Help needed with Tachometer Error

[FoxDB 17]

I have a 582 in my Kitfox with a Westach Quad gauge. The last 2 flights are showing an RPM drop of 1000 on one mag but only about 100 on the other mag, yet I can tell by the sound the drop is about the same. There is only one tach lead from the engine so I don't know how it could be the tach. I am wondering if there is a flaw in the ignition/electrical system that would cause this. Any help would be appreciated.

[akflyer 1427]

I have a 582 in my Kitfox with a Westach Quad gauge. The last 2 flights are showing an RPM drop of 1000 on one mag but only about 100 on the other mag, yet I can tell by the sound the drop is about the same. There is only one tach lead from the engine so I don't know how it could be the tach. I am wondering if there is a flaw in the ignition/electrical system that would cause this. Any help would be appreciated.

Check your grounds on the mag switches. Spend 40 bucks on a tiny tach. Chances are, your leaving alot of performance on the table with that westach gauge reading higher RPM than what your turning.

[TheDeltaFox 0]

Absolutley get a TinyTach. Best $45 I ever spent on my Avid. My old Rotax guage is off by about 400 rpm at the top end. That kind of difference would make anyone hate life after repeatedly setting your prop for the wrong RPM.

Now I just use the old guage for rpm drop during the Mag check because the Tinytach only goes on one ignition wire and goes a little wonky when the one mag is switched off.

D

[akflyer 1427]

Absolutley get a TinyTach. Best $45 I ever spent on my Avid. My old Rotax guage is off by about 400 rpm at the top end. That kind of difference would make anyone hate life after repeatedly setting your prop for the wrong RPM.

Now I just use the old guage for rpm drop during the Mag check because the Tinytach only goes on one ignition wire and goes a little wonky when the one mag is switched off.

D

You wrap the pickup wire around both plug wires on one cylinder . This gives you the mag drop on both ignitions!

I have seen the stock analog tach 800-1000 rpm off! The guys that need 1000' to take off and can only climb at a few hundy fpm are the guys that don't use a tiny tach

[FoxDB 17]

I have a generic Tiny Tach. I checked the grounds on the mags and the switches work fine so I'm sure the grounds are there at the switches. I did wrap 2 plug wires (1 from each coil) for the Tiny Tach rather than just the one and the mag drop is the same per ignition ~120 RPM. So I still don't know the cause but I could just disconnect the Westach so it does not bother me.

[TheDeltaFox 0]

You live you learn... I wish I would have figured out that I could have wrapped it around both wires for one cylinder

Oh well, in 4 more years the battery will be toast and i'll put in a new one.