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GRT EFIS/EIS interconnect

Scott Hersha

Well Known Member
This is a question for the GRT experts. It?s Saturday and I just completed my panel upgrade yesterday and have a couple questions about programming/configuration - and GRT isn?t open on the weekend, so maybe someone here can help. I have a new Horizon 10.1 EFIS and a new MINI-X for my RV4, with a legacy EIS from about 2003. The EIS is mounted behind the panel on a hinge so I can tilt it down and see it if I want to, which I doubt I?ll do. When I started the engine (new SureFly mag, and rebuilt Slick), I had multiple alarms. I probably have too many limits programmed, and I will change/eliminate some of those today, but a couple of the indications were way off. I set all limits to zero in the EIS, but configured them in the Horizon. But - I DID configure scale factors and offsets in the EIS, as well as the Horizon. I?m wondering if that might be wrong. I have 4 aux inputs in my older EIS: fuel level left; fuel level right; fuel pressure; and manifold pressure. The first three of these are fed power from the 4.8 volt EIS power pin and that power is filtered through a resistor - 470 ohm for fuel level, and 200 ohm for fuel pressure. I?m guessing all those aux inputs should only have scale factors configured in the Horizon EFIS and set to zero in the EIS, but unable to get any clear direction from the GRT install manual. That may be causing some of my weird indications.

Thanks
 
Not an expert

Thinking logically, unless the new EFIS allows direct sensor input, all engine data is configured where the probes go , the EIS. The EFIS is in many ways is just a different representation of the EIS data. Get the data responding correctly eg: offset, scaling factors , integer/decimal, -/+ sensing on EIS correctly. I believe moving the data over to horizon EFIS is just one pin. I have Sport SX, Mini-x and EIS 4000. I use same for AUX eg: left right tanks, fuel pressure, manifold pressure. Good luck Scott.
 
I agree with Butch. I have a Sport and one wire (RS232) connects it to the EIS. All offsets/factors are set on the EIS.
You can set limits on either unit (or both if you really like alarms :cool:). I do everything on the EIS for simplicity.
 
I agree with Butch. I have a Sport and one wire (RS232) connects it to the EIS. All offsets/factors are set on the EIS.
You can set limits on either unit (or both if you really like alarms :cool:). I do everything on the EIS for simplicity.

+1

Scale/offsets should be done in the EIS only. While I can't be certain, I would highly suspect that doing it in both will create inaccurate readings. Mine is done this way and works properly.

Larry
 
y=mx+b

The scale and offset are just slope and intercept. If you apply this twice (EIS and EFIS) the data is gonna go wonky. Set the scale and offset in EIS and set limits in EFIS. The EFIS is fed serial sensor data. I think the Sport has configurable inputs for minimal engine data and I would suppose the scale and offset would be able to be entered on those lines, but if all the sensor lines are going into the EIS, then only scale the data in the EIS.

Dave
 
Thanks for the input. This will be easy to change in the EFIS, since my EIS is hidden. There is a place in the horizon EFIS to configure the EIS scale factor and offsets for EIS aux inputs, but it makes sense not to do it twice. I do have to tell it what each aux input is for, like fuel pressure, otherwise it doesn?t know where to put it on the engine screen. But I don?t think I need to enter scale/offset info. Guess I?ll find out. You are right - just one RS232 line dumps all the information into both the horizon and the mini.
 
As it turns out, there isn?t a place to enter scale factors/offsets in the EFIS, just what the various aux positions are and whether decimal or integer. I?m still showing 27 gallons fuel on the left and 42 on the right for aux1 and aux2, but I haven?t calibrated them yet (I have about 5 gallons in the left and 3 on the right), and initial scale factor is 100, offset 0. Maybe that will change when I calibrate, but it seems very far off. Also my fuel pressure is indicating 57 psi with the engine running - on a carbureted engine. It was a normal 5 psi before the upgrade with the same sender and the same EIS....... not sure what to think about that.
 
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