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Date: Mon, 20 Jun 2005 16:43:23 -0500
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Fuel Injector Position (was  Re: Making progress
 on Chris n Dave's Velocity Engine)
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Jerry Hey wrote:

>
>
> On Monday, June 20, 2005, at 08:07 AM, David Staten wrote:
>
>     The injection controller will be the Real World Solutions EC2. It
>     does stage. No, you aren't wrong. That is what I want. It's not
>     overly complicated when you dont have to build it from scratch..
>     thats why Im using the stock TB. The only thing I am having to fab
>     is the runners and two injector bosses.
>      
>     I am using stock fuel injector ports on the primaries (which are
>     in the block). Those are less than 2 inches away from the primary
>     intake ports. I will not be moving them.
>      
>     As for secondary positioning, how far back can I go before I have
>     to start worrying about the fuel charge not being inducted all the
>     way into the secondary ports? As in... the fuel charge shot into
>     the secondary runner (when secondaries are active) gets sucked all
>     the way in on THAT intake stroke, and not, lets say.. the next
>     one...Or are you saying that doesnt even matter? If injectors do
>     better farther away from the port/way upstream, why are they not
>     like that in the stock config? Several other EFI engines I've seen
>     appear to inject RIGHT before the intake port (Noticed while
>     shopping for intake parts), not way upstream...
>      
>     It seems that the folks who have difficulty idling at low power
>     smoothly are the ones who 1) dont sequence their airflow into
>     primaries first, secondaries only at higher power... and who have
>     their injectors 20 something inches away from the ports. Thats
>     just an observation I've picked up over the past year... and maybe
>     its mistaken.
>      
>     Dave
>
>
> Dave, based on Paul Lamar's current p port testing there is no problem 
> with placing the injectors at the far end of the runners. This is also 
> backed up by an article on the internet (How to Fabricate an Intake 
> Manifold) The idle issue is not with injector location but rather with 
> butterfly location. The further the butterflies are from the port, the 
> worse the throttle response and idle. At least that is the current 
> theory and is born out by Ed's experience when he place the 
> butterflies at the far end of his intake runners. Jerry
>
Hopefully Ed will be back soon to confirm or refute this, but all of 
Ed's intakes that I've seen have had the throttle body on the plenum at 
the other end of the intake tubes. That's what he's using now, or was 
when he left here Memorial Day weekend. The manifold he had problems 
with had the *injectors* mounted over there with the throttle body. (See 
Rusty's post also.) Ed has no problems with throttle response using 
close mounted injectors & plenum mounted throttle body.

Tracy has confirmed that the only way to adjust injector timing is with 
the mechanical timing of the pickup on the engine. Moving the injector 
15-30" away from the rotor housing just seems like it would have a 
radical effect on injector timing at low power settings when the 
injector has a short 'on time' & there's a relatively long slug of 
unfueled air. It seems to me that if the slug of 'fueled' air isn't 
timed properly to enter the rotor chamber & get trapped there, part of 
it will bounce around in the (cold) intake tubing & condense out on the 
walls, especially at low power settings.  IIRC, one of the reasons auto 
makers went from throttle body injection to direct port injection was 
because fuel condensation on the tubing walls was causing inconsistent & 
unpredictable mixtures.

I visited Paul Conner back in November, before he had flown. At that 
time he was using a throttle body with the injectors mounted on the 
throttle body, away from the intake ports. The throttle body was mounted 
more or less in an 'updraft' configuration, similar to a typical a/c 
carb on a Lyc or Continental. With the engine idling fairly smoothly, 
fuel was dripping out of the throttle body in almost a steady stream. 
Now, if everything is working normally & the engine is idling smoothly, 
where was the fuel coming from? This is not a normal symptom of updraft 
a/c carbs or injector throttle bodies.

Charlie