Hi Terry,
You stated at the start that 7 rotors capacity was 4.5 litres, so I assume 8 rotors is about 5.14 litres?
Since these are Wankel engines, is that their "geometric" capacity or their "burn" capacity which, since 3 burns occur per rev, would be triple that?
Never used nitrous in me life... Since ""more"" is ""better"", where is the max quantity of liquid nitrous you can inject in a manifold before its gas expansion is too much for the rotors to accept and it reverses the flow in the manifold, preventing fresh air coming in? IE you cannot pressurize the inlet track above AP since it communicates freely with AP.
IE, would it be best to partially (if you need more nitrogen than the nitrous can give?) close the inlet manifolds upstream of the nitrous injection point as soon as you press the nitrous switch and regulate engine speed via plus/minus timing of the nitrous injection/methanol solenoid valves to get a supercharger/turbo effect?
IE, do you really need a big air scoop sticking in the wind?
I calculate the air speed through your duct entry (assumed 1 foot x 1/3rd of a foot as shown above) at 50mph at 8000rpm (approx 41m3 of air per mn) for 1 burn per rev and at 150mph for 3 burns per rev (approx 123 m3/mn of air)...
So you will get an aerodynamic disturbance around your duct entry above these speeds, whichever is right...
Patrick
Hi Patrick,
Mazda rates it's two rotor engines at 1.3 liters. So 1.3/2 = .65 *8 = 5.2 liters. I may have also misquoted 5.14 previously. Each rotor does produce 3 power strokes per rotor rev, but, they run on an eccentric output shaft which turns 3 times faster. That means each rotor produces one complete power stroke per output shaft (crankshaft) rotation.
A power stroke for a single rotor covers 90 degrees of rotor rotation which covers 270 degrees of crank rotation (90 x 3 = 270), where a single piston power stroke is 90 degrees (180 / 2 crankshaft rotations). So, where a V8 fires 4 times per crank rotation (4 * 90 = 360 total degrees combined power stroke), an 8 rotor engine fires 8 times for each rotor face that completes a full power stroke (8 x 270 = 2160 total degrees), AND, 8 times for each second face that completes 90 degrees of power stroke for each crankshaft rotation (360 - 270 = 90). Because each of the 3 faces of a single rotor fire sequentially throughout the 360 degree "rotor" rotation cycle, when we convert rotor rotation to crank rotation we see 90 degrees of crank rotation remaining that sees 30 degrees of rotor power stroke from the next sequential face of the rotor (90 / 3 = 30). So... 8 * 270 = 2160) + ( 8 * 90 = 720) = 2160 + 720 = 2880 total combined degrees; or 2880 / 8 = 360 degrees of crank power stroke per rotor per each crank rotation).
Although displacement per rotor face is 1/3 that of a V8 of equal total displacement (.65 / 3 = .216) vs (5.2 / 8 = .65) those 24 rotor faces (8 x 3 = 24) combined are producing 8 times more total degrees of power stroke per crank rotation than the V8. I believe I have all that correct but with rotary engines who really knows.
Concerning intake calculations: Each rotor takes in .288 L of displaced air per crank rotation (.216 L @ 90 degrees (single face)) + (.072 L @ 30 degrees ( next sequential face)); totaling 2.304 L (.288 *
per crank rotation. Whereas each piston of the V8 takes in .325 L of displaced air per crank rotation (.65 / 2) or 1/2 of the 4 stroke two crank rotation cycle totaling 2.6 L (.325 *
per crank rotation. So, we're looking at 11.5% less displaced air intake per crank rotation than a V8. Does this make sense on the face of it? We would have to say volumetric efficiency of a normally aspirated rotary engine is better than a 4 stroke NA piston engine given the numbers above.
Nitrous as I understand the principle is injected via bottle pressure which instantly expands to AP in an NA environment. The power benefit comes from the introduction of extra oxygen molecules relative to that available in natural air. Combustion heat releases oxygen from the nitrogen/oxygen compound which in turn combines with the fuel to create additional power by volume. You may be right that less natural air is needed via the intake scoop using NOs than without, but by total volume of air consumed by any internal combustion engine over the course of a run, I don't think you can carry enough NOs on board to cover the total volume of air needed given current pressurization systems used for this application. Also, intake scoops offer a degree of aerodynamic compression of air stacking up inside the scoop chamber depending on the speed of air contacting the scoop intake opening, size of the opening, size of the interior chamber, and volumetric efficiency of the engine at a given rpm relative to ground speed.
I do agree that we will see an aero disturbance around the scoop opening depending on the degree of compression stacking withing the scoop. Thanks again for your input Patrick. Terry