Where did you mount your EGT probe? Let's hear!

Uffe · **Posted:** Thu Mar 06, 2008 1:59 pm

Yes as the topic says, I would like to hear from the guys who mounted an EGT probe, where they put it, and if it is not too much trouble, what readings you have at some conditions you can remember

I just bought two Trisco electrical gauges and probes and will instal the EGT and boost sensor with a friend at next oil change, and I would like some input on the EGT probe. Some say a good probe does not break and there is no need to be afraid of installing it in the manifold, where others like to stay conservative and install it in the outlet of the turbo instead.

Advantages of this is no fear of breaking the turbo in the case the probe shatters and fills the exhaust with metal fragments.
Disadvantages is in the readings, because the turbo will pick up some of the heat, especially in low load situations.

Let's also hear from the technical guys who can give me fingerpointers at the importance of placing the probe in the manifold, because "so and so much" energy goes into the turbo and my reading becomes inaccurate if I install the probe in the turbo outlet.

Thanks in advance!

gmctd · **Posted:** Thu Mar 06, 2008 2:31 pm

Most accurate is in the exhaust manifold just ahead of the outlet flange - pre-turbine exhaust temps usually run ~300deg higher than post-turbine installs, gives you the real life-temperature of your engine - the temp difference is due to exhaust energy lost a.) in driving the turbine motor and b.) normal gas expansion

EGT probes don't break off - shade-tree redneck installation destroys inherent probe integrity, usually resulting in failure - procedure:

Gather your tools - drill motor, bit, tap\handle, safety glasses\face shield - install the drill bit, plug the drill motor into the ac outlet, and place everything for easy access

Determine good tap location with easy accessibility

Start the engine from cold, so you don't get burned, and immediately begin the installation:

Put on your safety glasses/face shield

Drill the still cool exhaust manifold with engine running, such that exhaust pressure blows the cast-iron curly-chips out of the hole (and into your eyes and mouth and nostrils and ears and into your hair and down your neck, if not properly protected with OSHA-approved safety equipment!)

Immediately tap the hole, running the tap down about 1/3rd of the thread depth - again, exhaust pressure will remove the chips.

Shut the engine down so the exhaust manifold will not be over ~180-200degF

Install the probe, connect the wiring, put up the tools, wash up, and yer good to go..............

Uffe · **Posted:** Thu Mar 06, 2008 2:41 pm

I knew I could count on you gmctd!

Thanks for the procedure! I have some questions though (obviously).

gmctd wrote:

Immediately tap the hole, running the tap down about 1/3rd of the thread depth - again, exhaust pressure will remove the chips.

When you say "tap down", do you mean making thread for the probe? I am not sure of the meaning of this word in this sentence.

What thread depth do you mean? 1/3 along the probe or 1/3 across the width of the probe?

Excuse my lack of knowledge of the mechanical technical english :oops:

ATXKJ · **Posted:** Thu Mar 06, 2008 2:53 pm

Looking at the exhaust manifold - I think most installs are post Turbo because of the space
The only place I could see putting in a pre-turbo probe would be straight up from the bottom
it looks like there's space there (at least on the parts manuals - I haven't tried it yet)
my EGT is still sitting on a table until I can figure out where to mount it.

gmctd · **Posted:** Thu Mar 06, 2008 2:56 pm

Two things to remember: a.) the cast-iron manifold walls are not very thick, and b.) the threaded tap creates the threads in the drilled hole, and c.) at 30psi Boost, there is ~30-45psi exhaust back-pressure in the exhaust manifold - as the fittings are usually tapered pipe fittings, the tap is therefore also tapered - if you run it all the way down into the hole, full thread depth, the resultant threaded diameter will be too large for the fitting, and it will not seal because the manifold wall is thin - run the tap down to about 1/3rd of the available depth, try the fitting for correct fitment

Lessee: a.), b.), and c.) - hmmm, that's three things, not two - ok, I lied, so sue me!

Uffe · **Posted:** Thu Mar 06, 2008 3:07 pm

I can't really see the stuff you explain to me, I think I will have to have a look at the probe when I get it tomorrow (or maybe not before monday).

Are you saying the probe connects to an adapter which creates thread when you screw it into the hole you drilled? (assuming the hole is the right diameter

)

ATXKJ · **Posted:** Thu Mar 06, 2008 3:21 pm

FYI 2.8 Exhaust Manifold

gmctd · **Posted:** Thu Mar 06, 2008 3:22 pm

Normally the probe is just that: a probe - therefore, some method of attachment\insertment must be provided with the probe to install it in a system - that's usualy in the form of a tubing compression\pipe fitting adaptor - thread the adaptor into the manifold, insert the probe to correct depth, tighten the compression fitting, and it's installed and sealed

Yeah, too bad, but I haven't seen ours in a month, or I'd have better sense of configuration on that - might could use one of the shield standoffs, by drilling thru into the manifold, running the probe down deep, using the NPT fitting dual purpose to seal the probe and attach the shield - should be some way to install from the top - need to remove a shield to see that - need to see the Jeep to remove the shield

drharv · **Posted:** Thu Mar 06, 2008 3:54 pm

GMCTD where on the above diagram would you intall the egt probe? I would aim for betwen 2 an 3 exhaust ports (going by the diagram not in situ).

BTW thanks for all of your knowledge and willingness to share.

gmctd · **Posted:** Thu Mar 06, 2008 4:06 pm

Anywhere that's accessible, except for that EGR port at the rear - no exhaust flow there with the ORM\SEGR mods - don't want the probe directly in an exhaust port, as that increases monitored temperature while reducing averaging, but that location is better than no EGT probe, particularly if towing

Should never depend on those drawings as factual, but that looks like a welded-up exhaust header, which would create even more difficulty when attaching a threaded NPT fitting to tubing

Anybody got pics?

Uffe · **Posted:** Thu Mar 06, 2008 4:26 pm

Many places on the net says you can install in a single outlet tube as well.

Problem is then that you don't know if the rest of the cylinders are the same

There is also the option of installing it after the turbo, which is what one guy on here has done.

I will have some problems accessing the manifold while the engine is running, as the easiest way is to remove the CAC inlet hose and a bunch of other stuff to get there...

Went and tried to take pics. All you can see is tubes. There is nearly no space to get to anything. It's impossible to get to the manifold without removing the boost hose, water hose, AC hose and the wire harness.

From underneath is just as impossible.

There is only a few spots from the top where you can access something, and you need to remove the heat shield first. Removing that and the tubes will take a while. Then you have to put the boost hose back in order to run the engine and drill.

My best option AFAIK is to drill into a single port from a single cylinder. Or find a spot after the turbo.

honey_don't · **Posted:** Thu Mar 06, 2008 7:06 pm

I have not installed an EGT probe in the Jeep, but if I were going to I would try to drill the bottom of the manifold directly in front of the turbo inlet. Properly, this is called turbine inlet temp (TIT) while post-turbo is EGT. It would be really cool to install a TIT gauge!

An installation technique I have used is:

-start with cold engine, not running
-coat the drill bit in grease
-drill hole, stopping frequently to wipe off grease/shavings and reapply grease
-coat tap with grease
-tap hole, stop frequently to wipe off shavings and recoat with grease
-install probe, run motor at idle for 10 min to blow any shavings through turbo

cast iron shavings are softer than the turbine so the risk of damage is relatively low

gmctd · **Posted:** Thu Mar 06, 2008 7:18 pm

Since we're not dealing with a jet turbine, but rather an infernal combustion engine, we are concerned with Exhaust Gas Temperatures anywhere past the exhaust valve, which defines a combustion chamber limit, preferably before entering the turbine motor - otherwise, it would also be proper to disconnect the driveshaft and let turbine exhaust pressure push us down the road - piston-engined EGT is ex-exhaust valve - jet-turbine engined EGT is ex-turbine.

I do like the TIT guage idea, tho not nearly as much as a booty meter.............

Pablo · **Joined:** Thu Feb 02, 2006 10:06 pm **Posts:** 1201

I just got mine back from getting gauges installed, and a cummins lift pump. I had mine EGT installed post turbo. That is good enough to give me an idea. So far it seems to live around 600 while cruising around town.

What are folks seeing for transmission temps? I am getting 150 cruising in lockup, 180 not in lockup and it sure does heat up in stop and go. I will probably 4x4 this weekend and it will be interesting to see what I get then.

Uffe · **Posted:** Fri Mar 07, 2008 3:30 am

Interesting thread this has become.

So to summarize the thread:

1) Engine running or not running while drilling manifold can be done, but not running the engine requires idling for 10 minutes to blow metal fragments through turbo without it spinning and eating metal
2) Installation of EGT should be at the turbo inlet
3) gmctd likes more information on a booty meter :lol:

How do I access the turbo inlet, again? I went to have a look at the engine bay last night (w. flashlight) and the heat shield is my main problem, or time consumer. To remove the heat shield, I need the CAC hose dismounted, pry away the water hose, oil catch tank hose and A/C hose to remove the heat shield. I then need to drill through the heat shield in a location where I can be sure to access the turbo inlet and THEN put the heat shield back to do an install with the engine running, or (more easy) leave it all dismantled and drill and fit heat shield hole with probe hole, with the engine shut off.

Would someone let me know if it is possible to go in from underneath the car and get a probe installed in the turbo inlet?

PhoenixCRD · **Posted:** Fri Mar 07, 2008 11:20 am

Pablo wrote:

I just got mine back from getting gauges installed, and a cummins lift pump. I had mine EGT installed post turbo. That is good enough to give me an idea. So far it seems to live around 600 while cruising around town.

where did you have the work done?

Gary

gmctd · **Posted:** Fri Mar 07, 2008 11:53 am

Long-time GM hi-performance R&D contractor\consultant Gale Banks suggests a probe location in the downpipe ~30" back from the turbo flange - 'course, being an old gearhead (with emphasis on the 'old') I interpret this as first defense against the 'sky is falling' syndrome, with multiple call-ins from skittish customers not accustomed to monitoring any of the instrument panel guages, much less a hi-temp EGT guage - a scenario very well-defined in the earlier 'idiot-light' concept.

I feel like the blind-folded kid swinging at the pinata - I know it's there, and I know what it looks like, but I can't see it to define any direction - but, it may come down to drilling thru one of the heat shield stand-offs to install the probe.

I would suggest drilling the turbine snail, but I can already picture the scenario of DCJ's reaction to any warranty claim upon seeing that - and it is not a pretty picture!

ATXKJ · **Posted:** Fri Mar 07, 2008 3:11 pm

FYI post Turbo has a lot more room

gmctd · **Posted:** Fri Mar 07, 2008 3:17 pm

Ah - show'n'tell rules!!

FWIW, my first probe was mounted similar to that in that locale - you had the bung welded on when the exhaust system was done?

Also looks like that brace could be removed to allow access to the exhaust manifold for drill\tap procedure from beneath

Uffe · **Posted:** Fri Mar 07, 2008 7:03 pm

That looks super tidy! Thanks a lot for that photo.

I will see what I can do, but that spot looks really well suited for the EGT probe.

My package is at the post office as I type, will pick it up tomorrow and see what I got to work with. Probably post pics of the gauges and sensors.

When I get to the next oil change (~900 miles) I will try to make a little how-to in the tech section. Depends what I can see - when my friend gets going he's fast and normally I help out by handing him the tools...not sure there will be time to take pretty pics...

Where did you mount your EGT probe? Let's hear!

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