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Date: Thu, 28 Jul 2011 11:45:13 -0400
From: Ernest Christley <echristley@att.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Injector mounting in top of block?
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Patrick wrote:
> Would this be using premixed gas & oil?  If not, could there be an issue 
> with the fuel washing the oil off the walls?
> 

I'm using premix, but that raises another possible issue I was thinking about.

The point of direct injection and timing the spray is to keep the fuel in the center of the chamber where it would 
actually burn.  Is there a possibility of being successful enough at keeping the fuel (which contains the oil) in the 
combustion chamber center that you end up starving the apex seals of lubrication?


> Heading to OSH this evening!
> 
> Patrick
> 
> Lehanover@aol.com wrote:
>> As you said, fuel pooling is a problem even for injected engines. So 
>> you see water heated manifolds, just as in carbureted  engines. Note 
>> the Lycoming with the distribution pot inside the oil pan. Heated oil 
>> keeps the mixture in a gas like state and the latent heat of 
>> evaporation helps cool the oil. On hot days there is a loss of power 
>> based on intake air temperature, but they suffer fewer carb icing events.
>> Injectors do a better job of cooling the intake tubes close by, and 
>> absent some warming agent, some condensation will return to the fuel.
>> At the least at lower power settings. So Mazda would appear to have 
>> moved the injector to the housing so that the fuel spray is facing the 
>> 300 degree plus rotor face. Plenty of heat to maintain a gas like 
>> state. So the rotor face is cooled some by the fuel. And thus a cooler 
>> oil in the rotor. There is no power loss because the chamber is closed 
>> and incoming air was not heated prior to entry so density was not lost.
>> Lower rotor face temps allow for more intake to enter, and thus more 
>> power.
>> The injector is firing into a low pressure unless turbo charging is 
>> involved. I am unable to detect a downside to this layout.
>> An idle at 2000 RPM can be tolerated, to protect reduction gears.
>> The racer idles between 2000 and 2200 RPM. So one big injector might 
>> do just fine, even if idle is less than ideal.
>> Lynn E. Hanover
>> In a message dated 7/27/2011 2:00:15 P.M. Paraguay Standard Time, 
>> echristley@nc.rr.com writes:
>>
>>     The MegaSquirt can time the injection based off of the ignition
>>     timing.
>>     I'm having some issues with my manifold.  The way I built it is
>>     causing
>>     fuel to puddle in the bottom (so, you live, learn and rebuild).  I
>>     can
>>     probably move the two fuel injectors to the oil injection ports
>>     easier
>>     than I can build a new manifold.  The other two injectors are at the
>>     stock position in the center plate.  Then I would tune the fuel
>>     injector
>>     timing to minimize EGT.
>>
>>     Am I fooling myself?  And, if so, how?
>>
> 
> 
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