BHP V's Torque

Darren Lamb

Which one of the above would you give the most consideration when buying a car, i.e
1.9 TDI: BHP = 128 Torque = 285NM
1.8Tquattro : BHP = 150 Torque = 210NM

Mr.David

torque!

Biro

The petrol is quicker, the diesel is more economical.

Darren Lamb

Darren Lamb wrote: »

Which one of the above would you give the most consideration when buying a car, i.e
1.9 TDI: BHP = 128 Torque = 285NM
1.8Tquattro : BHP = 150 Torque = 210NM

BHP. But I guess I'd never consider a diesel anyway.

Zube

Darren Lamb wrote: »

Which one of the above would you give the most consideration when buying a car, i.e
1.9 TDI: BHP = 128 Torque = 285NM
1.8Tquattro : BHP = 150 Torque = 210NM

It depends on how you drive. The car with more power will be faster if you keep the engine spinning up near peak power, but that is a very unusual (and noisy, uneconomical and tiring) way to drive. A turbodiesel won't rev nearly as high, and won't be as fast driven the same way, but in ordinary driving where you keep both engines spinning below, say, 4000 rpm, the higher torque of the diesel will make it quicker and more responsive.

maidhc

Zube wrote: »

It depends on how you drive. The car with more power will be faster if you keep the engine spinning up near peak power, but that is a very unusual (and noisy, uneconomical and tiring) way to drive. A turbodiesel won't rev nearly as high, and won't be as fast driven the same way, but in ordinary driving where you keep both engines spinning below, say, 4000 rpm, the higher torque of the diesel will make it quicker and more responsive.

Indeed. Although I'd say below 3000 rpm as regards the diesel.

peasant

in this case ...forget about the engine, go for the quattro

kayos

A bit of both is always good

Torque will get you up to speed quicker once your in the power range. BHp will give you a higher top speed.

But your looking at a quattro petrol with more weight and less torque...I drove a 1.8T quattro A4 before and it was sluggish compared to my ibiza 1.8T ok the engines where not pumping out the same power but it really did feel like the weight was too much.

Then again my Ibiza is running around 210BHP and 340NM. Well that was the last reading from a RR many moons ago.

Zube

Zube wrote: »

It depends on how you drive. The car with more power will be faster if you keep the engine spinning up near peak power, but that is a very unusual (and noisy, uneconomical and tiring) way to drive. A turbodiesel won't rev nearly as high, and won't be as fast driven the same way, but in ordinary driving where you keep both engines spinning below, say, 4000 rpm, the higher torque of the diesel will make it quicker and more responsive.

I wouldn't say it unusual. If you are going for maximum acceleration you would change before or in the redline. The next gear should drop you right in the powerband for more punch. The powerband is also much wider in a petrol engine car.

Biro

kayos wrote: »

A bit of both is always good

Torque will get you up to speed quicker once your in the power range. BHp will give you a higher top speed.

But your looking at a quattro petrol with more weight and less torque...I drove a 1.8T quattro A4 before and it was sluggish compared to my ibiza 1.8T ok the engines where not pumping out the same power but it really did feel like the weight was too much.

Then again my Ibiza is running around 210BHP and 340NM. Well that was the last reading from a RR many moons ago.

Torque won't get you up to speed quicker really, that's not essentially correct. Take your car for example, you'll easily out run a 140bhp diesel with the same torque output as your engine.

Owen

peasant wrote: »

in this case ...forget about the engine, go for the quattro

QFT!

Henry Ford III

1.9TDI again :eek: My primary concern would be lack of refinement.

Zube

ronoc wrote: »

I wouldn't say it unusual. If you are going for maximum acceleration you would change before or in the redline. The next gear should drop you right in the powerband for more punch. The powerband is also much wider in a petrol engine car.

Don't get me wrong, my favourite car ever was a Alfa, with max power at 6500, redlined at 8000 rpm. Great fun to thrash.

The petrol engine is better when you want to drop a few gears and wring its neck, but everyone spends most of their driving time in a higher gear at lower revs where the diesel's extra torque will be felt.

CPG

Imagine BHP is a sprinter pushing you car, then torque would be a rugby player pushing your car.

moleyC

Here is a good site for comparing torque to bhp.

http://www.vettenet.org/torquehp.html

kuro_man

To compare the bhp/torque figures, you most take revs into accounts

eg max power 150 bhp @ 5000 revs is better than 150bhp @ 6500 revs

VH

Zube wrote: »

my favourite car ever was a Alfa, with max power at 6500, redlined at 8000 rpm.

8k redline - interesting - what model was that?

Zube

VH wrote: »

8k redline - interesting - what model was that?

A 1996 2.0 16V twinspark. 150 bhp at 6200 rpm, the tacho was red at 8000, shaded from 6 to 8. The manual said "Do not drive with the needle in this zone for long periods".

My dials looked like this with mph added.

moleyC

kuro_man wrote: »

To compare the bhp/torque figures, you most take revs into accounts

eg max power 150 bhp @ 5000 revs is better than 150bhp @ 6500 revs

Is it not generally better to have peak power at higher revs. I think you generally change gear at peak power and slot into peak torque in the next

VH

Zube wrote: »

A 1996 2.0 16V twinspark. 150 bhp at 6200 rpm, the tacho was red at 8000, shaded from 6 to 8. The manual said "Do not drive with the needle in this zone for long periods".

My dials looked like this with mph added.

the redline is where it changes to red - in that pic the redline is 6.2k, not 8k

edit - looks like 7k on the 2.0 here

edit2 - this is a rev counter from a car i had a (good) few years ago - it goes to 10k but the engine doesnt

VH

kuro_man wrote: »

To compare the bhp/torque figures, you most take revs into accounts

eg max power 150 bhp @ 5000 revs is better than 150bhp @ 6500 revs

why do you say that - can that argument be carried on - ie is it best to have peak power at 900rpm or so?

guil

VH wrote: »

why do you say that - can that argument be carried on - ie is it best to have peak power at 900rpm or so?

exactly there no mention of torque there

bikki

BHP sells cars
Torque wins races

VH

torque is cheap

Anan1

A simple way to maximise your available torque is to drive everywhere in first gear.

mkdon05

thanks for all the replies,
I particularly liked the analogy about the Sprinter/Rugby player!!

bikki

bikki wrote: »

Torque wins races in cars with no gears

Fixed that for ya :pac:

Anan1

ronoc wrote: »

Fixed that for ya :pac:

That's my line!;)

Anan1

Anan1 wrote: »

That's my line!;)

Imitation, Flattery etc.

kuro_man

moleyC wrote: »

Is it not generally better to have peak power at higher revs. I think you generally change gear at peak power and slot into peak torque in the next

Actually, it is the torque curve thats important, the more it is shaped like Ayer's Rock the better, not the Matterhorn. From what I understand, cars that reach max horse power at high revs have less torque the cars that reach max horse power at lower revs, and would have a steeper, shorter torque curve.

All other things being equal (identical cars, different engine) compare the torque curve. In the real world, these are all irrelevant numbers because the cars have other differences (4wd, transmission etc.) and it depends on how the driver likes to drive and what he wants the car to do etc. For example, 0 - 60mph time is great for off-the-line speed, for overtaking ability 50 - 70mph (in different gears) would probably be better.

The only way to know, ultimately, is to drive both cars!

mickdw

If ya want economy go for the tdi obviously. it will feel quicker at lower speeds but it hasnt the power at the end of the day.

I recently had a 130bhp tdi A4 while my 170bhp 1.8T audi A5 was in garage.
the diesel felt good up to 2nd gear and was effortlessly powerful at those speeds but it really didnt do it for me. You get such a short rev range that its totally **** cause you are soon in fourth gear with feck all power or torque whereas a petrol will still be comfortable in 3rd reving its nuts off. I really think you need 530d type power in a diesel to make it worth while, they are truely quick but what annoys me are all the 1.9tdi people (100 bhp) believing they have the quickest car ever.

JimmyCrackCorn!

End of debate is in the formula above.

Now go drive both cars and see which one suites your driving style

HashSlinging

The thing I like about driving a (Relatively powerful IMO!) diesel is the mid range, I can potter along minding my own business, see a break and really take off. While at the same time get really good MPG. There’s pro's and con's to both, but depends on your driving style. I don’t cover the same mileage as I used to and only have to visit the pumps once every two weeks now, which from a convenience point of view is handy.

brundle

JimmyCrackCorn! wrote: »

End of debate is in the formula above.

Now go drive both cars and see which one suites your driving style

and obviously the diesels are limited by the rotation speed compared to petrol alternative so much higher torque is required to put out an acceptable bhp. hence they feel 'powerful' but only for a short squirt

robbie99

JimmyCrackCorn! wrote: »

End of debate is in the formula above.

+1.

I can never understand the obsession with torque. Torque is force by distance. Give me a lever long enough and my little finger I'll generate more torque than beemer's 335d. Engine torque must be combined with the gearing ratio before it has any relevance to a car's acceleration. Power is the rate at which you can do work or something. It's a function of both torque and engine speed. As Jimmy's equation shows, BHP encompasses torque. If you want to compare things on figures alone then you should compare BHP only.

Sandwich

For those who struggle with:

BHP V's Torque


remember that its quite similar to :

Power vs. Torque

http://www.boards.ie/vbulletin/showthread.php?t=2055293659&highlight=torque

maidhc

robbie99 wrote: »

+1.

I can never understand the obsession with torque. Torque is force by distance. Give me a lever long enough and my little finger I'll generate more torque than beemer's 335d. Engine torque must be combined with the gearing ratio before it has any relevance to a car's acceleration. Power is the rate at which you can do work or something. It's a function of both torque and engine speed. As Jimmy's equation shows, BHP encompasses torque. If you want to compare things on figures alone then you should compare BHP only.

You should, assuming the engine has a CVT box which allows to always run at maximum power. Otherwise your arguments is flawed.

.

Anan1

maidhc wrote: »

You should, assuming the engine has a CVT box which allows to always run at maximum power. Otherwise your arguments is flawed.

.

Any kind of a gearbox would do the trick.

diesels do great with 6 speed gear boxes keepin the revs low
who goes around at max revs the whole time? (awaiting a hands up):D

maidhc

Anan1 wrote: »

Any kind of a gearbox would do the trick.

Not really, if you look at the old Yank tanks which had big lazy torquey v8s they often only had 2 or at most 3 speed autos.

The force (torque) of the output shaft turning is able to bring the engine from low rpm to high rpm and consequently accelerate. In a car which uses the rpm side of the equation to make up the bhp will be dead at low rpm and won't have the torque to accelerate.

This is why diesels are so good a towing, going up hills and overtaking in high gears etc, because they have brute force which equivalently powered petrols do not have.

colm_mcm

I'd actually pick the TDI over the 1.8t - sure the petrol sounds nicer, but the 130bhp engine is pretty punchy.

Anan1

maidhc wrote: »

This is why diesels are so good a towing, going up hills and overtaking in high gears etc, because they have brute force which equivalently powered petrols do not have.

...in the same gear! If you want more torque, just drop a gear or two. This is the great thing about power, it can easily be turned into torque. Unfortunately for diesels, it doesn't work the other way.

Sandwich

Anan1 wrote: »

This is the great thing about power, it can easily be turned into torque.

No.

Now we are getting muddled.

Power is the rate of doing work (Work/time). Toque is force through a distance.

You cannot turn into, or convert one to the other or visa versa.

Climate Expert

Anan1 wrote: »

...in the same gear! If you want more torque, just drop a gear or two. This is the great thing about power, it can easily be turned into torque. Unfortunately for diesels, it doesn't work the other way.

Peak torque stays the same however and peak torque will usually always be less than a diesel car.

Anan1

Sandwich wrote: »

No.

Now we are getting muddled.

Power is the rate of doing work (Work/time). Toque is force through a distance.

You cannot turn into, or convert one to the other or visa versa.

Climate Expert wrote: »

Peak torque stays the same however and peak torque will usually always be less than a diesel car.

Torque is a function of bhp and gearing. This is why a car with 150bhp but very little low-down torque can be geared to produce more torque than a turbodiesel with 140bhp and bags of low-down torque.

Climate Expert

Anan1 wrote: »

Torque is a function of bhp and gearing. This is why a car with 150bhp but very little low-down torque can be geared to produce more torque than a turbodiesel with 140bhp and bags of low-down torque.

So why don't they quote the 1.8T as having more torque than the diesel?

Anan1

Climate Expert wrote: »

So why don't they quote the 1.8T as having more torque than the diesel?

Turbodiesels tend to have higher torque peaks than petrols, but very low down. To give you an example - let's say one engine produces 1,000Nm of torque at 1,000 rpm and another produces 500Nm of torque at 2,000 rpm. They are both actually producing the same power - if you geared the second engine down by half (from 2,000 rpm to 1,000 rpm), you'd double the torque (from 500 Nm to 1,000Nm)

peasant

Anan1 wrote: »

Torque is a function of bhp and gearing. This is why a car with 150bhp but very little low-down torque can be geared to produce more torque than a turbodiesel with 140bhp and bags of low-down torque.

emmm ...that would be torque at the wheel.

The torque figures quoted in car data are taken at the crankshaft, are they not?

Anan1

peasant wrote: »

emmm ...that would be torque at the wheel.

The torque figures quoted in car data are taken at the crankshaft, are they not?

This is the point i'm making - torque at the wheel is what makes our cars go, and this can be manipulated as needed with the gearbox. As I said once before, torque is king in cars without gearboxes.;)

peasant

correct ...but for practical reasons there is only so much gearing that you can do. A 15 speed gearbox becomes somewhat undriveable

At the end of the day it is largely a question of driving style. It can be fun to wring your (petrol) cars' neck and scream around at the redline and it can be equally fun to just put the foot down from low revs and enjoy the punch in the back (brief as it is in a diesel)

maidhc

peasant wrote: »

At the end of the day it is largely a question of driving style. It can be fun to wring your (petrol) cars' neck and scream around at the redline and it can be equally fun to just put the foot down from low revs and enjoy the punch in the back (brief as it is in a diesel)

That is about the size of it.