R56 Will there be an '08 TD?
#54
05-23-2006, 10:38 PM
The formula is actually
P = TN/5250
where:
P = Power, hp
N = Rotational shaft speed, rpm
T = Torque, lb-ft
This is a rotational horsepower breakdown of the 'classic' definition of one horsepower equalling 33,000 pounds lifted one foot in one minute.
Since 'horsepower' is not a directly measured unit per se (it comes from a measurement of torque over a period of time) this formula and it's results are often quite predictable. Slow revving diesel engines will always produce a higher torque number than horsepower numbers. Screaming, tiny engines will tend to have the opposite effect. The kicker is, no matter the type of engine, if it is able to spin at 5250 rpm and make power, the horsepower will always equal the torque.
P = TN/5250
where:
P = Power, hp
N = Rotational shaft speed, rpm
T = Torque, lb-ft
This is a rotational horsepower breakdown of the 'classic' definition of one horsepower equalling 33,000 pounds lifted one foot in one minute.
Since 'horsepower' is not a directly measured unit per se (it comes from a measurement of torque over a period of time) this formula and it's results are often quite predictable. Slow revving diesel engines will always produce a higher torque number than horsepower numbers. Screaming, tiny engines will tend to have the opposite effect. The kicker is, no matter the type of engine, if it is able to spin at 5250 rpm and make power, the horsepower will always equal the torque.
#55
05-23-2006, 11:28 PM
Greatbear is on the money...
Originally Posted by Andrewsky
Who's units? Which ones?
Power is not kg meters per second squared (in metric).
Power is kg meters squared per second squared (in metric)
This is called dimensional analysis.
Power isn't equal to acceleration. One is an apple, the other is an orange.
Matt
#57
05-24-2006, 08:04 AM
Don't knock it!
Originally Posted by kapps
Ugh, dimensional analysis...brings back memories (of last semester 
).
). FWIW, there's a unit set called natural units, where c=1 along with a lot of other constants that I don't remember any more (theoretical physicists use it a lot), and then they just add all the constants at the end to make the units work! Makes the algebra easier.... I was never good at it.
Matt
#58
05-24-2006, 08:08 AM
Originally Posted by Dr Obnxs
Acceleration is in units of meters per second squared (in metric).
Power is not kg meters per second squared (in metric).
Power is kg meters squared per second squared (in metric)
This is called dimensional analysis.
Power isn't equal to acceleration. One is an apple, the other is an orange.
Matt
Power is not kg meters per second squared (in metric).
Power is kg meters squared per second squared (in metric)
This is called dimensional analysis.
Power isn't equal to acceleration. One is an apple, the other is an orange.
Matt
When I said "Power is acceleration," what I really meant was "power determines the rate of acceleration (because gearing is indirectly involved)."
Sorry for the confusion.
#59
05-24-2006, 08:13 AM
I'm just a physicist..
Originally Posted by Andrewsky
Oh, I know.
When I said "Power is acceleration," what I really meant was "power determines the rate of acceleration (because gearing is indirectly involved)."
Sorry for the confusion.
When I said "Power is acceleration," what I really meant was "power determines the rate of acceleration (because gearing is indirectly involved)."
Sorry for the confusion.
Matt
#60
05-24-2006, 08:27 AM
Originally Posted by Dr Obnxs
looking to keep a little clarity on subjects that are abused by almost all. Fact is, power and acceleration are realted, but torque at the wheels is what detetmins acceleration. You can have a lot of power at higher speeds, with little acceleration. That's just the way it is.
Matt
Matt
You're also right that power is one variable in the formula to see how a car will perform.
I think the best thing to do is find the total area underneath the torque curve on a graph.