequencies are at or above the fundamental frequency produced by engine rpm, almost as if it were a hard cut off or high pass filter. We have eliminated the deep rumble.
    We see strong harmonics between 2,750 and 4,750 rpm. In this rev range we have four simultaneous notes plus their harmonics at similar loudness, giving us a very rich and full sound. I'd say this is the rev range that gives the most beautiful sound.
    After 4,750 rpm the harmonics seem to be drowned out by the dominant fundamental frequency. It has the wail and it does sound good, but it's a slightly flatter sound that is compensated by loudness.





    This spectrum plot shows a snapshot of the frequencies at ~2,900 [2930] rpm at full load. If we look at this in terms of musical notes, the fundamental frequency produced directly as a function of engine rpm is D4, as in the GTC4Lusso. But we have other notes present as well: G4, B4, F5. This is a G7 second inversion chord, or G7/D.
    http://www.pianochorddictionary.com/...version2.shtml


    We also have D5, G5, B5, F6 which are the 2nd harmonics of D4, B4, G4, F5. We also have F6 which is the 2nd harmonic of F5, and with this we punch above 1,300Hz. The wail!
    We have no undertones below D4 or frequencies below 120Hz.



    At 5,500 rpm [5510] at full load, the fundamental 551 Hz becomes louder than its harmonics and other notes, this is why at high revs we mostly perceive a single note. We also have an undertone at 275 Hz, which I find a bit strange and don't know where it's coming from. We have a 3rd harmonic at G6 and a second harmonic at B6 which gets us closer to 2,000 Hz.





    This is ~3,300 rpm [3330] with no load (stationary in neutral). Notes and harmonics are clearly defined. We have a chord.





    Dark blue: fundamental frequency produced directly by engine rpm.
    Blue: fundamental frequency of a note found in the spectrogram.
    Light green: 2nd harmonic present.
    Dark green: 3rd harmonic present.
    Orange: Missing harmonics that overlap between 'blue' notes. Maybe they are out of phase and are cancelling each other out (destructive interference).






    So far I'm very happy with my new exhaust. It's relatively quiet below 2,750 rpm and due to the low end torque of the M73 and the long gearing of the ZF 5HP30, in normal civilized driving I very rarely go above 2,500 rpm and most of the time stay below 2,000 rpm. In this rev range it's louder than stock but not annoying. Without deep rumble / low frequencies I am not rattling windows or setting off car alarms. Highway driving with cruise control is still comfortable and without drone. Idle is quiet inside the car (600 rpm).

  2. #2
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    That sounds really good. I like it a lot.
    Board Member of SoCalEights (Marketing, Web Development & Social Media), Vice President: BMWCCA/E31 Chapter, www.cartiologyfilms.com
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  3. #3
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    That does sound really awesome! I'd be surprised if major brands put as much sound tuning engineering as you seemed to have done.

    I have a full header back super sprint system and while I am happy with it I was expecting a more exotic sound as you seemed to have achieved. Very cool!


    Sent from my iPhone using Tapatalk Pro

  4. #4
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    Now this is super impressive!!!

  5. #5
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    Does it do anything to the performance of the car (motorwize)

  6. #6
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    Would this setup work on the M70? Fundamentally, the same engine, just a bit smaller displacement?
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  7. #7
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    That sounds really nice. The ingenuity is really something. Who would have thought to put FERRARI mufflers on an 8. I just wonder what FERRARI mufflers would cost. CSi mufflers are around 2K for a pair, ALPINA mufflers are around 4.5K a pair, but wonder where FERRARI prices would be.
    CSi #18 - Car & Driver Magazine 1994 actual test car
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  8. #8
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    I have seen them for 1500 dollars a pair on the net.

  9. #9
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    Ebay has them for $680 each
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    ...the price of cool ain't cheap!

  10. #10
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    Quote Originally Posted by peake View Post
    Does it do anything to the performance of the car (motorwize)
    I don't think so. Performance seems the same to me, if there is a difference I can't notice it.

    Quote Originally Posted by masbury View Post
    Would this setup work on the M70? Fundamentally, the same engine, just a bit smaller displacement?
    I think it should be very close.

    Quote Originally Posted by rogbmw View Post
    That sounds really nice. The ingenuity is really something. Who would have thought to put FERRARI mufflers on an 8. I just wonder what FERRARI mufflers would cost. CSi mufflers are around 2K for a pair, ALPINA mufflers are around 4.5K a pair, but wonder where FERRARI prices would be.
    The thing with stock Ferrari mufflers on the used market is that they are undervalued. These mufflers go for $3,000 USD MSRP new each, so $6,000 for the pair, but the owners of these cars take them off with very little use and replace them with Tubi or Capristo systems. If these cars get into an accident they'll almost surely be repaired with brand new parts, and not many people have a use for these parts so the market for used stock Ferrari mufflers has few buyers. I paid ~800 USD for the pair. For mufflers of this quality I'd say it's a very good deal.

  11. #11
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    Thats a pretty good deal!!!

  12. #12
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    Amazing work! Thank you for sharing the details, as I have no doubt it was a lot of time and effort.
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  13. #13
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    That's a great deal on the mufflers. You're right...seems like all the Ferrari ads say something about a replacement exhaust.
    CSi #18 - Car & Driver Magazine 1994 actual test car
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  14. #14
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    I was considering the Eisenmann exhaust but after seeing this I am torn

  15. #15
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    Quote Originally Posted by Fatandre View Post
    I was considering the Eisenmann exhaust but after seeing this I am torn
    Eisenmann sounds nothing like this. I had Eisenmann "race" version exhaust in my previous eight (m70) and i was disappointed. It was actually pretty silent. IMO Eisenmann needs atleast an x-pipe also to sound good. Still, this is alot better!

  16. #16
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    Love, love, LOVE the sound - Congrats!

  17. #17
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    That sound note, build and video is awesome! I'm curious has anyone put a QTP exhaust cutout on one of our beloved e31s?
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  18. #18
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    Thanks for the write-up.
    My mechanic and I have been discussing doing this for the V8 to get rid of the drone, I too have been looking to acheive that high-pitched but raspy note from the Maserati and Ferrari systems!

  19. #19
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    Wow, the sound is amazing! Dag...i do think much better than Eisenmann's.
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  20. #20
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    Great work, thanks for posting.
    I would think that this setup might not sound quite as good on the lower compression M70, the M73 is 10:1 correct?

    Thanks again.

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    OP: Sounds great, What year is the car?

  22. #22
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    wow.... the sound this car was missing !
    One of the best upgrades I have seen in years .....
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  23. #23
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    Thanks for the comments.

    This sunday I'll show off my 8 at Radwood LA (Dec. 2nd at the Petersen Automotive Museum). It's a 2,600km round trip so if there is any drone at all with this exhaust that I haven't detected yet I'll surely find it.


    Quote Originally Posted by LaurelSGX View Post
    Great work, thanks for posting.
    I would think that this setup might not sound quite as good on the lower compression M70, the M73 is 10:1 correct?
    The M73 is 10:1 and the M70 is 8.8:1. Although it would probably sound different (I'm not sure how much without trying it and measuring it), the fundamental frequency produced as a result of engine rpm should be exactly the same. The order of the exhaust pulses would be the same.

    Quote Originally Posted by 8eights View Post
    OP: Sounds great, What year is the car?
    It's a 1995 Euro-spec.

    Quote Originally Posted by tangcla View Post
    Thanks for the write-up.
    My mechanic and I have been discussing doing this for the V8 to get rid of the drone, I too have been looking to acheive that high-pitched but raspy note from the Maserati and Ferrari systems!
    http://www.projectm71.com/Cross_FlatPlane.htm

    Your V8 has a crossplane crank, so you're not going to get the exhaust pulses aligned like a Ferrari flatplane V8 without overly complicated headers (https://www.hotrod.com/articles/180-...drange-torque/).

    The Maserati V8 does have a crossplane crank.

  24. #24
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    tvjake2 is offline SoCalEights - CA BMW CCA Member
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    Quote Originally Posted by vgs View Post
    Thanks for the comments.

    Your V8 has a crossplane crank, so you're not going to get the exhaust pulses aligned like a Ferrari flatplane V8 without overly complicated headers (https://www.hotrod.com/articles/180-...drange-torque/).
    Yup.

  25. #25
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    I drove 1,300 km to Los Angeles, CA for Radwood.

    It's pretty quiet with cruise control set between 120-130 km/h. No droning, even uphill when engine load increases.

    I did notice a 'pop' (backfire) between 100 and 115 km/h when driving gently and I let off the accelerator then quickly press it again slightly. Inside the car it's not loud, but it's noticeable. It sounds as if I had left a loose water bottle in the trunk and it's moving around when braking. Driving over the little bumps that separate sections of road is louder than this. It also seems to only happen during a long drive, so maybe it's temperature related.

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