Engine monitor on avionics master?

I'm considering a Dynon or other engine monitoring instrument and have what may be a silly question. Is the unit on before starting the engine? I would assume so, given that you'd want to see RPM, oil pressure etc. right away. If so, what protection is there for the unit from power surges. It seems like it would make sense to have it on the avionics master circuit, just like your radios PFD, etc., but then you wouldn't be able to use the monitor until after the start-up. What am I missing?

Steve

It's been a few months since I read the Aeroelectric book, so don't quote me on this. I think the answer is that modern equipment should be able to handle moderate spikes. And you should have a good voltage regulator that will prevent spikes. Considering those two items, it's fine to have the engine monitor on during start up.

And for that matter, the "Aeroelectric way" doesn't have a main bus/avionics bus. Essential equipment is on one bus, the e-bus, and everything else is on the main bus.

Steve,
If you want to still use the Avionics master then just install a "Low Oil Pressure" lite and wire it to the master bus. When the lite goes out you have oil pressure and that is what is really important on start. I installed the idiot lite for me and the engine.

Enigine monitor damage from voltage spike during start?

Good Question.

Can starting and stopping the engine with the delicate electronics turned on damage it?

My engine monitor, a GRT EIS-4000, will be ON during start and not on the avionics master (switched buss). The reason is as you point out, you want it on during start, mostly for oil pressure. Although you could turn it on right after start, it goes thru a short boot-up period. The EIS-4000 is protected from voltage variation.

Throwing a master avionics switch is pretty well set in my habit patterns. As far as a master switch failure, that is rare and there are many ways to make the switch redundant. Also not having to turn each radio switch on and off is a nice thing to have.

Cheers George

start up and engine monitor

The only things I turn on for starting are the battery, alternator field, and aux fuel pump. As soon as the engine starts, I flip on a dedicated breaker switch for the engine monitor(EIS 4000) which boots up in about 3 seconds displaying the oil pressure. It might be safe to turn on all the other stuff, but considering the hassle-factor to replace anythign I just leave it all off until the engine is running and have checked for oil pressure.

My technique is based upon ignorance and laziness.

Thanks

It's nice to see I wasn't missing too much. It sounds like there actually is some debate about the best method, so I'll just take all of the great ideas mentioned and ponder a while. I've got time. Thanks a lot for the suggestions.

Steve

You could use a small (7 amp/hr) battery and a Schottky diode with a switch. Switch the monitor with the backup battery and the voltage drop incurred during start-up won't affect it.

To flip (a switch) or not?

redbeardmark said:

As soon as the engine starts, I flip on a dedicated breaker switch for the engine monitor (EIS 4000), which boots up in about 3 seconds displaying the oil pressure. My technique is based upon ignorance and laziness.

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That is good to know. I have not flown yet. I know the EIS4000 boots quick from bench testing but forgot how fast it was, so I may add it back to the avionics switched buss or give it a dedicated switch as you have. The only thing is my laziness is greater than yours and throwing more switches is not as easy as just having it tied to the master. As far as ignorance I know just enough to be dangerous.

I think it is a toss, from what Grand Rapids told me, starting with it on will not damage it, and it does not drain much juice. Flip a coin. Lets see,

>Master-on
>Fuel pump-on
>Start-push
>Engine monitor switch-on
>Avionics switch-on
>Fuel pump-off

Six steps, that is two more than it takes to start the Boeing I fly.
Except you don't have to yell "Clear Prop!"
Cheers George

Check out this post on the Dynon Forum

Steve,

This issue came up on the Dynon form, you can check out their reply here.

Thanks Bill. It's good to get that information from the source. Appreciate the link.

Steve

Starting with Dynon on line

N941WR said:

Steve,This issue came up on the Dynon form, you can check out their reply here.

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I called Dynon because I have a EFIS -D10 and it is fine to start the engine with it on line. I assume the EFIS is the same as the Dynon engine monitor. George