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Redline -- good or bad?

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by mugen86, Apr 21, 2008.

  1. I've read somewhere on the internet that redlining the engine once in a while will blow the carbon out of the engine. How accurate is this?


     
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  2. Try it and see.
    Most likely the rev limiter will cut in so you don't destroy the engine and cause excessive valve bounce.
     
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  3. Excuse my ignorance Smee ..
    Do all bikes have rev limiters??
    Been working in the car industry most of my life, and fairly new to the bike scene, I am genuinely keen to know.
     
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  4. Most newer bikes do, even my VL 1987 model commodore had a rev limiter.
     
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  5. :beer: Thanks ..
    Not that I'd ever intentionally over-rev the hornet, but its good to know
     
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  6. I am amazed at what modern bikes can put up with. I redline constantly ... the rev limiter usually cuts out a little later so it rarely occurs to me, and only ever on track (hard to redline a blackbird anywhere on the road without it being dangerous ...)

    Go ahead, it won't hurt it unless you do it every single time.
     
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  7. Any 4-stroke after about 1980 is not likely to have carbon unless the engine is already stuffed. The advice is good for 2-strokes, though.
     
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  8. The average engine won't have "carbon", unless it wasn't run in properly and there is a lot of blowby on the piston skirt and rings.

    Try as you might, you won't be able to remove that "carbon" by revving the engine. A change to a high detergent oil might dislodge or dissolve it, but that often leads to oil burning on a high mileage engine.

    There is always carbon (powder or dust) collected in the exhaust pipe - revving the bike hard might blow some of that carbon out, but I wonder what for?

    The ONLY reason to redline an engine is to get more performance out of it. The redline is set where it is usually because revving the engine harder than that will not produce any more power or acceleration.

    Summary: you rev the engine to redline for fun and performance, not to perform engine maintenance.

    All the best

    Trevor G
     
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  9. Also constantly changing gears at 18,000 rpm will wear the engine faster than if you change at 6,000. The higher the rpm the greater the friction.
     
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  10. Not if it's dropping below 6,000 on the shift and struggling (which it will be if it's a 250 that revs to 18k).
    High load and low rpm will kill an engine much faster than redlining it in every gear.
     
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  11. as long as you make sure the johnson rod is well lubed, it certainly wont hurt the engine.
     
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  12. Only on NR lulz..
     
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  13. Slight carbon build-up is usual, in fact it will slightly increase compression ratio, main cause for build up is leaking valve stem seals (whisp of smoke on start up then clearing) ring blow by and sucking oil down valve guides on the overun, and an over-rich engine will carbon-up.

    But never rev an un-loaded motor to red-line, you may have bits hit your feet as they exit the block!!!!

    As others have stated don't use it as an excuse to do proper maint!!

    The red-line is stated because the loadings and rotational forces involved are designed to work within certain limits and if you go beyond these mechanical failure will result!
    Just look at some powercurves and you will see that most of the power rises then dips before red-line is reached, so therefore there is no benefit in going there! short shift and use the "torque" part of the power curve to it's best, this is why most gearing is adjusted to suit the power curve on race bikes!

    Hope it helps
    Ozzyfzr
     
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  14. Actually hit the rev limiter for the first time this morning. Was interested to see when it does in fact cut in. ( 2nd gear around 17-18K, 105kph ).
     
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  15. even the manufacturers redline claim is a rough estimate. theres car engines that i know of that will never put up with sustained high rpm operation, even though below the manufacturers redline.

    i dont think theres any need to go to the redline unless your engines maxumim powerband reaches up to the redline. eg my across' power drops off after 15k so theres no use going further
     
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  16. Even more interesting is the fact that at those revs the piston has to accelerate to 100kph, then slow to a complete stop, all within 4.5cm - and it does that 1200 times a second.
     
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  17. This was something I was going to mention, actually - I've seen several car manuals warn against running the engine at faster than, say, 4500rpm for prolonged periods of time (redline of 6000rpm) because the oil pump can't maintain pressure at those engine speeds.

    I would assume that sportsbike engines, being intended for amateur racing and aggressive sporting use, would have an oiling system designed to cope with prolonged highspeed use... But then, one should never ass|u|me. :-k

    Also 'interesting' - Some motorcycles have a soft redline in the lower gears, to allow a brief overshoot of the marked redline before the actual ignition cut occurs. ;)
     
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  18. Yep, seen more than a few family sedans and economy hatches go "boom" at the hands of p-plate tossers that think they're sportscars. Always entertaining :LOL:.
     
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  19. snapped a piston and drove it through the engine block in my 2004 model automatic 'family sedan'. had the car in cruise control at 80km/h and about 2.1krpm. regularly serviced and well maintained.

    (although i'm certainly not a p-plater)

    sometimes things just go boom.
     
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  20. family sedan = commodore? :LOL: :LOL:

    the other day when i was at the mall carpark, there was an early 90's commodore with a LOUD knocking coming from the engine, something was smacking against the engine block, and really hard too.

    i dont know how people can ignore that then be suprised when it blows.

    though in many cases, like yours id imagine, it can come down to poor quality control at the factory.
     
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