Power per litre, ranked:

"Cé hé sin" (michael-m-mouse) 01/26/2015 at 09:07 • Filed to: Power per litre

5

22

1. Drag racing engine: exact figure unknown, thought to be 1,000 + bhp per litre. It'll do this for a few seconds before melting

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99. Wartsila RA96C. Approx 4.25 bhp per litre. Yes, four and a quarter. It'll do this for decades.

thebigbossyboss > Cé hé sin 01/26/2015 at 09:08

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4. 25 per litre? Oh wow.

Cé hé sin > thebigbossyboss 01/26/2015 at 09:16

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Will run almost continuously for twenty or more years, thermal efficiency of better than 50%.

More wow.

OPPOsaurus WRX > Cé hé sin 01/26/2015 at 09:18

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@ what rpm?

DoYouEvenShift > Cé hé sin 01/26/2015 at 09:21

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Pushrods!!

Cé hé sin > OPPOsaurus WRX 01/26/2015 at 09:21

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For the ship, 102. You could stand beside it and and count. For the car, rather more - 8,000 odd.

roflcopter > Cé hé sin 01/26/2015 at 09:23

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I'm willing to bet those torque figures are pretty much the inverse of that relationship though.

OPPOsaurus WRX > Cé hé sin 01/26/2015 at 09:24

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that would actually be kinda funny to do that.

Cé hé sin > DoYouEvenShift 01/26/2015 at 09:24

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But only on the little one. The big one has moved on and doesn't have traditional valve gear.

Cé hé sin > roflcopter 01/26/2015 at 09:30

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Maybe not. The marine engine produces 5.6 million lbs/ft (!!) from 25,480 litres so 220 per litre. The drag engine will only need 1,760 lbs/ft from its 8 litres to better that.

twochevrons > OPPOsaurus WRX 01/26/2015 at 09:30

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Skip to 16:45 in this video – Robbie Coltrane does almost exactly that!

thebigbossyboss > Cé hé sin 01/26/2015 at 09:32

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102 rpm?? I uhhh didn't even know you could engine that low.

DoYouEvenShift > Cé hé sin 01/26/2015 at 09:33

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I used to be really into RC airplanes when I was very young. Everytime the hp/liter conversation comes up it reminds me of those tiny engines.

Like this guy.

Im not sure what unit if measurement they use. CI or CC.

http://www3.towerhobbies.com/cgi-bin/wti000…

Laird Andrew Neby Bradleigh > Cé hé sin 01/26/2015 at 09:34

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And a Top Fuel Dragster does something like 500-600 revolutions from light to light.. I think they do less than 1000 revolutions including the Burnout pr race.

Cé hé sin > thebigbossyboss 01/26/2015 at 09:35

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You can divide that by five. It'll produce power from 22 rpm.

roflcopter > Cé hé sin 01/26/2015 at 09:39

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Well... HP is a function of torque and engine speed, so by the powers vested in me by the great state of math...

The drag motor would need to make 2680 HP at 8000 RPM, which I'm positive it handily beats, to make 1760 ft*lb. Looks like we have a winner.

thebigbossyboss > Cé hé sin 01/26/2015 at 09:40

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WHOAH! Thats less than one revolution per second. My car idles at 700 rpm and that's very slow for a car.

Cé hé sin > roflcopter 01/26/2015 at 09:44

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It does 8,000 bhp at something up to 8,000 rpm so we sure do!

Cé hé sin > thebigbossyboss 01/26/2015 at 09:48

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Bear in mind though that because the scale is so large the pistons, while only doing a couple of cycles per second, are moving rapidly because they have to go a long way down and a long way back up in that time. The stresses are greater than the low revs might lead you to expect.

Cé hé sin > Laird Andrew Neby Bradleigh 01/26/2015 at 11:41

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Now we need to work out how many revolutions the ship engine will do in its lifetime. Say a steady 80 rpm for 20 years....

Laird Andrew Neby Bradleigh > Cé hé sin 01/26/2015 at 11:48

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uhh.. could we skip leap years then? That would be 60 x 24 x 365 x 20 x 80 = 840960000

Cé hé sin > Laird Andrew Neby Bradleigh 01/26/2015 at 11:55

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I think this is much more impressive than some grenade engine that runs for ten seconds at a time.

Laird Andrew Neby Bradleigh > Cé hé sin 01/26/2015 at 11:56

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Oh indeed. Indeed it is. :)