robrecht

If a picture is worth a thousand words, a moving *.gif file must be worth a million:

http://www.rotaryengineillustrated.c...101/REanim.gif

How do they do it? Pay no attentionn to that gear behind the curtain:

http://www.rotaryengineillustrated.c...cyclodial3.gif

Falken

I was told it's because the rotors spin too fast for the fuel to fully burn and you get back pressure from fuel completing combustion in the exhaust chamber.

delhi

180hp/l non-forced induction engine generally has an impact on mpg.

shaunv74

From Wikipedia on the wankel:

Fuel consumption and emissions

Just as the shape of the Wankel combustion chamber prevents preignition, it also leads to incomplete combustion of the air-fuel charge, with the remaining unburned hydrocarbons released into the exhaust. While manufacturers of piston-engine cars were turning to expensive catalytic converters to completely oxidize the unburned hydrocarbons, Mazda was able to avoid this cost by enriching the air/fuel mixture and increasing the amount of unburned hydrocarbons in the exhaust to actually support complete combustion in a 'thermal reactor' (an enlarged open chamber in the exhaust manifold) without the need for a catalytic converter, thereby producing a clean exhaust at the cost of some extra fuel consumption. World gasoline prices rose sharply at the time Mazda introduced their Wankel engine, making the cleaner exhaust/increased fuel consumption tradeoff an unwelcome one for consumers.[citation needed]

In Mazda's RX-8 with the Renesis engine, fuel consumption is now within normal limits while passing California State emissions requirements. The exhaust ports, which in earlier Mazda rotaries were located in the rotor housings, were moved to the sides of the combustion chamber. This approach allowed Mazda to eliminate overlap between intake and exhaust port openings, while simultaneously increasing exhaust port area. The Renesis engine even meets California's Low Emissions Vehicle or LEV standards.

http://en.wikipedia.org/wiki/Wankel_engine

MazdaManiac

iTrader: (3)

Here we go again.

PAY ATTENTION

CyberPitz

Idiots? I'd rather say I'm ignorant to how it works. Well, either way, very informative. I'm assuming either you are really pissed at the camera, or you're being sarcastic.

MikeTyson8MyKids

iTrader: (1)

Of course its RPM dependent. The reason we are seeing less mpg is because, unfortunatly, we cant be at WOT all the time. haha

Ve is a just a measurement of pressure inside the chamber that is just filled with air/fuel vs atmospheric pressure. Since the Renesis is normally aspirated, it'll have a Ve of less than 100%. And that efficiency will vary with RPM.

Now, I stated that the overall thermodynamic effiency is lower. Its a measure of the heat content of fuel/air vs the work out. At cruising speed, say 75 mph, the Rx8 will muster around 20-22 mpg. A Z06 would probably muster 26-27. Fuels are the same. Hence, the thermodynamic effiency being lower at that state.

I didnt watch your link? Maybe it was saying the same thing?

neXib

Haha, that's what we call "getting it in with a spoon" here. Nice demo

VampireSix

Ok, I hate sounding like a noob.... but are you saying that the engine is more efficient/has better MPG at higher RPMs?

VolcomStoneX

not again...

MikeTyson8MyKids

iTrader: (1)

If you are looking at Ve compared to a piston type engine, then yes.

Does anyone have a plot of Ve vs RPM or thermodynamic efficiency vs rpm?

altspace

iTrader: (2)

My thread will help you understand.

https://www.rx8club.com/rx-8-media-news-11/how-rotary-saved-136641/

CyberPitz

^
Nice read! Helped a lot.

superglue

Thanks! I didn't start reading that mag till a year or two after that was published. Too bad he left, that mag sucks now.

Who would have thought moving the exhaust port to the side would reap so many benefits?

Raptor75

It seems a few on this thread know and understand what they are talking about and some don't. I have always found MM good with the facts IMHO.

The second thread had it in a simple nut shell. Because of it's combustion chamber design and the way it works it is some 15% less efficient in converting the fuel's energy into work then a piston engine. The energy lost is by heat through the coolant system and exhaust (the rotaries exhaust runs a few hundred degrees hotter then a piston engine). This is why no matter what you hear from the fan boys the Rotary has poor fuel economy.

The real killer for this car seems at ideal, my RX will burn approximately .48 gallons/Hr at ideal. To put this in real world terms let me use my driving and car as an example. I drive city streets 95% of the time and now average anywhere from 11mpg to 14mpg depending how hard I push it. I spend about 25% of my time at idle, estimate. Lets say that Mazda had the RX shut down at idle and restart at the tap of the accelerator, my gas mileage would jump from an average of 12.5 MPG to 18.5 MPG. Probably less in real world but still a significant increase. Highway mileage would be unaffected of course.

If the rotary does see another model, which is questionable at best, I hope it has direct injection. This would boost both HP, MPG and assure 87 would run fine on all cars.