Using thermocoupled twisted wires for EGT?

[2QUIK6]

With my new Innovate LMA-3 it came with a thermocoupled wire, you just strip the pair of wires down an inch or so, twist them together and attached to the exhaust somehow and then attach the other end to the LMA-3 for EGT temp sensing.

My question is, has anyone used this type of thermocouple on our cars instead of a probe, and how and where is the best place to attach it?
I know the uppipe before the turbo, but can I just attach it to the outside of the pipe?

How accurrate are the readings and what reading is good??

I'm assuming I could just camp it to the exhaust with a hose/band clamp or would that screw up the reading?

 

[Instro84]

you will get a temp reading this is we use them for measuring air temp. i wouldnt use a clamp to attach the twisted portion to the exhuast thou. the way thermocouple wire works is from a juction of two different metals, the clamp would be a third type and may screw up the readings. we have used exopxy to attach them but i dont know of one that can handle exhuast temps. hth

 

[salvageV6]

Usually the junctions are welded then covered for EGT use.

Twisting does work and should be accurate enough for EGT's but with all the vibration there plus the harsh environment I wouldn't use it.

Better off using it for A/C duct temps. or MAT's if you have a second input.

Use a good EGT probe for that harsh environment.

 

[ijames]

Where the two wires touch each other is where it will sense temperature. You really only want them to only touch at one spot, and either spotweld or tig them together. If you twist them together they will give an average reading over the entire area of the twist, so keep that short, less than 1/4". You can try clamping them to the outside of the tube but you may get lots of noise pickup - the readings will be all over the place. Have to try it and see. Maybe use a little of the insulation from the wire itself to cover up the bare twist. Ideally you want a probe through a hole, sticking into the exhaust stream itself. This gives the fastest response, which is what you want, especially for drag racing. For highway or road racing it won't matter so much since you will be on the throttle for longer periods (I guess). The slower your probe responds the lower your readings will be, compared to someone with a very fast sensor, at the dragstrip, so don't try to tune for a particular number immediately. Learn what your car likes with your probe, and then use it to keep the tune constant.

 

[2QUIK6]

Thanks for all the input. Looks like I would be peeing in the wind with the twisted pair touching the header wall and the clamp on the outside, so it would be introducing 2 more metals into the thermocouple.
I did find where someone twisted the pair together, soldered them, drilled a small hole in the ex pipe, welded on a 1/8 NPT fitting, then took a tube ferrel, like those on a boost gauge and connected that to the fitting, then fed the twisted pair wire into the ferrel so the wires were in the exhaust tract and then tightened the ferrel to secure the wire and ot gave an almost instant response compared to a probe. All the probe is is a covering over the twisted pair of wires so I can see how that would work faster, but don't think I'd want to do that before a turbo not to mention the extra heat would probably de-solder the pair. It also recommends welding together with copper.

Guess I'll just go with a K-Type probe and install it the next time I take the headers off. At least I can log fuel pressure, boost, rpms, and WB O2 AF with this LMA3/LM1 combo...use Direct Scan for all the rest!

 

[Ormand]

Solder generally melts well below the exhaust gas temperature, so soldering the wires together is not a good way to go. Brazing is better, welding is best.

 

[2QUIK6]

Solder generally melts well below the exhaust gas temperature, so soldering the wires together is not a good way to go. Brazing is better, welding is best.

I was figuring that when I read that at another site, maybe it was a different application something, definitely would melt on a turbo/SC app.

 

[Instro84]

silver solder is what we use for air beads, but for egt probe it the way to go.

 

[Ormand]

silver solder is what we use for air beads, but for egt probe it the way to go

The hardest silver solder starts to melt at about 1400 F, maybe a little lower. So, if you are SURE that your EDT will never get over 1400, then save a nickel, and solder the thermocouple.