Itinerant Air-Cooled

I have started a new post since my original has gotten sidetracked.
viewtopic.php?f=50&t=12618


So let us look at it this way. You have a ring terminal, I dont. You install the terminal under plug and go to tighten the plug. The end of the thermocoupler wire is in the way of the socket so you bend it out of the way and in the process it comes in contact with the head just beyond the plug recess. It looks something like this

This is what I have minus the ring.


In this case the ring has become a means to hold the thermocoupler ends in place. Yes the ring does conduct energy but any heat sent to the ends of the thermocoupler will be shorted out but the contact that the ends are making with the head and this is where the temp reading will come from. Some may say why not just get a new ring and be done. Well the reason that the ring is missing is from pulling the plug many times, it broke off, and I know that I will continue to pull the plug for whatever reason. I figured this was equal to the ring and this is a less destructive method on the thermo end. Granted I may have missed something so if someone has info that helps in this situation then please do tell.

Thanks,

I think you figured wrong as the thermocouple ring needs to be around the spark plug to get a accurate reading. A new thermocouple cost $11.95 so it's cheap to replace it what every 5 years? I change my plugs every 5000 miles which is at best every 3 years so I am still on my first ring.
Now accurate CHT readings to me are important especially when I was just in 110F temps hitting 410F CHT's going up hills.

I, on the other hand, have driven 5000 miles since October, and would really like to have a suitable alternative to the plug ring. My plugs are deeply recessed in the head, so the ring requires malformation just to fit.

...for what it's worth, I reordered v323701 VDO CHT 14mm sending unit and harness from aircooled.net. The sender seems to fit better than the original sender that came with the gauge kit... which got pretty mangled on my old engine. The downside is that I have a harness I don't really need, but I was under the impression that the sender was no longer available alone.
BellePlaine also has some CHT and thermocouple ideas on p.3 of his Type 2 thread entitled "resilience"...
Miz

Also, although I might be misremembering, I swear that Colin once told me that VDO CHT gauges read with respect to "ambient" temps. (~70*F). I interpreted this to mean something to the effect of: if you have a 410* CHT on a 110* day...you really have a ~370* CHT...and if you have a 410* CHT on a 40* day you really have a 450* CHT...that said, if I exceeded 425* CHT on a 100* + day, I might just pull over for a while. Again, I might be misremembering, misinterpreting...or just totally full of baloney...
Miz

I thought he meant the opposite...If ambient is 110, the VDO considers 110 equal to 70, and therefore 400° on the VDO is actually 440°. I have proven myself to be full of baloney...

...that's probably right, now that I think about it more, it makes more sense to add differential over ambient...or at least it's more prudent to think about it that way...
Miz

the miz wrote: BellePlaine also has some CHT and thermocouple ideas on p.3 of his Type 2 thread entitled "resilience"...
Miz

Thanks Miz. I took a look and he did some cool things but it is still the ring around the plug.

The way I look at it the ring serves as a means to connect the end to the engine with the least amount disruption to the head. The heat energy is still transferred to the end through the ring so if the end is placed at the point where heat is measured then it should be correct. My original question addressed the location. Is this close enough to get correct readings? If people are installing the ring as in the first pic I supplied, which seems to be accepted, then yes the heat energy should be the same on mine.

Within the next 2 years I will be rebuilding my engine so this is almost experimental. I will want to install a sender which is most sensible for accuracy and yet is not in the way of maintenance.

cegammel wrote:I thought he meant the opposite...If ambient is 110, the VDO considers 110 equal to 70, and therefore 400° on the VDO is actually 440°. I have proven myself to be full of baloney...

Yes this I the correct way to read the VDO. I do this on the fly and here in Mn the temps are very close to the ambient all summer long.