Multi Sender CHT Gauge

Wow, I go away for a few days, and all this happens!

I've been working on an Arduino-based 4 cylinder CHT gauge. I bought an Arduino Uno and an LCD shield that snaps right on top. Also got 4 K-type thermocouples and 4 drivers(temperature compensated!) that interface with the Arduino, totaling about $40 so far.

The display is 2 lines of 16 characters, more than enough to display all 4.

I also run a 911 fan, with a machined down ring and aftermarket base and fiberglass shroud. This year I added a 911SC vane on the back of the alternator, which I trimmed for the shallower shroud. I've noted about 10 degrees less on #4, but that is the only cylinder with a gauge so far, an Autometer.

So I am interested in how TP's work goes and will contribute with my own.

Cheers!

After seeing the Airkewled mount I am thinking about adding a Dakota Digital CHT gauge and an Innovate Air / Fuel gauge.

With the DD CHT gauge would there be an issue using the 12.7mm sensor with 12mm sparkplugs? With the oversize hole in the sensor I thought there might be a problem with the sensor deforming or the spark plug not sealing.

I think I read on thesamba that it is bad to run the CHT wires near other wires. Is that really a problem?

I understand the reason to put the sensor on cylinder #3 on a non-doghouse shroud. But it sure would be easier to put it on #4. Any comments about that?

I would like to install the sensor without pulling the engine. In that case what is the best  way to get the sensor wire to the outside of the shroud if installed on #3? If I install it on #4 I could probably do a hole and grommet.

What is the appropriate length for the sensor wire? Is 10' too short? The next option is 14'.

Michael.....I was able to use the 10ft. wire and ran it under the carpet on the drivers side. Dakota said that running it next to other wiring isn't an issue. I ran the wire right out thru the spark plug wire hole.

The new silicone rubber plug wire-shield formed nicely around it to seal off air escaping. Not perfect like you are thinking of doing with a grommet though. Dakota said use your plug gasket not just the copper ring terminal on the end of the sensor wire.

Yes, access to #3 is terrible and #4 would be easier and a cleaner install. A choice you'll have to make. Maybe it's time to remember what your trying to accomplish by installing a CHT gauge?

I haven't had any problems with the sensor terminal deforming such that it's a problem. They do deform though because the plug torque spec. is a lot and the copper ring sensor terminal is soft. I did have one of the other terminals (about 10 inches up from the plug come off due to a bad crimp so now I have a spare sensor ring rig.   Hope this helps.........Bruce

Bruce, thanks for your reply.

Please tell me more about the new silicone rubber plug wire shields.

Do you have 1/2" plugs?

Did you put the ring terminal or plug gasket against the head? I have read that someone put the ring terminal between the plug and plug gasket.

Remember when tightening up the spark plug to keep a tight grip on the ring terminal so it doesn't rotate.

I understand the need for that but that sure seems hard to do with cylinder 3.

Yes, it's a real b*tch to get at.  That's why I fabricated new engine 'tin' (mine is made of fiberglass) so they can be taken out to get at the spark plugs. 

I would think you'd want the ring terminal against the head. I've seen where someone notched the side of the plug hole out and bent the connector part of the terminal up so the whole piece stays on the head when changing plugs. That way the terminal doesn't get mangled after a few plug changes. 

Might be a winter project, Michael- taking the engine out, stripping the shroud and tin off it and then you'll be able to set it up so you can set the connector in place. Someone please correct me if I'm wrong, but a connector (thermocouple) such as the 1 down below would allow you to attach the plug end through a grommet in the engine tin and be able to remove the engine without disturbing the spark plug ring.

The thermo coupler has a splice about 10 or 12 inches out that has little bolts that attach the next strand of wire (10'or 14')

So the motor can be removed without pulling the plug end off.

Ring terminal against the head-- there's no other practical way to do it. Use the plug gasket. It's very possible to have the ring terminal slip off to the side, etc., so make sure it's centered over the hole and the plug goes through it freely. Keeping it from spinning is the hard part-- installing the sensor before the shroud is the only way to fly.

The sensors are the pain in the butt part of this.

I used a sparkplug tap to put a thread in the ring, maybe half a thread.

Hi Michael......Install the sensor ring between the plug gasket and your cyl. head. The silicone lug wire shields look like the stock originals but I can't remember what brand they are...Sorry

I have 1/2" plugs and Dakota sent me the smaller rings, not the reamed out ones.

Someone here mentioned the two tiny terminal connections at the other end of the sensor ring. They are a real pain to connect and then slide the insulating sleeve over each one. So much so that what I do now is not disconnect there.

What i do now is remove #3 plug with the sensor ring when I remove the engine. For me, this is the easiest way. Yes...the sensor ring will spin a little when torquing the plug but won't interfere with anything because that area around the plug is clear and, as I said, I run the wire out past plug shield. I use a dental mirror to watch as I re-position that shield as good as possible...........Bruce