Tech Topic - Horsepower and Torque
09-11-2010, 12:55 AM
#46
We had a choice?
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As soon as I read the thread title I giggled......
09-11-2010, 02:12 AM
#48
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I have a little old tractor, it has twenty something horsepower and probably 50 foot pounds of torque, but I'll bet a sixpack, it can tow Kiborts race car backwards. no matter how much of his horsepowers or torques he has!
Cheers Roy
Cheers Roy
09-11-2010, 04:55 PM
#49
Race Director
09-11-2010, 10:41 PM
#50
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Torque is the real deal, an engine dyno measures the torque available, and this is then measured against time ( RPM ) to create an output figure (horsepower, kilowatts, PS etc).
Without Torque you got nothing.
what you do with that torque is the next conundrum.
Twin Turbos make more torque than Centrifugal Superchargers at lower RPMs.
I like twin turbos.
Cheers Roy
Without Torque you got nothing.
what you do with that torque is the next conundrum.
Twin Turbos make more torque than Centrifugal Superchargers at lower RPMs.
I like twin turbos.
Cheers Roy
09-12-2010, 03:11 AM
#51
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As long as the "torque" you are talking about, is found at the rear wheels, and not the engine, you are right.
Keep in mind, a chassis dyno doest calculate hp, it actually measures power directly, without knowing torque. did you know this? It measures a rate of change of kinetic energy. it does this ONLY knowing the rate of speed change, and the mass of the drums. Now, it actuallly calcuates engine torque by taking a spark signal from the engine to give the RPM factor. without it, you will never know the engine torque, only HP.
Torque is the real deal, but its found at the rear wheels. Hp will dictate this and it is HP-seconds (or ft-lb - seconds at the rear wheels ) that determines who will win a straight line race. torque WITHOUT RPM is "nothing".
Keep in mind, a chassis dyno doest calculate hp, it actually measures power directly, without knowing torque. did you know this? It measures a rate of change of kinetic energy. it does this ONLY knowing the rate of speed change, and the mass of the drums. Now, it actuallly calcuates engine torque by taking a spark signal from the engine to give the RPM factor. without it, you will never know the engine torque, only HP.
Torque is the real deal, but its found at the rear wheels. Hp will dictate this and it is HP-seconds (or ft-lb - seconds at the rear wheels ) that determines who will win a straight line race.
torque WITHOUT RPM is "nothing".Torque is the real deal, an engine dyno measures the torque available, and this is then measured against time ( RPM ) to create an output figure (horsepower, kilowatts, PS etc).
Without Torque you got nothing.
what you do with that torque is the next conundrum.
Twin Turbos make more torque than Centrifugal Superchargers at lower RPMs.
I like twin turbos.
Cheers Roy
Without Torque you got nothing.
what you do with that torque is the next conundrum.
Twin Turbos make more torque than Centrifugal Superchargers at lower RPMs.
I like twin turbos.
Cheers Roy
09-12-2010, 03:16 AM
#52
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God also said:
a=P/mv
acceleration= power/(mass x velocity). rear end torque can be calculated by the engine torque gear ratio and vehicle speed. power can determine this at only a vehicle speed. God likes those that can save time in their calcuations.
a=P/mv
acceleration= power/(mass x velocity). rear end torque can be calculated by the engine torque gear ratio and vehicle speed. power can determine this at only a vehicle speed. God likes those that can save time in their calcuations.
09-12-2010, 03:32 AM
#53
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still doesnt matter. if you have more power out of the hole, you accelerate faster. if you accelerate faster, more torque was applied to the rear wheels through the gear box, regardless of engine torque "values".
only if the engine is attached to the rear wheels and substracting slip values. no work done, no power , no torque generated.
No, just plain logic and physics here. if you have 10,000peak HP at the rear wheels, there is some level of power that is applied to the rear wheels in 1st gear. what ever that HP number is, determines the rear wheel torque number. it could easily be hgher, if the power is hgher at that point of acceleration. again, acceleration is proportioal to power. (also proportional to rear wheel torque)
Yep, you are right, but more importantly, it the power level when you do get traction and start accelerating . who ever has more power at that point will have more rear wheel torque.
No, not really. A GT3RS with 500hp and half the torque as a 500hp viper, might accelerate exactly the same at the dump of the clutch. both might have the same power available at half their RPM top end, and therefor, have the same accerative forces at that same speed, due to the same power being available. the tires dont know if their engine is spinning two X as fast. .
Yeah, but if I am in a car with more torque and less peak HP than you, I will accelerate faster for the duriation of 1st gear. Your car could have 10,000HP, but you won't be seeing it until high RPM since you lack low-end TORQUE. By that time I will already be ahead, so I WIN!
See, you guys must understand. Mark must WIN whether it is sports, American Gladiators, racing, or an argument on the internet.
Dan
'91 928GT S/C
475hp/460lb.ft
See, you guys must understand. Mark must WIN whether it is sports, American Gladiators, racing, or an argument on the internet.
Dan
'91 928GT S/C
475hp/460lb.ftNo, not true. If you launch the car at the RPM where peak HP is achieved, then the car with higher peak HP will be faster, notwithstanding traction issues which would be a whole different topic.
Now if the car is an automatic where you are forced to go through the RPM range, then you're right. In this case, peak HP is irrelevant.
I'm not defending Mark. I just don't understand why this topic generates so much confusion.
Man, I feel so lame discussing this on a Friday night with a 928 get together going on an hour away. Oh well, I'm babysitting tonight. Looking forward to meeting some 928ers tomorrow.
Now if the car is an automatic where you are forced to go through the RPM range, then you're right. In this case, peak HP is irrelevant.
I'm not defending Mark. I just don't understand why this topic generates so much confusion.
Man, I feel so lame discussing this on a Friday night with a 928 get together going on an hour away. Oh well, I'm babysitting tonight. Looking forward to meeting some 928ers tomorrow.
Ok, so on an engine with a lot of low-RPM torque, in 1st gear from a standstill, you will be able to apply more torque to the wheels since the speed differential between the tires and road will be smaller for that torque value making the tires grip better, which means acceleration will be greater. So, low-end torque wins in this scenario. You know you want to say it.
Dan
'91 928GT S/C 475hp/460lb.ft
Dan
'91 928GT S/C
475hp/460lb.ft.
09-12-2010, 04:11 AM
#54
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So, for maximum acceleration do I shift my 928 GTS at the hp peak rpm or at the torque peak rpm. The torque peak starts dropping at 4500 rpm the hp peak is at 5800 rpm.
09-12-2010, 04:57 AM
#55
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No Mark, engine torque is all there is. after that you can change the gearing to create as much rear wheel torque as you like, My tractor scenario.
Horsepower is a result of torque , not the other way around.
I agree entirely with you, that the "Horsepower seconds" as you call them, I would call it the area under the curve on a dyno sheet, is important to the performance of a vehicle.
But you have the wrong end of the stick with regards Torque and Horsepower.
RKD in OKC, change at the point where you pick up in the next gear at your torque peak, how many RPM between gears, change that figure higher than peak torque.
Cheers Roy
Horsepower is a result of torque , not the other way around.
I agree entirely with you, that the "Horsepower seconds" as you call them, I would call it the area under the curve on a dyno sheet, is important to the performance of a vehicle.
But you have the wrong end of the stick with regards Torque and Horsepower.
RKD in OKC, change at the point where you pick up in the next gear at your torque peak, how many RPM between gears, change that figure higher than peak torque.
Cheers Roy
09-12-2010, 11:05 AM
#56
Rennlist Member
No, pistons are moving. The crank is rotating. Forces are generated; masses moved; and work is done. The wheels (when engaged) are just the endpoint of a mechanical system that starts with the pistons.
If the car is on jack stands with the wheels spinning, is the system generating torque and power? Of course. Same thing if the engine is rotating without the clutch or transmission engaged.
If the car is on jack stands with the wheels spinning, is the system generating torque and power? Of course. Same thing if the engine is rotating without the clutch or transmission engaged.
09-12-2010, 03:29 PM
#58
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While the GTS torque may be falling off as long as HORSEPOWER IS INCREASING spin it up and take advantage of the increased ability to do work over time. It also means you stay in the lower gear longer which takes advantage of the torque multiplication. Now the old very brown 1980 torque and horspower drop off after 5,000 RPM so spinning it just makes more noise Not that that is a bad thing !
Not that that is a bad thing !
09-12-2010, 05:54 PM
#59
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Roy, you are absolutely wrong and Ill tell you why . Let me know if you disagree after what I say here.
You can have a lot of engine torque, and not much power. right?
If you dont know the engine speed, you dont have anything at all.
would you want a 500hp, 250ftlb peak torque engine, or a 500hp, 500ft-lb engine to race with. why? show your work.
HP is NOT the result of torque. they are both inextricably tied together, BUT, HP incorporates torque, and torque is a factor alone with missing pieces. Torque, doest equal the total forces for acceleration at any given speed. HP does. you just need more informtion with torque alone. are you talking rear wheel torque? engine torque? etc??
Area under the curve ALSO doesnt do it. as it doesnt take time into effect. as you know, with torque, going down proportional with speed, acceleration rates go down with speed for the most part, so you spend more time at the top of each gear, than at the start. so, that skews the value. area doesnt do it.
lastly, you are falling into the same trap as many of my competitors, who usually make this mistake and end up behind me if we are close. shifting, to end up at max torque is very silly. Here is why. its all about average HP , or HP seconds. sometimes, most often, you will never hit a race engines max torque ability, because it doesnt have its max Power or increase the average power (hp seconds ) by doing so. you dont want to shift at max HP, you want to shift at an RPM that maximizes HP seconds. USUALLY, unless you have Jim Baley's engine, this happens at a point over max HP and near its redline. (or higher if it is mechanically possible)
You can have a lot of engine torque, and not much power. right?
If you dont know the engine speed, you dont have anything at all.
would you want a 500hp, 250ftlb peak torque engine, or a 500hp, 500ft-lb engine to race with. why? show your work.
HP is NOT the result of torque. they are both inextricably tied together, BUT, HP incorporates torque, and torque is a factor alone with missing pieces. Torque, doest equal the total forces for acceleration at any given speed. HP does. you just need more informtion with torque alone. are you talking rear wheel torque? engine torque? etc??
Area under the curve ALSO doesnt do it. as it doesnt take time into effect. as you know, with torque, going down proportional with speed, acceleration rates go down with speed for the most part, so you spend more time at the top of each gear, than at the start. so, that skews the value. area doesnt do it.
lastly, you are falling into the same trap as many of my competitors, who usually make this mistake and end up behind me if we are close. shifting, to end up at max torque is very silly. Here is why. its all about average HP , or HP seconds. sometimes, most often, you will never hit a race engines max torque ability, because it doesnt have its max Power or increase the average power (hp seconds ) by doing so. you dont want to shift at max HP, you want to shift at an RPM that maximizes HP seconds. USUALLY, unless you have Jim Baley's engine, this happens at a point over max HP and near its redline. (or higher if it is mechanically possible)
No Mark, engine torque is all there is. after that you can change the gearing to create as much rear wheel torque as you like, My tractor scenario.
Horsepower is a result of torque , not the other way around.
I agree entirely with you, that the "Horsepower seconds" as you call them, I would call it the area under the curve on a dyno sheet, is important to the performance of a vehicle.
But you have the wrong end of the stick with regards Torque and Horsepower.
RKD in OKC, change at the point where you pick up in the next gear at your torque peak, how many RPM between gears, change that figure higher than peak torque.
Cheers Roy
Horsepower is a result of torque , not the other way around.
I agree entirely with you, that the "Horsepower seconds" as you call them, I would call it the area under the curve on a dyno sheet, is important to the performance of a vehicle.
But you have the wrong end of the stick with regards Torque and Horsepower.
RKD in OKC, change at the point where you pick up in the next gear at your torque peak, how many RPM between gears, change that figure higher than peak torque.
Cheers Roy
09-12-2010, 05:56 PM
#60
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YEP! Doing work over time is the definition of HP for those of you not following that closely.
my new motor has such a flat HP curve that it doesnt pay to shft much over peak HP. however the holbert motor did pay to shift at redline. (6600rpm)
my new motor has such a flat HP curve that it doesnt pay to shft much over peak HP. however the holbert motor did pay to shift at redline. (6600rpm)
While the GTS torque may be falling off as long as HORSEPOWER IS INCREASING spin it up and take advantage of the increased ability to do work over time. It also means you stay in the lower gear longer which takes advantage of the torque multiplication. Now the old very brown 1980 torque and horspower drop off after 5,000 RPM so spinning it just makes more noise Not that that is a bad thing !
Not that that is a bad thing !