[GTT 280]

All...

Discuss

Cheers,
K.

[NeuroBeaker]

Torque is a wonderful thing.

[Bhozar]

Quote: Originally Posted by GTT 270 (original)

All...

Discuss

Cheers,
K.

Glad you brought this up. I didnt want to throw it into the mix on the Flywheel BHP > Wheel BHP thread, as it would confuse the discussion.

All I know about torque is the more you have, the further you push the wall when you crash into it Oh, and that BHP sells cars, torque wins races.

[MINIMANIAUK]

torque is a function of bhp and rpm , but is essentially the airflow through the engine with fuel at a given rpm at a given efficiency -that cleared that up -not

[NeuroBeaker]

My understanding is that torque is essentially the 'usable' power.

Since maximum BHP can often be at extreme revs (and enables high top speeds that you'll never get to use), while it's really the mid-range torque that enables quick acceleration (really what we're interested in here).

Although, I'm certainly open to having my understanding corrected if there are any experts out there who know otherwise.

[alski]

if only torque is the answer then derv is the question [or not ]

[minicabrio]

Hi,

I'm new to this forum! I was wondering if you could help me find a nice torquey motor that I can use to tow my caravan whilst I'm out on Sundays. I had considered the MINI Cooper D, but find the Kia Rio 1.5l diesel hard to resist also... any thoughts?

Yours,

Jon

[Roadrunner_1]

BHP for Show, Torque for GO

[slim_boy_fat]

Torque or moment is a force multiplied by distance and causes a rotation.

When your fuel ignites in the engine the piston pushes down the con rod is connected at the big end offset to the crankshaft, this offset distance is what creates torque in the engine.

Power is a function of torque not the other way round.

Torque is essentially a force measure in Nm or lbft. Power is a measurement of how quickly the engine can generate this force, expressed in kW or hp (bhp)

More revs for the same torque means more power, because the engine is making more pulses of torque in a given unit of time helping to rotate the crank and rotate your wheels after it multiplied via a gearbox..

Hope that clears it up.

[Woody'sCooper]

Quote: Originally Posted by minicabrio (original)

Hi,

I'm new to this forum! I was wondering if you could help me find a nice torquey motor that I can use to tow my caravan whilst I'm out on Sundays. I had considered the MINI Cooper D, but find the Kia Rio 1.5l diesel hard to resist also... any thoughts?

Yours,

Jon

That little Rio diesel is a great little car if you can't stretch to a Dooper!!

[Berthil]

Torque is there to overcome the limitations of high revving and gear ratios.

If one could run at high revs 100% of the time (CVT?) there is no need for torque and you're quicker with high bhp. The right gear ratios are there to keep you in the high rev range to deliver optimum bhp but in daily life this is not usable (in racing it is).

So torque is there to keep you moving at lower revs.

[MINI-Morgan]

Quote: Originally Posted by slim_boy_fat (original)

Torque or moment is a force multiplied by distance and causes a rotation.

When your fuel ignites in the engine the piston pushes down the con rod is connected at the big end offset to the crankshaft, this offset distance is what creates torque in the engine.

Power is a function of torque not the other way round.

Torque is essentially a force measure in Nm or lbft. Power is a measurement of how quickly the engine can generate this force, expressed in kW or hp (bhp)

More revs for the same torque means more power, because the engine is making more pulses of torque in a given unit of time helping to rotate the crank and rotate your wheels after it multiplied via a gearbox..

Hope that clears it up.

That sums up how I understand it too! Just much better put that I could have written

[GTT 280]

...but on a RR, how are we able to measure BHP and Torque at the same time? Is the torque the resistance that is overcome and BHP is how this resistance is maintained?

My question being - how do we actually measure Torque - and do we have flywheel Torque and Wheel Torque?

Cheers,
K.

[MINIAC]

Quote: Originally Posted by GTT 270 (original)

...but on a RR, how are we able to measure BHP and Torque at the same time?

Torque is measured at different speeds and horsepower is derived from these measurements:

Power (hp) = torque (lb-ft) * rotational speed (rpm) / 5252

Chassis dynos (Rolling Roads) measure horsepower and torque at the wheels and guesstimate those numbers at the flywheel.

[GTT 280]

Quote: Originally Posted by MINIAC (original)

Torque is measured at different speeds and horsepower is derived from these measurements:

Power (hp) = torque (lb-ft) * rotational speed (rpm) / 5252

Chassis dynos (Rolling Roads) measure horsepower and torque at the wheels and guesstimate those numbers at the flywheel.

So Torque could be derived as:

Power (hp) / (rpm / 5252) = Torque (lb-ft)

or, as an example:

270 / (6,900 / 5252) = 208 lb-ft

but if max BHP is achieved at lower revs:

270 / (6,000 / 5252) = 236 lb-ft

...and that is why diesels have high torque as they achive their max BHP at much lower revs, say 3,500. Am i correct in thinking that the JCW cars get their max BHP at around 4,500 rpm?

Incidentally, where is the "5252" taken from - or is it a recognised constant when working with BHP/lb-ft ?

Cheers,
K.

[Tüls]

ha ha so true... that's why I always tell people that since it's a little 4 banger... to just keep the revs up... TQ is not the strong suit of such little motors... but the HP is... so get those revs up! when I am driving spirited... I never let the revs fall below 4500 RPM...or in my case there is too much TQ so I would rather have the HP...

Quote: Originally Posted by Berthil (original)

Torque is there to overcome the limitations of high revving and gear ratios.

If one could run at high revs 100% of the time (CVT?) there is no need for torque and you're quicker with high bhp. The right gear ratios are there to keep you in the high rev range to deliver optimum bhp but in daily life this is not usable (in racing it is).

So torque is there to keep you moving at lower revs.

[Tüls]

I like the way you put this into perspective... I never thought of it that way... nice job!

as for JCW getting there max HP at 4500... they SHOULD recive it at red line... since it's forced induction...

as for the 5252... it's where the two cross...

Quote: Originally Posted by GTT 270 (original)

So Torque could be derived as:

Power (hp) / (rpm / 5252) = Torque (lb-ft)

or, as an example:

270 / (6,900 / 5252) = 208 lb-ft

but if max BHP is achieved at lower revs:

270 / (6,000 / 5252) = 236 lb-ft

...and that is why diesels have high torque as they achive their max BHP at much lower revs, say 3,500. Am i correct in thinking that the JCW cars get their max BHP at around 4,500 rpm?

Incidentally, where is the "5252" taken from - or is it a recognised constant when working with BHP/lb-ft ?

Cheers,
K.

[slim_boy_fat]

Quote: Originally Posted by GTT 270 (original)

...and that is why diesels have high torque as they achive their max BHP at much lower revs, say 3,500. Am i correct in thinking that the JCW cars get their max BHP at around 4,500 rpm?

Incidentally, where is the "5252" taken from - or is it a recognised constant when working with BHP/lb-ft ?

Cheers,
K.

NOOOOOOOOOOOO

Remember engines produce torque power is just a way to describe how quickly torque is produced.

Diesel engines produce a lot of torque because they are efficent and have high compression ratios. This produces large forces in the pistons, this produces lots or torque at the flywheel.

They cannot rev high because they have high compression ratios and the compression ignition doesnt use a spark plug, this means that as you try to rev higher the fuel will burn to early causing the engin to preignite.

So as you have see from the simple calculations if you produce a set amount ot torque at 4000rpm you will have a certain amount of bhp but if you produce the same torque say 6000rpm then you are producing more bhp actually 1.5 times more (6000/4000). Remember max power does not necesseraly happen at max torque.

We havent even discussed gearing which is the real reasin high reving cars have more performance.

P.s. your rolling road it measures torque at its rollers.

[MINIAC]

Quote: Originally Posted by GTT 270 (original)

... where is the "5252" taken from - or is it a recognised constant when working with BHP/lb-ft ?

How do you convert engine torque to horsepower?

[MINIMANIAUK]

the torque (rotational force) is converted by the crank from a linear force(the piston being shoved down by rapidly expanding burning air/fuel) the "torque" on each piston is not linear and has a maximum figure during the pistons travel - this maximaum is dependent on a number of variables ,heat transfer,gas expansion rate,flame speed,efficiency of cylinder,friction, yadda yadda
one of the biggest things is removal of previously burnt air /fuel (exhaust) as this reduces fresh incoming oxygen/fuel ,thats why bigger valves ,better exhaust ports,and better scavenging by exhaust manifold produce more torque-the engine is an air pump
the output torque a sum of all (in the mini 4) pistons ,maxing just after TDC
limiting factors are mainly the size of the inlet valves and the ability to scavenge,and the temp/pressure in boosted engines