Horsepower or Torque?

Jesus.

Which is the real rating you should be looking at in order to evaluate a car's potential performance?

I've come to the conclusion that Torque is where its at. At least for real World driving anyway.

What do you think guys? Which do you think is the best guide as to how nippy a Motor might be?

TheBully

Its all about girth in my opinion

conzy

How fast a car can accelerate and its top speed is all about horsepower.

Torque is what rotates the wheels, an engine with more horsepower applies more torque to the wheels through the gearbox.

The engines peak torque figure is pretty irrelevant but a car where it arrives low in the Rev band or is near peak torque for a lot of the Rev band will feel more "driveable"

Celly Smunt

I guess it all comes down to how much you like wheel spinning

ItsLikeThis

Jesus. wrote: »

Which is the real rating you should be looking at in order to evaluate a car's potential performance?

I've come to the conclusion that Torque is where its at. At least for real World driving anyway.

What do you think guys? Which do you think is the best guide as to how nippy a Motor might be?

Its all about how much "poke" you have

Cogsy88

More horsepower increases top speed.
More torque increases acceleration.

pajor

Well as I read before:

Horsepower is the measure of how fast you'll crash into the wall.

Torque is the measure of how much of the wall you'll take with you.

Jesus.

I was reading these Yanky Boy's comments earlier and they all seem to think Torque is the key measurement:

http://answers.yahoo.com/question/index?qid=20081214200954AA2VAsm



Conzy, the way I see it this: You could have a decent amount of horsepower and indeed she might go fairly quick but you'd have to cane the sh*t out of her. In other words, it feels like you're doing an awful lot of work to get the car up to speed. On the other hand, if you had a decent amount of torque (Diesel?), it mightn't be any quicker but it seems to do the acceleration without much effort and feels a lot "easier".

That's the best way I can describe what I've found to be the difference between a "torquey" turbo-diesel and a petrol with the same bhp but less torque. Do you know what I mean?

CianRyan

The most obvious answer seems to me to be, one is useless without the other.
Unless you're running a really light car, HP will feel weak without torque in a heavy car, torque may feel quick as it pushes you back but without the HP, if you look at the needle you'll realise the speed isn't going up all the quickly.

So in a performance car, I like somewhat equal measures of both.

CiniO

Jesus. wrote: »

Which is the real rating you should be looking at in order to evaluate a car's potential performance?

I've come to the conclusion that Torque is where its at. At least for real World driving anyway.

What do you think guys? Which do you think is the best guide as to how nippy a Motor might be?

I think the best measure of car performance is 0-62mph acceleration value.
Maximum power or maximum torque on it's own doesn't tell us much, without knowing car weight, revolutions at which they appear, gearing, wheel size and plenty of calculations.

CianRyan

CiniO wrote: »

I think the best measure of car performance is 0-62mph acceleration value.
Maximum power or maximum torque on it's own doesn't tell us much, without knowing car weight, revolutions at which they appear, gearing, wheel size and plenty of calculations.

I'd argue a standing 1/4 or 1/2 mile if you want it from 0, in the real world it's going to be 50-100 and the likes.

CiniO

CianRyan wrote: »

I'd argue a standing 1/4 or 1/2 mile if you want it from 0, in the real world it's going to be 50-100 and the likes.

Most cars have 0-62mpg (0-100km/h) specified by manufacturer.

If I see two cars. Car A does 0-100km/h in 8s, car B in 10s, then I know which one is faster. It nearly as simple as that.

dgt

Its not just about torque and hp but how they're used. A high revving engine might produce some serious hp but will be fairly high up the rev range and won't be great low down. Well tuned diesels have serious useable power and torque but are usually out of puff around 5k rpm.

A Decent petrol with a usable linear torque curve at lowish rpm and high power in upper ranges is the way to go for a good all rounder

CianRyan

CiniO wrote: »

Most cars have 0-62mpg (0-100km/h) specified by manufacturer.

If I see two cars. Car A does 0-100km/h in 8s, car B in 10s, then I know which one is faster. It nearly as simple as that.

They make for great reading and everyone loves a good launch but how often do you pull over at the side of a motor way to do a 0-60 test?
I far more often find myself pulling at speed.

CiniO

CianRyan wrote: »

They make for great reading and everyone loves a good launch but how often do you pull over at the side of a motor way to do a 0-60 test?
I far more often find myself pulling at speed.

Yes, but one usually follows the other.

If car A does better 0-100km/h than car B, then in vast majority of cases it will also better accelerate from 80km/h to 160km/h.

Exceptions would be very rare.

CianRyan

CiniO wrote: »

Yes, but one usually follows the other.

If car A does better 0-100km/h than car B, then in vast majority of cases it will also better accelerate from 80km/h to 160km/h.

Exceptions would be very rare.

Not totally true but I get where you're coming from.
Take my MX5 for example, it's quite snappy from 0-40mph but when you're at motor way speeds and fancy a lash it won't go half as well as it did low down.

Now take something heavy, (not my area of expertise), it may not be so quick from 0-60 but if it's a got a big turbo on it, it will absolutely fly when it's already moving and under boost.

Matt Simis

CiniO wrote: »

Yes, but one usually follows the other.

If car A does better 0-100km/h than car B, then in vast majority of cases it will also better accelerate from 80km/h to 160km/h.

Exceptions would be very rare.

Only when looking at "normal cars" and relatively uninteresting 0-100kph figures like +8sec. Apply that logic to across the board to cars with sub-6sec 0-60 and it fails big time as weight and traction have much larger impacts and in different areas while the sub-6 speed itself is a difficult target to reach but can be done via lightweight (and likely small engine) or lots of power (and likely heavier car).

corkgsxr

If you follow that you'd buy a tractor and wonder why its not a ferrari.

You need to drive them. Unless you can see a dyno to see where it makes power and torque your only guessing

keithclancy

corkgsxr wrote: »

If you follow that you'd buy a tractor and wonder why its not a ferrari.

You need to drive them. Unless you can see a dyno to see where it makes power and torque your only guessing

Indeed .... Drive them ... The numbers don't mean anything until you take around a few bendy bits of road.

Anan1

Jesus. wrote: »

Which is the real rating you should be looking at in order to evaluate a car's potential performance?

I've come to the conclusion that Torque is where its at. At least for real World driving anyway.

What do you think guys? Which do you think is the best guide as to how nippy a Motor might be?

At the end of the day, it's all about horsepower. If you have that then torque is only a gearchange away. Think about how horsepower is calculated.

jimgoose

I like to look at power and torque curves, as printed by a dyno, where possible. That gives a much more complete story.

Cienciano

Cogsy88 wrote: »

More horsepower increases top speed.
More torque increases acceleration.

No, definitely not because:

corkgsxr wrote: »

If you follow that you'd buy a tractor and wonder why its not a ferrari.

You need to drive them. Unless you can see a dyno to see where it makes power and torque your only guessing

Plenty of tractors have the same HP as a cheap underpowered hatchback
Gearbox ratio is another factor.

BTW, I'll admit, no matter how many times it's explained to me, I don't understand what torque is.

jimgoose

Cienciano wrote: »

...BTW, I'll admit, no matter how many times it's explained to me, I don't understand what torque is.

You have a piston connected to a main-shaft via a crank offset. Consider a torque wrench. The bolt is the mainshaft, the wrench is the crank offset, and your hand is the piston. The better the explosions that happen above the piston, the more torque. The larger the crank offset, the more torque. RPM is about how often that happens, i.e. how quickly the torque is produced, i.e. power. An engine that produces lots of torque lower-down in the revs will feel very driveable and "nippy" for the kind of driving most people do, but will tend to run out of puff with high revs and the limits of that engine's volumetric efficiency approaches, due to head/port/piston design, valvegear and what-have-you. A high-bhp screamer by contrast will go like sh!it-off-a-stick but will need more caning, i.e. revs.

This is mainly why most manufacturers are messing about with some variant of variable valve/camshaft timing, by the way.

Kenny Logins

Cienciano wrote: »

No, definitely not because:



Plenty of tractors have the same HP as a cheap underpowered hatchback
Gearbox ratio is another factor.

BTW, I'll admit, no matter how many times it's explained to me, I don't understand what torque is.

Think of your arm undoing a tight nut or bolt, or standing on the pedals to cycle uphill.

sebastianlieken

Consider some examples at the far end of the spectrum from eachother:

Motorbike: Yamaha YZF-R1

• Horsepower: 146 bhp @ 11,500 rpm (109 Kw)
• Torque: 98 Nm
• Weight: 177 kg

Tractor: John Deere 8335R

• Horsepower: 335 bhp @ 1,900 rpm (246 Kw)
• Torque: 1569 Nm
• Weight: 13003 kg

I'm sold, Gimme that tractor and i'll take on all ye' scally wags!

Ignore the fact that the R1 has 800 bhp per 1000 kg more than the tractor and that it's geared for speed rather than torque. :pac:

corkgsxr

sebastianlieken wrote: »

Consider some examples at the far end of the spectrum from eachother:

Motorbike: Yamaha YZF-R1

• Horsepower: 146 bhp @ 11,500 rpm (109 Kw)
• Torque: 98 Nm
• Weight: 177 kg

Tractor: John Deere 8335R

• Horsepower: 335 bhp @ 1,900 rpm (246 Kw)
• Torque: 1569 Nm
• Weight: 13003 kg

I'm sold, Gimme that tractor and i'll take on all ye' scally wags!

Ignore the fact that the R1 has 800 bhp per 1000 kg more than the tractor and that it's geared for speed rather than torque. :pac:

Ah but the tractors a turbo diesel I don't think you considered that.
On the minus its not a vag so wouldn't be as good.

dr.fuzzenstein

It's very simple:

https://www.youtube.com/watch?v=fgLNO3ThGD4

sebastianlieken

Jesus. wrote: »

Which is the real rating you should be looking at in order to evaluate a car's potential performance?

I've come to the conclusion that Torque is where its at. At least for real World driving anyway.

What do you think guys? Which do you think is the best guide as to how nippy a Motor might be?

To try and answer your question a bit better actually:

Consider a Golf GTI vs a GTD.

GTI 1,984 cc (121 cu in) I4 (CCZA) 150 kW (210 PS) @ 5,300-6,200 280 N·m (207 lb·ft) @ 1,700-5,200 6.9 s 240 km/h (149 mph)
GTD 1,968 cc (120 cu in) I4 (CBBB) 130 kW (170 PS) @ 4,200 350 N·m (258 lb·ft) @ 1,750–2,500 7.8 s 222 km/h (138 mph)


Both have 2 litre engines. One is a petrol, one is a diesel. As you can see - petrol has more horsepower, diesel has more torque. The petrol engine has a better 0-60 time if that's how you like to measure performance.

maybe that helps to draw a comparison of whether you prefer bhp or torque. You kinda have to take one with the other though and look at the whole picture.

jimgoose

sebastianlieken wrote: »

To try and answer your question a bit better actually:

Consider a Golf GTI vs a GTD.

GTI 1,984 cc (121 cu in) I4 (CCZA) 150 kW (210 PS) @ 5,300-6,200 280 N·m (207 lb·ft) @ 1,700-5,200 6.9 s 240 km/h (149 mph)
GTD 1,968 cc (120 cu in) I4 (CBBB) 130 kW (170 PS) @ 4,200 350 N·m (258 lb·ft) @ 1,750–2,500 7.8 s 222 km/h (138 mph)


Both have 2 litre engines. One is a petrol, one is a diesel. As you can see - petrol has more horsepower, diesel has more torque. The petrol engine has a better 0-60 time if that's how you like to measure performance.

maybe that helps to draw a comparison of whether you prefer bhp or torque. You kinda have to take one with the other though and look at the whole picture.

There are a couple of interesting things about that: one, the diesel makes it's peak torque at higher revs than the petrol. But look at how long the petrol hangs on to both peak power and torque! :cool:

conzy

Everyone is thinking about this too much

Horsepower is a measurement of how quickly the engine can get work done.

Two cars the same weight

One has 100Nm of torque and is 400HP (it probably revs to a silly rpm)

One has 900Nm of torque and is 300HP (very low revs)

Providing both are geared optimally.

The one with 400HP will accelerate faster AND have a higher top speed.

Engine torque is largely irrelevant since the invention of this magical box called a "gearbox" that can take low torque at high rpm and convert it to higher torque at a lower RPM.

jimgoose

conzy wrote: »

...Engine torque is largely irrelevant since the invention of this magical box called a "gearbox" that can take low torque at high rpm and convert it to higher torque at a lower RPM.

Ever driven a Dodge Charger? It's actually true - the planet spins backwards briefly!

Isn't it a case where Horsepower is a unit of measurement of power which means hp and torque ?

If I compare our old CRV 2.0L petrol, 150 hp and 160 lbs of torque to the old VAG 1.9 TDI PD 130 hp and 220 lbs torque, the Honda definitely feels much livelier.

While the TDI took off noticeably harder, I can spin the wheels a little in the crv on the open road when I drop a few gears to over take something the TDI couldn't do and the crv is a fair bit heavier.

The crv has decent torque at low rpm but the difference is the power band, I got power most way to the limiter where the tdi runs out of puff far earlier.

I can stay in 2nd much longer than in the TDI. and I got to tell you I love it much more than any tdi, especially the sound, I'd love a vtec.

The TDI however would be much better for towing a trailer or caravan or climbing mountains (at slow speed)

The Prius, well that's different altogether but it has a lot more grunt low (400 lbs) down than the crv which is great especially if climbing a mountain, if you come up to a hairpin bend in the prius and have a really steep hill after the bend the prius pulls off like a rocket, but it doesn't last long as the speed increases it feels then like a normal 110 hp car. But for those first few seconds it feels like it has a lot more power.

The crv on the same stretch of road with the big hill means I need more revs for power and that can mean lots of wheel spin to give me the power for that big hill, but once I'm going the crv goes like a rocket but the power lasts longer than the prius, but it's got 40 more total hp.

The tdi will climb from around that bend very well like the prius because the torque is much more than the crv at low rpm meaning much less wheel spin. But again the tdi runs out of puff far earlier than the honda in the rev range.

on a normal road between the honda and the tdi, I prefer the Honda because I still have all the torque I need for relaxed driving but when I drop the gears the honda feels a lot faster than any tdi with around the same power.

The main difference is the fuel consumption ! but if I want economy I'll convert to lpg.

Full electrics, well they are completely different experience to any ice, 110 hp in a leaf will feel a lot more powerful than a 110 hp diesel/petrol. HP in an electric is deceiving.

OSI

OSI wrote: »

What you want is a nice turbo petrol. Best of both worlds.

Indeed, or more cylinders !

Anan1

Deleted User wrote: »

Isn't it a case where Horsepower is a unit of measurement of power which means hp and torque ?

Exactly. As conzy said, in a world without gearboxes torque might be king.

jimgoose

Deleted User wrote: »

...Full electrics, well they are completely different experience to any ice, 110 hp in a leaf will feel a lot more powerful than a 110 hp diesel/petrol. HP in an electric is deceiving.

That's largely because the torque curve of an electric motor is like Table Mountain. Consider this'n, from a Tesla Roadster:

Does the roadster only have just over 200 lbs torque ?

It's what this all translates to at the wheels though is the important part, I think most people that drive high power electrics prefer them much more to the ice.

I know Tesla tried to make a gear box but they couldn't get one to handle the sheer torque of a leccy motor. A gear box might stretch out the torque curve more through the rev range.

jimgoose

Deleted User wrote: »

Does the roadster only have just over 200 lbs torque ?

It's what this all translates to at the wheels though is the important part, I think most people that drive high power electrics prefer them much more to the ice.

I know Tesla tried to make a gear box but they couldn't get one to handle the sheer torque of a leccy motor. A gear box might stretch out the torque curve more through the rev range.

Best thing to use with 'lectric is some sort of CVT. I believe the Prius has one?

jimgoose

jimgoose wrote: »

Best thing to use with 'lectric is some sort of CVT. I believe the Prius has one?

It does, but it's a very simplified version, the Prius box is a single speed driven by a chain. The torque of the motor eliminates the need for the lower ratios that are needed for an ice to get moving, so what effectivly would be gear (ratio) 1,2,3 for an ice is gone in the prius.

The MK III prius is even simpler as it has no chain, gust a fixed gear.

So if your looking for a 2nd hand automatic, the Prius is going to be one of the most if not (the) most reliable automatic you'll find.

MK II on the left, and MK III on the right. Very simple indeed and a lot of the complexities of a normal cvt or automatic are eliminated in the prius. Which is one reason they last well over 350,000 miles.

jimgoose

Deleted User wrote: »

...So if your looking for a 2nd hand automatic, the Prius is going to be one of the most if not (the) most reliable automatic you'll find.

Mmm. Except I'd rather Fred Flintstone it in a Hindustan Ambassador with no floor than buy a Prius!


















Just kidding ML, don't kill me!! :D:D

A cvt would be interesting in an electric, but I'm not sure it's necessary. I'm not sure it would improve efficiency enough but it may allow more efficient faster speed cruising.

Unlike an ice, electrics are more efficient at faster rpm, so I'm not so convinced there would be a benefit.

jimgoose

Deleted User wrote: »

A cvt would be interesting in an electric, but I'm not sure it's necessary. I'm not sure it would improve efficiency enough but it may allow more efficient faster speed cruising.

Unlike an ice, electrics are more efficient at faster rpm, so I'm not so convinced there would be a benefit.

Probably give a more satisfying take-off as well.

jimgoose

OSI wrote: »

I thought one of the big benefits of electrics was that they didn't need a gearbox

They don't "need" them in the way an ICE does, but some sort of CVT does improve things somewhat.

OSI

OSI wrote: »

I thought one of the big benefits of electrics was that they didn't need a gearbox

They don't, but they can in certain circumstances improve efficiency.

Like an ice they have a range in their rpm where they're more efficient.

But as battery capacity improves it would eliminate the need for the need to improve efficiency, as they are already pretty efficient.

For torque, well I think most people will find that having max torque up until 40 odd mph and still pretty decent torque to the speed limit of 85 mph in the case of the Leaf would be more than enough.

If you want to go much faster then yes a gearbox would make them more efficient.

You see electrics are different to ice,

If you want more speed you increase the voltage to the motor, if you want more torque you increase the current, all of this means more HP.

Now this can be manipulated through the controller, software and the single speed transmission.

Electrics need a reducer gear because the motor spins much faster than in an ice, (about 15,000 rpm or so) so you need to reduce this.

There are also different types of motors with different windings which will translate to more or less torque or higher or lower speeds.

I would love to see the power and torque graph of a leaf.

Paddy@CIRL

The numbers are irrelevant without context.

Every car is different and should be judged on the sum of its performance, rather than what's on paper.

Jesus.

dgt wrote: »

Well tuned diesels have serious useable power and torque but are usually out of puff around 5k rpm.

True but can't you just change down at that point? :P

Anan1

Jesus. wrote: »

True but can't you just change down at that point? :P

Or up?

Jesus.

Anan1 wrote: »

Or up?

Now THAT was embarrassing!

Dartz

Torque and power really only tell half the story.

The gearbox can also have a very strong effect on how a car feels because it's what determines the actual force at the contact patches of the tyres.

If I have two engines that produce the same power output - but one revs much higher than the other - I can use shorter gearing on the faster-spinning engine to achieve the same force at the tyres. But it'll require a lot more effort to keep it in the powerband and careful gearshifting because if the rev's drop it'll feel gutless because it just doesn't have the sheer brute force to move the car.

On the other hand, a big fat diesel engine will feel effortless. Put your foot down and it'll wind up and do something. But it runs out of breath at higher speeds. At lower speeds however, it produces much higher pulling force allowing you to carry larger loads. Also, at lower speeds the engine is under much less stress. This is why most trucks use big, high-torque engines.

You can build a truck with an 18000rpm-spining 1 Litre engine. And with the right gearing it'll still move a load quite happily. But that little fast-spinning engine will be in such a high-state of tune and so massively stressed to do it that it'll just explode after a few miles. And you'll need some clever gearing to make it work.

The best way to think of it:

Power is a measure of your top speed. How fast you can ultimately go.
Torque is a measure of how fast you get to your top speed. (Or how much load you can pull up to that speed). How easy it all feels.

You also need to look at the power and torque curves.

An engine with a lot of low-dow torque in the 1500-2500rpm range will feel lazy and effortless - but as you start to push it harder it will start to feel breathless and run out of puff. Much more relaxed for motorway driving or for cruising when you don't really give a **** you just want the car to 'work' when you put your foot down.

On the other hand, an engine with all its torque somewhere in the 6000-9000rpm range (Or higher) will be ****ing manic. Lots of revs, lots of gearshifting, lots of noise and lots of fuel burn but a ****ing hoot to drive if you're into it. Or very, very tiring when you're not. And then there's the downshifting three gears to overtake a truck.

AugustusMinimus

Cogsy88 wrote: »

More horsepower increases top speed.
More torque increases acceleration.

This is simply not true.

For a start, gearing is very important in determining top speed and acceleration.

Simply put, if you have 2 identical cars, but one with more torque and the other with more horsepower, and give both cars optimal gearing, then the car with more horsepower will still accelerate faster and have a higher top speed.

More hp is needed to go faster in other words.