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HELP Request ... Whole Lotta Shakin' Goin' On!

jclark

Well Known Member
Benefactor
Aircraft: RV6
Engine: ECI 340 Stroker
Fuel Delivery: Airflow Performance Fuel Injection
Propeller: Whirlwind Constant Speed

Problem: Upon significant reduction in power (quickly pulling the black knob back), as in for landing, if done quickly, I get significant shaking of the engine/prop.

Anyone with any ideas as to what MIGHT be the cause?

Previously, on this plane with a carbureted O-320 and Hartzell Constant Speed prop, I did not have this issue. Don't recall this being an issue with the 340 when it was carbureted and the prop was fixed pitch.
 
If you watch your EGTs and try this at cruise altitude, pulling power will raise EGTs. If I am cruising and leaned to 100-150 ROP I normally richen a bit before reducing power. Then I keep on progressively richening as I decend. Otherwise it will peak and go LOP if you descend without fattening the mixture.

You might be experiencing lean side shaking and mis firing.
 
Aircraft: RV6
Engine: ECI 340 Stroker
Fuel Delivery: Airflow Performance Fuel Injection
Propeller: Whirlwind Constant Speed

Problem: Upon significant reduction in power (quickly pulling the black knob back), as in for landing, if done quickly, I get significant shaking of the engine/prop.

Anyone with any ideas as to what MIGHT be the cause?

Previously, on this plane with a carbureted O-320 and Hartzell Constant Speed prop, I did not have this issue. Don't recall this being an issue with the 340 when it was carbureted and the prop was fixed pitch.

You might need to richen up your idle mixture adjustment. When you start the engine and idle, does it idle smoothly and come off the idle smoothly? If not, you need to richen this up. Failing that, I'd call Don Rivera at AFP.
 
Mine will do that occasionally if I'm still significantly LOP and pull the throttle all the way off - EGT's tell me I am losing fire in one or two cylinders that way, richening the mixture or adding a couple inches of MAP always cures it.
 
Sounds odd, James. My IO360 M1B was quite lean as arrived, partly due to cold weather for first flights. Stumbled lightly with throttle application, ran rough on idle and no rpm increase on shutdown, but it really jumped for TO with throttle application when off the idle circuit and then ran like a jewel. Lots of misfire and popping on final and did not like to idle. Richened it up (a lot!) and all ran smooth.

But - - - it never acted like running rough and vibrated on descent or final. The compression/firing torque reaction is much lower at low MAP and thus should not do that, if there are no intake leaks etc. Words fall short in describing an engine condition, but it just might be a prop imbalance causing a temporary orbit in the mounts, as the RPM drops rapidly. Just a wild stab. You probably have more indicators that might indicate that is not the case.

Good luck in the chase, you should have lots of help nearby.
 
Poor transitions into and out of the idle circuits range (500-1000) are most typically the cause of sub-optimal idle mixture. I would start there; Be sure your idle mixture is properly set. I prefer the lowest MAP method, but the small RPM rise method works.

Larry
 
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