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Suggestions for replaceing EGT/CHT gauge?

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dbier99

Well Known Member
Our recently acquired RV6A has an Allegro EGT/CHT gauge (see pic) that monitors all 4 cylinders (both EGT & CHT). It can display high/low temp #s or scan each cylinder and would be perfectly fine if not for its very hard to read LCD display - I struggle to see the temp numbers in even the best lighting conditions. Accordingly, I'd like to swap it out for something more graphical and color coded so we can determine at a glance that temps are okay.

I found what looks to be just what I'm looking for at Spruce (MGL VEGA TC-4 https://www.aircraftspruce.com/catalog/inpages/mgl-vega-tc-4.php) and am wondering if anyone has experience with it or has similar gauge suggestions.

I'd also like some feedback on the difficulty level of doing the swap. My son and I are pretty mechanically inclined - but still a little gun shy about getting behind our panel.

Ideally would love to be able to use the existing engine monitor's CHT and EGT probes but not sure that is possible. However, the product description does indicate: "Temperature probes can be common J, K or E type thermocouple probes as used in CHT and EGT senders" so maybe they are somewhat universal.

All thoughts/suggestions appreciated!
 

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RDAC

The thermocouples wire into a MGL RDAC and communicate via the canbus but also appear can be wired direct. I have installed 2 RDAC's and performed well.
 
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dmattmul said:
The thermocouples wire into a MGL RDAC and communicate via the canbus but also appear can be wired direct. I have installed 2 RDAC's and performed well.
Click to expand...
Thanks for the reply. Is there a benefit to connecting through a canbus versus direct?
 
dbier99 said:
Thanks for the reply. Is there a benefit to connecting through a canbus versus direct?
Click to expand...

Only three wires passing through the firewall for all info from the engine side.

The single gauge that you need can be wired direct without needing to purchase the RDAC.

I have the XTreme and am very impressed with the product.... It is a product that is VERY under rated.

If you already have the wires from the motor to the existing gauge, there should be no problem installing the new MGL gauge.

Call them.... http://www.mglavionicsusa.com/ to answer your questions before you order.
 
Direct vs Can Bus

gasman said:
Only three wires passing through the firewall for all info from the engine side.

The single gauge that you need can be wired direct without needing to purchase the RDAC.

I have the XTreme and am very impressed with the product.... It is a product that is VERY under rated.

If you already have the wires from the motor to the existing gauge, there should be no problem installing the new MGL gauge.

Call them.... http://www.mglavionicsusa.com/ to answer your questions before you order.
Click to expand...

Like Gasman advises MGL is an underrated product and their EFIS has good value. I am not sure how their DB-9 connection can handle 4 EGT's and 4 CHT's. Might need to talk with MGL. Seems you might need the RDAC for your application.
 
gasman said:
Only three wires passing through the firewall for all info from the engine side.

The single gauge that you need can be wired direct without needing to purchase the RDAC.
Click to expand...
If I want to reduce the number of wires running to the firewall to the instrument - would I be buying/installing a CanBus or RDAC? Sorry for such a basic question but I'm still learning the terminology.
 
A RDAC..... but you already have the wires from the probes running to your panel, right?
 
gasman said:
A RDAC..... but you already have the wires from the probes running to your panel, right?
Click to expand...
I have the sensors conncted The existing EGT/CHT gauge has 4 EGT & 4 CHT sensors and assume there is no existing RDAC - but I have not yet investigated the current wiring (I just decided today to upgrade and haven't gotten back to the plane)
 
Here is a RDAC....
rdac.JPG

You really don't need it for your application
unless you are going to upgrade to at least
an XTreme later....
 
dbier99 said:
I have the sensors conncted The existing EGT/CHT gauge has 4 EGT & 4 CHT sensors and assume there is no existing RDAC - but I have not yet investigated the current wiring (I just decided today to upgrade and haven't gotten back to the plane)
Click to expand...

RDAC only applies to MGL equipment. And will only work with MGL....
 
The MGL Vega TC-4 has 4 channels and can connect directly to max 4 thermocouples. More than 4 thermocouples (max 12) will require purchase and installation of RDAC. Since the sensor wires are already running through the firewall the RDAC could be potentially located on the sub-panel.
I have a Vega display for my radio and it is bright and easy to see. MGL documentation and support is something to consider before buying. ;)
 
I have the MGL Blaze egt/cht and I am super pleased with it (blaze is the larger diameter version, also good for 12 thermocouples without an RDAC). The display is simple and very bright and easy to read. Setup was no problem at all. The DB connector came with leads all labeled for the thermocouples. My thermocouple wires already went through the firewall so I simply trimmed everything to length and crimped them to the DB leads. In the setup you choose which type of thermocouple you have, and if you chose the wrong type the temps will be way off.

As far as getting the RDAC..in hindsight..there is a Blaze EMS that cost the same as the dedicated cht/egt. The EMS shows CHT/EGT as well as pressures, etc, if you have an rdac. Not sure if there is a vega EMS
 
One thing to consider is to get an engine monitor that will allow you to save data that you can use to analyze your engine health, using a site like https://www.savvyaviation.com.

No idea which systems in the MGL product line supports this, but I'm sure if you give them a call they will clarify.
 
gasman said:
RDAC only applies to MGL equipment. And will only work with MGL....
Click to expand...
Thanks for that clarification and pic of the RDAC. I found it at Spruce (https://www.aircraftspruce.com/catalog/avpages/mglenginemonitor.php) and based on the added cost and that they suggest a box be fabricated to protect it from water - seems simpler to just skip it.

Now I'm anxious to get to the plane to determine how the current CHT/EGT instrument is wired. I honestly don't recall a slew of wires heading from temp probes through the firewall - but they must be there. :)

EDIT/UPDATE: Based on an later post it seems I'll have to use an RDAC since the TC-4 can have a max of 4 temp probe feeds without it - and I need 8 (4 EGT / 4 CHT). I'll call MGL when they open to confirm what will be needed. Appreciate all the input!
 
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PaulvS said:
The MGL Vega TC-4 has 4 channels and can connect directly to max 4 thermocouples. More than 4 thermocouples (max 12) will require purchase and installation of RDAC.
Click to expand...

I'd planned to call MGL before buying - but your post makes it clear that I'll have to also use the RDAC since I'll have 8 thermocouplers (4 EGT & 4 CHT). That adds a bit extra cost and installation complexity (protecting RDAC if forward of firewall) - I should have known a simple swap was too good to be true. :)
 
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Figure out what thermocouples you currently have .. .type J or K.
I can be different between EGT and CHT. Or all the same.

Thermocouples have standard wire colors
type J: a red wire and a white wire
type K: a red wire and a yellow wire

From that we can better figure out what might be compatible.
 
I recently installed a EGT CHT from Aerospace Logic. 2 1/4 instrument, with all the smart functions.
It did not require a RDAC.
 
Don't hesitate to shuffle a couple instruments around if necessary. That is what I did. My cht/egt was in a small hole, but I wanted to use the 12 channel Blaze, so I got rid of a rarely used instrument in a large hole to make room for the blaze. Then you can fill that empty smaller hole with lots of cheaper but useful things, clocks, timers, g-meters.
 
OKAV8r said:
I recently installed a EGT CHT from Aerospace Logic. 2 1/4 instrument, with all the smart functions.
It did not require a RDAC.
Click to expand...
I was very excited when I saw your post - but if the Aerospace Logic EGT/CHT I found on Spriuce is the one you used - it's unfortunately too expensive for me right now ($1,600 - https://www.aircraftspruce.com/catalog/inpages/10-05171.php ).
Please let me know if I'm not looking at the one you used.
 
CATPart said:
Don't hesitate to shuffle a couple instruments around if necessary. That is what I did. My cht/egt was in a small hole, but I wanted to use the 12 channel Blaze, so I got rid of a rarely used instrument in a large hole to make room for the blaze. Then you can fill that empty smaller hole with lots of cheaper but useful things, clocks, timers, g-meters.
Click to expand...
Good suggstion. Unfortunately, no big holes to spare. In fact I had to get rid of the Rate of Climb indicator when we recently installed a Garmin G5 - in order to gain an attitude indicator (the G5 will provide ROC info too).
 
blaplante said:
Figure out what thermocouples you currently have .. .type J or K.
I can be different between EGT and CHT. Or all the same.

Thermocouples have standard wire colors
type J: a red wire and a white wire
type K: a red wire and a yellow wire

From that we can better figure out what might be compatible.
Click to expand...

Thanks for the info about identifying the thermocoupler types - I hadn't yet figured that out. We are planning to do our next oil change next week so I'm going to wait until them (canopy removal) to take a look at the current set-up to better identify what we have.
 
MGL VEGA TC-4

I think you would be happy with the readout of the MGL Vega just need to take your 8 thermocouples and wire to a RDAC on the cold side of the firewall (your thermocouples already go there) and then run 3 wires to the display. Later if you want to install a MGL EFIS in your panel you have the RDAC ready to go.
 
I had a MGL EGT/CHT gauge in my Mooney (yes, I know) and no RDAC required. Very easy to read if you get the color one.
 
dmattmul said:
I think you would be happy with the readout of the MGL Vega just need to take your 8 thermocouples and wire to a RDAC on the cold side of the firewall (your thermocouples already go there) and then run 3 wires to the display. Later if you want to install a MGL EFIS in your panel you have the RDAC ready to go.
Click to expand...

Yes, thinking that mounting it between engine baffle/wall and firewall would be the best place. Anxious to get cowls off next week to take a look and size it all up.
 
To me, the major advantage of the MGL RDAC is that it can be mounted in front of the firewall.
 

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Mikeyb said:
To me, the major advantage of the MGL RDAC is that it can be mounted in front of the firewall.
Click to expand...

Yes - between the engine baffle and firewall. I was thinking I'd need to find/make a spot on the firewall for it - but see from your pic that it can be mounted creatively too!
QUESTION: I see you have it in some sort of plastic box - did you buy or make that?
 
I made it with .030 polycarbonate. Formed it over a block of wood with heat and another block of wood. Used 4 threaded metric standoffs in the existing board mounting holes.
Been flying for more than a year.
 
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