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Thread: Eis 4000

  1. #1
    Senior Member DanB's Avatar
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    Default Eis 4000

    Hope everyone is having a great holiday break and enjoying the season!
    As I am home this week I'm finishing up some of my last electrical connections to the 912s. The wiring hasn't been too bad, just tedious as most know.
    I am using a Grand Rapids 4000 EIS and would like to tap into those who are familiar with the CHT connections.( I called GR, but they are enjoying the week off as well.) The EGT connections are straight forward because each bayonet probe (that goes into an exhaust pipe) has two wires to plug into. There are 2 CHT probes provided on the 912s at cylinders 2 and 3. My question develops due to having two CHT wires (per cylinder head) to be connected with only one fast-on connection provided at the engine.
    So the question is...How is the connection made? The GR manual was very specific indicating that the two (dis-similar metal) wires be used to properly allow the thermocouple to send correct info...
    My common sence (sometimes not so common) tells me one of the wires goes to ground...but I don't want to guess at this.
    Any help would be appreciated.
    Dan B
    Mesa, AZ

  2. #2
    Super Moderator Av8r3400's Avatar
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    Default Re: Eis 4000

    If you use the two cast in locations on the heads, what are you using for a coolant temp location (or are you)?
    Av8r3400
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  3. #3
    Senior Member DanB's Avatar
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    Default Re: Eis 4000

    I was not planning on setting up water temp at this time, however one of the guys here said he thought he used one of these for his water temp. I'm looking at the Rotax install manual which shows these fixed tabs to be the CHT locations...so not real sure how to proceed?
    Dan B
    Mesa, AZ

  4. #4
    Senior Member cap01's Avatar
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    Default Re: Eis 4000

    its been awhile , but i think i removed the rotax temp bulbs and installed a metric bolt with the thermocouple under it in the cylinder head hole . i did use the origional temp bulb for water temp but not really sure if it was worth the trouble since the water temp is seldom looked at . ive got the cowl removed and will probably head out to the hangar this afternoon and i can take a look for sure. also all my diagrams are at the hangar .
    chuck
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  5. #5
    Super Moderator Av8r3400's Avatar
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    Default Re: Eis 4000

    Quote Originally Posted by DanB View Post
    I was not planning on setting up water temp at this time, however one of the guys here said he thought he used one of these for his water temp.
    Head temp and water temp are measured at the same location on a "normally gauged" 912. On mine the #2 cylinder is the head temp and #4 is the coolant temp.

    I'd love to do an electronic panel on my 1200 project, but the $$ is not there for it at this time. I'll redo the panel with what I have but prepare for a electronic refit eventually... (I'd love to do a Dynon FlightDEK D180!)
    Av8r3400
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  6. #6
    Senior Member DanB's Avatar
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    Default Re: Eis 4000

    Chuck and Larry, Thank you for your replys and information. Every little bit helps when trying to solve a riddle. After a little more digging I found out some good information concerning the provided probes on the Rotax engine vs. the thermocouples that the EIS requires for reading...


    The Rotax CHT probes are not thermocouples (with a plus and minus lead).They are resistors whose resistance varies (inversely) with heat (also known as Negative Temperature Coefficient or NTC probes). One side of the resistor grounds through the body of the probe to the head.
    As Larry mentioned above in this thread...the water temp lead CAN be used from the EIS to the "CHT" probes on the engine because it IS an NTC probe and only requires the one wire. This is the same as we find for the oil pressure and oil Temp. probes.
    The EGT theromocouples are straight forward as the bayonet probes are inserted into the exhaust pipes and wired up. For the CHT thermocouples, there are a couple choices...one is a probe inserted into a housing that is threaded between the head cooling fins. The other choice is a ring that fits over the spark plug opening and is held in place as the plug is tightened. Either of these can be purchased from GRT or, come with the kit. I didn't have these and that is where my headscratching started
    I have decided to order a couple ring-type and call it good (I like easy).
    Hope this helps others in the future.
    Last edited by DanB; 12-28-2010 at 09:07 AM.
    Dan B
    Mesa, AZ

  7. #7
    Senior Member cap01's Avatar
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    Default Re: Eis 4000

    dan , i did check my engine last nite and i did use the ring thermocouples . i didnt install it under a spark plug but rather under a bolt in the cylinder head where the rotax temp probs was installed . for the water temp , i have a piece of pipe with a boss with the rotax temp probe installed . i think ive seen the same thing for sale in a lockwood catalog . and you are correct , the rotax probe does require a ground .
    chuck
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  8. #8
    Administrator DesertFox4's Avatar
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    Default Re: Eis 4000

    Dan, I used the thermocouples like Cap01. I should have taken my camera the other day and sent you a photo to go with my explanation. Maybe the EIS kits have changed since I installed mine. Mine are also not on the spark plugs but on the cylinder heads. They are black in color with a ring end. Might have been a choice available at purchase time from GRT per recommendation from others.


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  9. #9
    Senior Member DanB's Avatar
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    Default Re: Eis 4000

    Chuck, using those rings under the Rotax Temp probes sounds inviting to try. The down-side to the rings on the plugs just seem to be a little more tedious when time to check or change plugs. Thanks for the info!
    Dan B
    Mesa, AZ

  10. #10
    Senior Member Esser's Avatar
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    Default Re: Eis 4000

    Old post being brought to life. For the CHT temperature “probes” can I just put the two thermocouple wires together in a standard ring terminal and bolt to the head? I think this is fine I just wanted another opinion.
    ------------------
    Josh Esser
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