McNally EGT gauges - low readings

CharlieT · Aug 14, 2014

I have three McNally Boost/EGT gauges in my various TDIs, and I always trusted the EGT readings... until this week.

I have an Innovate datalogger setup that I was running on the TT TDI, and the logged EGT always seemed a lot higher than I saw on the gauge doing the log runs..

So I ran a quick experiment..
Three EGT gauges side by side:

McNally Series 2 with their EGT probe, 2.01 firmware
Auber Instruments SYL1813R with Auber EGT probe TC-KEGTS
Innovate TC-4 with laptop, and Auber EGT probe TC-KEGTS

All three EGT probes strapped together, and held in a propane torch flame.
This is the result

The McNally reads 350+ Deg F low at 1400 F.

Pretty scary really, I always thought my tunes must be amazing as I never saw EGT past 1200F on the McNally. I guess it was more like 1650 ?

Just to be sure, I swapped EGT probes around between devices.. no change.
And I tried all three McNally Gauges that I have, same result. All read way low.

I have email McNally about it, and I am in email dialogue with them. I will update when I have more.
At $250 a pop I really expected more. The $49 Auber is a bargain, and seems to read pretty accurately.

Disappointed...

Update 15th Sept 2014
Gauges back from McNally with 2.05 Firmware, and now read within 30 Deg F of the other devices at 1800F.
No longer disappointed ! thanks Bob !
So.. if you don't have 2.05 firmware (displayed momentarily at power up) then beware, especially if you have 2.01.

Bmckneely · Aug 14, 2014

I called Mcnally a couple of weeks ago to discuss repair/warranty of one of their boost/egt combo gauge. I left a voicemail and no callback ever received. Have you actually received a reply to your email to them?

CharlieT · Aug 15, 2014

Yes, I got an email reply back from Bob the next day. I sent my gauges back to them today, they will update firmware to 2.05 to see if that will fix it. I have my doubts, 400 Deg F error suggests something serious in the design, more than calibration.

JFettig · Aug 15, 2014

I hope mine wasn't reading 400F low when they were reading almost 1600F

They are very hit and miss for getting in contact with them. My old gauge still needs to be repaired but they still aren't responding.

CharlieT · Aug 15, 2014

Jon,

I wouldn't be surprised. I have seen 1450F on my McNally recently, and the Innovate log showed 1815F when I looked at it later that evening, scared the crap out of me. I guess the 2260 survived it ok, but it was not my intention to cook it that much. I guess 120mg/str will do that !

I would be very happy to find out that my McNally is damaged/broken, and this is not a systemic issue. However with 3 different McNally's, bought over 3 years at different times, all show 300-400F low when I tested them all side by side a few days ago. Makes you wonder....

JFettig · Aug 15, 2014

I wonder if it has anything to do with the pins on the end of the wire connectors? You know how thermocouples are.

CharlieT · Aug 15, 2014

I doubt it, more likely excess tracking on the pcb that is not material matched to the thermocouple.
I did confirm that their chipset does have cold-junction compensation built-in, so it cannot be that.

Curious Chris · Aug 17, 2014

I love my Analog EGT gauge. I am old school but I love analog gauges as you can read them faster. Oh I don't know the number but if the EGT needle is around 3:00 I am around 1400 F, 5:00 SHIFT NOW>

JFettig · Aug 17, 2014

Analog egt gauge? Too much LSD again?

Fix_Until_Broke · Aug 23, 2014

Hmmmm - Maybe this explains why my oil temps seem low. Always 20F below coolant temps which seems wrong in concept.

Let us know what you find from McNally

50harleyrider · Aug 25, 2014

Please keep this thread alive! My McNally Boost/EGT from Kerma may fall in here and I'm in the process of mods. I've only seen 1200F on it so far but 400F low? Scary.

AndyBees · Aug 30, 2014

I have a McNally EGT and Water Temp combo. I've had problems with the Water Temp aspect from day one! First the instructions that come with the set-up were generic in that they did not cover the Water Temp (for a boost gauge).

After a number of e-mails and them sending me a copy of the same instruction sheet that come with the gauge set, I just gave up. Through the process of elimination, I finally concluded that pin 8 was for the Water Temp. Once I got it going, the Temp gauge has never been consistant even with the sensor only about 1 inch from the OE sensor. I've installed a separate dedicated grounding system which is not connected to the internal light....no change! Just erratic readings.

So, this Thread is telling me that my EGT gauge is junk too! This really sucks, because I had to pay an extra $65.00 for a 16 foot lead with probe to install in my Vanagon.

All the rest of my gauges are non-McNally! Also, my experience so far is that VDO gauges are mostly junk too... unless you are lucky to find one made in Germany.

Rub87 · Sep 4, 2014

Are you comparing °C to deg F? hope not

I have 2 of these gauges and the values seem to make sense. I'll upload a video and then one can maybe judge from the color of the header the temp?

I sure hope not my 2 gauges have the same otherwise Im running way to lean! will test tonight..

As for communication, I was in contact with Bob and he always respondet very promptly. one of the gauges was linearized wrong but he just told me what to do and it worked out great. Normally they have a MAX6675 in there, which puts out a digital signal so it normally cannot be a linearisation error. Also the junction error ar the connector should only make a small offset and not a factor error

did some testing. I used 2 identical probes next to eachother heated by a propane torch. tips where next to each other. there was about 50 deg C difference between the gauge and the digital thermocouple tool http://benl.rs-online.com/web/p/digital-thermometers/2064315/ at 895 deg measured by the tool. gauge was reading 845 degC. this is quite bad as I was jetting the carb to end to about 950-1000 on the gauge which would have ben in reality more like 1050 deg. here a video of the header, on dyno we sw about 950 degC on the gauge. https://www.youtube.com/watch?v=NIUhdLI4Hxk&list=UU8M0YalkxF3OxpezSMf3vCA

BobGardner · Sep 4, 2014

How the Mcnally gauges work

The latest program is version 2.05, which uses the data from the MAX6675 without any correction factor. Older versions used a multiplier fudge factor that attempted to make 212 deg F right on because a couple of guys were using the gauges in water and noticed that it was reading high. The problem is the MAX6675 thinks the chip temp is the cold junction temp/ambient temp. This would be true if there was a screen door in the back of the gauge, but the temp in the can is always higher that the outside temp because of the displays, sun, etc. The MAX6675 data sheet says its within 2 deg over the range of the type K thermocouple. Its easy to shoot the newer prog into the computer. Boss says we will upgrade the sw for FREE if you pay the shipping. I sit at this computer every day. Best way to ask a question is bobgardner@mcnallyelectronics.com. No phone tag, no voice mail. I hope this refutes the accusation of being unresponsive! Send those boogers back!
Yo Andy... is that a Volts/WaterTemp or a pressure and temp? (an EGT/Water temp would need 2 tc chips... no can do yet...). The pressure sensor gets its regulated 5.00V from pin4 and the volts from the sensor comes back on the blue wire to pin8. Says that in the poop sheet doesn't it? Is it version 2.05?

CharlieT · Sep 4, 2014

Rub87 said:
Are you comparing °C to deg F? hope not

Ruben, thx, as a Brit living in the US, I can assure you I know the difference

Bob, Good of you to share the internals, I resisted sharing what you told me on the forum, thought it would be confidential.
My two gauges have been with you for a few weeks now, hoping you can send them back soon ? thx

Rub87 · Sep 4, 2014

BobGardner said:
The latest program is version 2.05, which uses the data from the MAX6675 without any correction factor. Older versions used a multiplier fudge factor that attempted to make 212 deg F right on because a couple of guys were using the gauges in water and noticed that it was reading high. The problem is the MAX6675 thinks the chip temp is the cold junction temp/ambient temp. This would be true if there was a screen door in the back of the gauge, but the temp in the can is always higher that the outside temp because of the displays, sun, etc. The MAX6675 data sheet says its within 2 deg over the range of the type K thermocouple. Its easy to shoot the newer prog into the computer. Boss says we will upgrade the sw for FREE if you pay the shipping. I sit at this computer every day. Best way to ask a question is bobgardner@mcnallyelectronics.com. No phone tag, no voice mail. I hope this refutes the accusation of being unresponsive! Send those boogers back!
Yo Andy... is that a Volts/WaterTemp or a pressure and temp? (an EGT/Water temp would need 2 tc chips... no can do yet...). The pressure sensor gets its regulated 5.00V from pin4 and the volts from the sensor comes back on the blue wire to pin8. Says that in the poop sheet doesn't it? Is it version 2.05?

Thanks for sharing the info. do you know what firmware is on my gauges? Do you have an idea how it comes I see a 50 degC difference between a calibrated tool and the gauge?

CharlieT · Sep 5, 2014

Rub87 said:
do you know what firmware is on my gauges

Firmware Rev is displayed momentarily during power up. Mine were both 2.01

Layerz · Sep 6, 2014

Hi all, question on the EGT's even with lag and I hope this does not seem like a silly/stupid question.

I am looking to add an EGT gauge however reading the issues seen here has given me some concern as my EGT will be a digital setup using arduino's. With the lag you see I understand this is not telling you instantly any issues but I assume it is still telling you roughly when you are in the zone that potentially you need to back off?

CharlieT · Sep 6, 2014

There is very little lag with a good quality thermocouple, it should get from 200F to 1400F within two or three seconds. The mass of the thermocouple has quite an impact, most thermocouples you buy for engine applications are thin/light and so read very fast.

The issue described in this thread is accuracy of the measuring device, not lag.

Layerz · Sep 6, 2014

Do you know what, I think I either saw that in a different thread or remembered this thread wrong when replying! I could of sworn seeing something about a lag in the readout.

So on a good thermocouple it seems the MAX6675 is a reasonable choice?

CharlieT · Sep 6, 2014

A MAX6675 isn't going to get you very far, unless you want to design your own circuit board and device.
If you re-read the thread, you will see that McNally gauges responded with the detail of the thermocouple interface chip they use, the MAX6675.

If you want to measure EGT in your car you need to buy a thermocouple (typically K-type) complete with gland fitting (typically 1/8" NPT) and an EGT gauge/readout.
There are many vendors and suppliers, I identified two in my original post : McNally Gauges and Auber Instruments.

Layerz · Sep 6, 2014

Yup

Kinda my plan, I will be using a 2 line display using an Arduino to show boost and EGT and maybe IAT. I have unused console buttons that I will put the screen into as I like things to look stockish.

Until reading through this I wasn't sure on a good thermocouple and would of helped myself by reading through a bit better!

50harleyrider · Sep 8, 2014

I've completed most of my mods and have a concern about my McNally egt: The temperature increase to about 1132 and levels. Jeff told me that's fine and shows the boost control is working properly. Also, should everyone send these gauges back and make sure the latest programming is in them? Mine was bought from Kerma about 6 months back.

CharlieT · Sep 8, 2014

On power up of the gauge, what Rev of Firmware do you show ? 2.01 ?

Mine were 2.01, results are in post #1. Mine have been updated to 2.05 by Bob, and should arrive back with me this week. I will re-run the test to see what impact the firmware update has.
I also purchased a K-type simulator / calibrator, so I will be able to check all my temp readings more scientifically and will post results.

SilverGhost · Sep 8, 2014

Oh S**t! mine shows 1.01 when it starts up. Sounds like I need to get it sent in...

Jason

Rub87 · Sep 10, 2014

My gauges have 205 firmware inside..

BobGardner · Sep 11, 2014

The 1.xx was the series I with an 8 pin connector. We redesigned the electronics with a bigger faster computer, more inputs, a 10 pin connector on the back, but one less circuit board for 'manufacturability'. The lastest rev for the series 1 gauges has the same max6675 routine as the later gauges. Send it in. It took me a while to find the max6675 update speed in the datasheet.... you cant read it faster than every 200ms, so a fast egt rise jumps up every reread of the tc. At first, the reading was 'smoothed' a couple of readings to hide the steps, but then someone complained about it not tracking the temp fast enough. Poor programmer cant get a break. It has to be fast AND smooth. After a while you learn more than you reckoned for about digital signal processing and moving averages and ... These gauges were originally conceived as single function, so you see the trend on the needle, and the quantity on the display, but the combo of two params was more popular. Hey Reuben... do you have the gauge mounted in the airconditioner duct? The max chip outputs the diff of the tc temp and the chip temp. Its usually 20 or 30 deg F hotter in the can in the sun, so the diff is smaller. Maybe take the guts out and cool off the max chip with an ice cube in some sandwich wrap. Does that bring the temp closer?

CharlieT · Sep 15, 2014

Good news !! my gauges came back from Bob @ McNally with 2.05 firmware. I ran the same test, and the McNally's now read within 30 Deg F of the other gauges, huge improvement.

Also Bob kindly also fixed the display on one of my gauges, much appreciated, great customer service.

I have bought myself a thermocouple calibrator, so I am going to test all my EGT devices from 0 to 2000F and see what I find. I will update this post when I have time.

I will also update the first post to include learnings.

50harleyrider · Sep 16, 2014

That's great. Mine is 2.05 should be OK. Curious how the thermocouple calibrator works and do you have to modify the thermocouple to calibrate it or hit and miss with a replacement? Also hope the next generation gauge has 4 digits.Thanks CharlieT.

CharlieT said:
Good news !! my gauges came back from Bob @ McNally with 2.05 firmware. I ran the same test, and the McNally's now read within 30 Deg F of the other gauges, huge improvement.

Also Bob kindly also fixed the display on one of my gauges, much appreciated, great customer service.

I have bought myself a thermocouple calibrator, so I am going to test all my EGT devices from 0 to 2000F and see what I find. I will update this post when I have time.

I will also update the first post to include learnings.

Rub87 · Sep 16, 2014

BobGardner said:
The 1.xx was the series I with an 8 pin connector. We redesigned the electronics with a bigger faster computer, more inputs, a 10 pin connector on the back, but one less circuit board for 'manufacturability'. The lastest rev for the series 1 gauges has the same max6675 routine as the later gauges. Send it in. It took me a while to find the max6675 update speed in the datasheet.... you cant read it faster than every 200ms, so a fast egt rise jumps up every reread of the tc. At first, the reading was 'smoothed' a couple of readings to hide the steps, but then someone complained about it not tracking the temp fast enough. Poor programmer cant get a break. It has to be fast AND smooth. After a while you learn more than you reckoned for about digital signal processing and moving averages and ... These gauges were originally conceived as single function, so you see the trend on the needle, and the quantity on the display, but the combo of two params was more popular. Hey Reuben... do you have the gauge mounted in the airconditioner duct? The max chip outputs the diff of the tc temp and the chip temp. Its usually 20 or 30 deg F hotter in the can in the sun, so the diff is smaller. Maybe take the guts out and cool off the max chip with an ice cube in some sandwich wrap. Does that bring the temp closer?

hi Bob,

No, the car is a racecar and therefore has no heating nor aircon. the gauges are at about 30-35°C MAX I would say..

As I reported I have the firmware v2.05 so could it be the difference I am seeing is because my gauges read °C instead of °F or not?

McNally EGT gauges - low readings

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