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It's not a direct connection. You do want efficient horsepower to drive a generator. More low end torque means the HP comes at lower RPM, which should mean les

It's not a direct connection. You do want efficient horsepower to drive a generator. More low end torque means the HP comes at lower RPM, which should mean less fuel consumption. Sibling says the achilles heel of the Wankel rotary is low end torque, but you don't take the direct output from the engine, it goes through gear reduction for final drive output. The real achilles heel is the awful emissions. It's more or less a 2 cycle engine from that POV. When driven at variable speeds it's hard to wrangle. The reason it's well suited for electrical generation is its mechanical simplicity, compactness, low weight, low NVH, and not least important, "rotary" brand value. I suppose that when run at constant RPM and constant or smoothly changing load, the emissions is easier to deal with.

pengaru 3y ago
The side-port exhaust used in the rx-8 generation RE substantially improved the emissions situation, but the fuel efficiency is still trash by modern ICE standards. It's been awhile since I gave a damn about wankels (or ICEs in general), but ISTR there being a relatively low limit to achievable static compression ratio due to the fundamental geometry of the swept volume. Modern ICE engines are largely exploiting the combination of direct injection and the high compression ratios it enables to improve their thermal efficiency. Between the relatively low compression ratio and sub-optimal combustion chamber shape and the fact that it migrates around the housing with the power stroke, the wankel is pretty much doomed in a world that cares about efficiency. disclaimer: I've worked hard to discard all my gearhead knowledge, but went fairly deep down the rx-7 rabbithole in my 20s-30s. Take the above with a big grain of "I may be senile and overconfident in stale once-deep knowledge" salt.
- jiveturkey 3y ago
  to the best of my knowledge, you are correct on all counts. the new rotary used as a generator does also have direct injection, but i don't think they gain much compression ratio from that, for the reasons you stated. it's more for efficiency. without reading up on it, i believe the combustion chamber mixture and flame front propagation is not great in a rotary (hence RX8 has 2 plugs per chamber, leading and trailing) and DI should improve on it.

pengaru 3y ago

The side-port exhaust used in the rx-8 generation RE substantially improved the emissions situation, but the fuel efficiency is still trash by modern ICE standards. It's been awhile since I gave a damn about wankels (or ICEs in general), but ISTR there being a relatively low limit to achievable static compression ratio due to the fundamental geometry of the swept volume. Modern ICE engines are largely exploiting the combination of direct injection and the high compression ratios it enables to improve their thermal efficiency. Between the relatively low compression ratio and sub-optimal combustion chamber shape and the fact that it migrates around the housing with the power stroke, the wankel is pretty much doomed in a world that cares about efficiency. disclaimer: I've worked hard to discard all my gearhead knowledge, but went fairly deep down the rx-7 rabbithole in my 20s-30s. Take the above with a big grain of "I may be senile and overconfident in stale once-deep knowledge" salt.

jiveturkey 3y ago
to the best of my knowledge, you are correct on all counts. the new rotary used as a generator does also have direct injection, but i don't think they gain much compression ratio from that, for the reasons you stated. it's more for efficiency. without reading up on it, i believe the combustion chamber mixture and flame front propagation is not great in a rotary (hence RX8 has 2 plugs per chamber, leading and trailing) and DI should improve on it.