I've always tried to make a connection backward by using units- but I'm not sure I have it right.

torque- ft-lbf - ok, makes sense, put a weight on a lever arm.

1 Horsepower - 550 ft-lbf's per second.

hold up, per second? Force per second ? I cannot visualize this.
so 2hp is 1100 ft-lbf per second ? usually when we put a unit over a time its "meters per second" or "

...or does "per second" mean "over a duration of 1 second" - because I can visualize this. 1 horse, could probably exert 550 ft-lbf's for a second. a lawnmower could probably exert that kinda force for a few seconds (until it slowed and stalled...).

-John

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Not force per second, work per second.

Apply a force of 550 lbs against a wall. No work gets done. Hang a 550 lb weight on the end of a 1 foot bar that won't move. You have 550 ft-lbs of torque, but again no work gets done.

Take a 550 lb weight and lift it one foot. Now you've just done 550 ft-lbs of work. If it took you exactly a second to to it, then you made 1 horsepower.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.

torque has always puzzled me a little.It used to be with gassers torque numbers were higher than horsepower.Diesels always had extreme torque over hp. Now a days I was looking at some newer rides,and hp is over 200 hp over torque.I was taught torque won races,and horse power was for bragging. Are these manufacturers just fooling people.

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In many ways and have been for a long time. Shorter stroke engines became common. Heavy flywheels history.

torque is when you can tow stuff with your jeep 4.0 while creeping at idle.

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1995 E300D - The original humming machine (consumed by Flood 2017)
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What is torque?



Baby don't hurt me, baby don't hurt me, no more...

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[GONE] - 1995 Mercedes E300 Diesel - 130k miles - Smoke Silver (702) over Mushroom leather (265) - Bladder blasting, coast-to-coast work machine.

Remember that Torque and HP are mathematically related - every engine generates the same ft-blf's and HP at 5250(?) rpm. Its in the equation.

Also remember that engines can be tuned to make more power at a certain rpm. Put a low-rpm cam, tune the intake and exhaust and you can make more power at high or low rpms....but usually not both.

...And this makes sense when you figure that a dynamometer probably just measures twisting force (torque) - so it probably measures torque and does the math to calculate HP (it must know what engine RPM is ?)

Where it gets sticky is the high and low revving engines.
My old motorcycle had 48ftlb and 94hp - it had a redline of 13k. I'm sure that that HP peak was close to 12k and the torque peak was lower. The higher you rev a gas engine (given that the cam/valves/intake/exhaust components are all ok for it) the more twisting force you get.

Big truck diesels that have huge torque numbers but only rev to 2500 rpm. If they revved to 5250 (...if diesel engines were capable of revving and making power that high...), I bet that the HP number would be the same - but in a Diesel, physics intervenes (IIRC diesel burns slower, flame front etc isn't as efficient above 4k or 5k rpm?... so even the Diesel race cars only rev to 5000-something rpm).

Hopefully I'm not far off.

-John

__________________
2009 Kia Sedona
2009 Honda Odyssey EX-L
12006 Jetta Pumpe Duse
(insert Mercedes here)

Husband, Father, sometimes friend =)