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wrote: > Rusty, I don't think anyone can answer that question - depends on too many variables. You would think that even if the fuel coated your long runners that eventually it ends up in the combustion chamber. Yes, but fuel that condenses on the sides of the runners finds its way into the combustion chamber as relatively large, unburnable, droplets. > My (admittedly limited) experience with rotary intakes leads me to believe that the number one, primary, uno, far outweighing all other factors, the key element, etc. etc., is AIR FLOW! > But you can't burn plain air, or we'd all be flying for free. There's that 14:1 thing. It not only has to be there, but but there needs to be enough ~vaporized~ fuel to support combustion. > If you DO have the airflow then it is simple to dump in more fuel and get more power. If you don't have the airflow in the induction system, then it don't make no never mind how much fuel you pour into it, it won't produce more power. That's so, and the extra fuel is not only wasted, but will usually lower the combustion temperature enough to reduce net power output. >Clearly, its not a simple matter to get great airflow for a number of reason mentioned. > It will be a while before I can prove it, but everything I know about the process at this point, suggests that Rusty is on the correct track in moving the injectors down close to the housings. Regards, Dale R. COZY MkIV #1254 ------=____1084379490167_6iMOpAYd?J Content-Type: text/html; name="replyAll" Content-Disposition: inline; filename="replyAll" Message

From: Russell Duffy

To: Rotary motors in aircraft

Sent: Monday, May 10, 2004 9:33 PM

Subject: [FlyRotary] injector relocation predictions?

Greetings,

As I mentioned before, one of the relatively easy options for improvement will be to move the 4 injectors, and keep the current intake. As they are now, all 4 injectors are in the TB, which is 30 inches away on the cold side of the engine. I believe I can mount the two stock primaries back in the block, and can probably mount the two secondaries in the intake, maybe 2 inches from the engine.

Here's the question, do you think this will increase power? In other words, am I losing power by having the injectors coating the inside of the long tubing, rather than efficiently delivering the fuel to the engine?

Thanks,

Rusty (thinking of draining one fuel tank, and filling it with helium to improve climb)

Rusty, I don't think anyone can answer that question - depends on too many variables. You would think that even if the fuel coated your long runners that eventually it ends up in the combustion chamber. My (admittedly limited) experience with rotary intakes leads me to believe that the number one, primary, uno, far outweighing all other factors, the key element, etc. etc., is AIR FLOW!

If you DO have the airflow then it is simple to dump in more fuel and get more power. If you don't have the airflow in the induction system, then it don't make no never mind how much fuel you pour into it, it won't produce more power. Clearly, its not a simple matter to get great airflow for a number of reason mentioned.

Tracy has (I think) shown that airflow velocity apparently plays a major role in producing power. His runners are 1.25 and 1.5" in dia - so clearly not oversized. This creates higher air velocity in the runners which in turn can cram more air into the chamber when the port opens (the momentum effect of the moving air)

Now taking the fact that at 6000 rpm and 100% VE a 80 CID rotary will suck approx 277 CFM of air, so each set of runners flow approx `1/2 *277 or 138 CFM. Assuming that the air divides between the two runners proportional to their areas 40% for the primary and 60% for the secondary. We have .4*138 = 52 CFM and 0.6* 138 = 82 CFM

To find the air velocity in each runner we divide the flow in each runner by the area of that runner we find that the average velocity of air in the intake is only on the order of 110 fps or approx 75 mph. Now most induction theory says you want an intake velocity on the order of 300 fps, but there of course as always a trade off. If you reduce the intake diameter in order to achieve 300 fps in the rotary you would have to reduce the runner dia even more and that starts to cause airflow restrictions especially at higher rpm. On the other hand, if you enlarge the diam of the runners much beyond what Mazda used, then the intake velocity will decrease and could adversely affect the inertia chamber stuffing effect. At least that is how it appears to me.

When I combined my primary and secondary runner, I ensured that the total area of the single tube did not exceed the combined area of both primary and secondary tubes in the attempt to keep the airflow velocity the same as in the Mazda.

FWIW

Ed

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