# Electrip Motor Performance



## ssophir (Aug 30, 2010)

Hi,
I have recently started considering a conversion, and was offered to use the following power system for a Toyota Sienna
http://www.azuredynamics.com/products/force-drive/documents/AC55_DMOC445ProductSheet.pdf
I realize the system is intended for trucks, but still, 60kW sounds just too low. Otherwise, why would the original car have a much larger engine?
I am not building a racing car, but I do not want it to be inferior compared to the original car acceleration wise. (I want top speed of 60mph)
Any thoughts about it?
Do I miss anything?
Thanks,
Ssophy


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## rillip3 (Jun 19, 2009)

1 HP =746 watts, roughly. That's 79 HP.

That sounds low, but you're comparing apples and cranberries. The HP (today, with SAE net, not the old SAE gross standard) is calculated with the engine connected to a flywheel, in turn connected to a dynamo. It has the exhaust, emission controls, alternator, etc. connected, but no drivetrain. This makes the number skewed upward of what you actually see in the car.

This also completely ignores gearing. You might get peak HP at 10,000 RPMs - not very much good for you in a car, where you won't get that. Typically you can expect to see as much as 40% of that HP number disappear when you put it in a real-world car. That 215 hp could easily be more like 129 HP available to you, and that's going to be at full throttle. 

By contrast, an electric motor offers full torque, and thus full HP, at any RPM. You'll see much better acceleration with the electric motor, but the top end is limited by the RPMs it can do. The best way to figure out your top speed is to do a ton of math. I couldn't produce all the work, but in effect you'll want to pick a gear so you know the gear ratio, get the total ratio (gear, differential, etc), incorporate the size of the tires (smaller tires will need more RPM to get to the same speed as a larger tire, because they're covering less distance each turn). Then you'll be able to see what the peak RPM of your motor will output. 60 MPH should be very doable with the motor; your bottleneck is more likely to be the amount of current you can safely pull from the batteries. 

That's a little light on the math (I hate rotational physics) but hope it gives you the right idea. 79 HP in an electric motor is a pretty good beast.


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