Where to install thermocouple

peppe_tdi

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Joined
Jan 19, 2016
Location
italy
TDI
PD105
Hello guys, I'm going to install a thermocouple before starting with the remap (1.9 TDI PD ex@105 with GTB2056VK Audi 70mm downpipe and stock injectors at the moment).

I would like to install the thermocouple in the egr inlet of the exhaust manifold, but I am afraid of destroying the turbo if for some reason the thermocouple should yield.

For this reason I would install it in the downpipe but I have heard that reading will not be accurate.

In your opinion, what is the best compromise between accurate reading and low risk of breakage?

Thanks to all of you, you are great.
 

Mongler98

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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
the only way to do this is to have it pointing directly into the turbo exhaust inlet before the turbo. If you get a quality one, it will not yield. i use them in ceramics and that gets up 2,400*F so your not going to see a failure EVER, NEVER NEVER EVER

get a quality probe rated for cone 11 for ceramics or one from Auber, its industrial grade stuff there. the closer you get the tip to the fins the better. Mine is about 3/4" away from touching the fins, and if the nut where to lossen up and let that drop down it would go about 1/4" past the fins and kill the turbo. I have seen over 1,600 degree temps before and never once had an issue. no locktight, nothing, just a auber gauge pyrometer.

if you dont do this, your not going to get an accurate reading and you can do more damage than without.

dont worry, those things can handle 3x the temperatures that the exhaust will put out.
 

crazyrunner33

Veteran Member
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Jul 11, 2006
Location
NC
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'10 Golf(bought back)
Like Mongler98 said, the turbine inlet is the only place worth placing the thermocouple.

One of my buddies performs abuse testing for one of the turbo manufactures, most K types and even the el cheapo K types hold up just fine. They have melted down thermocouples a few times, but the stainless steel manifold melted as well. I have a feeling you won't be pushing them as hard.
 

Mongler98

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COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
You can install this without taking the exhaust off. you need, a drill a tap and the drill bit for it, the parts, and a few ring magnets. took the intake off, put a piece of cardboard against the intake of the head but not stopping the air flow, got a center spot marked with the drill bit put the ring magnets on, started the car, drilled and tapped it when running, 99.9% of the filings go into the magnet and the cardboard keeps them from going into the engine. it was really easy, take your time. I have pictures but they are HUGE and i dont feel like getting yelled at again for uploading them here. i can PM you the pictures on how i did this but you get the point.
 

Mongler98

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Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
I highly suggest Auber, there gauges have relays in them, i run water meth injection with the relay from the EGT's
 

peppe_tdi

Member
Joined
Jan 19, 2016
Location
italy
TDI
PD105
So the best solution would be to mount the thermocouple near the turbo flange where the gases are warmer if I understand correctly.
can I use the input of the collector's egr?
Do you recommend a probe thickness?
Thank you a lot guys.
 

Mongler98

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Location
COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
Any thermo probe rated K type is fine
https://www.auberins.com/index.php?main_page=index&cPath=5_22

I depending on your manifold will determine how long you need. The closer you get to the turbo's impeller, the better. The only reason to have the probe is to make sure the temperatures do not go past (usual temp for most turbos VW) 1425 sustained. Anything more than this (depending on the turbo) is going to melt the impeller as it’s an aluminum alloy that can handle more than what aluminum can. FYI, Aluminum melts at 1,221*F but that’s going from a solid to a liquid, 1,100 is when aluminum starts to get soft and damage occurs. Your head is 100% aluminum but its water cold and same with the pistons; they are solid and cooled by a bit of oil so they can take more abuse. The thin fins on the impeller will melt and the turbo will kaboom if you go too hot for too long. SO the ONLY reason what so ever to have a probe is to monitor this temperature. There is this thing called heat soak. It will give you most of the readings, the impeller fins is the most important. Now when it comes to one other factor, the turbos oil supply. You really want to have an oil PSI gauge when you upgrade a turbo, they are cheap insurance. When your parking the car, you MUST wait at LEAST 5 seconds of 425*F or less to let the turbo's oil supply cool down. If you don’t, you’re going to COOK the oil in the journal bearing. Heat soak will do this and is the only other reason to monitor the EGT temp. The closer you get to the impeller the better a reading your going to get on the heat near the shaft but heat soak again will affect the entire area. You want to cool that turbo off. All automatic cars that have an aftermarket plug in or some with just modified ECUS all have cool down time. My Cummins 2001 dodge has a bully dog, you can park, take the key out and walk away but the engine will run as long as it needs to cool that EGT down and get rid of that entire heat soak before shutting off. In a manual Trans you can’t do that without risk so you just have to wait and count. It’s painful to do when you get to a friend’s house after driving like a jackass and it takes 10 minutes to cool off. It’s best to drive a bit at low throttle and cools down fast.
 
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turbobrick240

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maine
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2011 vw golf tdi(gone to greener pastures), 2001 ford f250 powerstroke
Any thermo probe rated K type is fine
https://www.auberins.com/index.php?main_page=index&cPath=5_22

I depending on your manifold will determine how long you need. The closer you get to the turbo's impeller, the better. The only reason to have the probe is to make sure the temperatures do not go past (usual temp for most turbos VW) 1425 sustained. Anything more than this (depending on the turbo) is going to melt the impeller as it’s an aluminum alloy that can handle more than what aluminum can. FYI, Aluminum melts at 1,221*F but that’s going from a solid to a liquid, 1,100 is when aluminum starts to get soft and damage occurs. Your head is 100% aluminum but its water cold and same with the pistons; they are solid and cooled by a bit of oil so they can take more abuse. The thin fins on the impeller will melt and the turbo will kaboom if you go too hot for too long. SO the ONLY reason what so ever to have a probe is to monitor this.
The turbo impeller, aka compressor wheel, is not exposed to the hot exhaust gasses. The turbine wheel is in the exhaust path, and is most certainly not made of aluminum alloy. Somebody needs a refresher course in turbos 101. :D
 

Mongler98

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COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
Sorry, mind fart, I always confuse the alloy as the way I remember is the melting temperatures of aluminum are similar. Memory patterns and whatnot mixed with my dyslexia. Regardless if I said aluminum or not the point is the same and I’m sorry if I use the wrong terminology when I’m posting. I’m like Carle from sling blade, really good at working on engines but dumb as a rock when it comes to the words lol.

Inconnel 713C or GMR235 Super alloy are the main two components that the TURBINE WHEEL is made of, both have somewhat similar failure temperatures, You can’t read the temperature of the TURBINE WHEEL but you can read the temperature of the gasses going into it so to be on the safe side we say that 1450 roughly is a safe max temperature on most of our TDI turbos. My gt2052 can handle the 1600 but it’s not going to last very long if I do, there is no reason to go that far for 99.9% of any applications.

other than my brain laps moments in memory i do know what i am talking about and no reason for me to go to school again lol
 

crazyrunner33

Veteran Member
Joined
Jul 11, 2006
Location
NC
TDI
'10 Golf(bought back)
Inconel 713C is good for 1800 degrees all day long, and that's a conservative rating. I'll ask my buddy what he's tested it to, I know he ran it at over 2500 degree TIT, not sure now long until the fins started to deform.

Edit: He said it can handle brief bursts to 2500 degrees. He's held it at 2500-2600 degrees for a few minutes, long enough to erode the exhaust manifold and be able to see the pules move the manifold on camera. Anyone getting close to that temperature better have their eyes on the road instead of their gauges.
 
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turbobrick240

Top Post Dawg
Joined
Nov 18, 2014
Location
maine
TDI
2011 vw golf tdi(gone to greener pastures), 2001 ford f250 powerstroke
Sorry, mind fart, I always confuse the alloy as the way I remember is the melting temperatures of aluminum are similar. Memory patterns and whatnot mixed with my dyslexia. Regardless if I said aluminum or not the point is the same and I’m sorry if I use the wrong terminology when I’m posting. I’m like Carle from sling blade, really good at working on engines but dumb as a rock when it comes to the words lol.

Inconnel 713C or GMR235 Super alloy are the main two components that the TURBINE WHEEL is made of, both have somewhat similar failure temperatures, You can’t read the temperature of the TURBINE WHEEL but you can read the temperature of the gasses going into it so to be on the safe side we say that 1450 roughly is a safe max temperature on most of our TDI turbos. My gt2052 can handle the 1600 but it’s not going to last very long if I do, there is no reason to go that far for 99.9% of any applications.

other than my brain laps moments in memory i do know what i am talking about and no reason for me to go to school again lol
No problem, a little bit of humble goes a long way though. You don't need to go into the weeds of gamma prime precipitates in nickel superalloys to impress anyone here. ;)
 

turbobrick240

Top Post Dawg
Joined
Nov 18, 2014
Location
maine
TDI
2011 vw golf tdi(gone to greener pastures), 2001 ford f250 powerstroke
Inconel 713C is good for 1800 degrees all day long, and that's a conservative rating. I'll ask my buddy what he's tested it to, I know he ran it at over 2500 degree TIT, not sure now long until the fins started to deform.

Edit: He said it can handle brief bursts to 2500 degrees. He's held it at 2500-2600 degrees for a few minutes, long enough to erode the exhaust manifold and be able to see the pules move the manifold on camera. Anyone getting close to that temperature better have their eyes on the road instead of their gauges.
Damn. I bet he's not using any old generic thermocouple. Probably running a fancy cast stainless manifold too.
 

crazyrunner33

Veteran Member
Joined
Jul 11, 2006
Location
NC
TDI
'10 Golf(bought back)
Damn. I bet he's not using any old generic thermocouple. Probably running a fancy cast stainless manifold too.
It depends on what's being tested, and it's definitely way too fun. Sometimes it's just a standard cast manifold that the OEM application will use, other times they're trying to force the turbo to fail. In some instances they had to use a stainless steel manifold, and they've melted it down within a few minutes. When reviewing footage, supposedly you can see the pulses from the engine force the stainless to expand before it ultimately fails.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
Damn. I bet he's not using any old generic thermocouple. Probably running a fancy cast stainless manifold too.
"worst part of an argument is when you realise your wrong" *Abraham Lincoln
JK, i have no idea who said that but its true
 

flee

Veteran Member
Joined
Sep 19, 2011
Location
Chatsworth, CA
TDI
2002 Jetta GLS wagon
So the best solution would be to mount the thermocouple near the turbo flange where the gases are warmer if I understand correctly.
can I use the input of the collector's egr?
Do you recommend a probe thickness?
Thank you a lot guys.
The EGR port is not a good choice. Much better to drill and tap a convenient spot
near the turbine and (gently) bend the probe to reach the desired point. Within
an inch (25mm) of the turbine is close enough. The exhaust temp is stable there.
A thin (1/8" aka 3mm) probe will bend easier.
 
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