Piggy back CHT probe

[Shadrach]

I elected to eliminate the spark plug gasket thermocouple for my JPI this year in favor of the ring that fits on the threads of factory probe.  The trouble is the ring circumference is larger than the recess in the cylinder (angle valve IO360). The installation drawings make it very clear that the ring  is to be held flat against the cylinder with the included crush washer and factory probe hosing holding it in place. No matter how the ring is oriented it will not fit in the recess around the mounting hole it's close but it will deform if I tighten the probe into the cylinder.  I called JPI and they lived up to their reputation for apathy and uselessness. Has anyone here been through this installation?

[Fly Boomer]

1 hour ago, Shadrach said:

I elected to eliminate the spark plug gasket thermocouple for my JPI this year in favor of the ring that fits on the threads of factory probe.  The trouble is the ring circumference is larger than the recess in the cylinder (angle valve IO360). The installation drawings make it very clear that the ring  is to be held flat against the cylinder with the included crush washer and factory probe hosing holding it in place. No matter how the ring is oriented it will not fit in the recess around the mounting hole it's close but it will deform if I tighten the probe into the cylinder.  I called JPI and they lived up to their reputation for apathy and uselessness. Has anyone here been through this installation?

I'm interested in the solution.

[Ragsf15e]

Solution is a simple avionics upgrade to a primary engine monitor and get rid of the factory probe!  Should be no more than $10,000-$50,000 depending on options. (Tongue in cheek)

[Shadrach]

1 hour ago, Ragsf15e said:

Solution is a simple avionics upgrade to a primary engine monitor and get rid of the factory probe!  Should be no more than $10,000-$50,000 depending on options. (Tongue in cheek)

I actually asked about trading up and the rep I spoke with was the portrait of apathy.  Could not tell me anything about pricing or if my old unit was worth anything in trade. 

[Pinecone]

The only trade in upgrade I know if is from a 7xx to an 8xx.   They offer a reduced price, but charge a $300 core charge refunded when you return the 7xx unit.

[Guest]

Because the ring thermocouple is still a compromise of accuracy, why not use a solid copper washer to fill the recess to make a flush surface for the thermocouple to sit against? 

[Shadrach]

2 hours ago, Pinecone said:

The only trade in upgrade I know if is from a 7xx to an 8xx.   They offer a reduced price, but charge a $300 core charge refunded when you return the 7xx unit.

They still make the 730 which is an upgrade from the 700.

[N201MKTurbo]

The one I have (EI), has the thermocouple crimped into the ring terminal. If yours is like that, just trim the edges with a Dremel tool.

Or do like Doc said and use a washer.

[Pinecone]

4 hours ago, Shadrach said:

They still make the 730 which is an upgrade from the 700.

But do they offer a reduced price upgrade?

When I bought my 830 (to upgrade from 700) it was $200 off.  And they sold it with no sensors.  You could use the existing 700 CHT/EGT/Tit probes, and add whatever else you wanted.

[Shadrach]

5 hours ago, Pinecone said:

But do they offer a reduced price upgrade?

When I bought my 830 (to upgrade from 700) it was $200 off.  And they sold it with no sensors.  You could use the existing 700 CHT/EGT/Tit probes, and add whatever else you wanted.

Apparently the tech I spoke with was not equipped with that knowledge.

[Guest]

2 hours ago, Shadrach said:

Apparently the tech I spoke with was not equipped with that knowledge.

Available at Spruce for $2200 CDN, so guessing Spruce USA will have it as well.

[Pinecone]

I bought from Aircraft Spruce.

I tried to buy directly from JPI, but they told me to order from a distributor

[Shadrach]

Success. The solution was to carefully bend and form the JPI ring to fit factory cht and cylinder recess.  I also ran a jewelers file around the recess. This was not a difficult install by any means, but the instructions were a bit ambiguous and while I’m happy with the finished installation it irks me a bit part of the ring is not flush with the cylinder surface. The gap is shown in the image with the arrow.

To those of you that suggested a second copper gasket, I may go that route if the factory set up does not remain seated or shows erroneous readings. 

 

[N201MKTurbo]

That’s as good as it gets. The thermocouple ends in the crimp for the ring terminal, so all the ring does is conduct heat to the thermocouple, so lying perfectly flat isn’t that important. 

[PT20J]

When I had the spark plug thermocouple, it read 40 F high (I know this because at the last annual for the previous owner, it got installed on cyl 1 instead of 3.)

When I changed to the ring probe under the factory probe, it read 20 F low.

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