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EIS tach unstable

billnaz

billnaz

Well Known Member
Any suggestions on how to trouble shoot an unstable tach reading on my EIS? (EIS4000, 0-360) With a stable engine speed, the reading bounces around by several hundred RPM. This aint normal is it?

Confused....
 
If you are using the electrical pickup from the mag P lead, did you include the resistor that they provided?

Also - you can double check the resistance by using an ohm meter to measure the resistor you used. If I recall correctly, they include two resistors - one for lycoming and another (lower resistance) one for rotax. You want the value that the instructions specify.
 
billnaz said:
Any suggestions on how to trouble shoot an unstable tach reading on my EIS? (EIS4000, 0-360) With a stable engine speed, the reading bounces around by several hundred RPM. This aint normal is it?
Click to expand...


On my friend Dave's RV-6 the EIS reading is rock solid. I was surprised the RPM readings don't seem to fluctuate at all in stable flight. He's using an EIS 4000 on an Aerosport 0-360 with one mag and an electronic ignition. Of course I can't tell you right now which brand though. Let us know what you find out.
 
Thanks for the input. I'll report when I figure it out. Anyone have the magnetic rpm sensor in a lyc? I'm thinking that might be better way to go. It would allow traditional mag function check, which the p-lead sensor precludes.

Bill
 
Are you picking up the pulses for your engine monitor from a Magneto P lead?

If this is the case the problem may be due to spurious pulses on the P lead.

I had a similar problem with my Slick magneto when it had about 500 hours on it.

It seems as though the magneto contacts wear and start to give a pulse with spikes on it. This causes the Engine monitor tho give a false reading for RPM. After OH the magneto there was no more of a problem with the RPM read out.
 
EIS Unstable

I know of one other RV that had the erratic readout problem and it was time for mag overhaul. After o/h the readouts became stable again. If the mags you have are nearing o/h that could be your problem, too.
 
Thanks to everyone for the great input. I suspect the A&P who wired my engine goofed on the resistor. Hopefully redoing that should cure my ill. Per Sandy at GRT no one is doing the magnetic sensor option on lycs and the proper resistor (27k ohm) should provide stable readings as reported above. I can do my old fashoned mag check with a 2nd mag hook up and a switch I suppose......anyway.....break out the cable tie cutters...again!
 
btw: Another good reason for having the resistor: It ensures that an internal fault of the EIS can not shut off the mag. :D
 
Similar Problem

I had a similar, but different problem.
I have a GRT EIS 4000 reading data from my IO-360 with Lighspeed ignition.
The tacho read double RPM when the "Tach/PR" in the CONFIGURATION SET page was set to 1 (ONE) as per the manual.
When I changed the Tach/PR to 2 (Two) -which is supposedly for Rotax Two Strokes- it read correctly.
By the way, all this was made easier by the fact that I took Lightspeed option on a RPM/MAP/Advance. LED display.
Pete.
 
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