Torque or HP on the road course????? Which is better?
02-04-2009, 08:30 PM
#18
Rennlist Member
Hp vs torque
Ok, if you havent had enough of this, Ill break it down into its very simple elements.
Torque means absolutely nothing without a speed attached to it. And guys, we are talking ENGINE torque.
Torque that causes acceleration at ANY vehicle speed, will be generated by Power (HP). (i.e HP is the rate of doing work. unit measure of measure of work might be something like HP-seconds, like the kilowatt hours on your power meter at home) It is HP that determines the torque at the rear wheels, not some level of ENGINE torque. Engine torque is one of two factors of HP.
Now, follow me here
Acceleration = power/(mass x velocity)
what this Newtonian identity tells us, is that acceleration is directly proportional to power and inversely proportioal to vehicle speed.
Why is this important?
Because if you are comparing two vehicles, all you need to do, is find out how much hp is made at any vehicle speed and you will know its comparable acceleration potential. (all other things being equal, like aero, weight, etc)
the main question you need answered is what is the average HP that the car will be producing between its gear shifts. in otherwords, what does the shape of the HP curve look like. the flatter the better, as your average or area under the HP curve, becomes higher.
It doestn matter what your peak torque values are on the engine. GT3RS engines can make 440rwhp and have less than 275rw torque. peak torque is flat and the peak could be anywhere! who cares? It matters on what the rear wheel torque is and that is determined by the HP. The HP curve can be looked at in HP-seconds between gear shifts through all the speed ranges. This determines the acceleration rates of any two cars with the same HP.
If one of those cars HP curve is peakier than the other, than the flatter HP curve'd car will acceleratate better off turns. if both have the same shaped HP curve, yet one has 1/2 the torque as the other, BOTH cars will accelerate exactly the same at ANY vehicle speed.
mk
Torque means absolutely nothing without a speed attached to it. And guys, we are talking ENGINE torque.
Torque that causes acceleration at ANY vehicle speed, will be generated by Power (HP). (i.e HP is the rate of doing work. unit measure of measure of work might be something like HP-seconds, like the kilowatt hours on your power meter at home) It is HP that determines the torque at the rear wheels, not some level of ENGINE torque. Engine torque is one of two factors of HP.
Now, follow me here
Acceleration = power/(mass x velocity)
what this Newtonian identity tells us, is that acceleration is directly proportional to power and inversely proportioal to vehicle speed.
Why is this important?
Because if you are comparing two vehicles, all you need to do, is find out how much hp is made at any vehicle speed and you will know its comparable acceleration potential. (all other things being equal, like aero, weight, etc)
the main question you need answered is what is the average HP that the car will be producing between its gear shifts. in otherwords, what does the shape of the HP curve look like. the flatter the better, as your average or area under the HP curve, becomes higher.
It doestn matter what your peak torque values are on the engine. GT3RS engines can make 440rwhp and have less than 275rw torque. peak torque is flat and the peak could be anywhere! who cares? It matters on what the rear wheel torque is and that is determined by the HP. The HP curve can be looked at in HP-seconds between gear shifts through all the speed ranges. This determines the acceleration rates of any two cars with the same HP.
If one of those cars HP curve is peakier than the other, than the flatter HP curve'd car will acceleratate better off turns. if both have the same shaped HP curve, yet one has 1/2 the torque as the other, BOTH cars will accelerate exactly the same at ANY vehicle speed.
mk
02-04-2009, 08:38 PM
#19
Rennlist Member
With the specifications of the two vehicles powered by 400hp engines below, both cars could have identical accelerations at any speed. The person that ever said "Torque wins races" was ignorant. HP is king, its what determines the torque at the rear wheels. want real life, 2009 proof. Look at the 24hours of Daytona Rolex race. who won???? the little flat 6 over the torquey V8. trust me, the flat 6 didnt have the torque of the v8.
In order for you to compare the below vehicles' acceleration rates at any speed, you would need to show me HP curves and gear spacing. Then, i could give you a hp-seconds graph of which car would theoretically produce more accelerative forces over any speed range. He who has the most HP-seconds, wins! (again, all other things being equal.. driver, weights, etc)
In real life situations, a supercharged 400hp might have a little bit of a peaky HP curve compared to a 400hp NA engine, especially one that is low reving.
this means when you compare the average hp put to the wheels over the operational speed ranges, the 400HP NA car usually will have more average HP. This means it will come off gear shifts with more accelerative forces. the only thing that the supercharged car can do to fight this, is to use a close ratio gear box to increase its average HP to match. If it can, it can narrow the gap.
mk
In order for you to compare the below vehicles' acceleration rates at any speed, you would need to show me HP curves and gear spacing. Then, i could give you a hp-seconds graph of which car would theoretically produce more accelerative forces over any speed range. He who has the most HP-seconds, wins! (again, all other things being equal.. driver, weights, etc)
In real life situations, a supercharged 400hp might have a little bit of a peaky HP curve compared to a 400hp NA engine, especially one that is low reving.
this means when you compare the average hp put to the wheels over the operational speed ranges, the 400HP NA car usually will have more average HP. This means it will come off gear shifts with more accelerative forces. the only thing that the supercharged car can do to fight this, is to use a close ratio gear box to increase its average HP to match. If it can, it can narrow the gap.
mk
I know this can't be over simplified but which is better for road course duties? Let's say all else the same on one car. But the only differences are.
Car A (supercharged)
400 hp 396 torque
Rev limit 6100 rpm
Peak torque at 3800 rpm
Peak hp at 6000 rpm
Car B (N/A)
400 hp 300 torque
Rev limit 8400 rpm
Peak torque at 6100 rpm
Peak hp at 8200 rpm
I'm asking because of the statement that torque wins races, however noting that the high revving NA motor has it's place in history as well.
Discuss.
Car A (supercharged)
400 hp 396 torque
Rev limit 6100 rpm
Peak torque at 3800 rpm
Peak hp at 6000 rpm
Car B (N/A)
400 hp 300 torque
Rev limit 8400 rpm
Peak torque at 6100 rpm
Peak hp at 8200 rpm
I'm asking because of the statement that torque wins races, however noting that the high revving NA motor has it's place in history as well.
Discuss.
02-04-2009, 08:48 PM
#20
Rennlist Member
If both of the other cars hp curves average 350hp and this engine you note below has a flat HP curve at 350hp, then all 3 of the cars will accelerate at the same rate at any speed, off corners, down main straights, etc. same same same.
Everyone is making generalized statements without knowing the details of the two cars , A and B in question. I can show you a bunch of engines that have the same HP as an other and a lot less torque that will run circles around the greater torque engine due to a flatter HP curve. Flatter hp curve, equals greater acceleration at ANY speed, of any turn and down any straight.
Remember, engine HP at any vehicle speed, determines rear wheel torque (accelerative forces)
Here are a couple of very different engines and their dynos below.
one has 450hp and the other 438Hp. One is from a viper V10 and the other is from a porsche GT3RS. the GT3 has half the torque, and if it had the same 450rwhp. (i couldnt find a graph of a viper with 438rwhp), look how close it would be at any same vehicle speed. the fact that the GT3RS has a close ratio gear box, makes up for most all of the HP curve shape short falls.
So, at ANY vehicle speed, if the porsche had the 455rwhp as the Viper did or the viper had 438rwph, (just in your mind, shift up or down that porsche or viper HP curve) at any speed both cars would have exactly the same torque at the rear wheels. Yet, the viper has double the engine torque! HP determines rear wheel torque. engine torque is really meaningless.
mk
Everyone is making generalized statements without knowing the details of the two cars , A and B in question. I can show you a bunch of engines that have the same HP as an other and a lot less torque that will run circles around the greater torque engine due to a flatter HP curve. Flatter hp curve, equals greater acceleration at ANY speed, of any turn and down any straight.
Remember, engine HP at any vehicle speed, determines rear wheel torque (accelerative forces)
Here are a couple of very different engines and their dynos below.
one has 450hp and the other 438Hp. One is from a viper V10 and the other is from a porsche GT3RS. the GT3 has half the torque, and if it had the same 450rwhp. (i couldnt find a graph of a viper with 438rwhp), look how close it would be at any same vehicle speed. the fact that the GT3RS has a close ratio gear box, makes up for most all of the HP curve shape short falls.
So, at ANY vehicle speed, if the porsche had the 455rwhp as the Viper did or the viper had 438rwph, (just in your mind, shift up or down that porsche or viper HP curve) at any speed both cars would have exactly the same torque at the rear wheels. Yet, the viper has double the engine torque! HP determines rear wheel torque. engine torque is really meaningless.
mk
02-04-2009, 09:32 PM
#24
Rennlist Member
I have a short attention span too, so I know those 4 paragraphs were like reading a book for some. 
Ok, lets just say there are a couple pre-emptive paragraphs to fight off the inevitable questions that usually follow in the beginning of such discussions. in a nut shell:
Hp at any vehicle speed determines rear wheel torque, and thus all accelerative forces. This is regardless of engine torque and engine rpm.
one example:
two cars coming off a turn in the meat of their 2nd gear, if both cars are at 350rwhp going to 400rwhp midway down the straight, one could be going from 4000rpm to 6000rpm and the other from 5300rpm to 8000rpm and both could have the exact same rear wheel torque, meaning both would have the exact same accelerative forces. (meaning: if one had 400ft-lbs peak torque and the other 275ft-lbs, their would be no difference between the performance of the two)
mk
02-04-2009, 09:38 PM
#25
Administrator - "Tyson"
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What if Wayne is driving car A and VR is driving car B?
How does that change the equation?
How does that change the equation?
02-04-2009, 09:58 PM
#26
Formula One Spin Doctor
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02-04-2009, 10:07 PM
#27
Formula One Spin Doctor
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