Power & Torque

[Porker]

You're right.

 

Don't worry so much about power figure if you're interested in ease of overtaking in city traffic. Low down torque is much more important than bhp output.

 

Torque and bhp are proportional to size of engine

[Slayer]

u mean like in the spec when it say max torque and max power?

 

i'd rephrase in this way :

torque is the measure of the turning force. in a way u are right, based on the spec u gave, u will feel the best 'punch' at 2500rpm. the is when the engine its strongest turning force.

 

power is the measure of the amout of work done by the force. base on the spec u have, your engine turns more efficiently up to 6000rpm, no point going further, beyond that, its counter productive.

 

say at 2nd gear, u feel the best acceleration force at 2500rpm, and this force will start to get lesser and lesser.. gradually going up the rpm range. question is, when to stop? i would read it at about 6000rpm. why? while the engine continue to give you more and more output at it rise over the rpm, and when it hits 6000, the output decreases. (that when u might want to change gear). in this case, if u are at top gear.. the engine cannot give more output to put the car even faster.. that where top speed ends.

 

In order to accelerate fast, i would change at about 6k. for the first 2 gear. and 5k for the next 2 gears.

 

why not just stick around the 2.5k range like u mentioned? practically , if I do that, i'll spend more time shifting gear rather than accelerating.

 

hello fellow petrolheads.

 

just want to clarify some doubts and gain some knowledge from the old birds.

 

Firstly, am i right to say that in general, torque is something that accelerates your car?

 

and power is something that determines the top speed of your car?

 

 

let say for a figure of ::

Civic Hybrid Engine Specs

Power: 82 kW , 110 HP SAE @ 6,000 rpm; 123 ft lb , 167 Nm @ 2,500 rpm

 

this engine produces the most torque when you keep your rev @ 2,500? and produces the most power when it's @ 6,000?

 

let say you wish to accelerate at its maximum best performance.

 

how will you go about doing it?

 

when you rev to 2500 - 3000, you change to a higher gear? since it generates the most torque at 2500.

 

thank you have a nice day!

[Hein]

Well, based on the above discussion, which car will be better for Singapore driving, and give better accelerations on our roads and overtaking:

 

 

CTR JDM

Torque 215 Nm/ 6100 rpm

 

Golf GTI

Torque 280 Nm/ 1800 rpm

 

Seems that the GTI is a better bet....

[Chisiang]

Ok, I think this will help u understand better.

 

Given:- Power: 82 kW , 110 HP SAE @ 6,000 rpm; 123 ft lb , 167 Nm @ 2,500 rpm

 

When the crank is rotating at 2,500 rpm, the amount of torque produce PER ROUND is 123 lb/ft. The key word here is PER ROUND. It means that the crank produces most torque at a revolution of 2,500 per minute. However, the crank can only produces 58.55 hp when spinning at 2,500 rpm. If you change gear now, you are only maximising 58.55 hp (53.23%) of your engine potential.

 

On the other hand, at 6,000 rpm, the amount of torque produced by the crank per revolution is 96.28 lb/ft. Although it is 26.72 lb/ft less than the maximum your crank can produce at peak, but your crank is producing this 96.28 lb/ft of torque 6000 times per minute! Giving you 110 hp! As compared to only 2500 times!

 

As such, if you want to fully capitalise on your 110 hp engine, you should only shift at at peak hp.

 

But fully capitalising your engine power does not equate to fuel economy. You shorten your acceleration time at the expense of your fuel economy. Maximum power do not means best efficiency.

 

To determine the best economical shifting point, you will need to match fuel consumption graph with acceleration graph. Both have got nothing to do with torque and hp because in practice, the gear ratio, vehicle weight, unsprung weight, will be the deciding factor of how efficiently your car accelerate to a speed.

 

 

[Slayer]

Seems that the GTI is a better bet....

I tend to agree with you on that one. I must say I have not driven a CTR or a Golf GTI in my life.