Somewhere in that ball park, George.  I think between 440 -550 cc/min or the
stock N/A engine injectors is what the Ec2 was designed for.  Tracy added
some features such as mode 6 to accommodate those who wanted to use
different size injectors (within a limit).

Smaller injectors can make a smoother idle for a car as they more finely
control fuel flow at lower rpm, however, few that I am aware of idle their
aircraft engines below 1200 rpm.  Both Tracy and I idle our older 13Bs at
around 1800-2000 rpm.  So that benefit of a smaller injectors is rather lost
to our use.

Plus a larger primary injector gives you that back up capability of running
on only one pair of injectors, only one size and type of injector to order
or keep a spare on hand and little need to mess with Mode 6 a some of the
advantages I see.

But, part of this "hobby" is doing it "your way" - so certainly no problem
seeing folks opt for smaller primary injectors, just not my personal
preference.

Ed


Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of George Lendich
Sent: Friday, June 19, 2009 5:44 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: 295cc vs 495 cc was [FlyRotary] responses to
responses, not developing full power

Ed,
295cc + 495cc = 795cc, why not a couple of 400cc injectors as the figures
suggest, what is the closest to 400cc injectors- is it the 440cc Tracy
recommends?

The engine won't be going over 7,200 rpm for most applications and the
495cc secondary Renesis is larger than our needs. I know larger is better
for the higher RPM as it dispenses larger amounts of fuel over a shorter
time, however for idle and low power their getting too big.

So I figure for the situation of having them the same size, I wouldn't have
them bigger than the 440cc Tracy recommends.
George (down under)

Don, if you are using stock Renesis (295 cc primary/495 cc secondary),
then
I am not surprised you find the running rough when switching to just the
secondary.  Here is why.

Once you tune the EC2 to idle/low rpm - you are doing it before the EC2
stages, therefore the Ec2 is opening only the 295cc primary injectors and
you have tuned your engine (presumably) to run well at idle on the primary
injectors.  When you switch the primary injectors off and secondary
injectors on - the EC2 is still providing the same pulse duration
(assuming
engine manifold pressure, etc are the same) for the almost twice as large
secondary injectors as it did for the smaller primary injectors. Ergo, you
are feeding the engine almost twice the fuel (for the same engine
conditions) as you did when on the primary injectors.  The engine is
choking
on too much fuel.

Those of use with the older 13Bs which basically had the same size
injectors
in primary and secondary roles OR those using the Renesis who have
replaced
the smaller 295 cc with the larger size secondary (which once again means
having same size injectors in both positions) can switch from primary to
secondary as the pulse duration is injecting essentially the same amount
of
fuel regardless of which pair you have turned on.

Since Many of us have found that the 13B will produce almost full power on

a
single pair of 460/550 cc/min injectors - I personally favor replacing the
smaller 295 cc/min injectors with larger injectors.  Although two 295
cc/min
injectors will probably keep you airborne - its nice to have the option of
running on either pair.  But, as I said that is just my personal
preference.

It sounds to me like the rough running on only secondary, the varying EGT,
etc, smacks of too much fuel for the operating conditions.  Try leaning it
more - you can't hurt the engine.

Let us know how it goes

Ed



Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Don Wallker
Sent: Thursday, June 18, 2009 10:07 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] responses to responses, not developing full power




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