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Thread: Asthetic Exhaust note

  1. #11
    I am thinking that with a tri-y design and the proper length of the primaries and matching of course, that one could reproduce the 180 pulse.
    This sounds to me like what you have called a 180 degree header. Using the exhaust pulse from another cylinder 180 degrees out of phase to scavenge is what you're talking about, right? Why is it that you don't want to use a 180 degree header?
    Owen Thomas
    University of Calgary FSAE, Schulich Racing

  2. #12
    Originally posted by Owen Thomas:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I am thinking that with a tri-y design and the proper length of the primaries and matching of course, that one could reproduce the 180 pulse.
    This sounds to me like what you have called a 180 degree header. Using the exhaust pulse from another cylinder 180 degrees out of phase to scavenge is what you're talking about, right? Why is it that you don't want to use a 180 degree header? </div></BLOCKQUOTE>

    space constraints, heat, weight.

  3. #13
    space constraints, heat, weight.
    Well, those are always the restraints on an exhaust system... What I'm getting from this is that you want the effect of long pipes, but you don't want long pipes?
    Owen Thomas
    University of Calgary FSAE, Schulich Racing

  4. #14
    Originally posted by Owen Thomas:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> space constraints, heat, weight.
    Well, those are always the restraints on an exhaust system... What I'm getting from this is that you want the effect of long pipes, but you don't want long pipes? </div></BLOCKQUOTE>

    That would be incorrect. I am after the aesthetic affect (the music created) that occurs when the puleses are spaces 180 degrees as per the ferrari toned exhaust caused by the 180 pulse.

    180 headers are not only very very long but imagine having 8 pipes piped under or over the engine 1 and 5/8ths diameter about 30 or more inches long connecting the primaries that are 180 degrees (firing order wise) apart, then again another y to bring them from a 360 degree header to a 180 degree. THIS is a HUGE header.

    so this is much more (size) than any other exhaust known. so the heat the space constraint etc was a valid response. Does this make sense?


    also as a note in any other configuration that i am currently aware of shorter pipes = higher freq note (which is what i am after) and longer pipes produce a lower freq note.

  5. #15
    The pipes should not need to be 30" long to pair with a 180 degree off cylinder, but yeah that would definitely make it more complicated. Especially with the 5-8 and 1-4 pairs you would have to do. Although, as a side note, that should get you a little more juice if you do it right.

    The only other thing I can think of to increase the pitch using header design is to decrease diameter, but if you're already planning to run 1"5/8 on that size engine it's going to kill your power (probably). You could look into different types of resonators and megaphones to put on the secondaries, or experiment with that magic x-pipe. Having not played with any of these things myself, I can't really give any insight, but as usual the best thing you can do is test out different setups.

    I'm sure there are lots of other ways to affect exhaust note, but unfortunately I think most of them would end up lowering the tone. Sorry I couldn't be of more help.
    Owen Thomas
    University of Calgary FSAE, Schulich Racing

  6. #16
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    To eliminate the "American vs. European" issue, is it safe to say that this, http://www.youtube.com/watch?v=pdi8tHbmAdc, is the sound that you do not desire?

    As you eluded to earlier, you cannot create frequency content that the engine does not produce. For 3000-7000 rpm, the firing frequency, the 4th order sound, will be 200-467 Hz. The exhaust sound will also contain frequencies higher and lower than this. Higher frequencies will come from the exhaust blowdown event and greater pressures will generally create more high-order noise. The most significant will likely be the 8th order, or double the firing frequency.

    Lower frequencies, the ones you are trying to avoid, come from uneven mixing of pulses due to geometrical discontinuities in the exhaust ducts cylinder-to-cylinder and odd firing orders. For a cross-plane v8, this will usually be the 1.5 and 2.5 orders.

    This video, http://www.youtube.com/watch?v=DnzxuS1HHpQ, has an interesting comparison between a C63 AMG and an M3 but with similar exhaust systems. The M3 has a higher-piched, raspy tone, while the C63 has more of the broad-range sound with more low-frequency content. The biggest difference I see between the cars is the log-style manifolds that come on the C63. Its uneven mixing of pulses creates odd-order sound and steals energy from the 4th order to do so.

    My advice would be this:
    -Don't skimp on the headers. Equal length will yield the least half-order sound.
    -Use an X-pipe or merge into a Y.
    -Keep it symmetrical
    -Long, uninterrupted pipes to the muffler(s) at the end of the system. The Innotec M3 system gets its rasp from this.
    -Corsa RSC (sounds great on E92 M3's) or one of the short-length Dynomax VT mufflers. The Corsa muffler kills the lowest frequencies with quarter-wave tuning, while the VT has a passive flapper valve for low frequency control. The flapper snaps open quickly at medium flow rates. The longer-length versions will contain more fiberglass, which might kill the character you desire to create.
    -Early exhaust valve opening to allow the sound wave to steep-front and create the raspiness that seems to help the M3 (with the right exhaust) sound like your ideal cross-plane v8.

    I've got a few FFT and sound analysis apps on my phone I like to play with. It was interesting comparing the C63 to the M3 in the video above when they switched from car to car. You might get a kick out of doing some quick analysis of exhaust sounds that you do and do not like. Being able to quantify the sounds with frequencies will help you decide which tuning elements to use.
    -----------------------------------
    Matt Birt
    Engine Calibration and Performance Engineer, Enovation Controls
    Former Powertrain Lead, Kettering University CSC/FSAE team
    1st place Fuel Efficiency 2013 FSAE, FSAE West, Formula North
    1st place overall 2014 Clean Snowmobile Challenge

  7. #17
    Originally posted by Owen Thomas:
    The pipes should not need to be 30" long to pair with a 180 degree off cylinder, but yeah that would definitely make it more complicated. Especially with the 5-8 and 1-4 pairs you would have to do. Although, as a side note, that should get you a little more juice if you do it right.

    The only other thing I can think of to increase the pitch using header design is to decrease diameter, but if you're already planning to run 1"5/8 on that size engine it's going to kill your power (probably). You could look into different types of resonators and megaphones to put on the secondaries, or experiment with that magic x-pipe. Having not played with any of these things myself, I can't really give any insight, but as usual the best thing you can do is test out different setups.

    I'm sure there are lots of other ways to affect exhaust note, but unfortunately I think most of them would end up lowering the tone. Sorry I couldn't be of more help.
    the 1 and 5/8ths dia is the correct dia for this size motor and rpm range. the 30 inches would be so the primaries stay equal length which is very important.

  8. #18
    Originally posted by Mbirt:
    To eliminate the "American vs. European" issue, is it safe to say that this, http://www.youtube.com/watch?v=pdi8tHbmAdc, is the sound that you do not desire?

    As you eluded to earlier, you cannot create frequency content that the engine does not produce. For 3000-7000 rpm, the firing frequency, the 4th order sound, will be 200-467 Hz. The exhaust sound will also contain frequencies higher and lower than this. Higher frequencies will come from the exhaust blowdown event and greater pressures will generally create more high-order noise. The most significant will likely be the 8th order, or double the firing frequency.

    Lower frequencies, the ones you are trying to avoid, come from uneven mixing of pulses due to geometrical discontinuities in the exhaust ducts cylinder-to-cylinder and odd firing orders. For a cross-plane v8, this will usually be the 1.5 and 2.5 orders.

    This video, http://www.youtube.com/watch?v=DnzxuS1HHpQ, has an interesting comparison between a C63 AMG and an M3 but with similar exhaust systems. The M3 has a higher-piched, raspy tone, while the C63 has more of the broad-range sound with more low-frequency content. The biggest difference I see between the cars is the log-style manifolds that come on the C63. Its uneven mixing of pulses creates odd-order sound and steals energy from the 4th order to do so.

    My advice would be this:
    -Don't skimp on the headers. Equal length will yield the least half-order sound.
    -Use an X-pipe or merge into a Y.
    -Keep it symmetrical
    -Long, uninterrupted pipes to the muffler(s) at the end of the system. The Innotec M3 system gets its rasp from this.
    -Corsa RSC (sounds great on E92 M3's) or one of the short-length Dynomax VT mufflers. The Corsa muffler kills the lowest frequencies with quarter-wave tuning, while the VT has a passive flapper valve for low frequency control. The flapper snaps open quickly at medium flow rates. The longer-length versions will contain more fiberglass, which might kill the character you desire to create.
    -Early exhaust valve opening to allow the sound wave to steep-front and create the raspiness that seems to help the M3 (with the right exhaust) sound like your ideal cross-plane v8.

    I've got a few FFT and sound analysis apps on my phone I like to play with. It was interesting comparing the C63 to the M3 in the video above when they switched from car to car. You might get a kick out of doing some quick analysis of exhaust sounds that you do and do not like. Being able to quantify the sounds with frequencies will help you decide which tuning elements to use.
    One thing i find odd is the ipe f1 exhaust is SOOO high pitched in comparison to many other systems and even more so from their factory headers as I have posted in my original post. in reference to the s65 bmw.

    they achieve this sound without the use of any special ignition system or a 180 header.

  9. #19
    also the c63 is a 6208 cc motor whilst the m3 is a 4.0lt

  10. #20
    F1 cars operate in a frequency range that is nothing like any production car. It should not surprise you that their exhaust note is different.
    -Charlie Ping

    Auburn FSAE Alum 00-04

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