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| Originally Posted by tartanski As far as I know Cube for Cube Rotary engines have far more torque than Reciprocating engines. Can it be they have torque characteristics like a Electric motor? |
I rather doubt this is true. One big indicator of the torque capabilities of the prime engine source itself would be to look at the ‘transmission gearing’ that accompanies its application. In general if it requires a lot of gearing to start motion from a slow speed, then the max-torque characteristics of the prime source must be at the upper RPM range rather than down lower.
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| Originally Posted by Ben …The mazda engine produces it's maximum power at something like 7500rpm and max torque at 5500rpm, suggesting it needs to wind up before it gives it's best. |
The lastest generation Mazda RX-8 engines, Renesis, - an engine boasting innovative technologies such as side intake/side exhaust porting - is a 654 cc x two rotor unit that produces 177kW (ECE at 8200 rpm and 211Nm (ECE) of torque at 5500 rpm when combined with a six-speed manual transmission.)
[http://www.rotaryengineillustrated.com/
Internal combustion engines in general are not good low-end torque producers. The older diesel engines with their ‘longer-stroke’ certainly outshone the gas engines. But nowadays many of the diesels are more compact with shorter strokes and turbo charging to give the compression ratios required to ignite the diesel fuel. Even their torque outputs come at higher RPMs. And incidentally this means higher piston speeds resulting in shorter engine life.
Electric motors on the other hand are noted for their low-end torque characteristics. I’ll let a more knowledgeable electrical person explain why. But look at the applications in cranes, trains, and previously big buses to name a few. Cranes need that initial hoisting capability, trains need that ‘start rolling torque’ to get heavy things rolling, and buses use to use electric motors to drive the wheels until the computerized multi-speed transmissions allowed for connecting the diesel engine to the wheels without the diesel-electric interface.
BTW, electric motors are much better suited to driving our cars, as their torque characteristics are a much better match to the auto’s needs…plus we could regenerate upon braking. Too bad we aren’t pursuing this with greater vigor. Maybe the current fuel prices will force the issue. I tried to get an Asian/American development program on this subject going back in ’97, but couldn’t arouse any interest in the USA. Sorry got off the jet-pump drive subject a bit.