Cylinder Head Temperature Gauge - Should I? & or Air Fuel Ratio

Yes. Drill a hole in your cylinder tin and you can screw a sensor into it.

Just checked the heads on my van engine - haven’t got the hole/boss. Bum. Should’ve had my Autolineas machined out instead of those

 

Interesting.

@paulcalf do you have these threaded boss’ on your heads? What Snotty is suggesting is doable with the engine in - depending on their location. The one near #1 can’t be done with the engine in, but if it was dropped it could be. The rearmost can be with the rear tinware removed.

Mainline Sensors do an m10 CHT sensor.

For me i’d still prefer to do the head modification for sensor option on all for spark plugs. Just need to pass this 6mm diameter diamond dremel bit underneath the spark plug recess. The groove will make locating the sensor easier too.


I might as well, do the above too while I can because I have an m10 temperature gauge that was installed under an alternator bolt. Only reads up to 125•c though, so may not be appropriate. What readings would be expected from there?

http://www.coolantalarm.co.uk/shop/index.php?_a=viewProd&productId=25

This is twice the price of a Mainline Sensor Paul, but has an alarm.


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If you want to use the VW sensor, it’s still available: 311906041A. As used on injected Mexi 1600 AJ engines. Actually the same one used on injected type 4 engines (see Ratwell).

Thermistor-based, so you’ll have to get your soldering iron out to match it to a gauge. Better than faffing with thermocouples, IMHO.

 

I don't think I have any threaded boss on my heads

 

Darn.
Not sure what exhaust you have, but in the absence of a Lambda Sensor nut, this EGT sensor kit just requires a hole to be drilled for the probe to enter through:

https://www.mainline-sensors.co.uk/...-kit-1-8-npt-egt-2-meter-sensor-clamp-40-63mm

Not the CHT temps you were after but would at least give you some info.


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Type-4 heads are apparently tricky too, except 1700's. I got lucky!
@paulcalf It's a pity you tried to retro-fit the sensors and found you couldn't but in general terms these things are far from accurate so any head temp monitoring should indicate what is normal for your engine and show you when/ if it drifts off. IMO

One of the funny things about uncompensated cold junction CHT is that it will read up to 30 deg C higher in the winter. lol - it's just another general health indicator at the end of the day.

 

An EGT gauge will tell you nothing useful, unless you’ve got a gas turbine in your van. It’s pointless.

A lamba sensor will tell you useful stuff if you’re in to that kind of thing, but it’s un related to engine temps.

 

I’ll look in to it.
Found them but as usual very little information on them or matched gauges mentioned.

The soldering iron comes out for melting nylon, plastic welding and engraving wood. Actual soldering is advanced stuff!

My CHT & EGT (i’ve read that can help diagnose all sorts of weird & wonderful things, but only in conjunction with other gauges and the knowledge to do so - which i’ll acquire over time) are already thermocouples.

@zedders that is a very odd phenomenon! The Mainline Sensors are Cold Junction Compensated. Will be interesting to see how they behave. I’ll write a report...in 2023!


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Information overload alert !

My head hurts just wondering if it's all worth it when the readings ain't accurate ?
If I fitted one I'd call it Jackie after an ex who turned out be a compulsive liar ...

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Readings don't really need to be accurate to real world numbers, gauges just notify you if something has changed from 'normal'.

If my oil temp always shows 100C, but then suddenly shows 120C I know something has changed & would slow down / pull over and have a look what may be causing it.

Your oil temp gauge showed you something was up with your engine / cooling and then you were able to sort it and see the temp come down.

I didn't have CHT or 02 gauges, but if i had i may have known of my 'issues' earlier.
The reason i wanted 4x cht readings was in the hope it would show me if i had an issue with any cylinder.

If an 02 sensor read 14AFR all the time and then started reading 18, then i would know i had an issue with my air fuel ratio and could be running lean.
I still have neither CHT gauges or an o2 sensor, plus my oil temp gauge has gone pear shaped Hopefully temporarily!

 

I’ll call them:
Jackie
Jackie I
Jackie II
Jackie III
Jackie IV
Jackie V
...and my favourite...Jackie VI!


Yes, information overload. I’m now just super interested in how these machines actually behave.
A lot to learn...plenty to ignore, as things will fluctuate madly i’m sure. They’ll pay for themselves, one day, preempting something.

Really I just like the pretty lights so I don’t have to carry Xmas ones with me - so they save space too!


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@paulcalf
I found my spare. 48" long.
Yours...


Mine...




Yours looks the biz, mine looks cheap and nasty in comparison but it did fit without adjusting the head. Pure luck!

 

Excellent, that looks like it may fit.

Where did you get them from again? As im going to need two

 

Good question. I got it from ECAS 2CV parts, but they no longer sell them or the gauge.

 

They are definitely 48" J-type if you search. You could get from the states for $5.99 but cotton braided (ebay) https://www.ebay.com/itm/J-Type-The...or-Cylinder-Head-Temperature-CHT/172302303136

I'm sure if you search enough you'll find them somewhere.

 

Fortunately if you use a module based on the MAX6675 ... " The MAX6675 performs cold-junction compensation and digitizes the signal from a type-K thermocouple" so it stays accurate. It also works off voltage rather than current so it doesnt get affected by lead lengths, although I use 1m or 2m cables.