View Poll Results: HP -> Acceleration... not Torque!
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HP -> Acceleration... not Torque!
Registered User
Joined: Jan 2002
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From: Redford, MI
Originally posted by Zoran
"At any given time" you choose what gear you want to be in for maximum acceleration (usually downshifting).
The gear that puts you the closest to your HP peak is the gear to choose, as that one will give you maximum acceleration at that given time.
If there's a gear that would put you exactly at your HP peak, that's the best you can do.
So really, at any given time, maximum acceleration occurs at the HP peak.
Again, reread my example above: If you are rolling at 60mph and 3rd gear puts you at your torque peak while a 2nd gear puts you at your HP peak, which gear do you choose for maximum acceleration at that time?
"At any given time" you choose what gear you want to be in for maximum acceleration (usually downshifting).
The gear that puts you the closest to your HP peak is the gear to choose, as that one will give you maximum acceleration at that given time.
If there's a gear that would put you exactly at your HP peak, that's the best you can do.
So really, at any given time, maximum acceleration occurs at the HP peak.
Again, reread my example above: If you are rolling at 60mph and 3rd gear puts you at your torque peak while a 2nd gear puts you at your HP peak, which gear do you choose for maximum acceleration at that time?
The formula is very simple.
F = m * a
Mass is fixed. Acceleration is maximized when force is maximized. Force is maximized when torque is maximized. End of calculation. If you're going to keep changing gear ratios and/or speed then your force keeps changing and you have to recalculate for each change. But "at any given time" you get max acceleration at max torque.
Don't confuse acceleration and speed. Torque is what "accelerates" a car. Horsepower is what makes a car "fast". Hence the title of this thread is both misleading and incorrect.
Registered User
Joined: Jan 2002
Posts: 250
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From: Redford, MI
Originally posted by Zoran
You also keep avoiding my question:
You and I are driving the exact same car, rolling at 60mph. You are in your 3rd gear, at your torque peak. I am in my 2nd gear, at my HP peak. Who is going to pull ahead if we both mash the gas at the same time?
You also keep avoiding my question:
You and I are driving the exact same car, rolling at 60mph. You are in your 3rd gear, at your torque peak. I am in my 2nd gear, at my HP peak. Who is going to pull ahead if we both mash the gas at the same time?
Registered User
Joined: Jun 2001
Posts: 1,610
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From: Atlanta, GA
Not that ya'll aren't doing a fine job of arguing with each other, but I just thought I would toss a curiosity into the pot.
If it is indead torque that is responsible for (or even the best indicator of) accelleration, then why are those CVT transmissions programed to keep an engine at it's HP peak instead of torque peak?
If it is indead torque that is responsible for (or even the best indicator of) accelleration, then why are those CVT transmissions programed to keep an engine at it's HP peak instead of torque peak?
Registered User
Joined: Jan 2002
Posts: 250
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From: Redford, MI
Originally posted by Zoran
"Yeah, if I was at 40mph in this gear I would be accelerating a lot faster". So what? You're NOT at 40mph and there's absolutely nothing you can do to change that (short of braking down to 40mph and losing the race big time).
"Yeah, if I was at 40mph in this gear I would be accelerating a lot faster". So what? You're NOT at 40mph and there's absolutely nothing you can do to change that (short of braking down to 40mph and losing the race big time).
Exactly! That's the only point I'm trying to make, nothing more. At your current speed you're accelerating slower because there's less torque. Nothing more.It is MUCH harder to accelerate at higher speeds than it is at lower speeds (and this has nothing to do with air drag).
It is MUCH harder to get 0.5g's of acceleration out of a car at 80mph than it is to get the same 0.5g's of acceleration at 10mph.
Therefore it is absolutely meaningless to compare car's acceleration at 80mph and at 10mph.