1 EGT probe to 2 devices?

[Cronus577]

Hey guys, was wondering what ya'll's thoughts were on running 1 EGT probe to 2 devices. I currently have my EGT probe hooked up to my ISSPRO gauge so that I could monitor the temperatures easily, but I wanted to make a Y connector connecting the 1 EGT probe to both my ISSPRO gauge and my Quadzilla so I can datalog and use backdowns. Would there be any issue as far as voltage drop causing inaccurate readings or would I be in the clear? I drew a picture in Paint to show exactly what i'm talking about. 

[BBHD]

I just tapped another spot for my Quadzilla probe. 

[Cronus577]

3 minutes ago, BBHD said:

I just tapped another spot for my Quadzilla probe. 

I would but i'm running a BD manifold and I'd like to not drill into it. It has 2 pre-tapped spots for an EGT/Backpressure gauge, one of which I'm using already but the other has a bung to plug the hole and after many heat cycles it's stuck in there. 

[kzimmer]

It's not impossible but definitely not recommended. Depending on the device(s) that are connected to the thermocouple, it's possible that they will affect each other. Very easy to induce noise in this scenario, as it is a millivolt signal. Either way, always use thermocouple wire with proper shielding.

[Cronus577]

13 minutes ago, kzimmer said:

It's not impossible but definitely not recommended. Depending on the device(s) that are connected to the thermocouple, it's possible that they will affect each other. Very easy to induce noise in this scenario, as it is a millivolt signal. Either way, always use thermocouple wire with proper shielding.

I'll keep that in mind, I wasn't going to cut into any preexisting wires or anything just simply make another connector. I might just do a couple of datalogging runs with the Quadzilla hooked up to it and get an accurate reading and make a Y connector and do more data logging to see if there are any changes. Hopefully running the connector in parallel won't give any odd readings. 

Edited September 12, 2017 by Cronus577

[MikeF509]

I wouldn't risk it, did this on mine and the Quadzilla only shows 32 degrees for the egts now. I believe it fried the egt output, will be sending it when I pull the truck apart for HG, studs, and injectors.

[Mopar1973Man]

8 hours ago, BBHD said:

I just tapped another spot for my Quadzilla probe. 

 

Exactly what I've done. Don't attempt to share one probe for two devices it won't work.

[Cronus577]

Hmm, I have the EGT probe for the Quadzilla just in my parts box, I just really don't want to tap into this manifold considering it's almost $500. But if I run the risk of frying anything or misreading I'll have to bite the bullet and tap it. Would just have to get a tap. I'll put the Quadzilla probe on the back of the manifold to monitor temps for cyl #5&6 so it can backdown from more effectively.

[Mopar1973Man]

I've got mine both stacked up on the 4,5,6 port about an inch apart.

[Me78569]

Nothing to add here, but I am curious as to the result.

[Cronus577]

1 minute ago, Me78569 said:

Nothing to add here, but I am curious as to the result.

I can test it and do some data logging and let you know. I read on another thread this morning where one guy did it and his read correctly.

[Me78569]

I don't see how it would damage the board, but who knows I suppose.  1 probe 2 devices is not the supported or recommended setup.  

[Mopar1973Man]

Being pyrometer probes create very very small voltage and splitting the pyrometer probe to two devices will for sure throw the accuracy out the window for sure. 

[Cronus577]

1 hour ago, Mopar1973Man said:

Being pyrometer probes create very very small voltage and splitting the pyrometer probe to two devices will for sure throw the accuracy out the window for sure. 

Like I said, I'll do some data logging and see if there's a big difference, I understand that adding some wiring will cause resistance which will cause the reading to be inaccurate, but how inaccurate would it be? I'll do some testing, if it's more than 50 degrees off i'll put in another probe.

[Scottfunk]

I would think it should be fairly simple to put a Y in the j1939 access at the ecm and run a j1939 compliant egt gauge like this https://www.massgenie.com/vdo-ocean-link-j1939-1700f-exhaust-temperature-gauge-f5jmrdcuah1unbop?utm_campaign=productdatafeed&utm_medium=cpc&utm_source=google

[Mopar1973Man]

That would be a mess having to have an oddball VDO gauge and 2 ISSPro gauges...

[Scottfunk]

I can't disagree with you there. I love having all my gauges right on the Quadzilla. Just offering suggestions.

[kzimmer]

It should be like having two millivolt meters in parallel, doesn't sound like a big deal, as long as the polarity is correct on both. However, having the second meter in the circuit might load the circuit a little bit, affecting both measurements. The other thing to consider is that the measuring device will more than likely use an amplifier to increase the millivolt signal to a level that is easier to measure. So if you have two devices with different amplifiers, possibly having different "common" sides of their respective amplifiers, and throw in the possibility of reversing polarity by accident, it's not hard to imagine the perfect storm where sensitive electronics could be destroyed. I'm really on the fence with this one. I want to see if it works, but I don't want to see you with any damaged equipment.

 

The perfect device would be a millivolt repeater with two outputs. But $$. Not worth it.

[Mopar1973Man]

2 hours ago, Scottfunk said:

I can't disagree with you there. I love having all my gauges right on the Quadzilla. Just offering suggestions.

 

I'm the reverse I want to have all the gauges on the A-pillar and leave the Quadzilla App turned off. That way I don't have to pack my phone everywhere. But now with data logging the MPG I'm kind of stuck watching MPG logs on the phone. 

[Scottfunk]

19 hours ago, Mopar1973Man said:

 

I'm the reverse I want to have all the gauges on the A-pillar and leave the Quadzilla App turned off. That way I don't have to pack my phone everywhere. But now with data logging the MPG I'm kind of stuck watching MPG logs on the phone. 

I am using a 10 inch tablet that will be making its permanent home in my dash. I'm going to remove the battery and supply key on power through a USB power adapter and try one of the auto run apps to force the Quadzilla app to open on power up, essentially creating a dedicated display for the Quadzilla so I don't have to touch it at all when I start up. Hope, I guess, is the operative word here.