how about this hybrid?

"wkiernan" (wkiernan)
06/16/2016 at 21:46 • Filed to: None

So I was checking out a Chevy Volt in the parking lot at the grocery store. A Volt can run for 40 or 50 miles on a charge, while a Tesla Model S can go 250 miles or more. However, a Tesla battery pack weighs about 1200 pounds, while a Volt battery pack weighs about 450 pounds.

But a Volt has a gas engine for a generator that actually gives you more overall range than a Tesla, plus a Volt can fill up at ordinary gas stations, which you can find anywhere, in three minutes. And that gas engine weighs at least a few hundred pounds, and when you’re in electric mode, which ideally the Volt driver will be in almost all the time, you’re carrying all that dead weight around.

So if you’re going to be in electric mode most of the time, but you want the security and flexibility of having an ICE engine, it seems like reducing the weight of the ICE engine optimizes the design, right? And also you want that ICE engine to be as compact as possible too.

Now what kind of gas engine is both compact and has a real high power to weight ratio? How about the Wankel?

If you are planning on driving your hybrid 90% of the time on plug-in power, then I think having a light, small Wankel engine might be a way to get the lightest hybrid drive train available. The traditional weaknesses of the Wankel, that is shorter life expectancy and inferior mileage, are minimized in this application, while its strength, compactness and high power-to-weight ratio, are exploited to the max.

Plus, you get to drive a rotary! For car nuts, that’s a big plus right there.

What do you Oppos think?

Pictures:

RX-7: Bring a Trailer
Wankel e !!!error: Indecipherable SUB-paragraph formatting!!! gine: Science Time by beehivedoom on Imgur
Volt: !!!error: Indecipherable SUB-paragraph formatting!!!

DISCUSSION (10)

HammerheadFistpunch > wkiernan
06/16/2016 at 21:51

what you are describing is called the BMW i3 with range extender.

EDIT: I though the i3 range extender was a rotary...there is one range extender out there that is though. oh its the A1 e tron

Quadradeuce > wkiernan
06/16/2016 at 21:52

I still think a micro turbine would be ideal in this application...

Bman76 (no it doesn't need a WS6 hood) M. Arch > wkiernan
06/16/2016 at 21:52

Here ya go:

http://jalopnik.com/tiny-rotary-en…

CRider > wkiernan
06/16/2016 at 21:57

Most people that buy Volts are concerned about things like fuel economy and emissions, you know. Not exactly the Wankel’s strong points.

wkiernan > CRider
06/16/2016 at 22:18

That’s true, but the customer I have in mind uses the plug-in battery 90-95% of the time. The Wankel would be reserved for the 5-10% of the time he or she has to drive more than 50 miles at a shot or between opportunities to plug in ( e.g. , the parking lot where I work has no electric power nearby, so if I had a plug-in car I couldn’t charge it there). Even then since it’s a series hybrid the ICE could be running at a constant RPM level for optimum efficiency and lowest emissions.

Compared with other hybrids, it’s a tradeoff between the worse economy of the Wankel vs. the greater size and weight of an inherently more fuel-efficient ICE such as the Prius’s Atkinson-cycle engine. And in comparison with the fully electric Tesla, it’s another tradeoff between the additional weight and complexity of an ICE vs. carrying an additional 750 pounds of battery and not being able to fill up in five minutes at any gas station.

samssun > Quadradeuce
06/16/2016 at 22:19

Turbines don’t work in cars because they really need to stay at one speed, and their efficiency increases as they scale up. If the turbine doesn’t power the drivetrain directly but instead charges the battery, you could leave it at its optimum speed and size it down. Don’t know if it would be enough to make up for conversion losses but it’s an interesting idea.

wkiernan > Quadradeuce
06/16/2016 at 22:22

Maybe, I’ll have to check them out. But manufacturing-wise, I don’t know of any car manufacturers who have mass-produced micro-turbine cars, whereas there’s that one manfacturer, of whom I’m very fond (I’m on my third Miata, o bless you Toyo Kogyo!) who’s mass-produced rotaries, and damn fun ones at that. So there it is, if Mazda wants to make a hybrid unlike any of their competitors (and go broke in the process, maybe not the best plan after all).

samssun > wkiernan
06/16/2016 at 22:23

Rotaries might have decent power to weight ratios, but their efficiency is pretty sub-par. A turbodiesel sized to run at a single efficient speed nonstop would probably be ideal (unless a turbine would gain more from running at steady speed than it would lose from being so small).

Quadradeuce > samssun
06/17/2016 at 08:40

That’s the idea, just have it drive the generator to extend range. I would love to read a study on this.

torque > wkiernan
06/17/2016 at 09:02

Best range extender engine? my vote is for the new liquid piston “reverse wankle rotory” engine (peanut inside the dorito instead of the otherway around like in a wankle). Extremely efficient and very high power to weight ratio (higher than any piston (gas or diesel) or wankle engine).

Supposed to be 57% efficient already (with 75% thermal efficiency theoritically possible) and intended for small engine to automotive applications (weedwackers, lawn mowers, portable generators, auto range extenders)

Does still have Apex seals (only potential drawback I can see) but they’re in the block, so you could make them out of a hardened material to extend their life + you could have them spring loaded so as they wear they still seal well (for a long, long time) b/f they need replacing.

Popular Mechanics has a good summary about it here: