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Date: Fri, 21 Jan 2005 12:16:37 -0600
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: P Port fuel Injection
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Hi Jerry,

Good to see you posting here.

I watched Paul Conner's engine run before he shortened the intake 
manifold. His throttle body is in the 'normal' position on the end away 
from the engine & the injectors are in the throttle body. With the long 
runners, there was a fast, steady drip of fuel coming out of the mouth 
of the throttle body *while the engine was running* even though it was 
idling smoothly. There was a discussion on this list a couple of months 
ago about intake pressure pulses (reversion ??) carrying fuel back out 
of the intake manifold. 
I'm in the same shape as you, with only gut feeling instead of 
engineering background at my disposal. My gut feeling is that one 
advantage of timed injection is the ability to 'insert' the fuel at 
precisely the right time to get it into and trapped in the combustion 
chamber so that only air is blown back out past the 'valve' as it 
closes. (A lot of the new 'hot ticket' super efficient car engines are 
going to high pressure injection directly into the combustion chamber 
like a diesel.) My gut feeling is that the further you move the 
injection point from the combustion chamber, the more the system acts 
like a simple carburetor with the fuel bouncing back & forth in the 
manifold, condensing on the cool sides of the intake runners, etc, etc. 
I'd bet that the better BSFC with remoted injectors that's hyped on the 
other list was only achieved (wasn't the info from the Mazda factory 
racing program?) with perfect injector placement & timing based on more 
testing than any of us can do in our proverbial garages. (Is injector 
timing variable on Tracy's or any other injection controller out there?)

 >From one neophite to another....

Charlie


Jerry Hey wrote:

> George,  yes I know Paul's intake manifold is for side  ports.  
> Still,  it is the only comparable system (injectors on cool side)  we 
> have to look at and it is not experiencing difficulty with fuel 
> adhering to the runners.  Correct me if I am wrong, but I don't 
> believe Alan Tolle and Everett Hatch ever worked with injectors on the 
> cool side.  I think they injected directly into the throttle body.    
> I suspect that if any fuel adheres to the runner it will only be a 
> very small amount.  I would not expect it to build up.  Of course I am 
> just"guessing" using my "imagination".  None of this matters very much 
> because I am going to build the system and test it.  If it does or 
> does not work, we will know this year.  I predict I will  end up with 
> a collection of intake manifolds before this is over.  I am with you 
> mon,   I love this stuff.           Jerry
>
> P.S.  any chance you could forward  Alan Tolle's comments  to me?
> .
>
> On Thursday, January 20, 2005, at 05:44  PM, George Lendich wrote:
>
>> Jerry,
>> I think the over the top runners are curently with side ports mate - 
>> just
>> keep an open mind on the fuel sticking to the walls and how that MIGHT
>> affect the PP for idle.
>> Alan Tolle has done a lot of work with Everett hatch on these very same
>> issues.
>> Food for thought -that's all !
>> George (down under)
>>
>>> It seems that the need for very large injectors for max performance
>>> argues in favor of  having smaller primaries also to have a smooth low
>>> rpm idle. This can be done without too much trouble using two fuel
>>> rails per Bill Jeppson' design.
>>>
>>> As far as fuel adhering to the runner wall in the sweeps,  I think some
>>> of the guys are already using Paul L's over the top intake manifolds
>>> and they have not  reported  a problem.
>>>
>>> I have not found much guidance thus far concerning how far the
>>> injectors should be placed from the bell mouths.   In one article it
>>> states that anywhere between one and four inches is o.k.  The advantage
>>> of  putting the injectors further away from the bell mouth is better
>>> mixing.  Never-the-less,   I tend to like the idea of putting the
>>> injectors about an inch from the bell mouth.
>>>
>>> One thought is just to copy the Renesis injection as it delivers enough
>>> fuel, idles nice and so on.  Does it resemble 13B fuel injection?
>>>
>>> Geezs,  four little paragraphs  and that is ALL  I know about fuel
>>> injection.   Jerry 
>>