M20E High CHT

[211º]

Last night while on a fuel run for some $3.79 fuel, I departed Snyder Field (K62) for Cincinnati Lunken (KLUK).  It was about 80 °F outside.  On climb out, I saw #3 CHT climb to 450 °F - The highest I usually see is about 395 °F.  I have an EDM 730 and usually monitor #3 - because it is historically the highest CHT.  

Well, over 400 made me unhappy and 450 made me even more so.

My #3 has a factory ring on the spark plug to measure CHT as well as the four CHT monitor probes.  The problem was that I wasn't 100% sure which lead was feeding the EDM 730 from #3 - the spark plug or the standard probe below.

So I decided to pull the spark plug out and take the monitor ring off then warm up the plane and make sure that #3 was staying relatively low.

Last night while thinking of this plan, I realized I could do something else...

My younger son and I headed to KLUK, took the spark plug out, took the ring off, then (while my son was videotaping) the EDM and me, surrounded the ring probe in a ziplock bag of ice water.

Confirmation made!   

For some reason, the people that installed the EDM used the ring probe - even though they also installed a screw-in CHT probe in the block too.

File Jun 12, 17 38 13.mov

[M20D6607U]

I have the same thing, the ring is for the factory CHT gauge. On my plane anyway. 

Edited June 12, 2017 by M20D6607U

[Guest]

Unless your engine monitor is certified as a OEM Replacement your CHT should be the standard bayonet style probe and the monitor should use either an adapter probe or a ring probe under the factory probe or in a worst case a spark plug ring.

Clarence

[cnoe]

Just like Clarence said. It sounds like the installation was correct. You'd gain some accuracy by purchasing and installing the optional piggyback probe.

The installation manual says... "Most factory installed cylinder head temperature gauges utilize a bayonet or screw-in resistive type probe that occupies one of the bayonet sockets. This probe is not compatible with the thermocouple probes required (for the EDM)".

Even with the plug ring 450 F. sounds excessive; what were your other temps? Also, those rings can get hard and might need annealed to seal properly. Just a guess.


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[carusoam]

+1 on getting the newer low buck ring TC. It goes close/under to where the ship's CHT gauge is. (Improved accuracy)

+1 dump the old ring under the spark plug TC. It gives crummy data and usually gets beat up each time the plug gets removed at annual...

PP ideas I have learned about on MS...

Best regards,

-a-

[211º]

In tracing the wires back, it appears that my spark plug style sensor does indeed come back to my EDM and my standard EDM probe comes back to the factory gauge. This evening I noted that the factory CHT was very similar in easurements with the CHTs on 1, 2, & 4 on the EDM.

 

 

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[75_M20F]

Does JPI sell a probe that will  attach to the OEM CHT probe? I don't see anything like that on the jpi website plus my mechanic said it's not available from JPI........

 

I too have that spark plug sensor on number 3. I would like to improve accuracy, as it reads 25 degrees hotter then the other 3 CHT probes.

Edited June 30, 2017 by Mooney_Mike

[carusoam]

JPI or EI have sensors of various styles...

1) the usual sits in the well type.

2) the one that sits under the spark plug. Large ring... goofy data and often destroyed by annual maintenance (about 50° F too high)

3) the one that sits under the TC well . Small ring... closest to the ship's TC (about 25° F high)

4) It is Best to leave the ship's gauge connected to the ship's TC.  Use the small ring TC mounted under the ship's TC retainer.

verify that all the TCs you have bought are the K type or whatever type matches your JP/EI/xxx

I think the EI website made it easy to select the proper TCs.  JPI made it seem like you needed an engineering degree to buy the proper device.  It shouldn't be that hard.  

If it was easy they couldn't charge so much?

PP thoughts not an instrument guru...

Best regards,

-a-

[Guest]

4 hours ago, Mooney_Mike said:

Does JPI sell a probe that will  attach to the OEM CHT probe? I don't see anything like that on the jpi website plus my mechanic said it's not available from JPI........

 

I too have that spark plug sensor on number 3. I would like to improve accuracy, as it reads 25 degrees hotter then the other 3 CHT probes.

The M113-3/8 is a ring style probe which you can install under the existing factory CHT probe.

https://www.jpinstruments.com/shop/m113-38-cht-gasket-probe/

Clarence

[Hank]

It doesn't pay to mix thermocouple types, a lesson we are still learning at work . . . Bought a new machine, used a spare TC from the old machine, wondered why we were having trouble getting the plastic to melt properly. Brought in a Service Tech for half a day before the error was found. Mixing Type J and K thermocouples gives poor results . . . .

[M20F]

Unless I am missing something he has a factory CHT so the JPI is not a replacement so he can use whatever probe for the JPI he wants?

[75_M20F]

Im saying the hole to stick the bayonet CHT probe in is already occupied by the one CHT probe that came from the factory this is on #3 cylinder only. 

Is there a way to put the JPI bayonet CHT probe in the hole and move the factory one out of there and onto the spark plug or somewhere else legally?

I don't see anything that JPI sells that will piggyback on the bayonet type to allow both the factory and the JPI probe to occupy the same port on the cylinder.

 

 

[DonMuncy]

Bear in mind that the factory gauge is a thermistor (variable resistor to ground). The JPI uses a thermocouple. Totally incompatible, in that you can't hook the wire on one from the other. However, thermocouples are available that will go under the thermistor, similar to the ones which go under a spark plug. Not sure whether JPI has them, but you can get them from other sources.

[Guest]

Unless your JPI system is certified as OEM replacement, your factory CHT system has to work as originally certified.  Therefore it will use the one and only Lycoming hole in the cylinder head.  You can use the JPI M113-3/8 ring thermocouple as stated above.  You remove the factory probe slide the JPI probe onto the probe and reinstall it.

Clarence

[takair]

211, I'm not following, do you think you are getting false readings?  It seems to me you may have actual high readings, especially for an E.  Do you have a cowl closure?  Have you checked baffles, mag check, injector, etc?

[211º]

I no longer think that I am getting false or high readings.  Initially, I thought that there was an issue and very high readings on Cylinder #3.  I now think that I am indeed getting high readings on the JPI on Cylinder #3 - but that is because the CHT probe for #3 on the JPI is around the base of the spark plug... not the cylinder probe sensor.  As someone noted, the Lycoming provided CHT “hole” on the cylinder (#3 in this case) has to lead back to the CHT gauge in the cockpit (not the JPI).  

So, my original CHT gauge (analogue gauge) is reading consistent with the Cyl 1, 2, and 4 on the JPI and the Cyl 3 on the JPI is reading about 50 degF higher (which is expected with the spark plug base sensor).

Hope that helps clear it up.

[211º]

Oh and mags and injectors check out - about 0.4 gph spread.  Baffles - could be fixed/improved, but the MSer on the forum that does them, doesn’t yet have a template for an E.

[jetdriven]

On 6/30/2017 at 6:43 AM, M20Doc said:

The M113-3/8 is a ring style probe which you can install under the existing factory CHT probe.

https://www.jpinstruments.com/shop/m113-38-cht-gasket-probe/

Clarence

That's simply a 12$ 10mm washer thermocouple. I put one on years ago. 

http://www.overnitesupply.com/wtk38-2424typekwasherstylethermocouplegrounded38studsize24stainlesssteelbraidedleadssplitwithspadelugs.aspx

better link / selection  http://www.tcdirect.com/deptprod.asp?deptid=180/40

Edited July 1, 2017 by jetdriven

[takair]

2 hours ago, 211º said:

I no longer think that I am getting false or high readings.  Initially, I thought that there was an issue and very high readings on Cylinder #3.  I now think that I am indeed getting high readings on the JPI on Cylinder #3 - but that is because the CHT probe for #3 on the JPI is around the base of the spark plug... not the cylinder probe sensor.  As someone noted, the Lycoming provided CHT “hole” on the cylinder (#3 in this case) has to lead back to the CHT gauge in the cockpit (not the JPI).  

So, my original CHT gauge (analogue gauge) is reading consistent with the Cyl 1, 2, and 4 on the JPI and the Cyl 3 on the JPI is reading about 50 degF higher (which is expected with the spark plug base sensor).

Hope that helps clear it up.

You may also want to confirm you don the have an exhaust leak that is heating the spark plug/thermocouple.  I have seen that throw these readings off.

[75_M20F]

3 hours ago, jetdriven said:

That's simply a 12$ 10mm washer thermocouple. I put one on years ago. 

http://www.overnitesupply.com/wtk38-2424typekwasherstylethermocouplegrounded38studsize24stainlesssteelbraidedleadssplitwithspadelugs.aspx

better link / selection  http://www.tcdirect.com/deptprod.asp?deptid=180/40

Which one on the tcdirect page will fit under the factory CHT probe, and is it compatible with the JPI EDM 700? The 201-250?

Edited July 1, 2017 by Mooney_Mike

[Heloman]

If your E is a not even certified to part 23 like my C, then I disagree you even need to keep your factory CHT at all. Is it in the TCDS?


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[gsxrpilot]

Just a note for anyone purchasing a new engine monitor... for roughly the same price as a JPI EDM-700 or an EI UGB-16, you can get an Insight G2. It is certified Primary for EGT and CHT for our airplanes. It also includes fuel flow, a MUCH better screen, and the best data recording capability of any engine monitor. 

I realize most of us already had the EDM-700 in the plane when we bought it, but I really don't understand anyone buying one today with much better options on the market.

[cnoe]

Which one on the tcdirect page will fit under the factory CHT probe, and is it compatible with the JPI EDM 700? The 201-250?

That looks like the right one. I have this style on my installation but sadly paid JPI full price for it. This CB wishes Jetdriven had made his post 2.5 years ago.


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[cnoe]

15 hours ago, Heloman said:

If your E is a not even certified to part 23 like my C, then I disagree you even need to keep your factory CHT at all. Is it in the TCDS?


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It's required under the CAR 3 certification that we share. This is true for a C too.

The factory CHT Gauge is part of the "required basic equipment" as noted in the type certificate and spelled out in CAR 3 section 3.675 (see below). Note that you ARE NOT required to have an EGT Gauge.

 

§ 3.675 Cylinder head temperature indicating system for air-cooled engines. A cylinder head temperature indicator shall be provided for each engine on airplanes equipped with cowl flaps. In the case of airplanes which do not have cowl flaps, an indicator shall be provided if compliance with the provisions of § 3.581 is demonstrated at a speed in excess of the speed of best rate of climb.

§ 3.581 General. The power-plant cooling provisions shall be capable of maintaining the temperatures of all power-plant components, engine parts, and engine fluids (oil and coolant), at or below the maximum established safe values under critical conditions of ground and flight operation.

[jetdriven]

2 hours ago, cnoe said:

 

That looks like the right one. I have this style on my installation but sadly paid JPI full price for it. This CB wishes Jetdriven had made his post 2.5 years ago.


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It was 5 years ago https://mooneyspace.com/topic/4422-cht-probe/#comment-56259