Engine vibration

[sailvi767]

Getting more time in the new aircraft. It has a stock 260HP IO540-C4B5. The prop is a MTV9B 3 blade. The engine is turbine smooth at 2650 RPM but has a noticeable vibration as you bring the prop back below 2600 RPM. Prop has about 870 hours total time and 50 since a complete overhual. The motor is at 870 since overhual. I would like to try and get the engine smooth across the normal operating range. Is a dynamic balance the best first step or are there other things to check first? All blades seem tight in the hub.
George

[lr172]

search for prop clocking. Several have had good success with an alternate prop clocking arrangement on the 540 and I plan to do that on my C4B5. You will need to move the prop bushings around to do that though.

Larry

[Walt]

Originally Posted by lr172

search for prop clocking. Several have had good success with an alternate prop clocking arrangement on the 540 and I plan to do that on my C4B5. You will need to move the prop bushings around to do that though.

Larry

Not sure you will have the same effect clocking as with a 2 blade.
I would suggest that you start with a Dynamic balance.

[scrollF4]

I agree with Walt. Beyond that recommendation, do your EGTs stay consistent across all cylinders when you throttle back? Why I ask: If a dynamic balance doesn?t fix it, and if one of your EGTs drops off during throttle-back, you might explore a stuck valve.

[sailvi767]

I will check the EGT?s carefully next time out. The vibration starts with a RPM reduction. Power does not seem to be a factor.

[sailvi767]

Flew today and EGT?s are consistent. If RPM is pulled before power there is vibration. If I do a small power reduction prior to the RPM reduction things are fine. Dynamic balance is in work but not sure it will help.
George