flyrotary@lancaironline.net Mailing List Archive

Ed,

Depending on the version of EC2, inductive spikes of over 40 volts are seen with the newer versions and over 60 volts are seen on the older ones. The current drawn through the resistor doesn't have to pull the injector open. It just has to delay the injector from closing. When this happens, the injector would appear to be working, but would deliver more fuel than the others. Remember the Alamo! ... oops... Snubber, that is.

Steve Boese

RV6A, 1986 13B NA, RD1A, EC2

From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of Ed Anderson [eanderson@carolina.rr.com]
Sent: Tuesday, May 29, 2012 9:18 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: injector imbalance

Mark, it does not take much resistance to protect the injector from current draws by other devices. I install a 200 ohm resistor between my EFISM and the driving injector. That way at a nominal 12 volts - the most current the other device would draw (if shorted to ground) is I = E/R = 12/200 = 60 ma (probably much less is the device is probably not a direct ground) not enough to pull your injector open.

I put it in there (as close to the injector as I could) so that if by chance my EFISM lead from the injector got shorted to ground it would not pull the injector open.

The resistance is not critical, I have used from 100-500 ohms. You could increase the resistance until your other device stopped working (and then reduce the resistance a bit from there).

The quickest was to see if that is the problem is simply to disconnect that aux lead to injector.

From: Mark Steitle

Sent: Tuesday, May 29, 2012 11:02 AM

To: Rotary motors in aircraft

Subject: [FlyRotary] Re: injector imbalance

Steve,

I almost understand what you're telling me. Bill Shultz commented on the Blue Mountain EFIS using the #1 injector for RPM. So, if the BMA EFIS is connected to the #1 injector lead, then it could be causing the over rich condition on that rotor. I'm not sure if I did that or not as my BMA RPM indicator has never worked. It has been many years since I installed the EFIS, so I don't recall if this was done or not. But this will be the next thing I will check.

Thanks,

Mark

On Tue, May 29, 2012 at 9:47 AM, Steven W. Boese <SBoese@uwyo.edu> wrote:

Mark,

If a device is connected to the EC2 side of the primary injector of rotor 1 and this device has diode protection from the inductive spike produced by the injector winding, then this injector will deliver more fuel than the injector pulse width would indicate. The appearance on the O-scope would more evident in the lack of an inductive spike for this injector rather than in a difference in the signal pulse width.

Steve Boese

RV6A, 1986 13B NA, RD1A, EC2

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