[Flying again!]

Just had the mags inspected and on the right mag the points were changed as well as the small plastic gear, and carbon brush. Mags were timed. However, at lower rpm (1500) mag check is fine but at my normal 1700 the rpm drops about 80 on the left mag and when I go to the right mag no noticeable change but the rpm displayed on my EIS 6000 and the GRT EFIS shows rpm from 1500 to 3200!

The mechanic and I checked the wiring to make sure nothing was disturbed and all seems ok. We decided that since the engine ran the same on right and left mag that it was an indicator issues. We went for a short flight and checked the mags in the air and the I indicated rpm behaved. After landing, ran up to 1700 and 80 rpm drop on both mags, indications normal.

However, yesterday, still have erroneous rpm readings when running on the right mag. I have heard that sometimes the points on the mags have to seat and are hard to time. Would this cause the strange indications?

 

[BobTurner]

The EIS is connected to the mag switch with a resistor in series with the wire, one for each mag. Try using a larger value resistor.

 

[vlittle]

This a common problem. P-lead waveforms can be affected by the condition of the mags, leads or sparkplugs. I experienced this with my io540 as documented here..

In the end, i developed a circuit that fixes the variability of the p-lead signal. Flight testing is complete and i have fabricated some circuit boards in preparation for releasing it as an open source design.

I'm planning on sending one to Jake Jansen at Aero Assist for evaluation, he just doesn't know it yet.

 

[RV10inOz]

I will tell him.....

Jake and I might test some. I am about to do a complete panel upgrade so if I see this bug, which I have seen before, I will give it a go.

 

[DanH]

....when I go to the right mag no noticeable change but the rpm displayed on my EIS 6000 and the GRT EFIS shows rpm from 1500 to 3200

TJ, mine has been doing the same thing about 20 hours now. Had the mags apart about 10 back, found/replaced a bad gear, but no change to the indication. Swapped p-leads at the mags to see if the problem stayed with the mag or the leads. Instead, tach indications were normal, both sides. Swapped back, 3200 RPM (at 1800) right mag indication returned.

I think I need a new capacitor in the right mag. Resistors don't drift do they?

 

[RV10inOz]

Resistors don't drift do they?

Checked your Champion plugs lately ?

The solution for me was disconnect the right tach wire.

Have not missed it.

 

[DanH]

Checked your Champion plugs lately ?

They're all in a box on the shelf.