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GRT EIS Monitor "gotcha"

f1rocket

Well Known Member
If you are using a GRT EIS and plan to use a Lightspeed Engineering ignition in place of one or both of your magnetos, be aware that you cannot drive the tach input of the EIS from the LSE unit without internal modifications to the EIS. If you tell them about this when you order the EIS, they can make the modification before they ship it to you.

What bums me out more is that you cannot drive the tach input from both ignition systems at the same time. Therefore, you can't do a mag check at run up. You have to pick one or the other, or add another switch to your panel to switch tach inputs. I don't care for that. I don't need another switch in my panel.

I sure hope the EFIS units are a little better thought out than the EIS unit is. The wiring diagram/installation manual makes your head spin.
 
Randy,

I really don't know anything about this as I am just a lurker, but what kind of switch are you using to control your mags? The key type? Toggle witches? I guess I'm wondering if there is a way the tach signal could be controlled by the same physical switch as your magnetos? And therefore would do the switching for you automatically. Maybe some type of double-pole switch?

-or-

Is there such an electronic 'switch' that you could put in-line between the ignition and EIS. It would have two wires going in, and one coming out. It would default to passing through the left mag (for example) signal (voltage?) unless there was no signal, and then it would switch over to the right mag, until the left mag signal was restored, when it would revert back to the default.

Just thinking, er typing, out loud.

-Jim
RV-10 want-a-be-bulder/flyer
 
Well, if you use a Gerdes-style key switch, you're hosed.

I don't. I'm using two toggle switches per the Aeroelectric Connection. That normally would be great because I could use the other side of the DPDT switches to also switch the tach inputs as well. However, I'm using a progressive transfer DPDT switch which allows me to use the temporary "UP" position to activate the starter. Unfortunately, this type of switch will not allow me to use it to switch the tach inputs because one side of the contacts are "ON" when the switch in in the center position, while the other side of the contact are "OFF".

The real solution is to use two DPST switches for the mags/ignition and use a push button for the starter. Then it would all work. Too late for all that. I'll just measure the RPM from the tach and get on with it. Otherwise, I'll be another 6 months before I get in the air.
 
Randy,
I am using the GRT EIS/one LSE/one mag and pick up the tach signal from the mag. This way, if the mag drops out (and you probably wouldn't feel it while in cruise), the tach reading will alarm on the EIS and I'll know that I don't have that mag for backup anymore.

Mag check during runup: easy to see (and hear) the RPM drop when running off the mag, but no change detectable by sound/feel when running on the single LSE.

There might be holes in this theory.
 
Just to help me visualize, do you have a switch for each magneto, with one of them having the temporary ?UP? position active the starter? Or do you have one switch that controls both magnetos and the starter. Is this for a dual electronic ignition, or one electronic/one magneto? Are the links below the switches and diagram you are using?

Still slightly confused?but learning. Thanks! :)

-Jim

P.S. purely for the sake of building a knowledge base on this site here's some research I did to figure out what you were talking about?you know, that whole NG/lurker thing. <g> Maybe it?ll save someone else a few google searches.

DPDT = Double-Pole, Double-Throw
http://www.aeroelectric.com/
http://catalog.sensing.honeywell.com/printfriendly.asp?FAM=tr&PN=2NT1-10
http://www.aeroelectric.com/temp/ProgressiveSW.pdf
 
I have two switches, one for the mag, one for the EI. They have three positions. Down for OFF, middle for ON, and spring loaded to up for ON.

My wiring diagrams can be found on my website. Look under F1 Rocket Project.
 
EIS with one mag

I have an EIS4000 with one EI and one mag. I have the tach signals wired so that the EIS reads the mag signal until the mag is turned off then it reads the EI signal. GRT will fax you a copy of the wiring diagram if you call them. The problem is the EIS will only take one tach calibration number and the Lightspeed batch fires so it's off by a factor of two. This really isn't much of a problem.

I ran my engine tonight for the first time and there is NO rpm drop with the mag off. I figure you are really only testing the one mag when doing a mag check, the EI will run or it won't.

I have two toggle switches and a starter push buttom.

There are some small things about the EIS I haven't liked but customer service isn't one of them, if you have a question give them a call, they are great to deal with.

Cam
 
grt eis "gotcha"

Randy, thanks for the heads up, I have an EIS 4000 on order and saw your advice, gave the GRT folks a call. Apparently "the fix" applies only to Plasma II ignitions which I also have on order (one side only mag on the other), they were more than happy to make the mod before sending it out to me, could not have been easier! Thanks again, these lists are great. :)
Mark Mercier
RV-7A C-GQRV reserved
 
EIS Tach hookup

I took a slightly different aproach. I got the tach sender from Vans. It's used for their branded electric tach gauge. It simply screws into the physical tach cable location on the back of the engine. You give it 12v, & ground and it gives you pulses per revolution back out. That way either the mag, or electronic ignition on or off, even all off, you still get a tach reading directly from the engine.
 
I just checked your pictures on your web site of the Van's tach unit. Good thing I did. It looks like it won't fit on my engine because I have an auxiliary alternator mounted on the vacumn pad. Darn.
 
Extension

I think they also have an extension cable to handle that situation. It's about a foot long and allows the sensor to be mounted on the firewall. Kind of a flex drive shaft of sorts. Look here: Van's Tach page
 
EIOS Tach drive

f1rocket said:
What bums me out more is that you cannot drive the tach input from both ignition systems at the same time.
akarmy said:
I took a slightly different approach. I got the tach sender from Vans. It's used for their branded electric tach gauge. It simply screws into the physical tach cable location on the back of the engine. You give it 12v, & ground and it gives you pulses per revolution back out. That way either the mag, or electronic ignition on or off, even all off, you still get a tach reading directly from the engine.
I also had the same question/issue and came to the same solution, using a Tach drive sender. However I used one from UMA instruments and it is much smaller than Van's sender. The unit is small, light and works on 5V, I think the sender puts out 4 pulses per revolution. The tach drive is at 1/2 RPM, so you get 2 pulses per crank revs; therefore tach setting on EIS is 2 (i think check manual).

Westach/Westburg makes a small sender also, but don't care for their products. :mad:

Some people have made little circuits to takecare of this, by switching the tach pickup to the active ignition during a "mag check". I saw schematics, but it seemed overly complicated. I can see that the Tack dropping to ZERO during a check would bother some. It is not a big deal, but as suggested, call Greg at GRT, I think he has one of these work arounds.

Cheers G RV-4, RV-7 project :D
 
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