46 replies to this topic

[BMWPower]

When comparing engines we too often talk only about horsepowers. Horsepowers give the topspeed but torque gives the acceleration. That is the major factor e.g. when coming out of curves and when trying to overtake another car.
I have not seen a single info of the hp/torque relationship of any of the engines! Mercedes's approach may be to increase more torque than hp, which would be wise. Obviously Renaults new engine with the wide v-angle gives higher relative torque, so they will be the top players in the future if they can make the chassis as good as Maclaren or Ferrari.
I hope that Norbert Haug has the same idea.
Just to give you an practical example: I have a street car (BMW) with factory torque of 380 nm. When we reprogrammed the computer and did some hardware changes the torque increased to 675 nm it was like another world. HP's did not increase in the same relationship, but the acceleration at any driving situation is just unbelievable!

[tony]

Rest assured that the engineers are more than aware of the relationship between torque and horsepower. In fact HP = Torque*RPM*(some scaling factors). Thus the real figure of merit is not peak torque but the torque curve, in other words if you plot torque vs RPM what does this curve look like? Does the engine have lots of low end torque, at what RPM does the torque peak, are there any RPM ranges where torque is lacking,etc...The HP vs RPM curve can easily be calculated from the torque vs RPM curve. People like to generalize and talk about peak HP, but it is really not the figure that matters.

[HSJ]

Last year the Macs were horrible in accelerating out of corners. It is what prevented MH from overtaking JVe at Sepang, and many other instances in which Macs were unable to overtake. To overtake you need to accelerate well out of corners. This year I don't know whether the situation is better.

Yes, it is true that torque curve is important, and unfortunately we have little idea what it is for each engine. Ditto weight, size, and center of gravity. This is unfortunate, but we'll have to manage with what we've got, that is with hp figures and try to figure out some of the torque curve by acceleration etc.

[Cocco_Bill]

Originally posted by BMWPower
When comparing engines we too often talk only about horsepowers. Horsepowers give the topspeed but torque gives the acceleration. That is the major factor e.g. when coming out of curves and when trying to overtake another car.

Not true. The output of hp at a given time will give the acceleration. That is evident from the definition alone - 1 hp = 75 k pascal m / s which is the output of energy per time unit. A large amount of torque at very low revs won't give much of an acceleration(think of riding a bicycle). What is important in a F1 is to have a high and even torque curve in the range of revs in which the engine works in during the race - that will translate almost completely into usable hp.

Originally posted by BMWPower
Just to give you an practical example: I have a street car (BMW) with factory torque of 380 nm. When we reprogrammed the computer and did some hardware changes the torque increased to 675 nm it was like another world. HP's did not increase in the same relationship, but the acceleration at any driving situation is just unbelievable! [/B]

The increase in torque must have had its greatest effect at low revs if it didn't effect the peak hp very much.

[da Silva]

Just to give you an practical example: I have a street car (BMW) with factory torque of 380 nm. When we reprogrammed the computer and did some hardware changes the torque increased to 675 nm it was like another world. HP's did not increase in the same relationship, but the acceleration at any driving situation is just unbelievable!

It could only be possible to have that increase in torque if it´s supercharged. Even still it´s sounds not possible. Accereration is an combination of torque, horsepower, gearing, revrange, traction.

I think the amount of torque is about the same of the F1 engines today, but in which rpm´s could differ a lot. From an naturlly aspirated engine it´s difficult to get more than 110Nm/ 1000cc if it´s
also tuned for high rpm´s.
High horespower is not everything, you need to have an driveable powerflow with an linear torque curve with a broad rpm range. Another important aspect is fuel consumption.
I think BMW decreased it´s fuel C. with about 5% with the P82 engine over the P80.

[berge]

Originally posted by BMWPower
Obviously Renaults new engine with the wide v-angle gives higher relative torque, so they will be the top players in the future if they can make the chassis as good as Maclaren or Ferrari.

incorrect.
the V-angle of an engine has nothing to do with it's HP/Torque curves.

[Arrow]

Originally posted by Cocco_Bill

Not true. The output of hp at a given time will give the acceleration. That is evident from the definition alone - 1 hp = 75 k pascal m / s which is the output of energy per time unit. A large amount of torque at very low revs won't give much of an acceleration(think of riding a bicycle). What is important in a F1 is to have a high and even torque curve in the range of revs in which the engine works in during the race - that will translate almost completely into usable hp.

I dont really get what ur saying.A F1 car is always in the usable rev range so increasing the torque will improve acceleration,which is what BMWpower stated.

[Tec Freak]

F1 engine designers don't care that much about torque. Or, more accurately, they are more than willing to trade torque for horsepower. HP measures an engine's ability to convert chemical energy to mechanical energy over time. The more chemical energy you convert to mechanical energy, the faster you will go.

Yes, yes, it is possible to dream up hypothetical engines with a torque curve so screwed up that the motor isn't fast, but that isn't reality. Reality is that with 7 speeds, semiauto gearboxes, engine mapping, and the abilty to gear the car for each track, designers really don't care that much about torque output or curve. The curve isn't going to be all that bizzare no matter what you do.
Heck, an F1 engine has about a 43 mm stroke. How much leverage does that create? And who cares as long as the motor will rev over 18,000 rpm and create lots of hp? F1 engine design for the last 12 years has been a constant search for higher rpm and higher horsepower. Torque is the loser in that search.

[Tec Freak]

Originally posted by Arrow


I dont really get what ur saying.A F1 car is always in the usable rev range so increasing the torque will improve acceleration,which is what BMWpower stated.

The basic problem is that torque is directly related to the engine's stroke. Think of each throw on the crank as a wrench twisting on a nut. A longer wrench handle equals more leverage/torque. Look at the two cranks below. The large "O" ss the center line of the shaft, and the small "o" is the outer journal.

O----o

O-o

Which one has the most leverage? Longer throws = more torque.

But a longer crank throw means less rpm, because the stress on the engine (due to piston accelerations, speed, crank weight, etc.) is increased by the longer throw.

So F1 motors have a stroke of about 43mm--about half the size of cigarette. Which creates almost no torque at all.

Assuming the engine is otherwise properly set up, the way to increase torque is to lengthen the stroke. But that will decrease rpm, which will decrease hp.

So F1 engines have very short strokes, but lots of horsepower. This allows more rpm, which means the engines are ingesting greater quantities of air/fuel mixture and converting more of that mixture to mechanical energy over time. More power. More speed. More wins (hopefully).

[HSJ]

Originally posted by Tec Freak
F1 engine designers don't care that much about torque. Or, more accurately, they are more than willing to trade torque for horsepower. HP measures an engine's ability to convert chemical energy to mechanical energy over time. The more chemical energy you convert to mechanical energy, the faster you will go.

Yes, yes, it is possible to dream up hypothetical engines with a torque curve so screwed up that the motor isn't fast, but that isn't reality. Reality is that with 7 speeds, semiauto gearboxes, engine mapping, and the abilty to gear the car for each track, designers really don't care that much about torque output or curve. The curve isn't going to be all that bizzare no matter what you do.
Heck, an F1 engine has about a 43 mm stroke. How much leverage does that create? And who cares as long as the motor will rev over 18,000 rpm and create lots of hp? F1 engine design for the last 12 years has been a constant search for higher rpm and higher horsepower. Torque is the loser in that search.

So are you saying that it is quite valid for us to rank the engines "blindly" (i.e. without knowing their torque curves) by their hp figures? That's what I got as one implication from your post.

Good post in any case.

[BMWPower]

I think that HSJ is wrong on this. When you get out of a curve you do not have the max revs. Then everything is up to torque. The more torque you have in and out of a slow curve the faster you accelerate from it. After that HP's will be important. Theoretically HP's are all you need if the race track is a straight line from start to finish. Torque is allways the most important factor in all "less than max. rev conditions" because then you never have the max hp power available anyway. If the engine gives 850 hp max. power at 18.000 revs it is fine, but you do not have that hp available after a break e.g. into a curve. Note also that the time it takes an engine to reach the max rev. limit (e.g. 18.000) is fully dependant on torque!
So my conclusion still is that torque is the most important single factor in a successful F1 engine design.

[Tec Freak]

Originally posted by BMWPower
I think that HSJ is wrong on this. When you get out of a curve you do not have the max revs. Then everything is up to torque. The more torque you have in and out of a slow curve the faster you accelerate from it. After that HP's will be important. Theoretically HP's are all you need if the race track is a straight line from start to finish. Torque is allways the most important factor in all "less than max. rev conditions" because then you never have the max hp power available anyway. If the engine gives 850 hp max. power at 18.000 revs it is fine, but you do not have that hp available after a break e.g. into a curve. Note also that the time it takes an engine to reach the max rev. limit (e.g. 18.000) is fully dependant on torque!
So my conclusion still is that torque is the most important single factor in a successful F1 engine design.

BMWPower

I think you are confusing acceleration with throttle response. Torque is not a time dependant variable, and thus high torque gives immediate response. Acceleration (time to distance) is a time dependant variable and thus hp measures acceleration.

I see this every day because my wife drives a V12 BMW (5 liters, 340hp, 290ft lb torque, 6400 rpm redline) while I drive a turbodiesel truck (5.9 liters, 235hp, 450ft lb torque, 3300 rpm redline). You want throttle response? You want to spin the rear wheels in 1st, 2nd and 3rd gears? Take the truck. You want to reach 120 mph fast? Take the Bimmer.

Torque = throttle response
hp = time to speed (or to rpm or distance, whatever).

This relationship holds true no matter where the engine is in the rpm range.

If torque was the single most important factor in F1 engine design all the teams would run diesels with 30cm strokes and 3000 rpm redlines, as such a set up would max torque. However, the opposite is true and the engines are designed to develop hp by increasing rpm at the expense of torque.

[slipstream]

When talking about HP and Torque you have to look at the different Types of Acceleration. For instance Acceleration of a low speed corners you need Torque because Torque is what gives you that Initial Acceleration. But flat out Acceleration through the gears is determined by gearing, Horsepower, and Engine pick-up. A famous Motorcycle tuner once said " Horsepower and aerodynamics determine your top speed but Acceleration determines how quickly it reaches that speed. Acceleration is how quickly you can pick up the next gear after each upshift."

[mclarensmps]

You want throttle response? You want to spin the rear wheels in 1st, 2nd and 3rd gears? Take the truck. You want to reach 120 mph fast? Take the Bimmer.

Which is why I would much prefer a Viper to your average Midrear Euro Supercar (Also taking into account front engine rear drive of the viper)... Exceptions INCLUDE Astons and TVR's.

[BMWPower]

Originally posted by berge


incorrect.
the V-angle of an engine has nothing to do with it's HP/Torque curves.

Yes it does if wider V-angle makes it possible to have longer stroke,

[Ricardo F1]

Originally posted by BMWPower


Yes it does if wider V-angle makes it possible to have longer stroke,

I can't get my legs any wider apart though!

[BMWPower]

Originally posted by da Silva


It could only be possible to have that increase in torque if it´s supercharged. Even still it´s sounds not possible. Accereration is an combination of torque, horsepower, gearing, revrange, traction.

I think the amount of torque is about the same of the F1 engines today, but in which rpm´s could differ a lot. From an naturlly aspirated engine it´s difficult to get more than 110Nm/ 1000cc if it´s
also tuned for high rpm´s.
High horespower is not everything, you need to have an driveable powerflow with an linear torque curve with a broad rpm range. Another important aspect is fuel consumption.
I think BMW decreased it´s fuel C. with about 5% with the P82 engine over the P80.

You are right, it is turbo charged. It is a BMW 745i, which has a factory installed turbo charger. The factory set up was 252 hp/380 nm. Now 400 hp/675 nm. The car is 17 years old, so the technology used is not very modern, but still quite exellent! If you like to see the power and torque curves go to my web pages at www.viinikellari.com. Those curves are from my earlier 745i. Since that I have bought a newer 745i, but the engine specs are practically the same.

[dynamite7]

I've no idea what i'm talking about but:

Don't F1 cars have pitifully low torque? Like 450 to 500 nm. Less than a WRC, less than most sports cars, less than a affordable Ford Falcon TE50 road car.

So it can't be very important.

[Pioneer]

All things being equal, torque is directly related to the amount of air the engine can intake in a given amount of time.

Air intake determines how much fuel you can burn, which in turn determines the amount of work that can be done.

F1 cars being 3 liter naturally aspirated will not make significantly more torque than any other 3 liter NA engine.

Horsepower = torque * RPM

If a Viper weighed as much as an F1 car, it would out accelerate it by a large margin. Why? Because being an 8 liter NA engine, it has more than twice the torque. Lower HP because it revs much lower, so it will never approach the top speed of an F1 car, but it would out accelerate it.
Again, assuming they weighed the same.

This is why its so easy to tweak turbo cars, and so difficult to tweak an NA engine. If you want more torque from you NA car, your only real option is to increase displacement. Intakes and exhausts can be very carefully tuned and retuned, but the gains are minimal. Whereas in a turbo, you can just turn a screw and crank up the boost.

[HSJ]

Originally posted by BMWPower
I think that HSJ is wrong on this. When you get out of a curve you do not have the max revs. Then everything is up to torque. The more torque you have in and out of a slow curve the faster you accelerate from it. After that HP's will be important. Theoretically HP's are all you need if the race track is a straight line from start to finish. Torque is allways the most important factor in all "less than max. rev conditions" because then you never have the max hp power available anyway. If the engine gives 850 hp max. power at 18.000 revs it is fine, but you do not have that hp available after a break e.g. into a curve. Note also that the time it takes an engine to reach the max rev. limit (e.g. 18.000) is fully dependant on torque!
So my conclusion still is that torque is the most important single factor in a successful F1 engine design.

My point was: if torque curve is not so important (i.e. it doesn't vary enough between engines) we can take the hp number as the quality indicator overall, not just top speed. Though of course weight, center of gravity, etc. will still remain a mystery.

[Cocco_Bill]

Originally posted by Pioneer


If a Viper weighed as much as an F1 car, it would out accelerate it by a large margin.

Bullshit!

If the Viper has an average output of lets say 800Nm at an average of 5000rpm, and the F1 engine had an average output of 400Nm at an average of 15000rpm during acceleration, the formula 1 accelerates faster. If all other factors are disregarded, the power output of the F1 will then be 1.5 times that of the Viper, thus a greater acceleration.

How about this for an example:

Imagine a hypothetical engine which revs at 1 rpm/minute during acceleration, an engine which creates its thrust from a 80kg guy standing at the end of a horizontal 1 meter pole stuck to the crankshaft . The torque of such an engine would equal the 800Nm of the Viper, while the horsepower would be 5000 times less. How fast do you think that such an engine would accelerate a 600kg object? Not very fast, right?

An increase in rpm won't increase the torque, but it will increase the hp, and thus the acceleration. Get it?

[slipstream]

If Torque is more important than HP then a Cart champ car would be able to out Accelerate a F1 car. A Champ car has about 500 nm of Torque and a weight of 1800 lbs and a F1 car has about 335 nm of torque and a weight of 1450 lbs with Driver and fuel. That would give a Champ car a ratio of 3.7 lbs/torque and F1 Car would have a ratio of 4.25. But Everything I have read says that F1 has much quicker Acceleration so HP must more important for racing.

[Toxicant]

Some people say horsepower is how long you can
continue to make torque. That's sorta true, but it's "long" in terms of higher rpms,
not time directly. Think of it in this old fashioned way. Put a pulley on the crankshaft
of the engine with a 1 ft radius (2 ft diameter). Attach a long rope to that pulley.
Dangle it over a 6283 ft cliff, (I chose that distance because the pulley diameter is 2 ft
and the circumference is 6.283 ft and I want to move it for one minute at 1000 revolutions
per minute.) add a 200 lb weight to the end.
If the engine can develop 200 ft-lbs of torque it can lift that 200 lb weight directly.
If it does it at only 1000 rpms then it takes 1 minute to lift 200 lbs, 6283 ft up. (incidentally
for those wonder where the acceleration is.. It's gravity acting on the weight at 1G)
But let's say it can't rev any faster than 1000 rpms (like a big cruise boat diesel engine),
then the max hp is only 200 ft-lbs * 1000 rpms / 5252 = 38hp. Pitiful.

We don't want to wait a full minute, so we need to lift the weight faster.
So now we use an engine that can make 200 ft-lbs of torque but at 2000 rpms, it
can lift that same 200 ft-lbs weight twice as fast, pulling it 6283 ft up the cliff in
only 30 seconds. max HP = 200 ft-lbs * 2000 rpms / 5252 = 76 hp.

Ok.. So let's give this engine some serious guts, better breathing, higher revving,
larger displacement. Rev it all the way up to 5252rpms, and get it to still
make 200 ft-lbs of torque (no mean feat). Now it takes only 11.4 seconds to lift a
200 lb weight up a 6283 ft cliff. And of course HP = 200 ft-lbs * 5252 rpms / 5252 = 200 hp.

There's the basics of hp versus torque as measured at the crank for any
given fixed rpm. When the concept of horsepower was dreamed up,
these are the sorts of applications the steam engines it applied to, were used for. Lifting big
weights, pulling things through or over the ground, or turning the entire contents of some
factory at a constant rpm.

So what happens when a Honda engine manages to make 150 hp but
only 100 ft-lbs of torque at 8000 rpms? (I didn't choose VTEC numbers because I want round numbers)
Well.. For one it simply won't be able to lift the 200 lb weight with a crank pulley that has a
1 ft radius. It can't. It's only generating 100 ft-lbs of lifting force.
What you need now is gears. Let's put a 2 to 1 gearset between the engine crank and rope
pulley. Now the engine is still turning at 8000 rpms, but the pulley is turning at 4000 rpms, and
we've effectively doubled its leverage so torque measured at the pulley is 200 ft-lbs again.
Torque at pulley = 200 ft-lbs @ 4000 rpms. So it now can actually lift the 200 lb
weight directly, and at 4000 rpms, thats 4 times faster than our original engine. So 15 seconds
to lift the 200 lb weight up 6283 ft. Not bad. Moving a 200 lb weight up over 1 vertical
mile in only 15 seconds. (Note, 100 ft-lbs * 8000 / 5252 = 200 ft-lbs * 4000 / 5252)

One interesting side note. It's possible for an engine or motor to make torque at 0 rpms.
A steam train engine, for instance has a direct drive from pistons to wheels so when it
needs to get moving it can actually generate some ungodly number like 10000 ft-lbs of
torque at 0 rpms and thus by our formula HP = 1000 ft-lbs * 0 / 5252 = 0 hp. Cute eh?
Electric motors also can do this. That's why diesel train engines drive use electric motors
to turn the wheels, and a big nearly constant rpm engine to power the generator that
powers the motors.

Summary so far.
So torque lifts the weight. We can convert low engine torque (Honda engine)
into high usable torque through gearing, but at the cost of speed.
Horspower tells you how fast the weight can be lifted at a constant angular velocity.

Ok.. In the next post I'll explain how this relates to acceleration.



Horsepower, Torque and how you use it to accelerate through gearing
So what's the whole deal with the "torque curve" and why's it important to acceleration?
Well.. only being able to make good torque at a single rpm is not very useful for a road going vehicle.
It's ok for a train engine driving a generator, or factory motor, but no sense for a car. If you
only make useful torque at the crank in a very narrow range of rpms then you need lots and
lots of gears to keep the torque at the wheels in a useable range as your vehicle's speed
increases. Maximum acceleration of a car is made possible by maximizing your output
torque at the wheels at ALL times. Let's say the torque curve for our original engine that
made 200 ft-lbs of torque at 1000 rpms can actually do it between 500 and 1000 rpms (absolutely
flat curve) and falls off sharply on either side. (below 500 and above 1000).
It can still accellerate, but it'd need maybe a 2:1 gear to get started, then 1:1 to
keep going, and then about 2 overdrive gears to go fast. like 1:2.. 1:4
So here's our gears. 1st: 2:1 2nd: 1:1 3rd: 1:2 4th: 1:4
In first gear at the output wheesl, it'd make 400 ft-lbs of torque to the ground between
250-500 rpms. Second gear.. 200 ft-lbs at 500 to 1000 rpms.. 3rd.. 100 ft-lbs at 1000 to 2000 rpms
4th 50 ft-lbs between 2000 to 4000 rpms.. This engine makes 200 ft-lbs * 1000 / 5252 = 38hp.

By the time you hit the top of 4th gear you're only putting 50 ft-lbs of torque to the ground, but
you're moving right along. If you only had to lift only a 50 lb-weight up our cliff you could get there
in 15 seconds (not counting acceleration though the gears).

Works the other way around too. A higher revving engine that makes a little torque
up high. Let's try a flat torque curve between 2000 and 4000 rpms of only 100
ft-lbs. Let's try to match the torque to the ground of our other engine with
gearing. 1st: 4:1 2nd: 2:1 3rd: 1:1 4th: 1:2
So at the ground. 1st gear makes 400 ft-lbs of torque between 500 and 1000 rpms
2nd: 200 ft-lbs between 1000 and 2000 rpms
3rd: 100 ft-lbs between 2000 and 4000 rpms..
and 4th: 50 ft-lbs between 4000 and 8000 rpms.

Oops.. I accidentally made a more powerful engine. I was making the same
torque to the ground at the top of 3rd gear and still have 50 ft-lbs
usable for the next 4000 rpms in 4th. Want to see something cute.
At the crank. 100 ft-lbs * 4000 rpms / 5252 = 76 hp.
At the wheels.. 50ft-lbs * 8000 rpms / 5252 = 76 hp..
(assuming zero drivetrain loss here). You see why it doesn't
matter if you make your dyno pull in 3rd or 4th gear?

So yes. Torque is what does the actual work. With our weight, any
output torque less than 200 ft-lbs will NOT lift it at all. But horsepower
is how FAST we we do the work. And acceleration depends on the engine's
ability to generate torque at more than just one rpm. The fatter
the torque curve is (no matter how small the max torque value), the faster
you can accelerate because the more rpms you have to work with, the
higher the gear ratios and thus the higher your torque at the ground.
You maximize torque to the ground through gearing keeping the engine in the rpm
range where the engine generates the most ground speed for a given torque value.

A car that only generates 50 ft-lbs of torque, but but can do it between 10,0000 and 20,000
rpms will still make 190 hp. You're saying "But Ian, I still need raw TORQUE to accelerate
right?" True. But the tires don't need to turn at 20,000 rpms, so there's where I'm going to
get my torque. Let's design a single gear. The tires only need to turn at 880 rpms to go 60mph at
the top of 2nd gear. So let's experiment with an effective gear ratio from crank to tires
of 20:1. That'd give me 50 * 20 = 1000 ft-lbs of torque at the ground between the engine
rpms of 10k and 20k. That'd certainly get you moving just fine. Does it
work speedwise? 10,000 rpms / 20 = 500.. 20,000 rpms / 20 = 1000.
with 205/50-15 tires that's a speed range of 34mph to 68mph.
Cool.. An engine that generates only 50ft-lbs of torque between 10k and 20k rpms
manages to put down 1000 ft-lbs of torque to the ground between 34mph and 68mph
in my imaginary 2nd gear. Now just design another half dozen gears and you're
good to go. And it'll *feel* like 1000 ft-lbs of torque the entire time too.

An old turbo formula 1 car that makes 1100 hp at 14 thousand rpms.. Lesee.. 412 ft-lbs of
torque up there in the stratospheric rpms. Whew. Try a 10:1 effective gearing, that's still
like 4000 ft-lbs of torque to the ground at 95mph. Not bad.

So yes, you *feel* torque, but it's torque at the ground, not at the engine. If you can
rev high enough, then gearing will increase your effective torque to the ground for
a longer period of time. Torque you feel.. torque applied for a large range of rpms
equates to faster acceleration, and the highest rpm that you can maintain useful
torque will be your peak horsepower number. The horsepower @ rpm value
gives you some idea of how long the torque curve extends into the rpms.
That's how you use it.

So there it is. Everything you never needed to know about torque and horsepower.

[HSJ]

Originally posted by slipstream
If Torque is more important than HP then a Cart champ car would be able to out Accelerate a F1 car. A Champ car has about 500 nm of Torque and a weight of 1800 lbs and a F1 car has about 335 nm of torque and a weight of 1450 lbs with Driver and fuel. That would give a Champ car a ratio of 3.7 lbs/torque and F1 Car would have a ratio of 4.25. But Everything I have read says that F1 has much quicker Acceleration so HP must more important for racing.

[olschak]

TecFreak
I believe you're 100% right saying that torque does not relate to accelaration times directly. Looking at the acceleration-hp relation from another perspective it is absolutely true to say:
Given a certain car, that is given the mass and the aerodynamics you imagine an acceleration curve, that is speed versus time plot. From that curve the hp needed at any time follows directly since it is only depending on the speed development. The speed all by itself is directly related to rpm of the engine by the all-inclusive gearbox ratio. The torque you're using at any time or rpm can be calculated by that gearbox-ratio. Say you want to reach your top speed without changing gear in that model your maximum speed also gives you a maximum rpm-redline. It does not matter at all to have any excess torque in your engine's torque curve since it is not translated into hp.
In F1 I can imagine that the teams figure out their entry speeds into significant corners and calculate their gearbox ratios to maximum rpm for the straights between.
Race-wise torque may be an important factor in fuel consumption over a race distance.
I remember my Camaro ( which I sold last moth ) used to do 200km/h at only 3000rpm. That way it did not waste too much fuel going that quick.

[palmas]

You can get very complex at times. Think of acceleration as transmiting energy. Energy is power x time, so the more power, the less time to accelerate!

When you are talking about torque, you're assuming the car will use from idle to top rpm for it, and then you say the torque curve is very important. But in a ideal transmission (CVT?) you would have the engine at top POWER and teh gears would make for the increase in speed. In F1 you have 7 gear and not CVT, and that is only a (relatively good) aproache, but good enough for my statement to be true.

By the way, top power is not at top torque, never, unless torque falls fron top to 0 in 0rpm!

[Tec Freak]

Toxicant,

WOW! We really hit a subject of interest for you, didn't we.

Excellent analysis.

I'd only add that mathematical examples are good as far as they go, but there are real-world considerations that drive engine design one way and not the other. With a mathematical analysis and a theoretically infinite transmission, one could put the same torque to the wheels using a 3000 rpm diesel as with an 18000 rpm F1 motor. The F1 motor makes power by converting huge amounts of air/fuel (BTU's) to mechanical energy. A slower diesel of equal displacement could never convert that much energy, but our theoretical transmission would make up for that by using more mechanical leverage to increase torque at the rear wheel.

The practical problem is the theoretical transmission doesn't exist and likely never will. No CVT has been made to date capable of handling F1 power levels, the ratios needed to match the diesel to the F1 motor would be ungodly, and I imagine that if one was made it would weigh about as much as the rest of the car. It also would be illegal by reg. An 18,000 rpm motor hooked to a 7-speed gearbox can do almost the same job at a total weight of 150kg.

[heki]

Toxicant, Tec Freak

[BMWPower]

Thanks Toxicant.
I saved and printed your reply. It may take a while for me to really understand all of it, but I will read it thoroughly.

[agni]

Thanks Tox !!
Thats the best technical post I have read in some time.

[metz]

This is one of the best theads on a serious subject.
I learned a lot.. Thanx !
And I only understood half of what you guys were talking about..

[eamo]

just bookmarked - think i'm drunk, must red later - it all sounds good

[PraetorAAV]

Well, here's yet another technical reply:

HP = Torque * RPM / 5252

Clearly the two factors that increase the power are the torque and the rev. speed. (duh!).
What means an increased torque ? Well, simply put - longer cylinders, more HP. provided that:

- we have enough time for admission, compression, explosion and exhaust.
- the explosion doesn't really matter because it's instantaneous compared with the others
- admission + compression - longer times (getting more fuel into a cylinder requires more time than getting less fuel !)
- exhaust - once again, longer times (more fumes, more time to evacuate them).

To keep the same RPM we would need either of the following:
- more cylinders (not going to happen)
- better valves (we could couple the times: admission + compression, explosion+exhaust)
- better materials for the pistons - more burnt fuel -> more powerful explsion -> more wear of pistons, crank etc.

The alternative: face the technical reality and raise the rev speed as high as possible, reducing the torque. It's likely that raising the revs is more realistic (although I couldn't give details).

Side note, inspired by Arrows (who shows that his only perception of F1 is, after all, sentimental).
An increase in torque would indeed increase the acceleration. Why ? because more power leads to a different mapping of the gear box. The smaller the gear, the more speed you get to the wheels and the less force (please don't confuse it with power - that remains constant).

Since there is a minimal force that needs to be applied in order to put a car into motion, the mapping of the gearbox is determined by the amount of power an engine generates. Which basically means that a more powerful engine quite directly translates to higher speed.

And to finish my longest post yet, hasn't this been discussed in the same forum about a year ago ? I don't remember the name of the thread, just that I read more about this same issue.

Cheers

[BMWPower]

I have now read Toxicant's exellent explenation ( and many other comments, too) of the horsepowers and torque really thinking what they said. Still don't understand everything, but couple of comments:
Of all I've read I understand that as the HP is related to torque and RPM's, the torque curve over RPM's range is then very important.
The other point is that the F1 designers want to keep the weight distribution as close to the ground as possible.
So as a conclusion if you design an engine with an as wide v-angle as possible engine you get
1) Room to increase stroke ( 43 mm was mentioned as practical limit for today's F1 engines). The wider the angle, the more you have room to increase the stroke without increasing the engine height=weight distribution remains very low.
2) When you increase the stroke you increase the torque. As explained in the answers the more time the engine has to take more air and fuel, the more power and torque you get. The drawback is theoretically lower rpm's.
3) Torque curve over rpm range is very important, because that gives the engine the acceleration power in less than max. rev. conditions
4) The more gears you have the more max. power you have available at any situation.

So here's my undertanding of an next generation ideal F1 engine:

1) As wide angle as possible because of low weight distribution and room for longer stroke.
2) New innovations to combine longer stroke with high rev's (higher torque=higher HP)
3) Flatter torque range over higher end of the RPM range.
4) 10 gears

I think Renault is on this path.

[Cocco_Bill]

Originally posted by BMWPower

2) When you increase the stroke you increase the torque. As explained in the answers the more time the engine has to take more air and fuel, the more power and torque you get. The drawback is theoretically lower rpm's.

True, but the basic reason for generating more torque when you increase the stroke is that you get more leverage. Torque is Force multiplied by leverage.
You do seem to be making some real progress in understanding the subject though.




Force (Newton)
v
----------o = torque(Newtonmeters)
(m)

[Pioneer]

Yes but given a fixed displacement, increasing stroke raises the leverage, but neccessatates a decrease in bore, which means less force.

No win situation there.

There are more important factors that go into choosing bore and stroke in an F1 engine.
Combustion time and available valve area for example.

[Cocco_Bill]

Pioneer,

Decrease in bore, yes, decrease in combustion volume, no, thus no or little decrease in force. The moment of inertia will increase though, which is the main reason for lower rpm, which in turn limits the power.

[Tec Freak]

Originally posted by Cocco_Bill
Pioneer,

Decrease in bore, yes, decrease in combustion volume, no, thus no or little decrease in force. The moment of inertia will increase though, which is the main reason for lower rpm, which in turn limits the power.

Not sure I can totally agree with this. While the displacement remains the same in terms of swept area, the potential amount of fuel/air mixture available for combustion is decreased because the decreased bore limits the valve size. The intake system must be tuned for the optimum volumetric efficiency for that smaller valve size, which will be at a lower rpm. Thus, both volumetric efficiency and moment of inertia contribute to the rpm limitations and consequent decrease in total power (rpm x torque).

[Cocco_Bill]

Originally posted by Tec Freak

Thus, both volumetric efficiency and moment of inertia contribute to the rpm limitations and consequent decrease in total power (rpm x torque).

Sure, you are right.

However, if they wanted to keep the original engine proportions and increase the stroke without increasing the total combustion volume, they could always make a V4 instead of a V10. Such a change would not alter the volumetric efficiency very much, but it would leave us with the problem of increased moment of inertia. That is why big engines don't rev as high as small ones in general, am I right?

[brad_d]

Here's how I think about it (and I'm no expert) :

Newton's 2nd Law applies to the car (and everything else) : Force = mass * acceleration. Or, a = F/m.

F, the linear force accelerating the car, is simply the torque at the rear wheels times the radius of the rear wheels: F = Tr.

a = Tr/m.

This in a wind-resistance free environment (pie-in-the-sky, yes)*. But in this scenario, acceleration is directly proportional to torque! (where T is engine torque times the gear ratios of the tranny & differential, and also a loss factor for internal friction)

I'm having difficulty imagining how horsepower can be more important to acceleration than torque.

* - OK, want some wind resistance? Fine. Drag D is 0.5*C*A*rho*V^2, where V is speed and rho is air density. C is the drag coefficient and A is the car's frontal area. Whatever - wrap all but V up into a constant (since they're all effectively constants) and say D = KV^2.

ma = F - D, or a = (F-D)/m

a = Tr/m - KV^2/m

I still don't see how horsepower (which can be translated to F*V because power = force * velocity) fits into acceleration very strongly.

[Blue]

brad_d

Your formula seems quite right. So let say its right. Now u have acceleration, and that means your car has velocity too (v), Agreed?

If so,

Your formula: (1) a = Tr/m can be developed more
P = power, w = angular speed of tyre, v = velocity of car

(2) P=T*w => T=P/w
(3) v=r*w => w = v/r

(1)&(2)&(3) =>

a=(P*r^2)/(v*m)

[Chui]

Torque is just as important to an F1 engine as it is to a street car. It's called "driveability." He who has the largest/broadest torque curve will be easier to drive. And if engine operating speed range is constant the broader torque curve engine will be "more powerful" to the driver. In other words, it'll have more power across the engine operating range. Peak values mean little.

I imagine that the engines make 90 lb-ft of torque per liter. Compare that to 80 lb-ft per liter for the S54 [BMW M3 engine], ~77 lb-ft per liter for the Ferrari 360 Modena and Honda S2K.

The name of the engine game is bmep, brake mean effective pressure. It's the best measure for engine performance and is essentially a measure of the engine's torque though the measure can be calculated referenced to the peak engine speed power.

Another horrible misconception: small stroke:bore ratio engines produce little or no torque. Not at all true. They probably produce more, but this is due to many things, not just the s:b ratio. The small s:b ratio engines need more engine rpm to produce the peak torque values they make. Also recall the FIXED relationship between Torque [what the dyno measures] and brake horespower [what we CALCULATE] bhp = [(Torque*rpm)/5252].

I'd say that to produce a really quick car the object would be to have the torque peak at a relatively high rpm. In fact, I'd want it as high as I could get it. Now why would I wish for this? Such that I could take advantage of the gearing. You see [as many already know] it's not just the flywheel torque, but the amount of thrust the front or rear [or both] input to the pavement.

[Tec Freak]

Originally posted by Chui
Torque is just as important to an F1 engine as it is to a street car. It's called "driveability." He who has the largest/broadest torque curve will be easier to drive. And if engine operating speed range is constant the broader torque curve engine will be "more powerful" to the driver. In other words, it'll have more power across the engine operating range. Peak values mean little.

I imagine that the engines make 90 lb-ft of torque per liter. Compare that to 80 lb-ft per liter for the S54 [BMW M3 engine], ~77 lb-ft per liter for the Ferrari 360 Modena and Honda S2K.

The name of the engine game is bmep, brake mean effective pressure. It's the best measure for engine performance and is essentially a measure of the engine's torque though the measure can be calculated referenced to the peak engine speed power.

Another horrible misconception: small stroke:bore ratio engines produce little or no torque. Not at all true. They probably produce more, but this is due to many things, not just the s:b ratio. The small s:b ratio engines need more engine rpm to produce the peak torque values they make. Also recall the FIXED relationship between Torque [what the dyno measures] and brake horespower [what we CALCULATE] bhp = [(Torque*rpm)/5252].

I'd say that to produce a really quick car the object would be to have the torque peak at a relatively high rpm. In fact, I'd want it as high as I could get it. Now why would I wish for this? Such that I could take advantage of the gearing. You see [as many already know] it's not just the flywheel torque, but the amount of thrust the front or rear [or both] input to the pavement.

With all respect, Chui, nobody in F1 gives a rats arse about "driveablity." Peak horsepower is, indeed, the name of the game. The practical fact is that no matter how much they screw up that broad, flat torque curve so prized in street engines, they can make up for it with 7-speed trannies, transmission and engine mapping, careful final drive selection, and, finally, a $28 million/yr driver who at that salary should be able to figure out a way around "driveablity" issues. Even if torque production is crammed into the top 15% of the power curve (which is about as peaky as one can get), the motor still has a useable 2700 rpm power band, which is more than enough.

Which is why we see 18,000+ rpm motors with 43mm strokes and 96mm bores. One will not see much "driveability" out of this combination.

I agree that s:b ratio is not the only factor in torque production. However, torque is a measure of the motor's mechanical leverage. At a given displacement and number of cylinders, the short-stroke motor is at an inherent disadvantage because the primary leverage device, the throw on the crankshaft, is shorter than on the long-stroke motor. It has a shorter wrench handle to press on, so to speak.

Yes, there are ways to get more torque out of the short-stroke motor. These ways inevitably mean trading off some of the motor's top-end power production. Short stroke motors, because of their inherent leverage disadvantage, are not efficient torque producers.

I agree, however, that high-rpm torque peak is, indeed, the object of F1 engine design. This is because it will contribute to peak hp, as having high torque at high rpm maximizes the torque x rpm portion of the hp equation.

[BMWPower]

Originally posted by brad_d
Here's how I think about it (and I'm no expert) :

Newton's 2nd Law applies to the car (and everything else) : Force = mass * acceleration. Or, a = F/m.

F, the linear force accelerating the car, is simply the torque at the rear wheels times the radius of the rear wheels: F = Tr.

a = Tr/m.

This in a wind-resistance free environment (pie-in-the-sky, yes)*. But in this scenario, acceleration is directly proportional to torque! (where T is engine torque times the gear ratios of the tranny & differential, and also a loss factor for internal friction)

I'm having difficulty imagining how horsepower can be more important to acceleration than torque.

* - OK, want some wind resistance? Fine. Drag D is 0.5*C*A*rho*V^2, where V is speed and rho is air density. C is the drag coefficient and A is the car's frontal area. Whatever - wrap all but V up into a constant (since they're all effectively constants) and say D = KV^2.

ma = F - D, or a = (F-D)/m

a = Tr/m - KV^2/m

I still don't see how horsepower (which can be translated to F*V because power = force * velocity) fits into acceleration very strongly.

So after all these exellent pro and against comments I was not very wrong after all!

[Cocco_Bill]

Originally posted by BMWPower


So after all these exellent pro and against comments I was not very wrong after all!

I am getting so tired of this, but as noone else wants to correct brad_d, I guess I'll do it.

The force F is measured in Newton (N), a = acceleration, M= mass, m= meter Newtons 2nd law: F = M x a ¨

T= Torque(measured in Nm) => F = T/r not F = T x r which is easy to spot since
N = N x m / m = N Newtons 2nd law gives; a=T/( r x m ), which is logical - if you increase the radius of the wheel(like a gear), the force on the ground will decrease as will the acceleration.

Now I am perfectly content with this result. It is indeed the force from the wheel onto the ground which gives the acceleration.

Although it doesn't seem sink in, it has already been pointed out that a given amount of torque from the crankshaft can be multiplied on its way to the wheels by the gearratios.

t = torque from engine, T = torque on wheels r = rpm of engine R = rpm of wheels G = gearratio

t x r = T x R (1) where R = r / G (2) : (2) into (1) => T = G x t

which shows that the engines rpm and torque are equally important for producing torque on the wheels. (rpm x Torque /5252 = hp)


Bottom line: horsepower can be directly converted into force from the wheels, hence hp gives acceleration!!!

[Top Fuel F1]

Re:

http://www.g-speed.c...que-and-hp.html

[Cocco_Bill]

Originally posted by brad_d
I still don't see how horsepower (which can be translated to F*V because power = force * velocity) fits into acceleration very strongly.

I found a way to show how Power is related to acceleration from P = F x v (1).

Lets use the following formulas: Newtons 2nd law: F = m x a (2) a = dv/dt (3) (1), (2),(3) give => P = m x dv/dt x v (4)

With some vector calculus we also have: d/dt(v x v) = dv/dt x v + v x dv/dt = 2 dv/dt x v (5)

(4) and (5) => P = d/dt(1/2 x m x v x v) which is a mathematical expression for the change in kinetic energy with respect to time.

The following information can be extracted from that formula.

(1) More horsepower is needed to accelerate a fast moving object than a slow moving one even if we neglect windresistance.

(2) Power(hp) is directly related to acceleration at a given speed.

Originally posted by Blue

a=(P*r^2)/(v*m)

I'm just wondering how you can even consider the possibility that your formula is correct?
Do you really think that the acceleration for a given output of power would increase with the diameter of the wheel squared? Does it not ring a bell that something is wrong?