I'd read in a recent thread that a British company had managed to make a tri-rotor engine which reached nearly 30mpg, and still generated mad power. What was done to accomplish this? And are any of those changes street legal (i.e. not having removed all emmissions equipment, etc.).

*disclaimer*
I'm not starting this thread because I'm the least bit disappointed with my gas mileage; quite the contrary. It's a price I'm happy to pay for the performance. Just wanting to learn a bit more about these engines.

 

a link to said article or a scan would be helpful

 

Can you tell me where you read about this engine? I’d love to know about it. I think the main thing about our engines, is that they are an evolution of an older design, and Mazda has had to balance cost with efficiency and reliability. After getting burned by the FD, I’m sure Ford didn’t give Mazda a huge budget to work with, thus they have to work with what they had. Obviously Mazda managed to make some fairly significant changes to the engine, but overall, they didn’t end up doing some things I would like to see on the next engine. Mazda’s next Rotary should be a 1.5L 2rotor with the following additions

1. 1.5L displacement – should give a nice bump in torque allowing for a powerful NA engine.
2. All aluminum construction (intermediate, rotor and side housings) - I’m pretty sure the metallurgy exists to make this one work now, it would also likely save another 30-40lb in weight.
3. Direct Fuel Injection – More cars are going to this, replacing the fuel injectors in the intake manifold and injecting straight into the engine combustion chamber. Mazda did this, or something very similar with the 4rotor race car they built. This allows the A/F ratio to run even leaner as you can exercise an even greater amount of control over the combustion and burn. You usually get both better economy and power. For our cars, I’m not sure if you would add the fuel through the side housings with a setup similar to the spark plugs, or if that would cause to much of a compression drop. I’d love to hear from someone who’s thought through this. Mazda actually had the race car injections right before the intake port openings I believe, so it wasn’t a direct shot into the chamber but damn close.
4. Use the flywheel as an alternator to drive an electric waterpump, A/C, power steering and other devices. Our A/C really hammers our mileage. I think we should make sure the engine is work as efficiently as possible to drive our wheels, not power our stereo’s off of a power sapping drive belt. You could have a small battery that could drive things will idling that could recharge while you drive.
5. 3 spark plugs per rotor – After reading several books on the history of the rotary engine, I noticed that several race versions of the engine used this, which I assume helped to assure maximum burn of the fuel for better power, more control over fuel and timing, and I think would also help with economy if you knew that you could extract more from less fuel as you would have less fuel being left unburned and thrown into the next combusion cycle. This would likely also help emissions.

These are a few ideas that wouldn’t add a huge amount to the cost of the engine that I feel would make a substantial difference in terms of economy and power, and may be things that other rotary engines have implemented.

 

That whole efficiency stuff has been discussed in other threads. Here's a bunch:

https://www.rx8club.com/showthread.p...ght=efficiency
https://www.rx8club.com/showthread.p...ght=efficiency
https://www.rx8club.com/showthread.p...ght=efficiency
https://www.rx8club.com/showthread.p...ght=efficiency
https://www.rx8club.com/showthread.p...ght=efficiency

I doubt your 3 rotor 30 mpg is true. Unless that engine was used to drive a car at 40mph and 1500 rpm or something.

 

How heavy is the vehicle. Throw a Renesis with proper A/F ratios(not pig rich like it currently is) in a light enough vehicle and drive normally (not like a racecar, extended high rpms), and I could see getting high 20's on the highway. I've hit 26 on the highway at 70mph average for a whole tank.

 

Well, this sucks... I think I just read this yesterday, or maybe the day before, right here on the RX-8 forums... And now I can't find it. Something to the effect of a british company that had been modding rotary engines for years, 3- and 4-rotor designs, and their tri-rotor was very fuel efficient... I honestly cannot find it.

 

He is referring to Hurley Engineering in England. Hurley really simplifies the rotaries. He is very fond of SU carbs but most others have an aversion to them. Using these carbs, Eamon Hurley has attained 30 mpg highway with a 12A engine and 24 mpg highway with a 3 rotor engine that still developed 300 naturally aspirated horsepower. These are nice numbers but certainly not a miracle. It's just very good intake, exhaust, porting, with good tuning.

 

Any idea why Mazda does not incorporate these concepts into their rotaries?

 

^That's it. Thanks. Guess I didn't remember the exact figures.

 

First of all based on the mpg number you can't really tell how efficient these engines were. You'd need to know lbs/HP/h to make a comparison with the Renesis. Also you don't know how clean these engines were.

If the RX-8 had an overdrive, you might get 30mpg as well depending on what speed you're driving (without having to change the engine).

 

If they could get another 4mpg in city & highway from the Renesis and maybe (for the RX8) another 50HP without a Turbo or SC, then the rotary would become an engine they might be able to put in other cars...thus expanding research, thus advancing the rotary engine.

3 spark plugs sound like a good idea
Larger rotors sounds like a good idea
Direct fuel injection does too

I'm probably dreaming with the above, but I just refuse to believe that the rotary engine has reached it's potential.

Here are some other ideas:

They use breaking to generate electricity but why not use a part of the car that is almost ALWAYS spining...the wheels? You could use each wheel as a generator and maybe add a EMS (Electric Motor Assist) to the rotary to help in fuel economy.

The problem is...the rotary does not like turning off and on, off and on...

 

All Hurley really did was to use a nice carb, a nice header (which matters on a peripheral exhaust port rotary) and tuen it good. He wan't concerned with emissions regulations.

FWIW: My old nonturbo RX-7 would get about 18 mpg city and about 22 highway when it was stock. After some intake, exhaust, and fuel system work (no porting), I could get 22 city and 29 highway. The engine has the ability if everything is done properly. Hurley didn't do anything impossible. I also did not have any emissions control devices either. Removed them all.

 

http://www.hurley-engineering.ltd.uk/mazda12a.aspx

 

That link doesn't work. It's this one.

http://www.hurleyrotary.com/mazda12a.aspx

 

I'm thinking about getting a 3rd rotor actually to improve gas mileage.
If one rotor gives opproximately 1-mpg then all three will give 30mpg.

Isn't it cool?

;-))))))))))))