Horsepower or Torque? You decide!

Pandoras Kitten 3 · November 5, 2010

I found some nice American writeups on the ever-present argument on horsepower vs torque.

http://everything2.com/title/The+problem+with+Harley-Davidson+motorcycles#JohnnyCashed

Don't be put off by the confrontational nature of the writeups - in a different part of the world, that's how we deal

The article also points to an often-overlooked trend in American engine design. Horsepower per ton, they're quite bad, compared to the latest tricked out Euro and JDM cars with their high compression rates and insane RPMs. TV shows like Top Gear frequently bash the "underpowered" figures of famous big-engined American cars for this reason.

But... American V8 engines of the classic days were designed for another purpose altogether: To get you and your payload cruising smoothly on the highway at minimum revs and running on regular fuel (92-95 local RON). Since they aren't designed to rev, they don't get very high horsepower figures sometimes!

Applied to bikes, I hope this pair of writeups explains why sometimes, we don't really care about the horsepower figure. A cruiser in theory relies on torque to move the mountain of itself over any road comfortably; low RPM, greater efficiency, lower temperatures = longer range.

Only crazy people like myself would daydream of converting a CBR6 into a cruiser by detuning and dropping the sprocket sizes. I have no idea how to fit the panniers

Edited November 5, 2010 by Pandora's Kitten :3

mechwira · November 5, 2010

i always wanted a middleweight v-twin sportsbike. i'm honest in saying i dun need all the hp of the inline-4 screamers, even a middleweight like my cbr6rr, even on track. i'm not pro-skilled enough to utilise all the hp, and the road doesn give me much chance to exploit it anyway. but more torque, now that sounds very fun.

but i've always been lamenting that the japanese dont do v-twin sportsbikes. the ducati 848 is way out of my budget, and the suzuki sv650 isn a full-on sportsbike.

endlessloop · November 5, 2010

Those who knows performance, even professional racers, will always care about (1) torque rather than Horsepower, and (2) exactly when and when and how the torque is delivered.

Horsepower is simply a correlation of torque x rpm (HP=Torque x RPM/5252).

Peak horsepower ocurring at very high rpm is seldom useful for most of us. But it is very good for drag racing, higher top speeds, bragging rights and selling bikes

Lots of torque readily available at low rpm is good for riding in s'pore and city commuting. It gives you the ability to get out of cars' way off the traffic lights and quick overtaking.

Even for circuit racing, peak horsepower is not that useful (unless in a very long straight). What you need is lots of smooth torque at mid-rpm, when you have precious split second window to side step in front of the competitor, when shooting out of the corner.

mild_slevin · November 5, 2010

Torque is indeed useful in street riding, getting out of situations

DeusExMachina · November 5, 2010

I found some nice American writeups on the ever-present argument on horsepower vs torque.

http://everything2.com/title/The+problem+with+Harley-Davidson+motorcycles#JohnnyCashed

Don't be put off by the confrontational nature of the writeups - in a different part of the world, that's how we deal

The article also points to an often-overlooked trend in American engine design. Horsepower per ton, they're quite bad, compared to the latest tricked out Euro and JDM cars with their high compression rates and insane RPMs. TV shows like Top Gear frequently bash the "underpowered" figures of famous big-engined American cars for this reason.

But... American V8 engines of the classic days were designed for another purpose altogether: To get you and your payload cruising smoothly on the highway at minimum revs and running on regular fuel (92-95 local RON). Since they aren't designed to rev, they don't get very high horsepower figures sometimes!

Applied to bikes, I hope this pair of writeups explains why sometimes, we don't really care about the horsepower figure. A cruiser in theory relies on torque to move the mountain of itself over any road comfortably; low RPM, greater efficiency, lower temperatures = longer range.

Only crazy people like myself would daydream of converting a CBR6 into a cruiser by detuning and dropping the sprocket sizes. I have no idea how to fit the panniers

That JohnnyCash guy is even differentiating between new and old Harleys? LOL.

If we put a new and old Harley on a dyno and they churned out the same curves, this guy would dispute it based on feel.

He's just one of those traditionalist clowns who believe in the "great American chopper" no matter how backwards and agricultural the engine is.

He should probably drive a farm tractor instead.

Now... for your case. Instead of desecrating a CBR6, you should consider getting a CBF6 or CB600 hornet instead.

There's a reason why manufacturers detune popular sportbikes and rebody them into nakeds or semi nakeds.

It'll save you time and money.

Edited November 5, 2010 by DeusExMachina

Wayang · November 5, 2010

yes.. torque is impt.. but wat use is torque if the engine cant rev.. its a balancing act. current generation of sportsbikes (600 n 1000 class) r developed as racing platforms.. so the focus is on speed n agility.. NOT cruising and comfort.

natgw · November 5, 2010

@ TS

Aurium · November 5, 2010

tt`s why my bike have CVVT,

liquidy · November 5, 2010

tt`s why my bike have CVVT,

CVVT? at first glance i thought it was CCTV. and i was like wth? hahaha

Pandoras Kitten 3 · November 5, 2010

Continuously variable transmission - uses a set of pulleys, or special gearbox with infinitely variable ratios.

Technical writeup can be found at Carbibles here:

http://www.carbibles.com/transmission_bible_pg3.html

The engine will always operate at optimum RPM - a bit boring, some say, especially the constant drone of the engine (at least in car examples), but you get maximum acceleration all the time!

Aurium · November 7, 2010

i`m sry to interrupt

CVVT is not Continuously variable transmission

but Continuous variable valve timing

nothing to do with gear box nor pulleys..

and the engine dont stay at a constant RPM,

rather, it alters the valve timing to accomodate the rpm the engine is at to give optimium performance, like tune and detune according to RPM

a simple check with wikipedia says it has something to do with cam phase and valve alteration..

in layman terms, it gives improvements in torque over low rpm and yet maintains hig BHP for higher RPM..

example of

High Bhp/Lower torque vs Lower Bhp/Higher torque

R1 vs FZ1 (tuned vs detuned)

for the matter, CVVT creates an `in between` in a sense for the very layman...

will the pros please correct my mistakes if you spot one..

CSV · November 7, 2010

hmm, i'll take torque. the acceleration will be more useful to me than the hp figures and the speed i can attain. how fast you wanna go in sg?

acceleration will help when riding off at standing stop. getting out of tricky situation (sudden car swerve in!), overtaking lanehoggers.

hp on the other hand helps mostly in speed.

you can't do without both really, since both serve their purposes. the key is the balance between torque and hp. i'll still take torque.

endlessloop · November 9, 2010

I will not go into detail but give a very quick summary.

There is Honda's VTEC and iVTEC, which CVVT is based on.

- The engine still revs through rpms. But it has either multiple cams or/and computer-controller continuously variable cam, to deliver higher engine efficiency across the rpm range, compared to normal single cam engine.

- In a nutshell, it is a more efficient engine. More efficient translates to higher torque over the same rpm, better fuel efficiency, better acceleration.

- Why need this? Because a characteristics of piston engines (bikes, cars, etc) has a limited "sweet spot". The Vtec and iVTEC spreads the sweet spot to a broader rpm range.

- The cams control the opening and closing of the valves in the piston engine. With one cam, the timing of open/close of valves is fixed. So when you swap different cams or alter the profile of the cam shapes, you can alter the timing of open/close of valve to achieve more optimum engine performance at different rpm.

- You will find CVVT/VTEC in Honda's Super4 and Honda VFR800. But it's perceived benefit is not as obvious as in cars. In many Honda and Toyota cars, you will find this variable cam design. Other followers include BMW, Mitsubishi. I highly recommend such engines for cars.

And there is Continuously Variable Transmission (CVT).

- This is not so much about the engine. But more about the transmission/gearbox.

- You mate a traditional engine to a continuously variable transmission (or gearbox) instead of the traditional cog/gear transmission (5-gear/6-gear/7-gear).

- Remember that traditional engine has a particular sweet spot, if you can maintain the engine revving around this sweet spot, you achieve better efficiency.

- In traditional gearbox, we try to stay within the engine sweet spot by switching gear cogs of different ratio. Because of the limited number of gear cogs you can put into a vehicle, there are gaps or steps of inefficiency. In CVT, there is a belt that links a cone-like gear cog so the gear ratio can be smoothly changed while maintaining constant rpm to maximise this engine sweet spot.

- CVT can be found in bike scooters. There are some cars with CVTs. However, CVT experience was not very appealing to users because they don't feel the omph, so some designers like Honda dropped CVT from their Fit/Jazz and switch back to normal cog/gear transmission.

I just came back from Japan. The road there is filled with Prius (Toyota), Insight and CR-Z (Honda).

I believe Hybrids are the thing to go (for cars, not so much for bike), until electric is possible. If you think Hybrid is green and slow, read the latest Straits Time Sat issue of the pure electric motor powered Elise (Telsa?). And the last version of Honda's supercar NSX was a hybrid.

Edited November 9, 2010 by endlessloop

endlessloop · November 9, 2010

To help better understand torque and power:

- Torque is the amount of force. Example measurement lb, kg.

- Power is amount of work done within a given period of time. Example measurement hp, ps, watt.

- They are correlated hence just as important but easy to confuse.

Because work done = force x distance. Hence power = torque x distance / time.

- Remember f = ma? Force = mass x acceleration. Therefore, the stronger the force, the faster the acceleration for a given bike mass. Which means that, the stronger the torque, the faster the bike accelerates (all things being equal).

What one feels from the push or omph from your bike as you open your throttle, is really the increasing force, that is, increasing torque.

- High power (ie horsepower) is definitely useful because it means you have the ability to do a lot of work within a specific time. Example: move the bike a long distance within one second.

- It is not that high horsepower is useless (of course it is!). For day-to-day riding, it is more of how quickly can you find high enough torque to be able to do your acceleration.

endlessloop · November 9, 2010