Siemens electric air plane engine, how does it stack up to Tesla engines?

Jul 16, 2016
science space
2 min read

Siemens made a press release about their new and super weight efficient electric engine for used in planes.

None of the coverage I read really put it into perspective. This engine has a power-to-weight ratio of 5.2, but what is that relative to other engines?

Here’s some simple calculations:

Motor	kW	kg	kW/kg
Merlin Rocket Engine	7457	68	109.66
Tesla Model S	270	32	8.44
Tesla Roster	215	32	6.72
Siemens	260	50	5.20
McLaren 12C	441	200	2.21
BMW 5M	423	228	1.86
Honda Accord	114	190	0.60

Which goes to show that these electric engines are super weight efficient compared to traditional combustion engines used in cars. That there have been huge leaps recently in increasing that lead. But lastly that this Siemens engine is already out shadowed by Tesla’s engines.

Perhaps I’m missing something about other characteristics important for flight?

Update from Hacker News:

Do the 32kg include the inverter and reduction gear? My guess is that with those included it weighs AT LEAST 100kg, probably closer to 200kg.

Interesting, that would put the power to weight ratio down to combustion engine levels.

I found this http://www.teslarati.com/tesla-model-s-weight/ that supports your thought by putting it at 150 kg.

I can’t find any details on what Siemens includes in their weight figure

Well they don’t have a transmission so that shouldn’t be a concern.

is able to continuously output 260kw, the Tesla motor isn’t even close to that. I’ve personally tried it a few times on the Autobahn and the Tesla limits the output to about 100kw (displayed) after less than a minute of full throttle.

In did try to correct for this sort of thing by picking one of the lower kW ratings for the Tesla. I was not aware it was that drastic. If we account for this the Tesla is almost in Honda accord territory. That’s rather disconcerting given Musk citing figures like the ones I outlined. https://youtu.be/PULkWGHeIQQ?t=41m30s

Sources

The quality of the number get’s increasingly more questionable as you go from Tesla down to Honda’s. I had to approximate the Honda engine weight assuming a 40kg transmission. The numbers are less interesting though, it’s more so the order the rough relative differences between the engines.