Dennis Madden

Dennis Madden

Active Member
Folks,
Read what I could find on the forums here about EI, but still have a question. I have an RV-4 with O-320 with a wood prop.(Warnke if it matters) Heres the deal. I have the idle set about 750 +- just to get it smooth. Any lower and it shakes too much for comfort. Before I turned the idle up, I used to worry about it quiting on final. And finally the question. Would Electronic ignition allow a smoother lower idle RPM setting? I know a metal prop, with it's higher inertia, would probably fix this. But this prop is doing fine so far. Anyone?
As an aside, the plane runs along at 30 mph on the ground at idle, if I let it. (I don't)
Thanks
 
Wood prop low inertia

Its the wood prop has low inertia. The fix is just keep the idle up. Electronic ignition will smooth out idle a little but it does not fix the low prop weight. Some RV's with fixed wood prop use a harmonic balancer. Here is a post I dug up:

Harmonic Balancer Write-up by Dane Deal:
"I have a Lycoming O-320 with the old-fashioned conical mounting with a fixed pitch metal prop. Like all Lycomings it likes to shake, especially around 1'200-1'300 rpm's.

First, I had the prop dynamically balanced for $250. This seemed to cut the "felt" vibration in half and gave me an increase of about 20-30 rpm when at full throttle on the ground. While it was a dramatic improvement, I still was not satisfied. It was pretty smooth in cruise, but when climbing at full power there was still enough vibration to get your attention.

Second, I purchased a harmonic balancer from:
Mark Landoll Starters & Alternators
1205 Redbud Lane
Newcastle, OK 73065
405-392-3847
[email protected]

The balancer was $375 and is of very high quality. It is a machined aluminum ring that is hollow and contains a steel ring suspended in a silicone fluid. It weighs 12 pounds and bolts to the front of the starter ring. It was very painless to install and required no modifications to my 6A.

I could feel the difference the minute I started the engine. Even sitting on the ground idling it seemed to smooth out the engine's firing pulses, and it was even better in the air.

Over the first several hours of flying I could feel and hear the engine's vibrations changing and disappearing. It takes a couple hours for the balancer to "break in". During the break in period I would feel a new, minor vibration slowly appear then disappear 15 minutes later. This repeated for about 2 hours. Each time the vibrations became less and less noticeable.

After flying with the balancer for about 4 hours I noticed no further changes. The vibration was dramatically reduced at all rpm's, and the engine idles very well down to 700 rpm. This was definitely money well spent. Dane Deal

I never used one since I typically fly with a metal c/s prop but Dane seems to be happy with it. A RV-4 should benefit from a little nose weight CG wise for max weight passenger w/ bags. The balancer has been around a long time. You might consider a metal Sensenich, you will be able to idle at lower RPM, but on the other hand wood props tend to feel smoother than metal props.
 
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