Here is another oldie from the my old collection of Rotary Engine & RX8 articles. Original publish date 1/24/2005
A brief introduction to Air/Fuel ratios
Definition: the mass of air supplied to the engine divided by the mass of fuel supplied in the same period of time. The Stoichiometric, or chemically correct, air-fuel ratio (A/F ratio) is the exact ratio necessary to burn all the carbon and hydrogen in the fuel to carbon dioxide and water with no oxygen remaining. The fuel-air ratio is the reciprocal of the air-fuel ratio.
Stable combustion conditions require the right amounts of fuel and oxygen. The combustion products are heat energy, carbon dioxide, water vapor, nitrogen, and other gases (excluding oxygen). In theory there is a specific amount of oxygen needed to completely burn a given amount of fuel. In practice, burning conditions are never ideal.
Continue reading RX-8: Stock Air/Fuel Ratio
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Renesis Rotary Engine
Yet another one of my old Rotary Engine technical articles (originally published on 2/2/2005) I managed to recover from my old site. Enjoy it!
Characteristics of a rotary engine compared to a 4 stroke piston engine:
A rotary engine’s rotor completes one stroke for every 270º of crank rotation:
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Intake 270º of crank rotation.
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Compression 540º of crank rotation.
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Combustion 810º of crank rotation.
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Exhaust 1080º of crank rotation.
In other words, it takes a rotary engine 1080º of crankshaft rotation to complete an intake, compression, combustion & exhaust cycle. Or 3 crankshaft rotations per cycle.
A piston completes one stroke every 180º of crank rotation:
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Intake 180º of crank rotation.
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Compression 360º of crank rotation.
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Combustion 540º of crank rotation.
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Exhaust 720º of crank rotation.
A piston engine requires 720º of crankshaft rotation to complete a cycle. In other words, 2 complete revolutions of the crankshaft.
A rotor rotates @ 1/3 of the rate of the crankshaft. In other words, for every 1 revolution of a rotor, the crankshaft has done 3 revolutions. For example when the tachometer on a vehicle indicates 9000rpms, one rotor is turning at 3000rpms.
Continue reading Rotary Engines: Volumetric Efficiency
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Renesis Rotary Engine
Here is an article I reproduced a long time ago from one of the most ungodly knowledgeable person I’ve ever heard regarding rotary engines.
Rotary engine displacement explained by Fred “rotarygod” Swain
The rotary engine is a 6 stroke internal combustion engine. I know, people will probably start screaming at me for this so let’s get into a little explanation as to why and how typical mathematical formulas for piston engines don’t work.
First of all, lets get the terms “stroke” and “cycle” defined (Some of you get your heads out of the gutter!) since everyone commonly gets these terms interchanged. They are not the same thing. Every internal combustion engine whether it is a 2 stroke, 4 stroke, diesel, gasoline, propane injected, etc. is a 4 cycle engine. Why? All of these engines take in air (intake), compress the air (compression), ignite the air whether by spark plug or glow plug (ignition), and expel it out the tailpipe (exhaust). There you go 4 cycles. Simple isn’t it. The term “stroke” in this context refers to how many times the crankshaft or eccentric shaft makes a piston go up or down to complete the cycle.
The connecting rods and pistons are just an extension of the offset lobes of the crankshaft. This is also true in regards to a rotor and eccentric shaft. When the lobe rotates upward, the piston goes up. When the lobe rotates down, the piston goes down. Every time it moves one way is considered a stroke. In a 2 stroke engine, all 4 phases or cycles of the combustion process are completed in only 2 strokes of the piston, 1 up and 1 down. This is only 1 complete revolution of the crankshaft. In a 4 stroke engine, it takes 4 strokes of the piston, up, down, up, down to go through the complete combustion process. This is 2 complete revolutions of the crankshaft. It’s all a very simple mathematical relationship.
Continue reading Rotary Engines: Are they really just 1.3L?
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