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+--- Thread: Please comment on my EGT probe placement (/showthread.php?tid=2023)
Please comment on my EGT probe placement - mcneil - 11-30-2010
This is for the probe that came with my VDO pyrometer. The bung is 1/4-18 NPT, drilled into the manifold and ground to the contour of the inside of the manifold. Filler material is Nickel-Silver brazing rod.
Took me two brazing attempts, the first one at home and I failed to clean and preheat sufficiently. I got the bung in there well enough, but the manifold cracked and there were inclusions in the joint. So I took it into work, ground out the crap, sandblasted everything, and preheated in an oven to 350. Second attempt came out much cleaner. The brazed-in #8 screw is there to fill the hole I drilled to stop the crack.
So, um, besides "your brazing sucks", what do you guys think?
![[Image: IMG_0927.JPG]](http://lh3.ggpht.com/_o_3o6xcLap8/TPUsJ4bKuaI/AAAAAAAADHA/8RJt7I8CKIQ/s800/IMG_0927.JPG)
![[Image: IMG_0928.JPG]](http://lh3.ggpht.com/_o_3o6xcLap8/TPUsKVGcCtI/AAAAAAAADHE/LkdB5VKwrjs/s800/IMG_0928.JPG)
![[Image: IMG_0926.JPG]](http://lh4.ggpht.com/_o_3o6xcLap8/TPUsJnCY81I/AAAAAAAADG8/7dHl0Wkbf4I/s800/IMG_0926.JPG)
![[Image: IMG_0925.JPG]](http://lh3.ggpht.com/_o_3o6xcLap8/TPUsJOE5quI/AAAAAAAADG4/08HxM9vuNDs/s800/IMG_0925.JPG)
RE: Please comment on my EGT probe placement - Alastair E - 11-30-2010
Looks good, My only fear would be the unequal expansion between the jointed material and the cast-iron...
--Then again, I know little about cast iron welding....
RE: Please comment on my EGT probe placement - ForcedInduction - 11-30-2010
Whats wrong with just a drill and tap?
RE: Please comment on my EGT probe placement - mcneil - 11-30-2010
(11-30-2010, 03:25 PM)ForcedInduction Whats wrong with just a drill and tap?
I was concerned (possibly overly concerned) with cracks growing over time. The manifold's wall thickness is less than 1/8" in most places.. which is actually pretty impressive for 30 yr old mass-production casting techniques. But 1/8" wall and 18 tpi leaves less than 2 threads.
It looked like there were a couple other places with thicker sections, and I was thinking about drilling out one of heat shield mounts. They might have worked too.
RE: Please comment on my EGT probe placement - Captain America - 11-30-2010
hmmmm .125" wall isn't much... I'd be worried too. Looks good though
Your not going to throw a non EGR manifold on it?
RE: Please comment on my EGT probe placement - mcneil - 11-30-2010
(11-30-2010, 05:03 PM)Captain America hmmmm .125" wall isn't much... I'd be worried too. Looks good though
Your not going to throw a non EGR manifold on it?
I was going to, but there's this thing.. you know.. I already have this manifold.. etc. Plus there was more meat right at the joint where the EGR outlet hit the collector, so I figured it'd be easier to put the EGT probe in this manifold.
My guess is that it doesn't matter much for the flow whether that EGR inlet pipe is there or not. I debated making a iron plug and brazing that in, then grinding it flush with the inner contour.. deemed that not worth the effort.
RE: Please comment on my EGT probe placement - ForcedInduction - 11-30-2010
Its more than thick enough. The pyrometer is not load bearing.
RE: Please comment on my EGT probe placement - George3soccer - 12-01-2010
Forced is correct. The only load the sensor might endure would be the vibration of engine rpm.
And my guess is that the sensor weights a few grams and the length of the sensor from manifold to the end would be 5cm. There is not much lateral load along the sensor. 2 threads and some super high heat loctite would do the trick.
Not to bad brazing there i must day.
RE: Please comment on my EGT probe placement - Captain America - 12-01-2010
I was thinking that the load would be from the tolerance fit of the pipe threads trying to expand the hole, not the weight of the sensor....
RE: Please comment on my EGT probe placement - willbhere4u - 12-01-2010
realistically it works either way! I've seen it done before with no I'll side affects!
RE: Please comment on my EGT probe placement - George3soccer - 12-01-2010
The heat expansion on that manifold shouldn't be the problem with the sensor in place.Only because it would all come down to the weight of the sensor moving around, when the threads start to expand. Such a tiny thing it should have no problem, with that.
RE: Please comment on my EGT probe placement - mcneil - 12-01-2010
Disclaimer: I tend to over-engineer everything. I am an engineer. It's what I do. Tapping would have worked, but I figured I'd get fancy.
That said.. the worst thing a manifold sees is cyclic thermal induced stresses which eventually cause fatigue cracking.
Forced is right.. the pyro probe isn't going to bust a manifold. But I did manage to make it crack with nothing but poor preheating in my first brazing attempt, and I didn't even get it above a dull red heat.
RE: Please comment on my EGT probe placement - ForcedInduction - 12-03-2010
Neither of my manifolds have cracked with a pyrometer installed, even without the support brace installed on one manifold.
RE: Please comment on my EGT probe placement - Rudolf_Diesel - 12-03-2010
You should not have an issue with te placement, You should have brazed up the EGR port while you were at it.
The manifold material is not your typical cast iron. It is VERY hard stuff, a real PITA to machine. I installed mine on the under side of the trubo inlet and had ~4.5-6.0 mm of material to drill and tap.