There seems to have been a bit of discussion over on the main boards about whether our favourite motor vehicle has any torque or not.

I'm confused though (nothing new there ). Whats the difference between torque and power?

I thought that torque was like pulling power. Can you tow a caravan, or get up a hill without having to change down a gear? Whereas power is about acceleration.

They seems to be using the word "torque" to mean the ability to accelerate at low revs. Surely this is power

Can anyone clarify?

 

I'll leave it to someone more technically able to explain torque, but so far as it relates to the S2000 and the accusation of 'no torque' I really do think it's a load of old bollox! Even up to 6K revs, I find I have no difficulty making very rapid progress and pulling away easily from most other traffic. I think the reason the S2000 comes in for this criticism, is that being a 4 banger, and only 2 litre at that, putting out 240bhp, it gets unfairly compared (In terms of torque) to much bigger 4 cylinder engines and even V6 and V8 performance cars.

The F20C engine is quite unique in it's power output from such a small plant. It's a busy frenetic exciting experience driving the S2K, and that's just how it was meant to be. Those who don't like working through that gearbox and staying in the power band shouldn't apply!

 

[QUOTE]Originally posted by Cedric Tomkinson
[B]I'll leave it to someone more technically able to explain torque, but so far as it relates to the S2000 and the accusation of 'no torque' I really do think it's a load of old bollox!

 

Here's an excellent write-up on torque vs. power

http://mclements.net/mrc-PowerTorque.html

As far as S2000 goes, 153 lb/ft is just the engine torque. High RPM and low gears transform that into quite a high wheel torque - about on par with pre-99 4.6 liter Mustang V8's.

The problem with S2000 is that it creates very little torque down low. If S2000 had a flat torque curve from 1000-9000 rpms (instead of 6000-8500rpms), even with its 153 lb/ft it would launch off the line like a monster V8. But it doesn't - it makes much less than 153 lb/ft at 3000-6000rpms, and much, MUCH less under 3000rpms.

 

Torque is the effort you engine is making, power is the amount of work being done.

If you could stop the flywheel on the engine, the force you had to excert to stop it is the torque. This is roughly how rolling roads work - they measure how much force is needed on the rollers to just stop the wheels accelerating at that instant in time. So they can measure the torque as the rpm changes. Since work is force multiplied by distance, you need to multiply the torque by the rpm to get the amount of work done, which as first stated is bhp. (Simplifying things a little).
That's why the S2000 makes a lot of power, but not a lot of torque - if you make the same torque at twice the rpm, that's twice the bhp.

Going back a little, an engineer figured out that an average horse could move 1,650lbs a distance of 20 feet in one minute. This amount of work is 1 horsepower. That's the UK standard bhp. There was also a german who figured the power of a horse to be a little lower. I can't remember the german word, but it's abreviated 'ps'. The spec for the UK S2000 is 240ps, or 237bhp. You see a lot of 'ps' figures quoted these days - that's where they came from, and as you can see there's little in it.

Anyway, there's an equation for deriving break horse power from the torque and rpm.

bhp = 2 x PI x torque (ft lbs) x rpm / 33,000

Simplifying the constants gives you:

bhp = torque * rpm / 5252

You'll see this figure of 5252 mentioned quite a lot. The power and torque on a dyno graph should cross at 5252 rpm - as this simplifies to bhp = torque at this point. So if you see a dyno graph where this doesn't happen be a little suspicous.

The complaints about the S2000's lack of torque are really complaining about the fact that the S2000 won't push you into the seat at low engine rpms. The S2000's engine is good at keeping making torque at high rpms - which gives high power, but can't compete with bigger engines for making torque, and hence power at lower rpms.

BTW, before you're all awe struct about my knowledge here, I looked it up to mkae sure I had the numbers right!

Edit: Follow Zoran's link for a better, more detailed explaination. I knew I spent too long typing!

-Brian.

 

PS = pferdestarke
1 bhp= 1.0139ps

Ian

 

FWIW

Pferd = horse
St

 

Of course there has to be a metric horsepower!

I think that the SI units help you internalise the concept better -

power or horsepower can be expressed in Kilowatts - gives you a sense of the equivalent in electrical energy terms.

torque is expressed in Newton metres (but is not energy) - i.e. a force applied at a distance to the thing you want to turn. So like the scaffolding bar you put on the tyre spanner after visiting Kwik fit - the longer the bar,the more twist you apply to the nut.

It's interesting that some words stick for so long - like horsepower - it gives people a relative understanding but nobody seriously believes we are comparing with horses - it's just a word. However despite this - I get chastised at work by my american colleagues for using the word "manpower" e.g. "we will need to reduce manpower levels" - apparently should be - "we will need to reduce effort levels"

However what do we do with a "manhole" - is this now an "efforthole"?

 

Bugger....

 

If our S2000 had 237 HP, it would equate to 860 BHP , we're talking Brake Horse Power (Is it not actually Braked Horse Power, perhaps a physics teacher of old could let us know?).