Wankel Rotary w/base/Atkinson/Miller cycle modes.

is this a "rambling" or from an actual article?

 

To what end? Normally there's "news" on the threads posted in the alt fuel / hybrid news category.

 

Another rotary enthusiast. I used to be one of them. Until Mazda messed up the engine and the RX-8.

It's dead Jim.

 

It is because of its light weight and high power to weight ratio.

 

It's not the weight or power to weight ratio. Try picking a rotary up. I have!! In fact you can put an aluminum V8 in a 3rd gen RX-7 and have the car about 100 lb -lighter-. With more power. It's been done and documented.

It's the power to size ratio and the possible reliability due to so few moving parts. In "hobby" aircraft.

It's definitely not the fuel economy!!

Fuel economy and Mazda's messing up the reliability killed the engine in cars, at least for now. The RX-8 is dead, as I said above.

 

Audi is considering a 125cc rotary for the genset of the A1 E-tron.

 

That doesn't sound right. The rx-8 engine is 247lbs. I don't know of a v8 that weighs that little. It also is about the same power as a high output 4 cylinder turbo like the bmw 2.0 twin power. The rotary can be turbo charged to give it better power to weight, but the advantage has shrunk. As you mentioned their is a power to size advantage also, but in the rx-7 the design and transmission left a space big enough for a v8. In this case a turbo 4 or turbo 6 might be smaller as a system. In the case of a generator for phev a small rotary should be possible.

The bmw engine should be much more efficient An advantage is low cost, but this has been hurt by low volume. These may have a place in range extenders in phevs with good ev range as audi is experimenting on. Mazda is committed to keep the engine alive, but it will never be mainstream unless they can solve the efficiency problems.

 

Chevy aluminum block LS2 engines weigh about 440 lb fully dressed (ready to run with accessories) I doubt the RX-8 weight you have is fully dressed, but everything I have read says the rotaries are lighter than an LS engine. There is a lack of good info, but a little over 100 lb heavier for an LS engine in an Apples to Apples comparison seems to be a fairly common number.

 

Mazda Atkinsonized an engine through value control for a the Miller cycle engine in the Millinia years before Toyota brought the Prius to market.

There is research on Atkinson rotaries.
http://white-smoke.wetpaint.com/page/Rotary+Engine

 

Let's assume the conventional wisdom is true, that a wankel using similar materials has better power/weight or lower cost than a otto ice which has better power to weight than an atkinson ice. The problem is efficiency. When efficiency is taken into account as well as pollution control its hard to beat one of the newer 4-cylinder turbo charged ices.

Now these things don't scale down. The ecoboost 1L 3cyl is about as small as you get. rotaries can get much smaller. This may make it worthwhile for a range extender on a phev. The key would be lower cost, weight, and size at the expense of some efficiency. If the ice is rarely used it may be a good trade off.

 

Yes, thermal efficiency a problem with Wankels. I've seen some amazing claims but no highly thermal efficient Wankels out in the wild.

I don't see any reason an ICE couldn't be made a lot smaller than 1L and maintain similar efficiency to what they have now. Efficiency doesn't fall of a cliff as cylinders get smaller although it does get lower, all else being equal.

 

The issue with smaller piston engine is running smoothness. Getting a 3 or less cylinder engine balanced is trickier than ones with more cylinders. The fixes will for it will eat into the weight and space savings. Decreasing cylinder volume while keeping the number of cylinders up will increase internal friction as the ratio of cylinder surface area to cyl. volume decreases.

 

+1

Yes, I'm not sure if advancements can be made, but we have had plenty of time with motorcycle engines. Below 1 liter, a 2 or 1 cylinder becomes more efficient and tricks are played to reduce NVH, which can reduce efficiency. That 3 cyl 1L was the size of the insight, so maybe DI allows us to shrink it a little more. VW is playing with a 2 cylinder 0.8 TDI, but I'm sure its rougher than a 3cyl.

Going power/weight/size that 3cyl 1 liter puts out an efficient 120hp. Its iron block to make it cheaper and smaller, it also heats faster so less of a start up penalty versus a engine like in the prius. It won't make is much smaller, but to make it cheaper and less powerful you can strip out the turbo and make it an Atkinson. This would drop it to about 60 hp. More cost can get squeezed by dropping DI, but this will increase NVH and decrease efficiency. For the bulk of the market 4cyl 1.3 is as small as people want to go, but cost size efficiency have gotten some of these 1L engines in cars.

Trollbait dropped a link for some Atkinson rotaries. RACE is what you are talking about.

I'll believe it when someone actually does it and the engine is efficient. I do not believe you will get close to the 38% thermal efficiency of the gen III prius engine, or the 45% efficiency toyota claims they can get from a small turbo di piston ice in the lab.