Why do engines sound different ( read before writing me off as a retard)

Thread in 'Technical Questions' started by nissanr34cal, Jan 9, 2012.

  1. nissanr34cal

    nissanr34cal Well-Known Member

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    Hello there,

    Right I was having a discussion with a tutor at college and I wondered if anyone had a technical answer. Why does, for example, a 2.5 BMW straight 6 sound differnt to a 1jz-ge, or why does an rb have a unique sound just like an Sr or a Ca or a jz.

    My idea is it is because of the way the head flows or the size of the bore or the firing order but its just guess work.

    I have often wondered what the answer is and I'm hoping stavros will come along with a technical answer and explains it to me.

    Cheers
    Callum
     
  2. Dori-points

    Dori-points Member

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    All of those things plus a million more! Displacement, stroke, construction materials used, thickness of materials, density, manifold header lengths, exhaust silencers and layout, fueling, different turbos, cam duration and overlap, engine balance/harmonics engine lay out? Endless list. Or in short... They're different engines lol
     
  3. CIH

    CIH Member

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    I've always wondered why Toyota JZ motors seem to have the same kind of wail when being caned. 'tis a sweet sound, totally different to, say, an RB or BM straight-6.
     
  4. Dori-points

    Dori-points Member

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    Ever heard an impreza with equal length manifold??? Doesn't sound like an impreza any more!
     
  5. Trailer TrAsh

    Trailer TrAsh Member

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    Cal,you're a retard :-)
     
  6. nissanr34cal

    nissanr34cal Well-Known Member

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    I'm quite aware they are different engines I'm not fucking thick. I just wanted a technical explaination.
     
  7. Snorky Brother G

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    callum guess what
     
  8. nissanr34cal

    nissanr34cal Well-Known Member

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    Yes bitch tits
     
  9. Shorty

    Shorty Member

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    I've read it and i'm still gunna write you off as a retard! :wack:
     
  10. Snorky Brother G

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    they are different engines :p
     
  11. nissanr34cal

    nissanr34cal Well-Known Member

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  12. Trailer TrAsh

    Trailer TrAsh Member

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    Alright,precious,calm down! Why didn't your tutor explain it to you?!
     
  13. nissanr34cal

    nissanr34cal Well-Known Member

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    Because he is fucking thick. He had no idea he thought it was all to do with exhaust systems he reckoned if you put the same exhaust design on every car they would sound the same. I don't think he should be near a class room
     
  14. Trailer TrAsh

    Trailer TrAsh Member

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    Stop swearing! You should take the class,Cal,you're the future...and in no way is that worrying!:-)
     
  15. Cowpatmatt

    Cowpatmatt Active Member

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    exhaust design makes a huge difference in the sound of an engine. Car manufactures tend to tune the sound of the car for how they feel best suits the car its in.
    As has been said listen to a subaru one standard then one with equal length manifolds is the best example of this.
     
  16. H05TYL

    H05TYL Member

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    Yeah exhaust plays a big part in it, but an sr20 with a gt35/40 and 3" straight pipe sounds a lot different to a 4g63 with a GT35/40 and 3" exhaust.

    In that case obviously the sr's alloy block will have a different resonance to the 4g's iron block, but a 3sgte would sound different again.
    As someone already mentioned, cams, shape of the ports, stroke lemgth, rod to stroke ratio - basically everything about the engine that could be different will change the way it sounds.
     
  17. Stavros

    Stavros Active Member

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    To show how even really similar engines can sound very different.

    Red Top SR20= Sounds fine.
    Black Top SR20= Sounds like a wet fart.

    Why? Fucking evvvvverything.

    People always blame the exhausts/manifolds, its got a BIT to do with that, and thats it. Same as people saying the Impreza noise is all manifold. You think an Impreza with a equal length manifold sounds like any other straight 4? You need your ears tested, lol.

    Fuck, even heat wrapping my rx7 manifold/turbo and system right to the tailpipe made the car sound totally different.
     
  18. MrLuke

    MrLuke #172

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    As above, you can always tell which cars have a JZ in them by the noise they make :D

    An engine is basically an air pump, everything that affects the air passing through it will alter the sound, from the air filter to the exhaust tips.
     
  19. Joe-sef

    Joe-sef -Broseph-

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    With you stav on the strait cam/bent cam. Drives me fucking nuts when people say sr's sound like fart. No your stock uk bent cam with a bin on the back does...
     
  20. m.d.

    m.d. Active Member

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    A proper equal length manifold on an impreza makes it sound very very close to a stock 4 pot. I had one of those crappy eBay equal length ones and it is far from equal length. So still sounds like a scoob.
    One of my best mates had a del sol crx for years that he got a "Megan" exhaust manifold for and it made the car sound like a scoob due to the unequal lengths of the runners. Went back to the stock cast one when the thing rotted out and back to the normal vTec wasp noise it went.

    Bore and stroke makes a difference but the biggest difference between one engine to the next is the shape of the head.
    The flow characteristics of the head and the shape of the ports all change the note just like changing the size and shape of a wind musical instrument.

    The easiest way to think of it is look at a trumpet then a trombone. Both blown by the same volume of air (pistons). They both sound totally different down to the shape of the airways the air has to pass through.

    So as stav said. The exhaust does have an effect but it's normally just tweaking the specific noise the engine has already made. Just like a sound engineer does on his mixing desk.

    It's the same with induction noise too. Your hearing the explosion of the combustion but then each engine has a different shape port or valve position/size for the air to travel through. Before it even leaves the head.
    Inlet manifolds effect the noise just like exhausts do.

    As silly as it sounds. Just like in music. It appears the more the engine is tuned (I mean mechanically with porting. Cams. Valves etc and not just whacking more boost in) the better it sounds.
     

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