EGT probe (dilema? help)

[TrrboJeep]

Ok guys, your probably thinking, not another one of these questions... lol

But my question is a bit different, due to my turbo setup. For anyone who was at SDAC15 (Edgewater) and saw my Jeep and it's setup, you will know my turbo is not mounted directly to my exhaust manifold. It is mounted on the opposite side of the motor, with about 4' of pipe connecting the two.

My question is, where is the best spot, in a setup like this, to mount the EGT probe? The gage instructions say 2" in front of the turbo exhaust inlet, which would mean in the pipe leading to the turbo. Will this give me the most accurate reading given that it is 4' away from my exhaust manifold? I was going to remove the exhaust manifold and drill a hole in it to mount the probe, thinking that the closer I keep it to the head the better, and more accurate the reading?

What are your thoughts, experience on this?
Should I mount it near the turbo, or in the exhaust manifold?

[Frank]

I would definently mount it about 1" from the port of a cylinder. This gives you most accurate results of avioding damage... which is the piston from going lean. Even if you are worried about the turbo, you have 4' of pipe to let it cool out of the danger zone.


Frank

[TrrboJeep]

Yep, that was my thinking as well. I'm not too worried about the turbo as I'm sure it doesn't run as hot as one that is bolted right to the exhaust manifold. I'll put it in the exhaust manifold then, as close to the head as possible.

It is soposed to be around zero here this weekend... may have to wait till warmer weather, or tear it apart and drive the Ram for a couple of weeks?

[cordes]

I too would place it in the manifold close to the head. Although many old timers put the probe down stream of the turbo, not quite the same aplication though...

[TurboGLH]

1" is just right, the other trick is to place it in the runner of the cyl that runs the hottest. If the jeep 2.5's have one cyl that runs leaner than the others, use that one for your monitoring.

[TrrboJeep]

Well, due to the design of the manifold, and how thin it is up by the head (because of porting the $hit out of it), I put the probe where the manifold had some meat to it. Given the picture and its location (approx. 8" from where it should be) how far off (cooler) due you think my temp reading will be with the probe mounted here? 100 degrees? 50?

Frank, got a formula for distance away = degree's of temp drop?

[cordes]

I have read that guys actually see a higher EGT when the probe is exposed to the exhaust of multiple cyls. such as yours. Perhaps it would off set being farther away from the head?

[Frank]

Well, due to the design of the manifold, and how thin it is up by the head (because of porting the $hit out of it), I put the probe where the manifold had some meat to it. Given the picture and its location (approx. 8" from where it should be) how far off (cooler) due you think my temp reading will be with the probe mounted here? 100 degrees? 50?

Frank, got a formula for distance away = degree's of temp drop?

I wouldnt sweat it. Really the drop is not going to be that bad. Your mister reliable, so I would say dont let them get above 1400 at that location. By reliable, it keeps the exhaust valves in awesome shape, etc. I know that the guys with EGT's in the swing valves were calling like 1300 as being their max. You could probably do 1500 as max, but 1400 is safer. I hope you dont expect anything but speculation at this point... tough calls because of type of metal, distance, blah blah blah.


Frank

[TrrboJeep]

I was thinking the same thing... 1,400 for my max EGT at that location. That should keep me "safe".
I'm going out in the 25 degree weather today and hook everything up and make some test runs... Runs with +40's at different boost levels, then +20's same boost, then with alcohol, without... I will get it dialed in this week, and post some numbers for giggles.

[TrrboJeep]

Well, I got it all back together... nothing ever works like it's soposed to!

What causes an EGT gage needle to bounce like crazy? It works ok until I turn on anything in the Jeep, lights, radio, doesn't seem to matter, but when I turn some accesory on, the needle starts bouncing like crazy, then if I turn on enough things it will stop functioning all together? WTF? I checked the 12v power wire. The ground. GRRRR! (autometer quality)

I've heard around 800F at idle, 1,200 at steady cruise, and 1,400 at WOT for temp readings... is that about what everyone sees? Except for turbovanman that pulls 1700F at cruise!

My WOT is around 1,500F and at a steady cruise it seems to be around the same? Idle is around 900F.

[cordes]

It is your ground. My auto meter EGT gauges don't like to be grounded to anything but the battery otherwise they will bounce around just as you stated.

[TrrboJeep]

OK, I'm gonna ground her strait to the battery!

[cordes]

OK, I'm gonna ground her strait to the battery!

That is what I had to do myself.

[TrrboJeep]

Well, I grounded the gage strait to the battery, and the needle still bounces like Dolly Parton running a 5K marathon. It gets worse when I turn on any accessories, so now I'm thinking it is electrical interference? My next step is to try shielding the wires from the probe to the gage?
If this doesn't work I'm out of ideas?

(hooking up gages is not soposed to be this technical!)

[Frank]

You should need to shield the wires. There isnt anything that should be causing EMI coupling on those lines. It is definnently a ripple current/voltage being put on either the ground or power. Try running the power directly to the batter and see if that works.


Frank

[TrrboJeep]

OK, I'll give that a try. I have a nice big power wire (10 gage) coming strait from the battery that runs to my amp. I could try taping into that for the 12V power source. With the Radio off it would be like a direct connect to the battery. If it doesn't bounce then, I'll know I have it solved.

[Frank]

That is a good plan. Typically a jumpy gauge is usually suffering from ripple voltage produced from high frequency bleed over in the electrical system - alternator, injectors, coil, fans. Injectors are always the least suspect with coil and blowers being the highest. Alternators tend to have more prominent effects besides gauges.


Frank

[jckrieger]

Buy a $45 Westach gage, it requires no connections besides the EGT probe. Of course, it's awefully difficult to read at night..

[TrrboJeep]

Buy a $45 Westach gage, it requires no connections besides the EGT probe. Of course, it's awefully difficult to read at night..

Nothing a pen light couldn't cure!

[jckrieger]

Nothing a pen light couldn't cure!

I've been driving around with my dome light on during night time test runs in the CSX. It's not too bad, but it sure does attract attention when the dome light comes on right before the car goes WOT.