Fuel Injection & Wood Prop on 0-360

Hello to all on VAF:

First post on VAF and hoping someone can help. First flight on my RV-6A was Thanksgiving after 12 years of slow build. Talked to lots of RVers over that time and chose a new Mattituck TMX-IO360 with airflow performance fuel injection and Sterba prop to power my bird. Since Mattituck didn't set idle mixture and RPM, first couple flights were exciting as we dialed in the mixture from lean to rich and finally (I think) to where it should be.

Unfortunately I was also struggling with a rough idle problem that didn't want to go away. Engine would start and run fine when cold but gradually ran slower and rougher as it warmed up until, at 450 RPM it quit. On advice of some fellow builders I did some investigation and found an intake leak at the right front intake pipe. After tighting the hose clamp, the engine started and ran well but after taxiing around and running up, it went rough again and quit.

Pulled the cowl for more investigation and, after checking the lycoming overhaul manual, discovered the intake hose clamps and pipe flange bolts (at the cylinder heads) not torqued to spec. After consulting with Mattituck I re-tightend those items and ran the engine again. It started and ran fine albiet a little bit higher RPM (800). After warming it up and taxiing back to the hanger I thought I finally had it fixed but...when I was sitting in front of the hangar with the engine idling smooth at 800 RPM, it all the sudden went to 650 RPM in a "step function" fashion (the first time I actually witnessed it doing it). The only good thing was that the engine continued to run fairly smooth and didn't want to quit this time. Checked under the cowl again and noticed that two of the intake pipe flange bolts had loosened to where they were when I first torqued them (~50 inch pounds as opposed to the Lycoming spec of 96 inch pounds). Note, when I originally did the intake leak investigation these flanges did NOT show leakage even at their orignal torque of 45 inch pounds).

My question is: is there anyone on this forum that has this same combination of 0-360, wood prop and fuel injection (AFP preferably) and have you had this rough idle problem? If yes were you able to figure out what exactly was wrong and fix it?

Some very well meaning fellow builders at a well known airport nearby said I need to change to a metal prop. Thier experience with a Glassair powered by an 0-360 with fuel injection and wood prop was much the same and could not be cured until the wood prop was replaced by metal (which is heavier and has more inertia to keep the engine turning at idle). I can't argue with thier success but I can't help wondering that maybe the problem lies elsewhere, especially since my recent investigations have yeilded some improvements, albiet short lived). I installed a Landoll inertia ring, adds 11 pounds to flywheel, but no big help with the idle (definately adds inertia, wood prop used to stop immediately, with the ring the engine will turn another 1-2 blades before stopping).

This is really frustrating, especially flying out of a private strip with trees and houses all around. Any ideas? Or is this premise that "0-360s with fuel injection do not go together with wood props" a valid one (I hate to spend another $2200 on a metal prop but if that's what it takes to cure this I will do it for piece of mind)?

wood prop

is your problem. I have heard more than one account of this problem with that combination. In each case the problem was solved with a heavier prop.

Bruce
N98bj
N2156v
N63858

Light prop....

I have a friend with a 180 HP AFP fuel injected engine and a Prince prop. The prop probably does not weigh any more than your Sterba. He had a problem like you describe at first, I believe it ended up being the fuel servo. I think he sent it back for repair and has had no problems since.
There is a service bulletin out on the servo. Is yours effected and or been inspected? http://www.airflowperformance.com/

I would get expert assistance with your engine/fuel system before buying a metal prop.

Beware multi-factorial causation . . .

I used to run a Warnke ACS wood prop on my Bendix injected, parallel valve, 360. I experienced the same problems that you describe, deltamike.

It turned out that my engine had an intake leak and the RSA-5 was set too rich. Once I fixed those problems, the engine stopped alternating between too lean and too rich. So, the engine ran more smoothly in terms of less gasping and choking. But, the wood prop simply did not have enough mass to dampen RPM variations on a windy airport ramp. Consequently, my annoyance was reduced but not eliminated. Eventually, I bought a Sensenich 72FM. I did so primarily because the Warnke was underpitched for my application. But, I also I wanted an all-weather prop that did not need to be periodically re-torqued. As a collateral benefit of having a correctly pitched metal prop, the aforementioned RPM variations all but disappeared. The 72FM is heavy compared to the Warnke!

IMHO, you're on the right track with the inertia ring and injection unit adjustments. The devil's in the details! Good luck!

You might want to try a Landoll Balancer to give your engine a little more mass to work against.
Works well for me....O-320 w/ Catto.

Glenn Wilkinson