Engine/Transmission (1994 - 1998) thermocouple/pyrometer experts???

[JMauro]

wanted to get some input on thermocouples and installation.



there are three different types of thermocouples. ungrounded, grounded and exposed junction. ungrounded is the slowest responding, grounded in the middle and exposed junction is the fastest. also the smaller the diameter of the thermocouple the faster it responds. wondering if anyone has comments on this.



it seems that preturbo is the preferred spot for the thermocouple but is there a preferred side to the split manifold? one of the reasons for wanting the pyrometer is cool down so what temps would you look for preturbo before you shut the engine down?



thanx

 

[SEmerson]

I think most os us just use what comes with our gauge of choice.



Either side of the mantifold is fine.

 

[Cooker]

I would put it in the rear portion of the split as #6 is typically the hottest cylinder and therefore the rear may possibly read a bit higher temp than the front.

 

[Texas Diesel]

My gut feeling is the ones that are self powered, i. e. , not needing 12V will stay in calibration longer even is they are a little slower to respond. A good way to tell is if the gauge reads a temp with the key off. Cooker is correct about putting it in the 4-5-6 side (not in the dead middle 3-4 because the manifold is prone to crack there) I have mine pre right where 4-5-6 come together. I've been told and observed that #6 runs the hottest. The 1/8" pyros read faster than the 1/4".

 

[KLockliear]

The gauges most people run (like what we offer) use the ungrounded Type-K thermocouple probe. It's the slowest responding of all the probes, but we're really not looking for egt temp, we're looking for an idea of piston temp... and that just won't climb like egt will. The ungrounded probe response is still way faster than the piston temp.

 

[FreeBMW]

300F pre turbo seems to be the consenses on safe shutdown temp

 

[Cooker]

Originally posted by FreeBMW

300F pre turbo seems to be the consenses on safe shutdown temp

I'm pretty certain that 300 post turbo the the general consensus.

 

[FreeBMW]

Originally posted by Cooker

I'm pretty certain that 300 post turbo the the general consensus.

I am waiting too long then!!!! Still cant hurt.

 

[CGriffith]

300 F post and pre turbo are nearly the same thing. There is very little difference across the turbo at 0 boost or idle conditions.



300F is recommended by most, but I know many guys who don't know or care what their EGTs are at shut down and their turbos have lead a long life.

 

[Cooker]

Originally posted by CGriffith

300 F post and pre turbo are nearly the same thing. There is very little difference across the turbo at 0 boost or idle conditions.

This is not accurate. After a hard run or while towing during cooldown I might see 300 pre turbo several minutes before I see 300 post turbo.



I agree most do not care about EGT's at shutdown and their turbos still live a long life. Maybe they are just lucky? I don't know, to each his own.

 

[KLockliear]

Mount the probe pre-turbo, in the back half of the exhaust manifold, about 1 to 1. 5" up from the turbo flange.

 

[1dslram]

I have had both probes on one gauge and 300 pre turbo is what Holset and Cummins recomend for shut down. cooker is correct the pre turbo will cool faster after a hard run and just the opposite the post turbo will climb a lot slower under hard acceleration.

Bruce