Eis 4000

[DanB]

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.

[cap01]

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 .

[DesertFox4]

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.

[DanB]

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!

[Esser]

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.