CHT differential greater than 100 degrees in cruise

[Buckeyechuck]

2 hours ago, PT20J said:

Curious what the difference in temps was between the bayonet and ring on cyl #3. 

For mine it was about 80 degrees. 

[PT20J]

I’m really surprised that the ring connector on the bayonet is showing so much lower temperature. Mine, installed on cyl #3, on a 1994 M20J with a IO-360-A3B6 only reads 20 F lower than the factory gauge.

Skip

[Buckeyechuck]

12 hours ago, PT20J said:

I’m really surprised that the ring connector on the bayonet is showing so much lower temperature. Mine, installed on cyl #3, on a 1994 M20J with a IO-360-A3B6 only reads 20 F lower than the factory gauge.

Skip

We removed the bayonet mount, to look for an irregular surface or paint that could be insulating and reinstalled it with a new washer. No change at all. Talked to JPI, no help. Looked for the old style TC that replaced the bayonet mount but couldn’t find one. A friend had the same issue on his bonanza and solved that way. JPI says they discontinued them due to issues with grounding. 

[rcwagner]

Another item to think about:

 

When buying the ring type probe, you have the option of a "J" or "K" thermocouple.  They read about 100F different in this application if you get the wrong one (I learned by experience and they are not returnable after being used.)

[PT20J]

3 hours ago, rcwagner said:

Another item to think about:

 

When buying the ring type probe, you have the option of a "J" or "K" thermocouple.  They read about 100F different in this application if you get the wrong one (I learned by experience and they are not returnable after being used.)

I bought mine from JPI. All their probes are Type K according to their website. There is a review on Aircraft Spruce that says "reads a little low." 

[jaylw314]

20 hours ago, PT20J said:

I’m really surprised that the ring connector on the bayonet is showing so much lower temperature. Mine, installed on cyl #3, on a 1994 M20J with a IO-360-A3B6 only reads 20 F lower than the factory gauge.

Skip

I'm guessing the fact there was no bayonet probe installed in it makes a big difference?

[Buckeyechuck]

26 minutes ago, jaylw314 said:

I'm guessing the fact there was no bayonet probe installed in it makes a big difference?

My installation is standard; a ring type thermocouple under the bayonet mount with a crush washer.  The factory bayonet type thermocouple is installed as originally intended. What I was referring too was an old style thermocouple made by JPI that took the place of the factory bayonet mount and eliminated the ring thermocouple. It was discontinued due to issues with grounding causing problems with the unit. 

[MBDiagMan]

Have the injectors been cleaned?

[PT20J]

17 minutes ago, Buckeyechuck said:

My installation is standard; a ring type thermocouple under the bayonet mount with a crush washer.  The factory bayonet type thermocouple is installed as originally intended. What I was referring too was an old style thermocouple made by JPI that took the place of the factory bayonet mount and eliminated the ring thermocouple. It was discontinued due to issues with grounding causing problems with the unit. 

Ah, now I understand. Thanks for the clarification.

Skip

[Buckeyechuck]

1 hour ago, MBDiagMan said:

Have the injectors been cleaned?

M20C. 15 hours on Penn Yan overhaul. Installed JPI with engine. Factory gauge reads same as cylinder no. 4. 

[jaylw314]

17 hours ago, Buckeyechuck said:

My installation is standard; a ring type thermocouple under the bayonet mount with a crush washer.  The factory bayonet type thermocouple is installed as originally intended. What I was referring too was an old style thermocouple made by JPI that took the place of the factory bayonet mount and eliminated the ring thermocouple. It was discontinued due to issues with grounding causing problems with the unit. 

My bad, I was conflating you with the OP

[Buckeyechuck]

So latest update for me. I got frustrated with the ring TC and found that Insight still makes the bayonet mount TC. Both TC’s are type J. Any reason I couldn’t replace the JPI ring TC with Insight Bayonet mount?

[carusoam]

Chuck,

You may want to ask your mechanic before he swaps things out for you… 

Confirm the type of thermocouple being used…

From fuzzy memory… I’m thinking K type is the one most used…

Sooo… confirm which one you need.  Because mixing different TC types will be disappointing…

The wires and jacket are color coded so you know what type they are…

PP thoughts only… not a mechanic…

Best regards,

-a-

https://www.jpinstruments.com/FAQ/thermocouple-wire-type-2/

[Buckeyechuck]

I have confirmed they are both type J.  I believe J’s are typical for CHT and K’s are typical for EGT.  K range is -330 to 2460 degrees F. J range is -40 to 1382 degrees F. 

[kortopates]

19 minutes ago, Buckeyechuck said:

I have confirmed they are both type J.

That's the main part, there is also grounded and ungrounded Type J. If memory is right JPI uses grounded but you'll have to check and Insight may not.

[Buckeyechuck]

Could be why JPI doesn’t make the bayonet mount TC anymore. When I called about my readings and ask about the old style they said it was discontinued because of grounding issues. 

[Buckeyechuck]

SO my idea about using the Insight bayonet mount turns out to be a dud. The JPI CHT ring type TC turns out to be a type K.  I’m either back to the ring connector which has erroneous reading or installing a bayonet on no. 3 and removing the factory TC. I could always tie it up for re-install when it’s time to sell. For now the decision is, do I want it FAA correct or do I want to know what is really going on with my engine.  No I’m not ready to go to the 930 primary gauge route. 

[PT20J]

According to JPI’s website, all their probes are type K. They still make bayonet CHT probes (I purchased one recently). All current JPI probes are grounded. It is the ungrounded probes that were discontinued 35 years ago. 

Skip

 

[Buckeyechuck]

26 minutes ago, PT20J said:

According to JPI’s website, all their probes are type K. They still make bayonet CHT probes (I purchased one recently). All current JPI probes are grounded. It is the ungrounded probes that were discontinued 35 years ago. 

Skip

 

I talked to them a while back about purchasing the bayonet mount probe and got absolutely nowhere. Guess I need to try again. In my opinion, it’s a no-brainer. 

[PT20J]

55 minutes ago, Buckeyechuck said:

I talked to them a while back about purchasing the bayonet mount probe and got absolutely nowhere. Guess I need to try again. In my opinion, it’s a no-brainer. 

https://www.jpinstruments.com/shop/cht-bayonet-probe/

But I don’t see how this helps unless you have a primary instrument because you still need the factory probe.

Skip

[carusoam]

16 hours ago, Buckeyechuck said:

I talked to them a while back about purchasing the bayonet mount probe and got absolutely nowhere. Guess I need to try again. In my opinion, it’s a no-brainer. 

Interesting pirep for JPI customer service…. 

I’m pretty sure JPI doesn’t actually have a customer service group…. (When compared to other companies)

When looking for JPI info I always ask @Jeev.  Jeev sells their products out in the Vegas area… and knows insiders at JPI…

 

When it comes to addressing the 5 TCs in four locations there are known best methods for handling this on Mooneys…

Last I checked, JPI has all the parts…

Jeev’s Wolf Aviation sells the JPI parts…

You can get good data, and be FAA compliant, at the same time…

Best regards,

-a-

[Buckeyechuck]

I’ve contacted Wolf Aviation to see what they have.  Thanks for the help. 

[Buckeyechuck]

I think there is some confusion with what I was looking for. I was trying to get the mounting boss for the bayonet mount where the thermocouple wires are welded to the mounting boss. I have a bayonet mount but that would replace the factory unit. Insight makes this but it is a type J. JPI used to make it in a type K but they don’t make it now. 

[carusoam]

Chuck…

There is always going to be some confusion…. There are a lot of people around here…

Count me as one of the confused to what you are looking for…

1) Pics always help the rest of MS understand what you are looking for… 

2) From the JPI link at the top…

“GEM/INSIGHT uses J-type –ANSI* color code of White and Red in a Black jacket: ‘White’ -Iron –positive (+) magnetic
‘Red’ – Copper-Nickel – negative (-) “Constantan” –non-magnetic.”

3) Not sure why JPI is giving so much detail about the other guy’s probes… unless they sell them as well…

4) generally speaking there are three parts to have…

• The well… threaded hole in the cylinder…
• The part that screws into the well… the adapter… https://www.aircraftspruce.com/catalog/inpages/grandrapidchtadp01.php
• The thermocouple… with the spring loaded part that holds the TC at the bottom of the well… bayonet style, type J or K…

5) For the ship’s gauge… the FAA required one… Most MSers leave that in place and use a separate TC to supply the best data possible to their engine monitor… some Mooneys use a ring type that fits under the adapter… a few use one that doubles as a spark plug gasket…  
6) Some Mooneys got a thermistor, and not a TC…

 

7) The Good news… if you have an EI engine monitor… we have a great resource for that…

 

PP thoughts only, all stuff I learned around here…

Best regards,

-a-

 

[Buckeyechuck]

https://https://www.aircraftspruce.com/catalog/pnpages/2856.php?gclid=EAIaIQobChMI1pqP56Wu8wIVZAp9Ch1gJwk2EAQYAiABEgJIJPD_BwE

This is the Insight piggyback thermo couple probe. JPI used to make this in a type K. My avionics guy has installed them.  A friend has one in his Bonanza. Much more accurate than the ring under the mounting boss.