Pre turbo pyrometer a really bad idea?

[GTX_Joel]

Hi Guys,



I installed the sensor for my pyrometer in the exhaust manifold, just upstream from the turbo.



Today I had a conversation with a guy who runs a turbo repair shop. He said that is a bad idea, because if the sensor burns off it will go thru the turbo and wreck it. He recommends mounting it downstream so it is cooler and is less likely to burn off, plus if it does it will just rattle out the exhaust pipe. As far as readings, he said just deduct 300 degrees for a downstream temp. Seems to make sense to me, I am considering moving it.



What do you guys think? Has anyone ever had one mounted pre-turbo burn off?



Thanks, Joel

 

[AggieJustin]

This topic has went through a few times before, do a search and you'll find plenty of info on it.



But to sum it up, the pryo probes are rated for a pretty high temp. If you're exceeded that temperature, then a busted probe is probably the least of your worries... you engine might be a little outside it's operating range. The other thing would be debris hitting the probe and breaking it off... but once again, the probe is the least of your worries if debris is flying around your exhaust manifold.



Also, the 300 degree factor doesn't always hold true. The amount of temp difference depends on a number of other factors. Also, the post-turbo probe is slower to respond so you're not getting real-time readings of the temps flowing into your turbo (which is one of the items you're trying to protect).



But post-turbo probes are good for monitoring engine shutdown temps, which is why some people have both pre and post probe mounted.



JM

 

[BushWakr - RIP]

I ran mine "post-turbo" for a long time... I finally got tired of having to "do math" to "estimate" my actual temps.

Mount it PRE-TURBO and don't think twice about it. .

You will get far more accurate readings, faster response time on the gauge and should not have to worry about probe disintegration.

Yes, the post-turbo mount does help with cooldown readings but lets face it, you should just plain wait until your pyro is well below 300*F before shutdown anyway...



The probe only has to protrude 1/4" to 3/8" into the stream for a good reading and it is very uncommon for it to fail and result in turbo damage. . very uncommon.



Pastor Bob. .

 

[R-N-R]

I have seen temp differences from 200* to 600* between pre/post probes during a variety of driving conditions .

 

[Deezul1]

I was told that aircraft EGT probes are pre turbo and it doesnt seem to be a problem there. If that is not true I would like to hear about, hate to spread bad info.

 

[GTX_Joel]

Ok, it stays where it is!



Thanks for all the input. I'm going over to this guys shop tommorrow to pick up a 16 cm exhaust turbine housing. 125 bucks dosen't sound too bad.



TTFN, Joel

 

[MCummings]

This should help you...



https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=78335



Merrick Cummings Jr

 

[TSuter]

I've worked on aircraft for 18 years, I've personaly never heard of a thermocouple breaking off unless it was helped ie, engine shelling out or bird ingested into engine. In which case as stated above you have alot of other things to worry about besides the thermocouple breaking. I've worked on aircraft with EGT (Exhaust Gas Temp) and TIT (Turbine Inlet Temp). TIT is kind of misnomer the probe actually installed in the 5th-7th stage of the compressor section. My thermocouple is installe pre-turbo, I'm not concerned at all.



Just my . 02



Tom

 

[Bob Beauchaine]

If you're worried about it coming apart why not just pull it out a couple of times a year and inspect it? Mine has been in for 9 years now and still run quite well.

Bob

 

[JMorrow]

How far should the thermocouple be sticking in the exhaust manifold, pre turbo? Mine blew out twice on vacation so I stuck it all the way in!



John

 

[formula]

Originally posted by BushWakr

The probe only has to protrude 1/4" to 3/8" into the stream for a good reading and it is very uncommon for it to fail and result in turbo damage. . very uncommon.



Pastor Bob. .

Mine used to extend almost to the bottom of the exhaust port. Never showed any signs of deterioration. Got it installed in the same spot on the ATS manifold, but due to the thickness of the mounting boss, it only sticks into the exhaust port about 1/2" now. Works just fine that way.



One thing you want to be careful of is to make sure that the tip of the probe is NOT touching the bottom of the manifold. This will skew your temp readings and allow for stress to be placed on the probe.



Sean

 

[dpuckett]

GTX_Joel-

THis topic has caused as many battles as dino vs synthetic or which auto transmission is best. I sold a pickup to a guy who said the same thing about the pyrometer, and I told him it was an urban legend. He was a mechanic on bigger engines, but knew squat about the B series- said messing with the AFC would make NO difference in response time, power, mpg, etc. ANyway, I had the pyro post turbo on my current rig for about two weeks, never saw 1000 deg, under ANY conditions. I moved it PRE turbo, and I could hit the red line pretty easy. Going up the same hill, same gear/ speed, empty, I saw a difference of over 400 deg. THe 300 deg theory doesnt work; neither does the 1 psi boost= 10 deg off, either. I was only making 15 psi boost to make the 400 deg difference. Unless you plan to keep your truck stock, never tow with it, and stay below 3000 ft, I would keep it where it is. Good work, guys.

Daniel