Question: EGT probes keep "dying"

A forum for discussing the MegaSquirt related (but non-B&G) board development, assembly, installation, and testing.

Moderators: jsmcortina, muythaibxr

Question: EGT probes keep "dying"

Postby hobieboy » Mon Jul 31, 2017 9:57 pm

The EGT probes that I installed seems to be "dying" constantly and I'd like to know if there's any way to truly verify that and if I am doing something wrong re:installation.

The probes that I have are these: https://www.pegasusautoracing.com/produ ... p?RecID=67

When I mentioned "died": They are connected to JBPerformance's EGT board. Normally, they would register correct temp but after 3 days on the track, they all start to die in that they start recording random, totally out-of-range and oscillating temperature from, say, 100-2000 degF non-stop. Some decided to read 34 degF when engine's not running (instead of ambient temp), etc. As all of them went from "read ok" to one-by-one start reporting random figures, I ascertain that it can only be the probes. If I disconnect the probes from the EGT board, I get a constant 32 degF reading which is what I expect.

So, my questions are:
1) How can probes be "killed"?
2) Is there any way I can measure to make sure they are "dead"?
3) Any suggestion on what I can get as replacement that will last more than a few days? (This is the 3rd time I replaced them :( )

thanks!
hobieboy
Master MS/Extra'er
 
Posts: 671
Joined: Mon Jun 27, 2005 1:13 pm
Location: Up North

Re: Question: EGT probes keep "dying"

Postby Marek » Tue Aug 01, 2017 2:05 am

The probes are nothing more than two wires spot welded together at one end and then insulated along their length.

They produce only a tiny voltage and so cannot be soldered in the conventional manner except when soldered directly to the legs of their respective amplifier chips. When using connectors, they use special connectors which are ofd the same metal type as the wiring. Not observing these rules means that the tiny metal to metal voltages they produce may be overprinted by similarly produced metal to solder or metal to connector voltages which would obscure the metal to metal voltage produced at the tip only.

To verify that it is the probes which are failing, you ought to be able to connect up another manufaturer's probe in place of the suspected faulty ones providing you observe the polarity of the red and yellow wiring correctly. Indeed you could simply buy some of the red and yellow chromel and alumel wiring and connect that up directly - it'll record the temperature from where the red and yellow wires touch each other.

kind regards
Marek
Marek
Experienced MS/Extra'er
 
Posts: 371
Joined: Sun May 10, 2009 1:20 am
Location: Guildford UK

Re: Question: EGT probes keep "dying"

Postby racingmini_mtl » Tue Aug 01, 2017 9:18 am

Marek, the special connectors are only needed if they are not at the same temperature as the amplifier chip and/or if the chip does not have temperature compensation. The chips used on the board mentioned here do have temperature compensation and they are close enough to the connectors that they are at the same temperature. So this is not the issue in this case.

As for the probes, I know that people have used the ones sold by DIYAutotune successfully. But I'm not sure if this is the issue here.

Jean
jbperf.com Main site . . . . . . . . . . . . . . . . . . . . . . jbperf.com Forum
Image
racingmini_mtl
Super MS/Extra'er
 
Posts: 8012
Joined: Sun May 02, 2004 6:51 am
Location: Quebec, Canada

Re: Question: EGT probes keep "dying"

Postby hobieboy » Wed Aug 02, 2017 12:49 pm

This is the 3rd time that I have to replace them so will definitely give DIY's a try instead.

As Marek explained, these should just be 2 types of wires spot welded at the tip to measure temp so I am dumbfounded about why/how they stop working. I took one out from the exhaust side and the tip looks ok other than a bit of rusty color; which I think is expected due to the heat cycle? Is there any way to test them before spending another few hundred dollars to try a replacement set?

thanks!
hobieboy
Master MS/Extra'er
 
Posts: 671
Joined: Mon Jun 27, 2005 1:13 pm
Location: Up North

Re: Question: EGT probes keep "dying"

Postby nathaninwa » Wed Aug 02, 2017 1:39 pm

I look to make sure mine all read very close to ambient before each race. With that said, I'm running the 40 dollar 10 pack off eBay (before they became a 5 pack now) and diy's egt box. Been on the car for 2-1/2 years and over 200 1/4 mile passes and all are still reading normal
Volvo 940, 2jzgte, MS3Pro, 815/692 @ 27psi.
240z, LS3 MS3pro/micro I/O 8.28@173
86 454/4l80e, ms3pro/micro. Tow rig
nathaninwa
Super MS/Extra'er
 
Posts: 2325
Joined: Tue Sep 14, 2004 4:17 pm
Location: Aberdeen, Wa

Re: Question: EGT probes keep "dying"

Postby hobieboy » Thu Aug 03, 2017 5:45 am

Thanks for the heads up on the probes Nathan... I'll look for those to try.
hobieboy
Master MS/Extra'er
 
Posts: 671
Joined: Mon Jun 27, 2005 1:13 pm
Location: Up North


Return to Expansion boards

Who is online

Users browsing this forum: No registered users and 1 guest