7hevin

I was wondering if it was possible,with the right engine management system or fuel map to have the fuell injectors inject fuell into the engine every other time,alternating between the front and rear rotors,I'm thinking during crusing speeds like on the freeway,,instead of each rotor getting fuell every time the rotor face passes the intake it would get fuell everyother time,and alternate between front and rear.

dgeesaman

iTrader: (7)

You could do that and risk damaging the car under load, or you could just move the gas pedal less. Either strategy decreases the amount of fuel being injected.

farberio

iTrader: (7)

I am judging by 'with the right ems' means that you don't have any engine management system.

So unless you go with Megasquirt its going to take you years if not a decade to get your money back.

Aaron Cake

iTrader: (1)

With ANY EMS, proper tuning will result in better mileage then stock. But alternating between rotors....no.

7hevin

My thinking was more for highway cruising,I know a lot of 8 cylinders can shut off 4 of their cylindes and essentialy be a 4banger,,,I was thinking of something like this for the rotary.

farberio

iTrader: (7)

You are thinking of cylinder deactivation.

I don't think any EMS has this option for a rotary.

Aaron Cake

iTrader: (1)

The rotary doesn't have enough displacement to use cylinder deactivation. Notice that it's only large 6s and V8s that can do it. Halfing the displacement of a 6 litre V8 still means that you are even firing on 3 litres worth of engine.

farberio

iTrader: (7)

*Gasp* You just supported the 'there's no replacement for displacement' argument!

Shame on you Aaron!

Aaron Cake

iTrader: (1)

There is no replacement for displacement. Even rotary people who want a lot more power up the displacement in the form of a 20B. I'm upping the displacement on my car in the form of a 4 rotor 2.6 litre...

joff

iTrader: (1)

Good tactics for increasing fuel economy is tune cruise to 16 AFR, have good atomizing primary injectors, have minimum exhaust restriction, let the motor run real hot, use thinner engine oil, underdrive pulleys, run CDI/multi-spark ignition, run a hot air intake, minimize frontal area (keep 93 spec front-end for FD), plug all air holes in the nose, keep high tire pressure, use small skinny tires, minimize weight, stay out of boost, change to a 3.9 final drive rear end, and use 87 octane fuel.

joff

iTrader: (1)

"Displacement on demand" is a gimmick that only reduces air pumping inefficiencies by permanently closing intake valves via a fancy electronic valve/cam setup. The piston still moves up and down.

joff

iTrader: (1)

The most fuel efficient motor is one where intake temp is equal to exhaust temp and no heat is radiated out of the engine bay/radiator. Unfortunately materials science has not yet let us get away with that. We dissipate 2/3 of the fuels energy as heat out the exhaust and via the radiator.

joff

iTrader: (1)

Another possibility is run 2 engines in series as a way to recover some of the exhaust energy.

Harness'ing a turbocharger turbine to spool something other than an air compressor would be nice too... somehow turn that energy back into mechanical.

joff

iTrader: (1)

Or run a sterling engine in parallel off the heat dumped into the cooling system.

(Sorry for rambling, wanted to get my 5 posts as newbie out the way)

farberio

iTrader: (7)

And no fuel is being used....

It may not be turning off cylinders but its not a gimmick. The wording just may be a bit misleading.

joff

iTrader: (1)

I still personally think its a gimmick.

If you're going 55mph on 8 cylinders, then switch to 4 cylinders, those other 4 cylinders will need twice as much fuel now to maintain the same torque to the wheels to maintain speed.

Despite what many people think, any efficiency advantages it gets are not realized by simply cutting fuel. You have to be able to block both the intake and exhaust ports and run high vacuum in the crankcase to minimize the "drag" of the extra cylinders. Also, better pumping efficiency is acheived with more widely opened throttles-- but as you open the throttle, your crankcase vacuum will also decrease and those 4 dead cylinders start causing drag again (compressing/decompressing the crankcase).

Pumping inefficiency is just one small reason 4 cylinders get better fuel economy. Another is because they're usually put in small lightweight cars and are lightweight themselves. Also there is less moving parts and less moving parts have less internal frictional drag. You know what has less moving parts, is lighter weight, and gets good fuel economy and has the power/torque of a 8 cylinder? Turbocharging a 4 or 3 cylinder.

7hevin

That's why I'm not talking about deactivating a rotor,just altering when the fuell is actually delivered to each rotor,instead of the rotor getting fuell every time the rotor face passes the intake it would get fuell every other time,and alternate between front and rear so there's allways one rotor producing power,,,,,,,anyway that's the way I see it in my head.

joff

iTrader: (1)

So (e.g.) instead of a 4 ms injector pulse every rotation, do a 4 ms injector pulse every other rotation? Sounds absurd. Why would you want a less smooth running motor?

joff

iTrader: (1)

I don't see how thats different than just changing to a 2 ms injector pulse every rotation.

If you're cruising at 55mph and you suddently cut half the fuel sent to the motor, you'll have half the power and will start decelerating. Not anything more to it than that.

joff

iTrader: (1)

Our (fuel injected) RX7's have 4 intake ports and 4 injectors. At low load and low throttle, 2 of the ports are blocked by the throttle body and 2 of the injectors are unused. "Displacement on demand" -- rotary style.

Icemark

Mazda did considerable research on this back in early 2002 and 2003 with Reni based test engines. The draw back was two fold.

The first issue was that the oil injected through the MOP is only part of the lubrication for the apex and side seals. There is a good percentage of fuel that is used as well. In earlier Rotary engine designs this was part of the reason that the engine was ran so rich, so that proper distribution of the oil and fuel not only helped momentarily cool the rotor face but save the seals. Anyone taking apart an older 13B can clearly see more wear in the expansion cycle location of the housing, from that reduced (due to being burned) lubrication.

The second was that without the combustion event on every single face rotors tended to warp and the emissions from unburned metered oil skyrocketed as did the O2, often clogging and overheating the cat converters.

Now they experimented with 1,1,0 and 1,0,0 events on the "variable displacement" style engines, forcing either two combustion events followed by a single non combustion event, or a single combustion event followed by two non events, rotating through the two rotors. In the end however neither worked as well as increasing the combustion chamber size and relocating injectors out of the intake ports and into a "direct injection" location. The direct injection ended up also increasing power, with the revised bath tub combustion chamber.

It should be noted that 3 spark systems were also tried and seriously considered using the 13B based Reni, but typically of 3 spark systems, the only gains are at lower RPM where the combustion event can often only partially complete due to lower load and temperatures.

Actually most of the non turbo 13B engines are 6 port, not 4 port. 4 port is only used on older designs, or designs not requiring intake timing adjustment (such as forced induction) for the proper torque curve.

And both the S1 HO Renisis (and post '05 non HO units) and current version of the 16X use 6 injectors and 6 ports.

7hevin

Thank you Icemark for your knowledgeable and insightful response,it makes sense now.

joff

iTrader: (1)

Interesting.

Wait -- so you're saying FI does not require intake timing adjustment? Surely you can't mean what I think you mean (spark timing). Many a tuner would be out of a job if proper timing had no measureable results on the torque curve. You must mean intake helmholtz/velocity adjustment, right? Even then, velocity/helmholtz tuning is still seems important for FI-- maybe less so, but a lot of guys playing around with the VDI, SSV, etc open/close points on turbo 6 port renesis's have shown significant and real effects to the torque curve.

Actually in 09 I hear they changed the renesis back to 4 injectors on the 6 port. Also, I thought the idea with the 16X was more of hybrid direct injection setup -- pics I've seen show the injector on top of housings with injection timing somewhere after intake port closes but before TDC of compression stroke. A traditional DI setup being injector right at spark plug.

You can see the single DI injector at the top of the housing here: http://www.mazda.com/mazdaspirit/rotary/16x/.