EDM 700 Installation

[RobertGary1]

It looks just like and mounts like the spark plug ring but is the diameter of the bayonet probe.

Not sure I'd describe it like that. It is threaded at the top and the factory probe screws into the JPI CHT probe. I installed mine 10 years ago so its possible its changed I suppose.

 

-Robert

[DonMuncy]

I'm sorry to belabor the point, but I have gone through this on my plane, trying to make the JPI read consistently and keep my original factory probe operative. Are you saying that the JPI probe is the one which is much like the spark plug sensor, but with a 3/8 inch ring and the factory thermistor is threaded through it into its original position.

[DonMuncy]

Sorry, Robert made his post while I was typing mine.

[BigTex]

I actually installed the bayonet CHT probe that piggybacks on the primary probe.  Mine reads around 40 degrees lower than the other cylinders so you'll just need to know what's typical with the style of probe you select.

[DonMuncy]

I have the factory sensor (#5 cylinder) in the ordinary position and the JPI on the spark plug. I reads consistently, but  somewhat cooler. I wanted to switch the JPI probe to the cylinder position, but I don't think there is another type thermistor to feed the factory gauge. I was questioning whether switching the JPI from the spark plug to the "piggy back" under the factory thermistor would read closer to the others. (I know; I'm anal about this, but sitting in front of my laptop, it doesn't take any effort to muse the possibilities)

[N601RX]

Here is the piggyback probe that jpi currently sells. I noticed a difference in cht when I removed it and replaced the 830 with 900 which used all bayonet probes.

[BigTex]

I have the factory sensor (#5 cylinder) in the ordinary position and the JPI on the spark plug. I reads consistently, but  somewhat cooler. I wanted to switch the JPI probe to the cylinder position, but I don't think there is another type thermistor to feed the factory gauge. I was questioning whether switching the JPI from the spark plug to the "piggy back" under the factory thermistor would read closer to the others. (I know; I'm anal about this, but sitting in front of my laptop, it doesn't take any effort to muse the possibilities)

 

Me too.  my piggyback probe reads around 40 degrees cooler and it drives me nuts.  How close is is your spark plug thermocouple?

[DonMuncy]

It is hard to know what it should be reading, but comparing it to #6 (the other one on the front), it is 50 to 55 degrees cooler. 

[RobertGary1]

Here is the piggyback probe that jpi currently sells. I noticed a difference in cht when I removed it and replaced the 830 with 900 which used all bayonet probes.

Yea, that probe will read off. I'd avoid that one. The one that you want is the one that screws directly into the cylinder probe port but also allows the factory probe to be screwed into the back of it. I've not noticed a difference in temp with that set up. It's not what the JPI comes with but an upgrade I got when I ordered the unit.

I'll try to snap a pic this weekend.

-Robert

[Tommy]

I think if there is cowl flap on your aircraft, you need to keep your factory CHT. 

 

Pardon my ignorance, can someone please point to me exactly where is the exhaust stack? Seems like a tiger country to avoid!

 

Thanks!

[Awqward]

Exhaust stack / header / manifold....they're talking about the exhaust pipes that bolt on to the cylinder heads...(same terminology as Australia)...the EGT probes need to be a consistent distance from each cylinder head in order to get meaningful relative readings...but seriously, you should probably go through it all with your LAME...if you are on the VH reg I'm not sure you can install it yourself or not...but in any case I'm sure you will need a certified mechanic to sign it off...

And the CHT is required equipment in accordance with the Type Certificate Design Specification (TCDS) for 2A3...you should get a copy of this for your files...I can send you a copy if you like.... The EDM900 and the EI CGR30P have Supplemental Type Certificate (which over-rides the original TC) allowing those units to be Primary...meaning you can remove the factory CHT....but this is NOT the case for the EDM700 (or 830)...

And one thing to bear in mind for foreign registered aircraft is that, in the case of Australia, the CASA (DCA originally) would have approved the original TC for the Mooney back in the late 50s/ early 60s allowing it to be registered in Australia on the VH register...I think with current bilateral agreements this is pretty much automatic these days for new types....BUT each STC also needs to be approved for use on VH reg planes....again this may well be automatic in Australia for FAA approved STCs but worth double checking...

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[Tommy]

Thanks Awqward!

 

Yes I am installing the unit with my LAME for sure but I love to arm myself with as much knowledge as I can possibly can as to help him out a bit.

 

So do I need CASA approval for installing EDM 700? - I am keeping the factory CHT / Oil Temp but will be replacing EGT.

 

Cheers

[Awqward]

Despite being an Aussie I'm not that familiar with the process in Australia...my Mooney is on the N register so I only really know the FAA requirements....however, assuming the STC which comes with the unit is acceptable to CASA (which as far as I know it should be), then I imagine it is no big deal and the LAME will sign off the aircraft logbook...he may need to advise CASA if they consider it a Major alteration but I don't know....the point of an STC (which includes your aircraft on a blanket Approved Manufacturers List (AML)) is that all the necessary data is there to support the alteration and no special "field approvals" are necessary... and I know there are hundreds of EDM700 installations in Australia so I'm sure the STC is CASA approved...

And yes, the EGT is not a required instrument by the TCDS and so the factory gauge can be removed if you want (unless of course CASA has imposed some requirement on top of the TC....your CASA approved POH will tell you if that is the case....but I doubt it

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[RobertGary1]

I apologize. I didn't describe the factory cht probe accommodation correctly. EDM provided me (as an upgrade) a cht probe that is the EDM probe but additionally has a post for the factory sensor wire. So it's one sensor but it feeds both the factory gauge and the EDM. With this set up there is no error in the temp readings between the factory cylinder and the others. This is an improvement over the spark plug loop solution. I snapped a picture. I just installed this engine and haven't flown it yet so I'm at the airport a lot putting the final touches on the engine install.

[Guest]

There are several variations of Adapter probes from JPI and Insight to accommodate OEM CHT installations

One version is a stainless steel fitting which is able to accomodate either screw in CHT probes or bayonet lock probes. You would remove your existing CHT probe, screw the adapter into the cylinder head the screw in the OEM probe into the adapter or lock your bayonet probe to the adapter. I've searched the JPI site and can't locat this one.

The second version as shown in Robert's picture above is JPI part M113-3/8 CHT, it is a 3/8 diameter ring style probe. You remove the OEM CHT probe, slip the ring probe over the OEM probe and screw it back into the cylinder.

Don Muncy,

in the absence of this type of probe you could simply switch the probes with cylinder 3, go for a test flight and determine the difference between the two cylinders, now you would know the difference in readings. However after all that work you would have paid the cost of the new probe.

Clarence

[DonMuncy]

Clarence,

Thanks for the tip. It is so simple, I should have thought of it.

It isn't the price of a probe, it is the fact that there is only one hole in the cylinder to put a probe in. To be legal, I need the original (thermistor) sender for the ship's gauge, and it only goes in that hole. So it seems that the JPI sender has to go somewhere else. That is what my part of the discussion was all about. Where is that "somewhere else" that will give the reading closest to the other ones.

[Guest]

This may depend on whether your GEM is a legal replacement. On my K model, with my earlier JPI, it is not a primary instrument, so I have to keep the factory CHT. The factory gauge uses a thermister which has to go in the bayonet hole. So I am stuck with the spark plug ring for the #5 CHT. You just have to learn that the #5 is going to read a little different, and take that into account when checking CHTs.

Don,

You could install the JPI CHT probe M113-3/8 under your OEM CHT probe as shown in picture posted by Robert. It would surely be more accurate than the spark plug probe.

Clarence

[DonMuncy]

Clarence,

You are right that the 3/8 in ring would work OK.

I haven't done any testing yet, but it appears that the ordinary JPI probe stick up into the hole about 1 inch and presumably bottoms (tops?) out against the wall of the cylinder. So the ring under the factory sensor would have some distance to dissipate some of the heat. How much, I have no idea.

Conversely, the spark plug sensor is the length of the spark plug threads distance from the combustion area of the head. But is the spark plug in a slightly hotter area of the head? I sure don't know.

I think the idea of swapping the 3 and 5 probes, and checking the readings might be helpful.

Otherwise I suspect one would use whichever he has, or prefers, and find a baseline from which to watch for changes. 

[BigTex]

I used the JPI Bayonet Adaptor probe (PN:5050A).  It allows you to piggyback off of the factory CHT probe.  This eliminates the need for the spark plug probe but it still doesn't read the same as the other cylinders.  Mine reads ~40df low.  I just make a point of looking at the primary CHT for #3.

[carusoam]

Send Mooney an idea...

It is very easy to build a sensor with two outputs. One for the ship's gauge and one for the JPI...

Certification would be a typical exercise for an airplane company. This one would be as easy as it gets. There would be zero risk of failure. Great project for a new engineer getting his feet wet with a simple certification project.

The ring is a 'nice enough' alternative. But we are not agreeable with nice enough.

If you have to have an offset number...

It would be better to be an offset number from the ship's CHT than the spark plug.

The spark plug ring measures a somewhat different source of heat. (Plug area vs exhaust valve area). Exhaust valve is hottest.

JPI technology was not widely accepted when they built my O. It was an added option by the first owner.

I guess owners have changed, or is it just MS owners?

What are other airplane manufacturers doing?

Best regards,

-a-

[Guest]

Clarence,

You are right that the 3/8 in ring would work OK.

I haven't done any testing yet, but it appears that the ordinary JPI probe stick up into the hole about 1 inch and presumably bottoms (tops?) out against the wall of the cylinder. So the ring under the factory sensor would have some distance to dissipate some of the heat. How much, I have no idea.

Conversely, the spark plug sensor is the length of the spark plug threads distance from the combustion area of the head. But is the spark plug in a slightly hotter area of the head? I sure don't know.

I think the idea of swapping the 3 and 5 probes, and checking the readings might be helpful.

Otherwise I suspect one would use whichever he has, or prefers, and find a baseline from which to watch for changes.

Don,

I would suspect the the spark plug probe would show a higher reading than the ring probe under the OEM probe. One end of the plug is in the fire inside the combustion chamber exposed to 1400-1500 degrees, where as the spring bayonet probe contact the bottom of the well in the cylinder head. The OEM probe is screwed into the head but does not touch bottom.

Clarence

[carusoam]

Clarence,

Doesn't the spring hold the T/C against the bottom of the well?

It does in process equipment with a very similar design.

Wondering,

-a-

[DonMuncy]

Carusoam,

I agree with you. If the probe did not "bottom out", you wouldn't have to compress the spring to get the threads started.

[carusoam]

Unless the T/C is the wrong size for the hole. Really common for old process equipment...!

Best regards,

-a-

[Guest]

The hole is normally a 3/8-24 national fine thread, the spring must be compressed in order to engage the threads of the retaining nut.

Clarence