Long story, help!!!!

Last year I purchased 2 EGT probes from Russ at PCS, I also purchased the 0-5V converter so I can log the EGTs. When I first setup the probes, I was getting very low voltage readings. I called them up and they thought the probes may have been bad, there was a bad batch and sent me 2 other probes. I swapped the probes and that did not help.

I called them again and this time dealt directly with Russ and this time he sent me 1 other probe, he mentioned something about being grounded or ungrounded but it was different from the original one. I put this one in and the readings were much higher. I thought this was the issue so I called Russ and asked him to send me the other one and they did. PCS has been awesome with dealing this but I still have the same issue.

At WOT with E85 I am getting 2.2-2.4volts. The converter chip came with conversion chart and when I convert it, I am only getting readings in the 1000F area which I know is way off. So far I have:

- swapped probes

- used a multimeter and measured the voltage coming out of the converter BEFORE it gets into my TEC3. I did this to make sure there were no issues with the TEC unit.

At this point I am not sure what to do since the readings are very low. I guess it can be a bad 0-5 V converter maybe? If anyone is willing to help, I can also send any of these items over for you to compare with your setup. Any ideas? Thanks in advance for any help!

Thanks,

Anthony

 

So the last probe he sent, the temp readings came UP to 1000F? As in they were lower then that with the first set of probes?

Is there any high voltage stuff (tec coil wiring?) running along or close to the EGT wire (pre convertor)? I know that they can be affected much like a trigger wire.

I'm stumped

 

first off... your thermocouples are Type K correct? if so they put out a tiny voltage that connects to an amplifier. the fitting where the wires from the thermocouple connects to the wires to the amp is generally of ceramic body w two spade connnectors. due to the low transmitted Vs it must be of a special quality.

your amp probably has an Analog Devices AD595 chip? it converts the voltage to zero to ten volts and there is another circuit that steps it down by half. so you should be reading anywhere from 2.5 to 5.1 volts into your CPU. 2.55 V being about 932 F and 5.1 V being 1832.

most probable, the connector or the amp.

where did you get the amp?

hc

 

Everything is pretty close since it's in the car near the ECU. I had it mounted temporarily outside and it was the same reading. I'm stumped too lol.

Howard, they are K type. I am only reading a max of 2.4 or so under 30 psi so something must be way off. At the end of the probes, there are 2 wires, a red one and a yellow one. I have that connected directly to the amplifier. I was thinking it may be the ground wire for the amplifier but that is grounded to a clean ground as well as the battery negative. I tried both and the reading never changes.

Anthony

 

what is the logged range of your V readings?

 

The red wire of the thermocouple is always the ground. Are you sure you have the correct connections?

 

I'll check later today or tomorrow. I'll check the voltage coming out of the thermocouple as well as the amp.

The thermocouple has 2 wires, a red and a yellow. The amp was labelled with a "Y" and a "R" so I simply but them in there and tightened the screw. Is yours not the same way?

Thanks for the responses.

 

I use the Innovate TC-4 and log through their software (wish the TC-4 had an output to use with other loggers). The Innovate is simply labelled + and -. If yours says red and yellow then it's taken the guess work out of hooking it up.

 

Another thought. Where do you have the amplifier and the ECU grounded? You might simply be seeing a ground offset between the two if they're grounded to different locations. Also, having multiple lugs attached to one spot stacked on top of each other can contribute to a ground offset. I prefer to ground the ECU and other important electronics directly to the engine block.

 

That's a good point. I think I need to work on grounding. I have all my grounds on a ring terminal but I have that grounded directly to the battery. I think I'll run a separate ground from the battery terminal to the engine block. The battery right now is only grounded to an area of the chassis in the hatch area of my FD.

 

Would be a good idea. The battery should always be grounded directly to the block. May help ignition performance as well.