by "traderQAMobileTestAutomationMobileBoostOn" (el-peasant)
Published 01/16/2017 at 22:44
by "traderQAMobileTestAutomationMobileBoostOn" (el-peasant)
Published 01/16/2017 at 22:44
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What’s better, horsepower or torque?
Both, which combine to make Average power .
We shall establish 3 things after the break:
-Torque measures instantaneous acceleration
-Torque applied over several thousand RPMs measures total acceleration
-Gearing scales torque at the wheels
Now picture this:
Car A makes 600 lb-ft from 1000-4000 RPM
Car B makes 600 lb-ft from 1000-7000 RPM
Identical weight, gearing, wheels.
3,2,1, Takeoff!
A and B are neck and neck UNTIL 3000 RPM where A shifts into 2nd gear, dropping its torque at the wheels. Meanwhile, still in 1st gear, B rockets ahead, and eventually wins the race.
What’s the difference? Car B applied more torque at the wheels for a longer period of time, because 1st gear lasted longer). Car B had more average power because its rev range lasted twice as long.
"Flynorcal: pilot, offshore sailor, car racer and panty thief" (flynorcal)
01/16/2017 at 22:48, STARS: 1
So to get a theoretical top speed you solve for when you’ll run out of torque to accelerate vs the drag on the car from gravity and wind. Sounds about right.
"Bman76 (hates WS6 hoods, is on his phone and has 4 burners now)" (bman76-4)
01/16/2017 at 22:49, STARS: 6
That’s just more horsepower, that’s all you’ve described.
"Stephenson Valve Gear" (stephensonvalvegear)
01/16/2017 at 22:56, STARS: 3
“What’s better, horsepower or torque? Both, which combine to make Average power.”
Well... I would say Torque and RPM are combined to calculate Horsepower.
Torque x RPM / 5252 = HP
Car A makes 600 x 4000 / 5252 = 457 HP
Car B makes 600 x 7000 / 5252 = 800 HP
I mean, I do see your point, but Car B has an extremely wide, flat torque curve with almost twice the horsepower. It would indeed be faster. But, it would be difficult to make an engine do that in the real world.
Make of that what you will...
"MonkeePuzzle" (monkeypuzzle)
01/16/2017 at 22:56, STARS: 5
I bought a civic so I dont have to worry about which is horsepower and which is torque, I have neither.
"DC3 LS, will be perpetually replacing cars until the end of time" (dc3ls-)
01/16/2017 at 23:00, STARS: 0
Beg to differ. I could be wrong, but I don’t even think “instantaneous acceleration” is even a thing. Since it takes time to change speeds. It could be relatively instant though.
Here’s my take on the two. Imagine someone’s going to hit you with a ball. Torque would be the weight of the ball and HP would be the speed. Getting hit by a baseball thrown at you by Roger Clemens is going to hurt more than a bowling ball rolled at you by a child.
So in car terms. Torque is how much weight you can put on the wheels and they’ll still turn. (Why you want diesel for towing because it can move massive weight without reving high.
And HP is essentially speed. Plus since HP=TQ x RPM you could make a high torque engine that revs to 7k and be very fast. Or go the Honda route and make a 2.0L that reves to 12k or whatever and is fast.
So to sum it up. You need enough torque to move the weight of the vehicle plus cargo (and possibly burnouts) and you need hp to make that move fast.
Of course all of this theorizing is holding gearing constant. You could once again go the Honda route and have a Vehicle make 98 ft/lbs and have a 4.11 final drive. Or go the old skool American route and have a V8 and 2.7 final drive.
TL;DR Torque is how much force acts on the wheels in one revolution. HP determines how fast the wheels can spin.
Edit: Even in your scenario. If gearing wasn’t a factor the higher reving engine would still be faster. Because as the RPMs go up it’ll produce more HP assuming torque doesn’t fall of a cliff.
"Daily Drives a Dragon - One Last Lap" (ddadragon)
01/16/2017 at 23:03, STARS: 0
To answer your first question, More of both is better.
"The AE86 of Mt. Akina (Hachi)" (theae86)
01/16/2017 at 23:09, STARS: 1
Being able to tell the difference between hp and torque is one of those things where either you get it or you don’t.
"HammerheadFistpunch" (hammerheadfistpunch)
01/16/2017 at 23:15, STARS: 3
Its easiest if you ignor torque as a motive force and as only a component part of power which is all that matters. Torque produces no motion, its only a force therefor its meaningless to speak of it in terms of acceleration. The way it clicked for me was to think it terms of electricity. A light bulb with lots of volts but no current produces a feeble light, a bulb with lots of current but no volts is the same story. Volts (amount) x amps (rate) = power (watts). Think of torque as volts and amps as rpm which (with a conversion factor of 5252) is power and power is what lights the bulb, so to speak. More power over a greater range means greater acceleration.
"tromoly" (tromoly)
01/16/2017 at 23:19, STARS: 1
Not necessarily, acceleration is a function of torque alone. If the torque curve is higher on an engine that doesn’t rev as high it’ll out-pull a lower torque high revving engine because its torque hits sooner (to an extent, of course).
Find a copy of Fundamentals of Vehicle Dynamics on the Internet (a pdf is rather easy to find) and browse the section on acceleration, it’s interesting stuff.
"DipodomysDeserti" (dipodomysdeserti)
01/16/2017 at 23:21, STARS: 1
Instant acceleration? Total acceleration? Wut?
Torque is basically the amount of work done to rotate something (force exerted over a certain rotational distance). Your engine rotates your driveshaft. Power is the rate at which work is done, or in the case of a vehicle, how much work is done to rotate your driveshaft (or wheels) in a given amount of time (RPM). The greater force you can exert to rotate your driveshaft (torque) in the quickest time (RPM, power), the faster your car will be. Gearing changes the amount of torque and power that is actually applied to your wheels. There is no either or. You want both, hence why people use either big or turbocharged engines when building fast cars. You choose gearing depending on what type of speed you’re looking for.
"DC3 LS, will be perpetually replacing cars until the end of time" (dc3ls-)
01/16/2017 at 23:30, STARS: 0
To late to edit. But I wrote the HP formula wrong. HP=TQxRPM/5252.
"NYankee1927" (nyankee1927)
01/16/2017 at 23:35, STARS: 0
You are by far the most on the right track. Especially compared to people in your comments. I have a few page write up about this describing all the math (I sent it in to the tip line in hopes of getting an article about it so I’ll save it) but the TLDR version is what really matters is the integral of the power curve over the relavent rev range set by gearing and driving situation. That is all you really need to know. Do the math yourself integrating up and differentiating to prove it all out. It gets way easier if you use metric units.
"HammerheadFistpunch" (hammerheadfistpunch)
01/16/2017 at 23:41, STARS: 2
http://oppositelock.kinja.com/power-under-the-curve-1714778421
"PetarVN, GLI Guy, now with stupid power" (petarvn)
01/16/2017 at 23:55, STARS: 0
simply said, more of both is better always
"DrJohannVegas" (drjohannvegas)
01/17/2017 at 01:06, STARS: 0
I am either too drunk or not drunk enough to even begin to respond to this.
"Nick Has an Exocet" (nickallain)
01/17/2017 at 01:50, STARS: 1
Came here to mention the same thing!