Tach error

[anelon]

Well, here I am again with another instrument question. My tach bounces around quite a bit and it just bugs me. The engine is a C-85-8, wood Sensenich W72GK44. The tach is counter-clockwise and has the 90 degree fitting on the back to clear the fuel tank. I routinely see an out of range 2600-2700rpm on takeoff which should not happen with that engine and prop combination ... reducing power the rpm indication stays in that high range and comes down only a little when I know by the sound of the engine that I should be turning 2100-2200.

A little reading is a dangerous thing ... I saw tach cables in the Univair catalog (several, in fact) and mention is made of length of the cable and also models for recording and non-recording tachs.

My questions begin with (1) What could cause the discrepant readings, and go on to (2) what is the difference between a cable for a recording and non-recording tach (I've bought a new recording tach since I don't want one with "Cessna" on the face).

I've never had a tach problem with any of my airplanes or others I've flown ... maybe I'm lucky? This airplane is a recent rebuild (Airframe & Engine) and I have just over 15 hours in it since purchase ...

 

[huston marlowe]

 

[JimC]

 

[Renkou1]

 

[anelon]

 

[bob turner]