Just a thought,

 

Don't know what kind of wires you are using, however if they have a metal shield on the outside, sometimes there is unobservable arching between the inner wire and that shield which could cause the problem. If the problem increases as you ascend, it may be that the thinner air,with its lower dielectric is allowing some arching somewhere where otherwise it doesn't happen. (remember mooney, and others arching problems in their magnetos before pressurizing them? )

 

Rich

 

Bill,

Yes that is correct. I find it best to completely remove the wire to do this test. They can be delecate so wiggle them gently in different directions while watching the ohm meter. Usually if there is a problem it is at the connector, all though it can be anywhere along the wire. The ignition wires have a certain resistance per foot that you should look for. I don't know what that resistance would be because different brands of wires have different specfications but as you check each wire you will get an Idea what to expect. While you have them off check every inch for damage sliding your fingers over the surface. See if you can feel any anomalys that might be hidden under the surface coating that may indicate a break or compromise of the wire in some way.

I know you will find the problem eventually.

Robert

 

 

----- Original Message -----

From: Bill Bradburry

To: Rotary motors in aircraft

Sent: Wednesday, January 09, 2013 1:59 PM

Subject: [FlyRotary] Re: Aeroquip hose changed to hiccup

Robert,

I will check that the next time I am at the airport.  I am using the stock Renesis wires and igniters.  You just wiggled the wires with the VOM connected??

 

Bill

 

---

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Rob
Sent: Wednesday, January 09, 2013 12:51 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Aeroquip hose changed to hiccup

 

Hi Bill,

Another thing you might check.

 

I had a similer problem to yours in my fuel injected Ford V6 BD-4 with Tracys EC2 and EM2. For about a year I was plagued, while flying, with a brief miss with a jerk from the engine at random times even hours apart. It would mostly happen at higher RPM's then cruise, but sometimes at cruise. I checked everything I could think of.

 

My problem was that one or two of my ignition wires (MSD's 8.5mm Super Conductor wire set, brand new no less) had some intermittent connectors. I discovered this by checking the resistance of each wire while working the connectors a little bit to see if the resistance fluctuated excessively or even became an open circuit. Once I fixed these intermittents my problem was solved.

 

I know how unsettleing this can be while flying. I hope you find your problem.

 

Robert Bollinger

 

----- Original Message -----

From: Ernest Christley

To: Rotary motors in aircraft

Sent: Wednesday, January 09, 2013 8:38 AM

Subject: [FlyRotary] Re: Aeroquip hose changed to hiccup

 

A problem that mimics a poorly wired VR sensor, but 

-only happens occasionally, 

-with various levels of "response"

-and is getting worse.

 

Bill, if you haven't done so already, I would suggest changing the wiring to the VR sensor completely.  It sounds to me like a textbook example of the worst sort of electronic malfunction you can have…an intermittent open.  You'll never find it under normal test conditions, and it will manifest at the most inopportune times.  The only way to completely rule it out as a failure scenario is to completely replace the circuit path.

 

 

 

On Jan 8, 2013, at 11:42 PM, Bill Bradburry wrote:

No, I have the 2.85 gearbox.  I have the MT electric prop, so I fly WOT and use the prop to govern the engine speed. 

I have changed the plugs with no effect.  The mixture is fine when this is happening.  Fuel pressure also.  I had an incident once on take off like you describe where the plane was backfiring like crazy just after I lifted off.  I had the mixture too rich.  I dialed it back and everything smoothed out.  This is different.  It doesn’t really backfire.  It is a thump and it jerks the engine and plane.  You can hear and feel it.  It seems to be a single thump and it has varying degrees of violence.  Some are just a little miss and some are so bad it shakes everything.  These are less frequent, but they are bad enough that I don’t think they are good for the PSRU, prop, or engine mount.

That is why I have been bugging Tracy about the change for the EC-2.  I have my fingers crossed that this will fix it.  :>)

Bill B