Mine is pre-turbo, but in the runner from cylinders 1-3, because at the time when I did it, I was hearing stuff about there being a small restriction in the number 1 intake runner, making it be slightly hotter than all of the rest... maybe someone else can shed some more light on this.

 

I've never heard this.
Mike

 

This is where the 12 and 24v engines seem to differ.....#6 on the 24v is supposed to run the hottest and depending on who you talk to about 12v's, 1 or 3 is the hottest......so, on a 24v, the probe should be in the rear runner and on a 12v, the probe should be on the front runner.

 

There you go. That is why I never heard of it...I have a 24 valve.
Mike

 

BIGBLUE, how far back on the turbo did you have the probe when you were running it post turbo? I can understand if its mounted on the down pipe, not a very effective place to mount it. I have mine mounted smack dab, right behind the houseing. Wish I had a pic, time for a digital camera.

 

Mine is pre-turbo. For accurate readings on exhaust temps pre-turbo is the ONLY way to go, and even MORE critical when towing. Because it will react almost instantly and accurately to the "go " pedal, you can simply back off of throttle when temps get and stay too high, before engine meltdown.

 

Hmmm, I have a 12V and stuck it on the back 3. Hope it will be OK. Maybe I'll get another probe to put on the front, and see how big a difference between the 2 there is.

 

Dave88LX - Yeah, I was just wondering how many of us 12V'ers have their probe mounted in the rear of the manifold.

 

You could drill another hole and use a pipe plug to seal up the one not in use....have seen that done.

If I remember what I've read, you might be looking at 50* difference (average) between front 3 and back three, with #1 running 100* hotter than the coolest cyl. So you could just drive accordingly and just don't go too close to the EGT edge!

RJ

 

My post turbo is mounted in the middle of the elbow that comes out of the turbo. Probably about 2" away from the turbine.

 

How about 1 in the front, 1 in the rear exhaust manifold, and 1 in downpipe,and average out all 3 .Don't forget muffler bearings(they get very hot also)

 

For real? Darn! Then how come every *gosh dang* set of instructions on the net says to drill it into the rear of the manifold. GRRR.

If I had an extra $117 laying around, I'd run another gauge, to get the exact answer to this once and for all.

 

Well, I found a way to run one gauge and two probes. (Pic in my photo gallery) Switching between the probes, thinking about giving it a try.

 

The K type thermocouple produces very little voltage which is non linear as temps go up. Every time you add a conection in the wiring, it is like adding another thermocouple in the curcuit and will throw the guage reading off. K type thermocouple extension wire should also be used. For example, using copper instead of K type extension wire, temp readings will be as much as 200*, or more, lower. Because the voltage is soo low, and non linear, little details can make big differences in readings. Guage manufacturers compenste for wire lengths, and the number of connections in the curcuit, in the design of their guages.

 

Yeah, switching between two probes seems like a good idea but I think you would build enough resistance in the switch to throw the reading off by at least 50 degress. That's why I'd never get too close to critical EGT, because even the wires of a perfectly good gauge get corroded over time; thus, having a greater resistance than when it was new.