2nd Generation Specific 1986-1992 Discussion

Gas mileage mod. What do you guys think

Old 01-19-2011, 10:09 AM
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1991 Mazda Rx7 non turbo running premix (the servo for the OMP went bad, i still have the OMP hooked up but it only puts out idle amount of oil.)





Looking on Akins website i found a single rotor engine they make for boats. Couldn't help but tihnk that i could get better gas mileage from a single rotor engine but at a lose of power. Then GM's displacement on demand came to mind. So, my idea is that if i can turn off the two injectors to one rotor and mod the position of the O2 sensor so that it doesn't read the extra O2 in the exhaust, could i run one rotor while highway driving and get better gas mileage? The the main worry i have is that running pre mix, will the deactivated rotor get enough oil to prevent damage to the engine? Any input on this idea or anything i'm missing in making this work would be greatly appreciated. And if i more forward on this project i will post my mods and results.



piston engine takes two rotations to cycle it's displacement

rotory engine cycles displacement every rotation, So 1.3 rotory engine = 2.6 fuel economy. Subtract one rotor, 1.3 fuel economy?
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Old 01-19-2011, 10:22 AM
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I blew a rotor, had compression on 1 face only, other rotor was fine. I still drove it like that, for at least a month (maybe longer, I can't remember). I was quite surprised at how much power it still had!
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Old 01-19-2011, 11:09 AM
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Yeah, that one rotor Akins marine engine was still 100 hp.
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Old 01-19-2011, 01:37 PM
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The GM system also affects the valves to reduce pumping losses. If you just cut fuel/spark to one rotor you are going to create a lot of pumping losses from compressing the air in the unfiring rotor still, and the increased load on the other rotor will likely negate any gas savings.
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Old 01-19-2011, 02:41 PM
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In order to deactivate a cylinder, the exhaust valve is prevented from opening after the power stroke and the exhaust gas charge is retained in the cylinder and compressed during the exhaust stroke. Following the exhaust stroke, the intake valve is prevented from opening. The exhaust gas in the cylinder is expanded and compressed over and over again and acts like a gas spring. As multiple cylinders are shut off at a time (cylinders 1, 4, 6 and 7 for a V8), the power required for compression of the exhaust gas in one cylinder is countered by the decompression of retained exhaust gas in another. When more power is called for, the exhaust valve is reactivated and the old exhaust gas is expelled during the exhaust stroke. The intake valve is likewise reactivated and normal engine operation is resumed.





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



Basicly using the compressed air in a deactivated cylinder to help compress air in another.
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Old 01-19-2011, 04:07 PM
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There also comes a point where an under powered motor is going to work it's *** off trying to move the car and end up burning more fuel then the more powerful motor. I've seen this a lot in boats for that matter. Guy goes from a 200hp to a 150hp thinking he's going to save a fortune on gas and ends up burning up twice as much at cruise because his cruise RPM is significantly higher.



Honestly what's the point in having an underpowered sports car, it's like having a girlfriend with big **** and being an *** man.
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Old 01-19-2011, 06:01 PM
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Lmao can I quote that Phins?
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Old 01-19-2011, 06:07 PM
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In typical light load driving with large displacement engines (e.g. highway cruising), only about 30 percent of an engine’s potential power is utilized. Under these circumstances, the throttle valve is only slightly open and the engine has to work hard to draw air through it. The result is an inefficient condition known as pumping loss. In this situation, a partial vacuum occurs between the throttle valve and the combustion chamber—and some of the power that the engine makes is used not to propel the vehicle forward, but to overcome the drag on the pistons and crank from fighting to draw air through the small opening and the accompanying vacuum resistance at the throttle valve. By the time one piston cycle is complete, up to half of the potential volume of the cylinder has not received a full charge of air.



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Old 01-19-2011, 06:16 PM
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With a rotary there is no way to seal the nonrunning rotor. The one still operating rotor will have to provide enough power for compression in it's own housing, and also for the dead rotor causing much more load on the engine, fuel consumption, and heat buildup.
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Old 01-19-2011, 08:56 PM
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Originally Posted by thatpoorguy View Post
Lmao can I quote that Phins?


ha ha yea of course.
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