How to build a 35 MPG RX-8
 

Has anyone seen this before? http://www.rotaryeng.net/RX8.html

Hrm... Sounds good.. not sure how he plans to deliver power through from the small rotary while the others aren't spinning...

If this idea worked.. why not just shut off one rotor.. and run on the other...
Oh well..

Why not just use the computer to shut off some of the fuel injection cycles to effectively reduce the displacement of the engine?

That's what they're doing on some of the V8s to get better mileage. With a rotary engine this should work even better since vibration is so low to begin with.

I drove my old 12A RX-7 about 12 miles one time on just one rotor. Didn't idle worth a crap and didn't have very much accelleration, but I could cruise on the highway at about 65-70. I had to keep my foot on the gas at stop lights so that it wouldn't die.

The problem with just shutting of an injector, is that it still is pushing air through. The clean air will raise the Cat converter temp, and it will also put LOTS of drag on the ohter running rotor, as compressing air is the hard part of ANY spinning engine.

The MDS systems from Dodge and GM both DISABLE valves, so the air inside is trapped, and acts like a spring (Hard to compress, but once it starts going the other way.. it helps push the piston down)

We would need 2 valves on the rotary... could be butterfly valves... they would completely seal off the intake and exhaust of a single rotor, providing the same "spring-like" benifits of the MDS system on the piston engine cars...

Interesting....cool, thanks for the link!

I don't know enough to comment any further, but I'm always happy to hear rotary developments...or possible ways of making it better.

" Right
now the RX8 engine is running at about 3250 RPM at 65 MPH and getting 25
MPG. "

well there is your first problem right there...lol Im sure many of us would love to get this on the highway. I get 22 city and 24 highway and I know im lucky.

Still a good read.

interesting

Also, maybe I'm wrong, if you shut the injectors the rotors will still need to be lubricated and by that you'll need to controle the oil injected in the rotor housing to not over oil the housing 'cause when the engine will start again it will smoke like hell. That's only a point of view. ;)

He's got the right idea, but way off on the numbers.

Rotaries are gas hogs, mostly because they don't extract as much heat from the exhaust as pistons do - and we use pistons as the MPG benchmark. Adding anther engine to the mix such as a turbine could be a solution but that also adds cost and other economic complexities. For example should it be designed for a limited range of operating efficiency to keep cost reasonable? And how much extra cost vrs the overall savings? Gas has a variable cost; today we pay 3 bucks later this year we may see 4 bucks, and in a few more years it may drop back to 2 bucks - or climb to 6 bucks. No one knows.

BMW has been playing with the turbosteamer. Nice idea, but it won't be cheap.

Detroit Diesel has been testing a disk turbine as a PTO system for diesels - pretty clever since it uses exhaust gas to power a series of disks that progressively power an array of disks as exhaust flow increases. Disk tubines are cheap to build.

Caterpillar has a turbo driven alternator downstream from the FI Turbo - it cools the exhaust too much for effective catalysts on US motors. This system adds about 3% fuel efficiency for applications that require a lot of electricity.

I have a feeling we'll be seeing downstream exhaust energy recovery devices on automobiles over the next decade. It wouldn't surpise me to see the Rotary take an early lead in this technology, but at the same time I don't expect it either.

I just don't see how that little rotor is going to help?? I think someone is thinking Northstar system that GM has but I don't think it will work with rotaries.. especially small tiny rotor and housing (LOL!)... Maybe we had 3 rotor engine and the third one kicking in to give that extra power but not the way this guy is proposing..

"Having faith in old rotaries is like being an Islamic fundamentalist.
You have to accept the fact that you're going to blow up sooner or later."


You really need to change that. Everybody wants to be a comedian these days, sounds more redneck than funny. :thumbsdow

I actually did play with shutting fuel off to one rotor a couple of years ago. The oil injectors still worked and so did the spark plug. There is so little oil being injected at any one time and so much turbulence inside the housings that odds are the oil is moving around just fine in there. I had a horrible imbalance when the rotor was shut off and I had to floor it just to hold 55 mph. In the end after all of the experimenting I get worse gas mileage. The vibration was terrible. I'm sure it wasn't good for the bearings having those kinds of uneven loads exerted on them. Needless to say this was probably far worse of an effect on the engine than any oil metering concerns.

i recall reading about that.. i thought is was someone else..

thanks for clearing that up..

beers :beer:

did you guys miss the bit about adding 50 hp via peripheral porting ?

The larger rotors can stop spinning because of the hole drilled through the center of the eccentric shaft, through which a smaller diameter driveshaft can be powered by the smaller rotor. I can't even begin to imagine the amount of friction and drivetrain losses that would be loaded onto the smaller rotor with this kind of system...

P23

Not to mention if the larger rotors stopped spinning completely, you'd need a whole 'nother clutch system to start them up when they are "needed for acceleration and climbing hills."

-P23

Thanks for clearing that up RotaryGod. :)

I have thought of a method that would let you shut off injectors in cycles, and not just kill one altogether. Each face fires each time, and gets fuel each time. What if we had a controller or programmer that would interrupt fuel injection to faces in a given pattern, not adjacent faces or on the same rotor at the same time.

For instance, if rotor 1 has faces A, B, and C, and rotor 2 has faces D, E, and F. All faces A through F get fuel every time they rotate. What if we skipped one face every so often in a standard pattern. To prevent it from seeming like the engine is misfiring and keep the power loss down, you could combine an electric air valve on the plughole side of the rotorhousing to vent compressed air, lowering pumping losses on the "skipped/dead" face. I have not thought it out far enough to figure out the pattern and frequency of skipping each face, but I dont see why it couldnt be done.