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

I don’t know if my CHT gauge is accurate or not but I know it works. I know that in normal driving in normal temperatures it will read to the left of vertical – that’s probably less than 300F. If it’s hot it will run hotter and I know the needle will be closer to vertical. If I’m on a motorway or climbing a long col in the Alps I back off when the needle goes much past vertical – that’s probably 400F but it might be 390F or 410F, I just know it’s hotter than normal so take some load off the engine, and that's the point for me.

2316cc Type 4 with the temp sender under #3 plug.

 

A single gauge with two senders and a changeover switch? Or just measure #3, or measure each cylinder in turn under the same conditions and choose the hottest to connect to permanently.

 

One gauge.
Showing 2 readouts (number 3 cylinder temp. Number 1 cylinder temp). No changeover switch etc
2 sets of wires - permanently going into the gauge: one set of wires from number 3, one set from number 1 cylinder

 

I have overheated between 2 and 6 cylinder heads (dont know about the state of my original engine, but the heads were cracked the first time I looked at them.) Definitely cracked the heads on my middle engine. Dont know about this one yet.
All 1641's pushing hard. So I use some kind of cylinder head monitoring as a matter of course now.

Its a pity but the sensor setup I am using uses maybe £50 worth of components, but theres is a lot of extra work put in there to tie it together.

But one thing you can do is with those Arduino boards is drive little dashboard instrument cluster stepper motors , so that you have "analog" dials with pointers on them. This is an example - a £5 circuit board and a £3 stepper motor. Add one voltage regulator, a resistor and a BBQ temperature probe and you have over 270 degrees of rotation on an analog meter, where you can easily extend the sensor wiring over 5m. Now work out how to fit it into a case and put that in a dashboard. The circuit board is about 5cm x 3cm.
The pointer on the stepper motor is a bit of rubber jammed on the shaft - stops me breaking it while messing with it.

 

I know you want a double gauge but if you can’t get one a single gauge with two senders and a changeover switch might work – but I wouldn’t bother, just measure the hottest cylinder.

 

I did the bbq thing just as a play to see it worked and easy to test accuracy and as I was building it was easy to pop in to existing head sensor holes so was stuck with no2 and no3 cylinders and it'll let me get an idea how oil/ head temps compare with dipsticks or sump and if turning engine off or leaving running is better etc

I'll have the twin spark plug set up on a twin gauge like the £40 one above on no 1 and 3 which are probably the hottest two just in case one carb goes over lean.. if i get it to work.. and a sump sender for oil long term... and afr.... and pressure..

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oh yeah i'd not thought of one gauge, but two senders and a switch, thanks.

 

One double gauge and 4 senders! . If 14mn ring senders were easier to find!

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How about this? https://www.ebay.co.uk/itm/Type-J-T...2349624.m46890.l49286&mkrid=710-127635-2958-0

Then make this... Worth experimenting?

 

That is what i'm thinking now. I've just been on the phone to a thermocouple cable supplier!

 

Right I have gone for this gauge & after speaking to them on the phone I ended up ordering 2 gauges!


He told me K type thermocouple 'cable' was what he thought I needed.

I then re read this thread and am now confused!

@zeddeers Correct me if I'm wrong but I now need to order 4 lots of 5m long Type K thermocouple.

Or will that mess up the readings as its too long?

 

If it takes K-Type then you can order 14mm ring sensors with 5m cable from Mainline Sensors. But that’s another £100 total for 4.
What’s the connection like on the gauge itself?
Is it illuminated?


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He said it came with about a foot of cable on the back. 2 inputs per gauge.

I'm hoping the mainline sensors cables (or other cable) will fit right onto the back of the gauge or i'll have to sell the gauges! At least i've not paid VW Jim prices for the gauges!

I doubt they are illuminated!

Perhaps 2 Mainline gauges (& 4 sets of cable) would have been more sensible, but when I looked into a switch for thermocables it looked like even more of a nightmare with voltage drops etc etc.

This entire CHT situation is beyond me, I should have paid more attention in physics!
I'm just going round in circles. Driving round in ignorant bliss has some appeal!

 

Could put K-Type connectors on them then.
I didn’t pay attention in physics either.


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Right i've changed my mind

Im getting 2 gauges and cables from mainline sensors
https://www.mainline-sensors.co.uk/...r-cht-5-meter-sensor-cable?variant=1127439593

I will measure temps at one and three: if there is a difference between the temps on each gauge it may highlight that i have a problem with that cylinder head.

If the temp on either of the gauges change from the 'norm' then it will also hopefully highlight i have an issue!

Not really happy with the look of them but i've had to give up as i've lost the will to live!

I'll consider Air Fuel Ratio gauges etc at a later time as that should be possible with the engine in place as i already have some wiring for this in place.

Thanks everyone

 

I don’t know how you intend to route the cables but I doubt if 5m is enough to go from the spark plugs under the engine to the front of the bus and up to the dash.

I liked physics, but it’s easier to read a tape measure.

 

Just want to throw my input...
I recently received my 2387cc beetle from a friend speed shop. Took years to do it, hence I don’t want to kill something in the engine.
Just read the entire thread on thesamba regarding the Autocraft 2.8 beetle (performance section).
On one hand, my friend told me oil pressure and temp is good enough (which I have) but no need for CHT knowing the CHT will vary depending on the load.
On the other hand, this Autocraft guy went all over the place with 4 CHT and 4 EGTs and O2 sensor readings through Innovate TC4s and wideband LM2.
I honestly don’t know what to do yet, go overkill or not, anyway, those 4 CHTs wired to the TC4 box is a nice setup, the box is behind the firewall (close proximity). It is linked in someway to the MSD 7AL (maybe just for the 5V ?, I don’t know), but at some point it gets complicated and confusing for me.

If you go the normal way, I guess you can check your reading on your CHT gauge with a thermo gun and see what is the difference at different temperatures, and maybe tweak the reading with a small resistance (?), if that is possible.

 

i measured from the back of the engine bay to the front which is less than 4 metre. Then i measured from floor up the dash which is less than a metre.

So hopefully i'll be good to go.

I'll probably go through the holes either side of the engine bay, along with all the other cables and have one gauge on either side at the dash end.

I would have gone for 8 meters per side but they are sold out!

 

Yep, that’s close to what I measured. Need a bit extra for easily routing in to each spark plug but I think that’s within the 5m. That’s if you aren’t adding connectors - in which case just don’t screw them up.

That link I sent you was for their 14mm, 8m long cable sensors. In stock buddy.
That’s if you have 14mm plugs - soz, I only checked them.


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That seems highly unlikely. Link to the gauge?