torque discussion..
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From: ec
torque discussion..
was just overlooking the rsx board and came upon a thread.. thought it'd be interesting to see what ya guys got to say.. UL CHIME IN!
http://forums.clubrsx.com/showthread.php?s...25&pagenumber=2
Theory 1 , IF CAR A CAN BEAT CAR B ON A STRAIGHT , IT WILL ALSO BEAT IT ON AN INCLINE DUE TO PHYSICS
THEORY 2, IF CAR B HAS MORE TORQUE, IT WILL BEAT CAR A..
shrug.
SANG
http://forums.clubrsx.com/showthread.php?s...25&pagenumber=2
Theory 1 , IF CAR A CAN BEAT CAR B ON A STRAIGHT , IT WILL ALSO BEAT IT ON AN INCLINE DUE TO PHYSICS
THEORY 2, IF CAR B HAS MORE TORQUE, IT WILL BEAT CAR A..
shrug.
SANG
Joined: Jul 2002
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From: Hong Kong
Don't want to start flame war here as in RSX... but here is my theory 
It's just a transformed question of low end torque vs high end power question again... the hard part is because of the facts that engine torque is not constant over all revolution speed and gearing is usually ignored...
Note that if the engine torque is constant over any rpm and gear ratios of two cars are the same, the question is really reduced to a simple force-diagram, high school level Physics. Theory 1 is definitely true under that case.
But if taking into consideration of engine torque characteristics, and gearing:
Theory 1 is more theortical, which will be true if both cars were already compared in optimal form in straight (say driven by professional driver, both with optimal launch and optimal gear, , and the car gear ratio is close enough.)
Theory 2 is more practical, which will be true if both launch at idle engine speed or the gear is not close enough to keep the engine at high power region for the lower torque one. In that case, more torque at lower rev can make initial acceleration faster, which will then make more power earlier and shift to next gear earlier.
It's just an amplified effect by uphill, which is the same as adding more weight to the car (like someone pointed out in the RSX forum.)
Actually, in both theory and practice, both can be right or wrong depending
a) on how long is the distance under comparison and
b) engine driving method of two cars (FF, FR, MR, RR or 4WD). RR and MR will be better at uphill.
It's just a transformed question of low end torque vs high end power question again... the hard part is because of the facts that engine torque is not constant over all revolution speed and gearing is usually ignored...
Note that if the engine torque is constant over any rpm and gear ratios of two cars are the same, the question is really reduced to a simple force-diagram, high school level Physics. Theory 1 is definitely true under that case.
But if taking into consideration of engine torque characteristics, and gearing:
Theory 1 is more theortical, which will be true if both cars were already compared in optimal form in straight (say driven by professional driver, both with optimal launch and optimal gear, , and the car gear ratio is close enough.)
Theory 2 is more practical, which will be true if both launch at idle engine speed or the gear is not close enough to keep the engine at high power region for the lower torque one. In that case, more torque at lower rev can make initial acceleration faster, which will then make more power earlier and shift to next gear earlier.
It's just an amplified effect by uphill, which is the same as adding more weight to the car (like someone pointed out in the RSX forum.)
Actually, in both theory and practice, both can be right or wrong depending
a) on how long is the distance under comparison and
b) engine driving method of two cars (FF, FR, MR, RR or 4WD). RR and MR will be better at uphill.
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From: Redondo Beach
Theory 1 is always true, assuming the only thing that changes is the incline.
As for Theory 2: as I learned, ahem, the hard way,
the basic answer is that in a given gear, a car's acceleration is directly proportional to its torque curve. So, for two otherwise identical cars (esp. weight and gear ratios), the one that has the higher torque (average vs. rpm) will win.
OTOH, if those two cars were equipped with continuously variable transmissions that could keep their respective engines operating at the optimal rpm, the one with the higher peak power would win, regardless of whether it makes more or less peak torque. This is because, in the higher-power car, the CVT would be able to adjust the gearing to get a better torque multiplication factor to the wheels. (In other words, if the gearing isn't fixed, it's optimal to run the engine at the power peak, not the torque peak.)
As for Theory 2: as I learned, ahem, the hard way,
the basic answer is that in a given gear, a car's acceleration is directly proportional to its torque curve. So, for two otherwise identical cars (esp. weight and gear ratios), the one that has the higher torque (average vs. rpm) will win.OTOH, if those two cars were equipped with continuously variable transmissions that could keep their respective engines operating at the optimal rpm, the one with the higher peak power would win, regardless of whether it makes more or less peak torque. This is because, in the higher-power car, the CVT would be able to adjust the gearing to get a better torque multiplication factor to the wheels. (In other words, if the gearing isn't fixed, it's optimal to run the engine at the power peak, not the torque peak.)
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From: Hong Kong
Originally posted by twohoos
Theory 1 is always true, assuming the only thing that changes is the incline.
As for Theory 2: as I learned, ahem, the hard way, the basic answer is that in a given gear, a car's acceleration is directly proportional to its torque curve. So, for two otherwise identical cars (esp. weight and gear ratios), the one that has the higher torque (average vs. rpm) will win.
OTOH, if those two cars were equipped with continuously variable transmissions that could keep their respective engines operating at the optimal rpm, the one with the higher peak power would win, regardless of whether it makes more or less peak torque. This is because, in the higher-power car, the CVT would be able to adjust the gearing to get a better torque multiplication factor to the wheels. (In other words, if the gearing isn't fixed, it's optimal to run the engine at the power peak, not the torque peak.)
Theory 1 is always true, assuming the only thing that changes is the incline.
As for Theory 2: as I learned, ahem, the hard way,
the basic answer is that in a given gear, a car's acceleration is directly proportional to its torque curve. So, for two otherwise identical cars (esp. weight and gear ratios), the one that has the higher torque (average vs. rpm) will win.OTOH, if those two cars were equipped with continuously variable transmissions that could keep their respective engines operating at the optimal rpm, the one with the higher peak power would win, regardless of whether it makes more or less peak torque. This is because, in the higher-power car, the CVT would be able to adjust the gearing to get a better torque multiplication factor to the wheels. (In other words, if the gearing isn't fixed, it's optimal to run the engine at the power peak, not the torque peak.)
Say, if Car A got extremely low low-end torque, but extremely high high-power, and Car B got a high low-end torque but relatively lower high-end power.
On a straight, car A can get through the low torque region faster and catch up and catch up then beat car B, say in 200m.
However, on incline, car A takes longer and more distance to go through the low torque region, while car B still got pretty good initial acceleration. Car A may catch up on 400m instead of 200m...
So for the incline case, if people take 200m comparsion, that Theory 2 is true... if they take 400m comparison, then Theory 1 is true...
What I want to say in earlier post actually is similar to your CVT point... that if both is doing optimal launch (at highest power) and optimal shifting similar to CVT, Theory 1 is always true as there's no initial acceleration problem, just comparing power.
Feel free to correct me if I'm wrong. Everyone should learn more by discussion.
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From: ec
well my interpretation of the thread when i was reading was.
theory 1: if car A beats car B on a straightaway, it will ALWAYS beat car B due to simple physics.
theory 2 : if car B has more torque, the car B will win since it catches up with its power faster.
both discussions IMO were good, just trying to figure out what more people think. of course relative to the weight , depending on FF , MR , RR it will always vary but in this simple scenario of RSX S vs cougar V6 it wasnt the case.
Sang
theory 1: if car A beats car B on a straightaway, it will ALWAYS beat car B due to simple physics.
theory 2 : if car B has more torque, the car B will win since it catches up with its power faster.
both discussions IMO were good, just trying to figure out what more people think. of course relative to the weight , depending on FF , MR , RR it will always vary but in this simple scenario of RSX S vs cougar V6 it wasnt the case.
Sang
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From: You wish
Compute the thrust curve over the given speed range of acceleration. Find the average thrust (taking points every 500 rpm should do) and the car with the higher average thrust to weight will win.
Oh, this assumes you've got reasonably similar aero drag.... :-)
UL
Oh, this assumes you've got reasonably similar aero drag.... :-)
UL
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From: Redondo Beach
Oops, you're right, peterwusc. For competitions to achieve a final *distance*, Theory 1 is false.
Hypothesis: Theory 1 is true iff the incline is constant, and the competition is to achieve a given final *speed*.
Hypothesis: Theory 1 is true iff the incline is constant, and the competition is to achieve a given final *speed*.
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From: Transporter
Torque delivery at the tire patch is a dynamic thing.
What if a car produces extremely high torque over 500 RPM range? As long as the car has a discrete number of gears it's accleration will suck. (Of course a CVT might make it fly)
Regardless of peak torque, the important thing is being able to deliver constant horsepower. For manual transmission cars, the engine needs to be very flexible, meaning the torque curve better stay high for the entire gear.
The two theories proposed have no meaning.
What if a car produces extremely high torque over 500 RPM range? As long as the car has a discrete number of gears it's accleration will suck. (Of course a CVT might make it fly)
Regardless of peak torque, the important thing is being able to deliver constant horsepower. For manual transmission cars, the engine needs to be very flexible, meaning the torque curve better stay high for the entire gear.
The two theories proposed have no meaning.