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Power vs Torque

Discussion in 'Technical and Troubleshooting Torque' started by hornet, Jul 10, 2005.

  1. I would urge all riders interested in the technical aspects of the modern motorcycle to buy the May 2005 issue of BIKE magazine (U.K.)
    Read the Cover Story Japan vs BIKE, page 84.
    The magazine DE-tuned an R6 engine back to FZR600 specs, lost only 4 HP, brought the torque figure UP by 2 lb.ft at 2,000 revs lower (10,100 vs 12,100) and created a bike which 18 out of 20 riders who tested both bikes back to back, said they preferred to the stock R6. Top speed was down by only 3 mph (148 vs 151) but the roll-on test showed the de-tuned bike MURDERED the stock R6.
    40 - 80 mph R6, 9.65 seconds, de-tuned R6 7.05 seconds
    40 - 120 mph, stock R6, 19.7 seconds, de-tuned R6 14.55 seconds!!!!
    They were making the point that most modern bikes develop more power than older machines, but that the power is so high up the rev range as to be useless 90% of the time, and comes at the expense of rideability.
    Anyway, read the article and see if it's of interest, I was fascinated.

  2. fcuk me they are big differences.

    Even though obviously i didnt expect alot from a 600cc engine, a little bit of extra torque is what the r6 really does lack just for cruising around town...
  3. Mick they said THEY didn't expect to see the torque UP by so much and brought 2000 rpm lower into the rev band, nor the power to be so little effected. They were expecting to lose around 15 hp and they were stunned when thy only lost 4 hp.
    Incidentally, the article wasn't a shot at Yamaha, it was a comment on modern high-powered bikes in general.
  4. fark that sounds interesting.

    Do you have a scanner hornet? :LOL:
  5. Why yes, yes I do Dan. Consider it done! (How do I make the results generally available?)
  6. If your scanner has a 'Scan to PDF' function try that. PDF will be the best option for storing the document, if that fails just save them as images of some sort.
  7. Interesting, must buy the mag if I can find a copy.

    Being an Old fart (and ex heavy vehicle mech) I've always been been bemused by the infatuation with power, and the ignorance of torque in both modern bikes and cars.

    Seems that the current popularity of V Twins is correcting things, but slowly.

    Personally, I've always favoured lots of Torque over Power.

    In a gross simplification, power is derived from torque and time (I think the formula in an automotive sense is something like... power=[measured torque X rpm] / 5252 ) Without torque, there is no power.. grasshopper.

    To get useful work from a little bit of torque, you need to get that torque happening at a very high rate, hence the very high revs of the modern bike, esp the smaller engined bikes. This means high reciprocating forces, need for light pistons, rods, cranks etc (honda's engineers just kept adding cylinders at one stage, iirc they produced a 5cyl 125cc once)
    This led to "oversquare" engines (shorter stroke than bore) that allowed piston travel to be very short, higher and higher revs, and more complexity in valve gear (double overhead cams and associated chains, belts, adjusters) to cope with higher revs. (up to 22,500 in some 250cc bikes)

    But if you have ample torque.. you don't need to have a high rate to get useful work happening, so the engine will be responsive over a wider range, work at slower revs, be way less "stressed", valve & induction technology can be so much simpler and easier to setup and maintain. Hence most hi-torque bike motors still use pushrod valves, more than adequate at teh 2,500-5,000 rpm required.

    It's also (IMHO) a much more enjoyable way of riding if your not constantly working the throttle/gears to keep your bike in the "power band" when riding.

  8. JJ, you should be doing special comments on RPM :LOL:
  9. Which is why my VFR750 suits me perfectly!!!!
  10. Yeah RC...

    And why I want a mid 80's 750 to litre sized bike to restore and ride, IMHO a much better ballance of torque/power, and probably why they sem to survive longer.

  11. Ok Dan, I've scanned to .pdf, it's about 2.4meg, but good quality, how do it get it onto the forum?
  12. RC36 honda... a VFR750 (whilst a nice bike) is hardly a high torque motor... not is it pushrod actuated :)

    My ZRX1200R is what most jap bike riders think of as high torque (retuned for midrange ZZR1200 motor less forced induction), but to be honest it has _lots_ less low end torque than my Moto Guzzi Le Mans V11 1100cc pushrod twin.

    That motor pulls hard from 3000 to 7000 and tails off after that, but is perfect for most road riding to be honest...
  13. Sorry, my point was not that it is a high-torque motor or that it was a pushrod motor. It was that it is a motor where torque is more important than power. It pulls strongly and smoothly from about 2500RPM right through to redline and has no noticeable "power band" Thus the power is "useable" power and allows me to ride in almost every circumstance without having to rev its head off.
    Hope that explains it better.

  14. Being in Tas, and without a digital receiver, I don't get to see such programs, instead I'm force fed afl crap or soap. (so watch v-little idiot box)

    But if it's like the technical comments spewing out of the mouths of the knobs who commentate the V8 "racing"(sic), then I reckon anyone could do a damn sight better job.

  15. hmm that's pretty big. can anyone host the file?

  16. There may be copyright issues in placing it up on the forums Hornet, better ask the Admins first, if OK, they'll probably put it in the articles section.

    Be safer for now if you got anyone interested (me! me!) to PM you with an email address and send it to them.

    JJ (pm heading your way :wink:)
  17. Just e-mail the authors for permission . :D
  18. Couldn't agree more....torque will always "win" on the street where most of us ride in the range it works well within. A bike with a strong midrange usually has wide ratio gearing as well. What it means is I can be lazy!!!! But also enjoy the ride as well.

  19. Go nakeds!!

    Stonks of torque, sportsbike handling, best looking bikes around!!

    Yay yay yay!
  20. On its way, JJ check your PM
    I will contact the authors, but in the mean time if any one else of you want the .pdf, pm me and I'll send it to you