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Engine Tone

Discussion in 'General SAOCA Discussions' started by Eleven, Jul 30, 2020 at 4:26 PM.

  1. Eleven

    Eleven Gold Level Sponsor

    Aside from exhaust systems, I have always been curious why engines of similar size and configuration will have different sounds (tone). My Alpine has one small muffler in the system (much to my neighbors dismay). The car has a very low and aggressive sound to it. My old Triumphs (Spitfire and GT6) were much more mid range pitched. I don't remember MG's being low pitched but engine size and configurations are the same as my 1725. I remember hearing Chris Amons Matra 12 at the Nurburgring and the howl of that was different (and cooler) that Ickyx's Ferrari.
    Apropos of nothing.
     
  2. Bill Blue

    Bill Blue Diamond Level Sponsor

    Don't know how it applies to old sport car engines, but a lot of "exhaust" sound from today's engines is actually intake. Some engines are very noisy even with effective mufflers. The Duratec is one example. I think Charles Johns mentioned this a few days ago, saying it had to do with exhaust noise from the intake due to valve overlap. If so, valve overlap could be responsible for exhaust tone. Maybe even if not so. Could it be that while tuning the intake you are to an extent tuning the exhaust?

    Bill
     
  3. alpine_64

    alpine_64 Donation Time

    Firstly the compression exhaust path inside the head and the intake system contribute heavily to the sound.

    The BMC engines you compare against are veey different as they have Siamese ports in the head whereas rootes had individual ports for intake and exhaust on each cylinder.. So no mixing of combustion exhaling till they meet in the headers.. Mgs have a distinctive farty sound.

    Your gt6 was a small straight 6 so a very different configuration of both bore/ stroke ratio and header design and mixing.

    Capacity makes little difference compared to bore and stroke ratio, compression, firing order ( think of flat plane crank v8 vs standard.. Or when you hear a gt40 v8 with cross headers.. No opposing thumping sound as it comes out merged like a straight 8)
     
  4. Eleven

    Eleven Gold Level Sponsor

    Huh. That is interesting. The Alfa GT's at our vintage races are much lower pitched than the BMW 2002.'s That surprises me as I expected them to sound higher reving (which they probably are). The comment on the flat plane crank is also interesting. We have at least three Fords here in our Vintage racing club that I think are running them. They sound like Indy cars of years ago. Having worked on a Trans Am car back in the day, I don't recall Fords sounding like that... I think the Spitfire and GT6 were bad examples but the MG thought was more what I meant. Anyway, that's the type of deep thoughts I get being isolated for so long. Weather here is outstanding so Alpine decided to pee oil all over the garage floor. Argh,
     
  5. alpine_64

    alpine_64 Donation Time

    The bmw ohc engines especially in m10 form are screamers.. Get near any chevron b10 or same era formula car that ran the m10 based motors... Music to your ears ;-)

    As for the MG the siamesed ports would have a big impact on their sound.
     
  6. MikeH

    MikeH Platinum Level Sponsor

    The Fords could be running X-pipes. It gives then a completely different sound.
     
  7. alpine_64

    alpine_64 Donation Time

    Having an X pipe or balance pipe in the exhaist on the V8 will mellow the spund amd smooth it out. Especially as they get higher up in the RPM. They will still sound like a traditional v8 at idle woth alternating pulses.

    The cross over headers like the GT40s have would be almost impossible to fit to a non mod engine car.. ( gt40, detomaso, Lola) but ive heard rumors some people have fitted flat plane cranks to Windsors....

    For reference the cross over headers that exhaust the motor in a straight firing order.

    [​IMG]
     

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