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How is it that Motor Bike Engines Produce So much Power?!?

Discussion in 'Technical and Troubleshooting Torque' started by djdude1010, Jul 15, 2005.

  1. How is it that Motor Bike Engines Produce So much Power?!?

    How is it that a 1000cc Motor Bike engine can produce 120+Kw no worries

    But a car engine with larger capacity like 1.5L will only produce 70 - 80 Kw if that?

    Whats gone into these things that make them so good at performing....

    Do they use lighter, better performing parts as a sacrafice for reliablity.... (not saying there un-reliable, but more that a car engine will travel many more k's than that of a bike)
  2. bikes rev faster..

    when was the last tie you saw 10- 12,000 revs on a family sedan??

    apart from that..dunno... s

    maller piston mean not so much inertial weight for the engine to move...therefore it moves faster and produces more kinetic energy
  3. You're comparing apples with pears. You need to look out how much torque a car engine produces compared to a bike engine.
  4. Alien technology... i'm sure of it :LOL:
  5. Re: How is it that Motor Bike Engines Produce So much Power?

    Sort of, most high performance engines such as those found in bikes and in highly tuned/race cars will be built to much tighter tolerances and use more expensive components than your average passenger car which usually allows for higher revs, greater compression ratios and better engine efficiency which all create a greater power output. The trade off to this is of course that such engines cost more to produce, require greater maintenance and will ineviatably wear out faster. Car makers could produce engines with similar kw/L outputs to a bike (Honda s600 actually had a bike engine) but it is usually easier to just increase the capacity of the engine.
  6. as above comparing to very different vechiles, simple answer is power to weight ratios
  7. Nova --- ah yes... didnt think of that, i guess because they dont have as much wieght to push around they dont need as much torque......

    now makes me wonder why they called a bike movie torque... LOL

    Well it was a Crap movie Ne way -- i want the 2hrs of my life back
  8. You have answered your own question!


    Look at a dragster for instance they are in affect a car engine! The tolerances and quality of the parts allows them to perform as they do but they can only do one run down a strip before it needs to be pulled down and rebuilt. These teams do this very quickly thou!

    Bike engines use state of the art technology at the current time where as car engines generally lag with this technology. Smaller engines can spin faster before going out of balance where as car engines spin nowhere near as fast, have longer piston strokes which encourage more torque and is suited more to pushing heavier vehicle weight around.

    I think the biggest difference is Induction systems, a bike engine will run in most cases seperate throttle bodies or carb's for each cylinder The engine porting and camshaft profiles allow for extra induction of air into the motors where as most standard cars will run a common manifold so their air flow will be lower!

    Look at the exhaust systems. The pipes coming out of modern bikes these days are general bigger (wider in diameter) than a cars. This helps the engine to breathe as well.

    Most horsepower and torque figures a quoted right up in the rev range for bikes, cars don't rev as hard but get different characteristics because car engines run bigger and heavier flywheels which keeps the engines turning over at lower engine speeds

  9. Bikes are great and ridden by COOL people so they make much more power.

    Cars are crap and driven by UNCOOL people and wannabies so they make less power


    (hope I wasn't too technical there)

    :D :D :D
  10. They don't have a choice in that; not having the room for a 1.5L powerplant, bikes_can't_make 1.5L-type torque... the fact that they don't need that much torque is more of a fortunate coincidence than a consequence of design.

    As for why bikes make so much power... state of tune. Simple as that. Take a bike engine, drop its compression ratio, calm down its cams, reduce the size of its valves and ports and lean out its fuelling down to the levels of a car and you'll have a litre bike making Daihatsu Charade power in no time.
  11. Plus bikes are woefully innefficient compared to cars.

    Cars have had to go the increased efficiency route as govts. have forced them to decrease pollution outputs. Bikes seem to have escaped the same treatment that cars get. Otherwise there would be cat converters on your bikes along with other unfun stuff.

    All the anti smog stuff on a car engine sucks a lot of power and along with tuning a car to minimise pollution will make it go further on its fuel. Fuel efficiency is a big selling point on a lot of cars, even top end cars. There are recent ads on tv about the 3 tonne 5 ltr v8 Jeep that can shut down 4 cylinders to save fuel. What's the point of that? May as well buy a four cylinder car... In the seventies, Jaguar produced a 5.3 ltr v12 sports car, that was fast but sucked lots of fuel. You'd think that Jag sports car drivers wouldn't car less about fuel efficiency, but the next model was called 'HE' for high efficiency.

    Bikes have almost no anti pollution crap on them, and are tuned and built for perfomance. So they produce a lot of output, use lots of fuel to do it and are far more fun.
  12. oops
    I think you will find all new road bikes have a combo of antipollution
    devices on them....most now have catalytic converters tucked up either inside the actual zorst pipe or the muffler. In addition most now run EFI simply to get the fuelling right to meet emmission standards and tucked away under tanks will be clean air feeds into either inlet manifolds or zorst headers to promote better burning. Even crankcase gases get sucked backed into the induction system and burnt.
    even so, bikes are still very powerful when it comes to per litre outputs

    didn't wanna be too technical... 8)

  13. True, also never got into the same ADR shyte that cars did, simply due to the ADR's not effecting smaller motors.

    A lot of earlier ADR's weren't repealed when newer technology was applied to later regs, instead anti pollution regs tended to become "cumulative" adding to a loss of performance, but not really helping pollution control.

    An example... manufacturers started to introduce "lean burn", not for the obvious "use less fuel".. but to increase combustion temp, so that less CO (Carbon Monoxide) was produced to match the pollution control laws, Trouble is raising combustion temp to the levels required for CO control started introducing Oxides of Nitrogen NOx, (not the Nitrous Oxide, of rice movie fame) NOx causes photochemical smog when it reacts with sunlight.

    So the original "lean burn and increase heat" got overlayed with the mutually exclusive "don't burn so hot and stop NOx" ADR's, (IIRC ADR's 27a and 27b) The only way to do both reliably throughout an entire rev range is with electronic control, aka EFI

    They tried all sorts of things in the meantime, some forced by ADR's, some just to get around ADR's.

    Have a look under the bonnet of a mid 80's carbied car It's a nightmare of hoses, wires, valves, solenoids, etc. The same car with an EFI option is so much "cleaner". EFI negated ADR's relating to Carby emissions, so the performance and fuel saving advantages were even more apparent

    Generally, bikes were exempt, so they didn't lose the potential to be refined into the beasts of today, EFI introduction helped keep them immune, but the beaurocrats will tie them down soon enough, cos they think that regulating people is there job.


    (Edit...sorry.. ADR is "Australian Design Rules")
  14. My own personal opinion on this whole debate, is thus:

    1. Bikes don't need a lot of torque because they weigh so little. Ergo, they are built, and tuned, for high rpm and high power, but low torque.

    2. Cars need a lot of torque, because they weigh so much. Ergo, they are built, and tuned, for more torque.

    There is no substitute for torque than ENGINE SIZE (turbos and superchargers effectively create a bigger engine). Sure you can build a big engine to make high torque *and* high power, but then it becomes a sports engine with much higher costs to make it reliable. Take a big engine with lots of reciprocating energy (heavier pistons, etc) and it becomes a hard job to do both reliably. BMW's M3 engine is a straight-six 3.2 litre DOHC with variable intake *and* exhaust cam timing. It also has six throttle boddies (one for each cyliner like a bike) and is a fantastic engine, putting out 260+ kilowatts and over 350Nm of torque. However, it's expensive to produce.

    So anyway, power = top speed and torque = acceleration. Bikes are so light that even a modicum of torque helps you pull wheelies and take off *very fast*, so they're better tuned for very high horsepower (160+hp for the latest 1000cc weapons) and less torque than a car engine of similar displacement would put out.

    Harley engines are much more like car engines in that they are low-revving but have stonking torque. They take off mighty quick but don't have the top speed of, say, a CBR1000RR. But then ask any Buell XB9R owner if that's a problem. :)

  15. For a simple answer, it's all about the revs.

    Power is torque x rpm and since bikes rev so high the power output is higher.

    So what allows them to rev higher? As the others said, I guess it is the better designed, made and tuned engines. Also most average bikes are closer to race bikes than an average car is to a F1 car.
  16. interesting you say that
    its not entirely true and the theory was recently tested...
    the whole theory being that a bike is easier to ride the more torque it has
    and less it needs to be revved ..

    the uk bike mag 'BIKE' took 2 Yammy R6s.....
    and with one they actively set out to increase its torque and reduce its revability .....
    they reduced the size of the EFI throttle bodies (pinched a set off a 600Fazer)and stuck a set of camshafts from a '90 FZR600 in it

    and they reckoned they succeeded. They got 18 bike testers to ride both bikes back to back....and 17 of the 18 said that the 'torque enhanced' R6 was a much better bike to ride, on the road and track. It pulled easier, was more responsive and a better midrange. and then they put the 2 against the stopwatch!

    the standard R6 vs the modified R6
    Top speed 151mph..........148mph
    ¼ mile 11.7sec..........11.9sec
    0-60mph 3.6sec............3.9sec
    40-80mph 9.6sec.............7.0sec (thats impressive)
    40-120mph 19.7sec...........14.5sec (amazing!)

    food for thought, on this whole subject

  17. I have a problem with these figures,
    12 second ET's wouldn't be doing much over 120mph ?
    so if the mod r6 is only .3 of a second slower to 60 but 5.2 second quicker from 40-120 mph there is no way that it could be .2 seconds slower on the qt/mile I havent studied this with scientific but simple maths wouldn't allow. this is only my opinion. Any comments?

  18. Re: How is it that Motor Bike Engines Produce So much Power?

    There once was these little creatures called Torcs.

    Once they were related to the larger species called Orcs, but as time went by the smaller orcs, lived and bred together. Since they were smaller, they had to run much, much faster than their cousins the Orcs, otherwise they got eaten.

    But the Orcs were clever, and started laying traps for the smaller Torcs. Loose gravel on corners, ice on tracks and similar. So the Torcs needed some where to hide.

    About the time, man was starting to get around in cars, so the Torcs moved into the engines there, living off the fossils in fossil fuels. The problem was when put so many Torcs in a big engine space, they started to fight amongst themselves, and boom, car would blow up.

    So the Torcs moved to motorbikes, as only a couple could live in there.

    Now they run faster in bikes than they used to in cars, as being fairly stupid animals, they think the cars are the Orcs still after them.

    And that's why bike engines have so much power.

    /it's friday, and now I'm off to the pub.
  19. Don't Quote me on this but i think that the 40-80 and 40-120 times are both run in TOP GEAR (6th gear) and therefore the 'enhanced' R6 will peform much better in these 2 categories as it has more Torque.