Dynon D-180 tach questions

[jbstok]

In retrofitting a D-180 onto the RV-8 I recently bought, I'm a little confused about how to hook up the tach input.

The airplane came with a UMA 1A3 tach sender hooked up to an electronic tach.

The D-180 manual describes two different wiring scenarios for the tach input. I could (I think) use the UMA tach sender, or I can wire a pick up off the P-leads. My helper thinks we can use both since there are two tach inputs into the Dynon harness, but I'm wondering if that wouldn't confuse the D-180 into thinking the airplane was a twin and displaying two tachs on the EMS screen. I don't have a problem using the UMA 1A3-4 sender, but my buddy is more old school and wants to use the P-leads, despite losing the RPM during a runup on when the mag is switched off.

Is it possible to use both? Would that be helpful at all? Is the UMA 1A3-4 sender even compatible with the D-180?

Thanks for your suggestions.

......JB

 

[Rockyjs]

Use A From Your Plead

I can't speak for your sender, but I've wired a D180 using a connection from both Pleads into it. If you wire both Pleads from the mags the Dynon will automatically swap to the working mag during a check. Make sure that you use the recommended resister inline in the installation. You might want to contact Dynon on your particular sender to check on compatibility.

 

[DakotaHawk]

My engine has a Light Speed and a Bendix Mag. I have inputs from both ignitions to my Dynon EMS. Without the input from both, you would lose RPM indication during your pre-flight mag test.

My Lightspeed is a simple wire connection from the Lightspeed harness to the Dynon.

My Bendix mag is a wire with a resistor that runs from the magneto switch to the Dynon. Dynon recommends a range of resistors. I tried the smallest resistor value at first, but got transient RPM spikes. After increasing the resistor value to the maximum value recommended (I think it was 150k ohms / 1/4W) the RPM spikes are gone.

 

[jbstok]

Thanks guys. After further research we've decided to use both the sender and take a pickup off one of the p-leads. I hope to get that done tomorrow, but probably won't start it up until early next week.

 

[jbstok]

Followup: Used both the UMA tach sender and picked up off one P-lead using a 100K ohm resistor and it works just fine. In fact, everything works except the Kavilco fuel pressure sender. Won't move off 0 psi, so after double checking everything, it's on it's way back to Dynon for testing and hopefully replacement. It's supposed to read 4 psi even with the engine not running, so something is wrong. The smoke test was successful and the biggest problem was flooding the engine trying to test that fuel pressure sender. Now I have a bunch of programming to do, but plenty of time to do it (and put the panel back together) while I wait on the fuel pressure sender. Since this is/was a flying airplane, I'm in a bit more of a hurry than a builder might be.