How to test engine specs?

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How to test engine specs?

Postby Epic_SkyPilot » Tue Jul 14, 2015 8:10 pm

I just recently created a 3cyl spawn engine which I plan to use for a geo metro car build. I'm keeping it as realistic as possible. The Geo's motor weighs 100lbs IRL so I made mine 45kg. The 5-speed trans also comes in at 40 lbs, so my algodoo counterpart is 18kg.

So as you can see I'm pretty determined to make this as realistic as possible, but I just have one problem. How do I test how powerful the engine is? I know that the torque is pretty hard to match since you get way more out of engines in algodoo, but I want the horsepower to be correct at least. I know there's people that know how to do it, and you can just ask them and they'll "dyno" it for you.

I don't want to wait on anyone though, so I'm coming to you guys. What can I do in my scenes to test the power of the engines?
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Re: How to test engine specs?

Postby pnvv » Tue Jul 14, 2015 8:21 pm

Me and another user are currently working on a super complicated dynamometer to measure power, but there is another method.

So load your engine by applying a brake on the flywheel and increasing torque until it slows down but does not stop completely, like ~50 rad/s is a good speed. then take however much torque you put and do this equation -

(rad/s) * (torque in NM) * 9.55 / 7124 = horsepower!

An example, if I build an engine with 1000 NM at 50 rad/s, we do this -

50 * 1000 * 9.55 / 7124 = 67.0269512 horsepower! (Just round it to 67, since those .02 hp don't really matter)

If you're wondering what the 9.55 is for, it's to convert rad/s to rpm. (The totally accurate number is much longer and uglier but 9.55 will get you as close as you really need to go)

Hope that helped... :)
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Re: How to test engine specs?

Postby Epic_SkyPilot » Wed Jul 15, 2015 2:20 am

Wow, that's perfect pnvv, thanks! So does that mean that in your example that the peak torque is 1000nm @ 50 rad/s? Or is finding the torque figure much more complicated than that :crazy:
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Re: How to test engine specs?

Postby pnvv » Wed Jul 15, 2015 4:06 am

I tend to do several different test at different RPMs to try to find out where the peak power output is.

If you want to be really advanced, make a torque curve. A user made one for me concerning this engine. It came out looking like this -
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The engine has around 3200 torque maximum, at a slice above 200 rpm. However - the horsepower curve comes out very different.
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This is because horsepower is essentially an equation concerning torque and speed, so effectively from 300 to 500 rpm, where the engine has peak power, the torque is decreasing, but the speed is increasing, so the speed makes up for the decreasing torque, and the power output remains fairly constant. However, past 500 rpm, the torque begins decreasing faster than the increasing speed can keep up, and the power output drops.

Some engines reach peak power at lower speeds, some higher. The engine shown here happens to be a rotary, and all the ones I've built of this type tend to reach peak power at similarly low speeds like this one.

I know too much about algoengines, don't I? :lol:
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