GRT EIS, and Vans tach sender

I just wanted to let folks know about a "Gottcha" that has been driving me a bit crazy for a while now.

When I discovered the tach signal from the Slick "Laser" ignition box was not compatible with my GRT EIS, I decided to install one of the transducer that Vans sells, Part Number = IE VTACHGEN 12, so the tach signal would be forever separate from the ignition, should the Laser ever fail---make that "when".

The transducer that I got generates 8 pulses per revolution, and after conversation with GRT, I set the EIS to 8 P/R as per their advice.

The tach was reading an absolute max of 1350 RPM at full throttle, and low prop pitch, which seemed to be half of what it should be.

Late last night, it hit me, the tach drive off the rear of the engine------I'll bet it runs at the same speed as the mags, which are right next to the tach output.

A quick phone call to Mattituck, and Mahlon, and suspicion confirmed----the transducer was only going half of the crank RPM.

So, instead of getting 8 pulses per engine revolution, the EIS was only getting half of them, or 4 pulses.

Now, I have to go reset the EIS to a P/R of 4, and all should be golden.

This seems to be a "gotcha" on many of the EFIS equipped first flights. The sensors are not properly programmed for the engine/sensor/ignition system in use.

I've seen a first flight where the EFIS units were set to metric, causing the pilot to see that he was at 300 (meters) when he was sure he was at 1000 (feet).

Another example is not setting the EMS for the correct transducers. For example, I've also seen fuel pressure showing about 10psi on a fuel injected engine. After programming the EMS to recognize the correct style of transducer, fuel pressure was correctly displayed at about 28psi.

I had the problem with rpm indication with my engine run-ups prior to first flight. RPM was showing only about 800 rpm when I knew that the engine was around 1600 rpm. Again, a simple perusal of the installation and setup manual, and I got the EMS programmed correctly.

Finally, it's equally important to set alarm conditions to prevent spurious alarms during flight. For example, if you expect oil pressure on your Lycoming to be between 50 - 70 psi during your flight, it might not be a good idea to set your low oil pressure alarm at 45 psi. You don't want to get alarms if you're only a few psi out of your expected range. Instead, it would be wise to set the low oil pressure alarm at 25 psi, still high enough to give you warning before the engine starts chewing itself up.

I just made a change to my (fuel injected) fuel pressure alarm setpoint. I had it set to alarm on Hi Fuel Pressure at 30psi. Normal range is around 28.5 psi, but on cold days, the pressure hovers around 29.5, and I was getting spurious alarms. I reset the alarm setpoint to 32psi. Take a look at every alarm condition. Make sure that you have set the set point, the units (psi, knots, rpm) are correct.

Glass panels are nice, give you lots of information, and have great audible/visible alarms - but they have to be properly set up before the first flight in order to be useful.

4 should be right

That's what I have my EIS set at with the same transducer/encoder.

Bubblehead said:

That's what I have my EIS set at with the same transducer/encoder.

Click to expand...

Thanks, nice to have a confirmation from the "database" out there.

Thanks guys

This was timely. I also have the GRT EIS with a Vans tach transducer with cable extension. I will keep this in mind when I go to program the unit.

spreadsheet

I have a spreadsheet with all my settings in it. One page for alarms and the other for settings. I'd be more than happy to post if somewhere for people to download. Any idea where I could do that? (hint to Doug)

The settings and alarms would be a good starting point for people. I think GMCjetPilot posted or offered one a year or so ago. That one helped me but I took it a little farther.

Bubblehead said:

I have a spreadsheet with all my settings in it. One page for alarms and the other for settings. I'd be more than happy to post if somewhere for people to download. Any idea where I could do that? (hint to Doug)

The settings and alarms would be a good starting point for people. I think GMCjetPilot posted or offered one a year or so ago. That one helped me but I took it a little farther.

Click to expand...

Can you email me a copy of it please???

Also, Doug has a list of stuff on the front page, under POH. That might be a good home for it also.

starkey.mike at comcast.net

Thanks,

Emailed it a few minutes ago.