Quote:
Originally Posted by Nevermore
I don't have a problem with the car's power, it's the most powerful car I've driven/owned so it's plenty for me. Though I am kind of curious about the torque number, purely from an observation standpoint. I've noticed older cars, with smaller engines/less HP with more torque than our cars. I've seen some where the torque and HP numbers were the same, and some where the torque number was higher. I'm a pretty big noob when it comes to engines, but I've always wonder why our 200HP engine had such "low" torque by comparison.
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Power is Torque multiplied by RPM. If you think of it like lifting weights at the gym, torque is like how much you lift in one go, power is how much you lift in one minute. So there's an infinite combination of Torque and RPM to create a given horsepower. You could lift 500 lbs once per minute, you could lift 250 lbs twice per minute, you could lift 50 lbs ten times per minute, you could lift 5 lbs fifty times per minute, it's all 500 lbs per minute.
For the units we use in the US for power and torque, the formula is Power (in horsepower) = Torque (in ft-lbs) * RPM / 5252.
So if we had a motor that made exactly 100 lbs of torque at all RPMs, it would make 50 HP at 2626 rpm, 100 HP at 5252 RPM, and 150 HP at 7878 RPM.
However, engines don't have constant torque. It varies by RPM. And, since power is a function of torque and RPM, it also varies by RPM.
Since the numbers quoted are always the peak numbers, as a rough rule of thumb, if peak HP happens below 5252 RPM, the peak torque (in ft-lbs) will be higher than the peak horsepower, and if peak HP happens above 5252 RPM, the peak torque is lower than the peak HP. If the peak HP is pretty close to 5252 RPM, the numbers will be pretty close.
For a lot of older engines, they had a harder time doing high RPMs, and the torque starts to drop off as RPMs increase. If the torque is dropping off at a faster rate than RPM is increasing, you lose power going higher. (i.e. if a 5% increase in RPM causes a 10% decrease in torque, you'll end up making less power).
The FA20 can work better at high RPMs, so it can keep making torque at high RPMs, so it's got a peak horsepower close to 7,000 RPM, since in that range, the torque is staying constant or diminishing slightly, but the RPMs are increasing.
I don't think it's fair to think of the FA20 as a 200HP engine with low torque. I'd rather think of it as a 150 ft-lbs engine that operates well at high RPMs and thus creates more HP.