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    Racing Engine Amazing Revving Question

    I saw a serious race car tachometer on video. The driver repeatedly revs the engine and the tach needle almost instantly hits redline and then _instantly_ goes back down. Again and again the needle is bouncing back and forth really fast.

    Meanwhile the engine is growling fiercely, from high to low pitch extremely fast too.

    My question is: how such fast revving speed change possible?

    Our engines do the "same" thing but take muuuuuch longer to bounce up and back by comparison.

    Does the racing engine have a lot less weight/inertia so it's possible to make these extreme rev changes so fast?

    Is it the throttle system?

    What's going on in an engine which can do such an amazing speed change so amazingly fast?

    Thanks!


    Re: Racing Engine Amazing Revving Question

    Very light flywheel and clutch is a big help with this. Carrera GT does this very well for a street car...

    Re: Racing Engine Amazing Revving Question

    race car flywheel-clutch, low weight internals, race car throttle setup (no delay like in street cars for safety and control), high reving engine speeds, etc.


    The extreme is a motoGP bike for example. You see the mechanics give very short throttle twists to warm it up and maintain the engine going before the rider jumps on it, and you can see the rev needle fly instantly up and down, with just a little twist of the throttle, its like on/off. Amazing. Sportnikes are similar, much much faster reving up than a car and more instantly, but those race bikes are ridiculous.

    Re: Racing Engine Amazing Revving Question

    lighter and balanced crankshafts as well

    Re: Racing Engine Amazing Revving Question

    Thanks guys for the lighter flywheel "clue."

    Makes perfect sense now! I just surfed the net learning how light vs. heavy flywheels change things. Verrrrry cool stuff. Again: thanks for your help.

    Re: Racing Engine Amazing Revving Question

    For F1 engines, they also have extremely short strokes, so it doesn't take much to complete 1 rev.

    Re: Racing Engine Amazing Revving Question

    Lighter balanced cranks..., shorter strokes..., lo mass or no flywheels..., no wonder F1 and hot bikes _scream_ like a model airplane engine times a million.


    Re: Racing Engine Amazing Revving Question

    ....very low mass valve train, pneumatic valve actuation. etc.

    Re: Racing Engine Amazing Revving Question

    Knife edged and balanced cranks to go through the oil easier, boat tailing and shuffle pinning the case to lighten the engine, stiffen it and ease air and oil passage at high RPMs. Titanium springs, rods, valves and retainers reduce friction and lighten weight. better oil coolers to allow ligher weight oil as to casue less drag, low back pressure and proper resonance to aid exhaust and with cam overlap help pull in new charge.

    I've had a 2994cc 911 engine make just over 370 hp at 8,500 RPM and redline at just over 10,000. For about 40 hours...

    Re: Racing Engine Amazing Revving Question

    I seem to recall that the McLaren F1 had no flywheel...

    "The McLaren F1 has no flywheel in order to decrease inertia and increase responsiveness of the system, resulting in faster gear changes and better throttle feedback."


    Re: Racing Engine Amazing Revving Question

    I just read that the BMW F1 engine weights only 98 kilograms (amazing !!!)

    Re: Racing Engine Amazing Revving Question

    Quote:
    Markdsv said:
    I just read that the BMW F1 engine weights only 98 kilograms (amazing !!!)


    Not bad for 750hp+ and 20,000rpm from normally aspirated 2.4L V8

    Re: Racing Engine Amazing Revving Question

    Quote:
    Boxster Coupe GTS said:
    I seem to recall that the McLaren F1 had no flywheel...

    "The McLaren F1 has no flywheel in order to decrease inertia and increase responsiveness of the system, resulting in faster gear changes and better throttle feedback."





    But it will have a clutch, albeit a very small one - I believe a nominal diameter of about 5 1/2 inches may still be "standard" for F1 engines.
    The ultra-light clutch friction face (normally the surface of the flywheel on conventional engines) and the pressure plate will have a certain flywheel effect.

     
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