Torque

[lucid]

Originally Posted by BMW-videos.com

I don't get it. Are some of us trying to say torque isn't too important? How about when you're coming out of a sharp turn? If I recall correctly, the AUDI R10 is destroying the competition in lemans because of all the torque its twin turbo diesels produce. if you can hook, low rpm torque will catapult you out of corners. IMO, f1 cars have so little torque because there engine displacement is so highly limited. To make the horsepower and torque they have to rev to 19,000rpm plus period or else they wouldn't make the power. I'm sure if they weren't so liter limited you could have F1 cars that could run endurance races (since current engines will not withstand extremely long durations). What would an f1 car with a 7 liter engine and almost seamlessly fast shifting be like? I think if useable that torque will fling them out of corners at dangerous speeds. I think torque is underestimated.

You just need to gear the lower torque output Lemans car more aggressively, and if it can make as much power at that vehicle speed as the R10 by revving higher, it will more or less (depending on the specifics of the torque curve) accelerate just as fast coming out of a corner. The R10 might be taking that corner at a lower engine speed than your higher revving lower torque engine's speed, but that is inconsequential. Torque at the engine shaft is not a determining factor as gearing determines torque at the wheels. On the other hand, power at the engine shaft will determine the final outcome, and as Bruce is saying, is a useful "shorthand".

If F1 cars had 4x as much torque, all of the structural components in the drivetrain would have to be reinforced and heavier to deal with the significantly higher forces. You don't need a lot of force to be fast. You just need to apply the force at a higher rate. That said, it gets harder to reliably control breathing and combustion at higher engine speeds and inertia of moving engine parts is an issue, so that's why we don't have a bunch of street cars running around at 10000 rpms.

[footie]

BMW-videos.com,

I think you are making the mistake of thinking all other things being equal as is the case with the R10 and the competition. All of them are producing around 650hp but only the R10 is producing a monstrous amount of torque all over the rev range. The difference in the comparison between the 335i and the M3 is that one has approx.110hp more and only producing at peak 5ft/lbs of torque less. There is a big difference between the two examples.

I harp on and hi-performance diesels on these site mainly because the US haven't sampled them yet, the 335d has only 20hp less the 335i but mountains more torque and in fact out accelerates it after the 60~70mph mark. In real world situations I would choice the 335d in a heart beat over the 335i and if it had a M-diff and chipped to 360hp I would pick it over the M3 as well.

As an example of torque being more important than HP, check out MTM's two Audi A5 versions, the A5 3.0TDi with 300hp + 640Nm was actually quicker on the same track than their S5 supercharger version with 500hp. When torque is developed at the right rev range and with the correct gearing it can truly be magical.

This is not to say that HP doesn't have it's place but for the road a engine with more torque and equal or there abouts amounts of HP will always get my vote.

[J08M3]

Remember you only get horsepower because of Torque. Horsepower is just a mathematical number based on torque and time. Torque is an actual measurement.

[footie]

Originally Posted by lucid

You just need to apply the force at a higher rate. That said, it gets harder to reliably control breathing and combustion at higher engine speeds and inertia of moving engine parts is an issue, so that's why we don't have a bunch of street cars running around at 10000 rpms.

I don't believe it reliability that is stopping such high revving engine, it's trying to reduce the noise levels entering the cab is the problem. With revs comes noise and only in sportscars would such a problem by accepted to an extent. Place this type of engine in a luxury saloon and it wouldn't sell, period.

Plus with revs comes excessive economy figures, you can't have one without the other, especially if you want decent amounts of HP. That is why many companies are switching to forced induction, you get the power and performance without any of the minus points.

Would I pick the RS6 engine over the M5, HELL YEAH. Imagine which sort of a monster the M5 would be with an RS6 engine under the hood, the only problem would be trying to put all of that extra power and torque to the road with only two wheel drive.

[JEllis]

These kinds of threads are sucking my will to live

[lucid]

Originally Posted by footie

I don't believe it reliability that is stopping such high revving engine, it's trying to reduce the noise levels entering the cab is the problem. With revs comes noise and only in sportscars would such a problem by accepted to an extent. Place this type of engine in a luxury saloon and it wouldn't sell, period.

Plus with revs comes excessive economy figures, you can't have one without the other, especially if you want decent amounts of HP. That is why many companies are switching to forced induction, you get the power and performance without any of the minus points.

Would I pick the RS6 engine over the M5, HELL YEAH. Imagine which sort of a monster the M5 would be with an RS6 engine under the hood, the only problem would be trying to put all of that extra power and torque to the road with only two wheel drive.

Higher revving engines need to have the lightest possible moving engine components. There is an obvious trade off between component weight and strength. So, reliability will always be an issue. That is the structures point of view.

Then there is breathing and combustion. The valve timing and combustion characteristics of a high revving engine will most likely not lend themselves to smooth operation at lower rpms. That is the really cool thing about the M3 engine although it is by no means high revving by F1 standards. It is very much drivable in any scenario. The torque curve is pleasantly flat. I doubt that is the case for the ALMS version.

I am not going down the FI vs. NA road with you.

[footie]

Lucid,

I was just trying to keep the basics when memtioning the noise issue, there isn't a problem designing an engine to rev to 10K or produce 160hp/litre, bikes have been doing this for years and reliability haven't been an issue. The problem with high revs in a closed compartment is noise, have a 4L engine revving to 10K and you will need a lot more sound deading to make it bearable which would partly defeat the hard work making the thing rev that high in the first place. Then there is the thirst, more revs means more fuel and air and the thing will drink like no tomorrow.

Next problem you hit with such a wide rev range is the power band, if peak power is close to the 10K then you will struggle to produce much below 4K so torque will be non existent below this level either.

P.S.
I don't want a FI vs N/A debate either.

[ArtPE]

T is a force
HP is power, the rate of work, and work is energy or force x distance...
they are inseperable

HP = T x rpm/5252

also, the torque band is critical...
300 lb-ft from 1500-5000, will not do as much work as 2000-8000...

but it's a all a moot point if gearing is selected correctly, as it is in these cars...

[ArtPE]

Originally Posted by J08M3

Remember you only get horsepower because of Torque. Horsepower is just a mathematical number based on torque and time. Torque is an actual measurement.

some old dynos (actual generator type dynomometers) measure power, and convert to torque...

a generator (the load) is spun by the measured driver...
a voltage and current is measured...
P = V x I, then T is calculated based on rpm...

at least in the old days

[alvinjamur]

Torque : http://en.wikipedia.org/wiki/Torque

HP : http://en.wikipedia.org/wiki/Horsepower

[lucid]

Originally Posted by footie

there isn't a problem designing an engine to rev to 10K or produce 160hp/litre, bikes have been doing this for years and reliability haven't been an issue.

Really? Can you track that kind of a high strung bike engine with 150000 miles on it safely and quickly? Will it even make it to 150000 miles? Motorcycles are not my thing, but I don't think so...

[BMW-videos.com]

Originally Posted by footie

BMW-videos.com,

I think you are making the mistake of thinking all other things being equal as is the case with the R10 and the competition. All of them are producing around 650hp but only the R10 is producing a monstrous amount of torque all over the rev range. The difference in the comparison between the 335i and the M3 is that one has approx.110hp more and only producing at peak 5ft/lbs of torque less. There is a big difference between the two examples.

I harp on and hi-performance diesels on these site mainly because the US haven't sampled them yet, the 335d has only 20hp less the 335i but mountains more torque and in fact out accelerates it after the 60~70mph mark. In real world situations I would choice the 335d in a heart beat over the 335i and if it had a M-diff and chipped to 360hp I would pick it over the M3 as well.

As an example of torque being more important than HP, check out MTM's two Audi A5 versions, the A5 3.0TDi with 300hp + 640Nm was actually quicker on the same track than their S5 supercharger version with 500hp. When torque is developed at the right rev range and with the correct gearing it can truly be magical.

This is not to say that HP doesn't have it's place but for the road a engine with more torque and equal or there abouts amounts of HP will always get my vote.

I can say I agree with you. I believe that people are heavily underestimating torque in road racing. Torque developed at the right RPM range is monstrous for getting out of corners.

[skierman64]

Originally Posted by bruce.augenstein@comcast.

Behind the wheel, the 335i does indeed feel a bit livelier than the M3 in everyday driving, and in fact it probably really is livelier. This point has been debated at great length in these pages, both with and without rancor, but the primary point is, as footie has said, "you get all the thrill without the speed" in the turbo car. To the driver, the 335i feels effortless, since you can give it gas at low rpm in a higher gear and the car will pull very hard without the sturm and drang associated with high revs. By contrast, the M3 will actually be quicker from pretty much any speed to any other speed, but because of its gearing, you will always be looking at greater revs, and the associated feel to the driver of greater effort.

In regard to horsepower vs torque, quite simply horsepower rules. Take any two cars that weigh the same, and in a side-by-side acceleration contest, the car with more horsepower at any given point will be accelerating harder than the car with less horsepower. Torque and gearing simply don't matter at all. In fact, horsepower is kind of a simple shorthand in that context. You can do all that computing of torque at the drive wheels if you like, but you'll find that more power equals more torque at the drive wheels, pure and simple.

I've used an example of a waterwheel generating some 2600 pound feet of torque - at 12 rpm. If you hooked that waterwheel to the drive wheels of a car, that car would jump from zero to 12 rpm of the drive wheels very quickly. But since 12 rpm of the drive wheels is equivalent to about one mph, what if you wanted to go faster?

Well, you'd have to gear it up. If you wanted to go 60 mph you'd need to gear the waterwheel up by 60 times - thus netting you about 43 pound feet of torque at the drive wheels. 43 foot pounds of forward thrust in a car weighing thousands of pounds just isn't enough to get the job done. In fact, it almost certainly isn't enough to overcome wind and rolling resistance at that speed. If you do the math (horsepower equals torque times rpm over 5252), you'll find that the waterwheel is only making about 6 horsepower.

The solution would be to speed the waterwheel up. Using a convenient flood (and assuming the waterwheel wouldn't fly apart), what if we could speed the water wheel up to, say, 120 rpm, while making the same amount of torque?

Well, the car would then be going 12 mph. Gearing it up to go 60 mph would now reduce the drive wheel torque to about 215 pound feet. That's still not a lot, but it's plenty to keep the car rolling at 60, and you could probably still accelerate at that speed. Doing the math shows, TA DA!, about 60 horsepower - so you can see that raising the rpm by a factor of ten gives you an increase in power by a factor of ten.

In fact, that's the horsepower story. It's torque at rpm. Raising the rpm at which torque is delivered gives you more power by a like amount - and more power gives you a greater ability to accelerate, period.

Bruce

Edit: PS - For a more complete explanation of power vs torque, go here, in note 31.

I love that explaination, even a business major can understand that.

[lucid]

Originally Posted by skierman64

I love that explaination, even a business major can understand that.

From what I gather, Bruce, too, was a business major. So, of course, it all made sense to you!

Bruce is a good guy when it comes to this kind of stuff--especially considering he was a business major!

Bruce, were you really a business major, or am I making shit up?

[Dascamel]

Yes the torque is great on the 335i for powering out of sharp corners, BUT w/o a proper LSD putting that all on the ground is fiction. Now for everyday driving I love my 335i, but when time comes to pick one for the track, M3 all they way. (Assuming I'm ready to thrash it a bit.) At one time modded the car(335i) was making well over 350 ft/lbs, fun as hell but not very practical. In the end, I'm sure the wife and I will FIGHT to death every morning to see who gets the M.

[mixja]

Originally Posted by southlight

The problem with the above comparison is that although it takes into account the gearing of the car in terms of torque to the wheels, it doesn't take into account the effect of the gearing in terms of vehicle speed.

Because the 335 has a taller ratio in 1st gear, it travels further in a single engine revolution - the best way to take this into account is to plot vehicle speed (rather than engine RPM) vs torque to the wheels - this gives a more accurate picture of what will actually happen in terms of the relative acceleration of the two vehicles.

In effect, the taller gearing will stretch the torque curve of the 335 to roughly the same width of the M3 curve, when you apply vehicle speed on the X axis rather than engine speed...

[J08M3]

My last car '05 GTO had similar horsepower but 100 ft. lb. more torque. Both cars were pretty fast, I'd say my M3 is faster (definitely in turns since it handles and stops, both things the GTO don't do). But most importantly the difference is just how they are setup and driven. I was used to 400 ft. lbs. after having the car for three years. Totally different driving experience without that extra 100 ft. lbs. Biggest difference is how you drive the car. When it comes down to it though, numbers on a graph really don't mean shit. It's all about being in the car and driving it.

[IWC Doppel]

I do get frustrated by the confusion here as it has been covered for years and people still droan on about big torque figures. The way to look at this is torque at the road wheel. This is what will drive the car forward at any point

Do the maths and it all becomes clear. A high torque engine with an 'amazing torque' figure at low rpm (Grimey diesel) will need the appropriate gearing which will reduce the torque at the road wheel for a given road speed.

HP makes life easier to understand as it factors in engine speed. Look at the shape of your power curve and the rpm it is achieved at and it will make sense. Hey we all know if an engine has a broad spread of power you will still accelerate reasonably if you are a little off the best point on the curve. Vanos endeavours to do exactly this. The HP / torque debate was demonstrated beautifully in the 60's when the Cosworth DFV's destroyed high capacity high torque motors on the track.

On the road if you expect to accelerate hard at 2,000rpm get in the right gear and try again or go buy a diesel

[bruce.augenstein@comcast.]

Originally Posted by lucid

Bruce, were you really a business major?

Yup.

Originally Posted by lucid

or am I making shit up?

Not in this case.

Nothing wrong with my deductive powers, but my formal training (or lack of it) shows up in my posts, of course. You and Swamp are quite comfy discussing derivatives of the cube root of infinity squared, but I need to stay closer to sea level, so to speak.

I'm reminded of an old Bill Cosby bit, wherein he discussed his experiences while a student at Temple. He spoke of the philosophy majors earnestly debating why there was air, but as a phys ed major, he knew why there was air.

It was to fill up basketballs.

Bruce

PS - Speaking of Philosophy, I have the married man's cut at that old chestnut:

"If a tree falls in the forest, and there's no living thing present to hear it, is it still the husband's fault?"

[ersin]

Originally Posted by bruce.augenstein@comcast.

"If a tree falls in the forest, and there's no living thing present to hear it, is it still the husband's fault?"

Yes, according to my wife.

[BMW-videos.com]

Originally Posted by J08M3

My last car '05 GTO had similar horsepower but 100 ft. lb. more torque. Both cars were pretty fast, I'd say my M3 is faster (definitely in turns since it handles and stops, both things the GTO don't do). But most importantly the difference is just how they are setup and driven. I was used to 400 ft. lbs. after having the car for three years. Totally different driving experience without that extra 100 ft. lbs. Biggest difference is how you drive the car. When it comes down to it though, numbers on a graph really don't mean shit. It's all about being in the car and driving it.

I can bet your GTO weighs a decent amount more then your M3. I'd probably agree that your m3 is a bit faster. Lighten that GTO a bit, probably stiffen the suspension and it could turn pretty well. Either way i'd probably also prefer the m3.

[lucid]

Originally Posted by mixja

The problem with the above comparison is that although it takes into account the gearing of the car in terms of torque to the wheels, it doesn't take into account the effect of the gearing in terms of vehicle speed.

Because the 335 has a taller ratio in 1st gear, it travels further in a single engine revolution - the best way to take this into account is to plot vehicle speed (rather than engine RPM) vs torque to the wheels - this gives a more accurate picture of what will actually happen in terms of the relative acceleration of the two vehicles.

In effect, the taller gearing will stretch the torque curve of the 335 to roughly the same width of the M3 curve, when you apply vehicle speed on the X axis rather than engine speed...

Sure, that will stretch it out, but the numbers won't change. So, the M3 will still have more torque at the wheels. The 335 reaches redline and has to shift at a lower vehicle speed than the M3 actually. I did the math on that one, but can't find it now.

Swamp ran the analysis you are referring to using a simulation tool. The simulation output confirmed the above; at no point in an open-ended acceleration run the 335 experiences higher instantaneous acceleration.

Some more relevant variables that the plots I made do not take into account are rotational inertia effects and some other dynamic variables that affect engine output under acceleration. The plotted torque at the hubs numbers are from the same reputable tester for both cars, but they are obtained in a steady-state test. Acceleration tests would yield lower numbers for both cars.