Hello everyone,

I'm still in a dilema over a pre turbo or a post turbo pyrometer. As I said in my prior post, I know the pre turbo is a more accurate gauge than the post turbo gauge, but is there really that much of a risk of a piece of carbon coming loose or the thermocouple probe breaking off and going through my turbo? Are these guys exaggerating, pulling my leg, and just trying to scare me, or is it a real possibility? Anybody ever had this happen to them? Everyone please give me your opinions and let me know what you are running in your trucks. I want to know what is going on with my engine, but not while I'm sitting on the side of the road.

Thanks everyone for the fantastic information you have given me. You guys are just loaded with useful knowledge.

Scott

 

Again its personal preferance. I have read of thermocouplers coming apart once or twice. I have mine preturbo, and It seems most do. Our 10 wheeler Cummins powered dump came factory with it post turbo. I wouldent get to worked up over it. consider this, If you fry the engine from to high egts it will cost big$$$$. If you loose a thermo, it will cost a turbo. the odds are like winning the lottery IMO. You could always change it out every year or so for cheap insurance.

 

I had always thought it was stupid to put it pre-turbo . . .

However, I have not found any first-hand examples of pyro failure destroying a turbocharger, and I have found a lot of articles saying that they have had no trouble with their pre-turbo pyro, including shops that do work on million-mile OTR trucks.

I also realized that once I changed the turbo housing on my truck, I would have no idea what the pre-trubo EGT's were, because the efficiency of the turbo would be dramatically altered over its operating range, and decided that it was better to risk the pyro going into the turbo, than to be running at 1400 degrees instead of 1200 . . .

So, I put my pyro pre-turbo when I put the new turbo housing on.

 

I've run mine post turbo for a number of years with no problems. I never let EGT get above 850 to 900F and always let it cool down to 250F before shutdown. I don't work the motor real hard, really no reason to. Speed is not my objective, getting there is without a breakdown.

Just came off vacation carring a 2800# camper through some very hot country without a problem. Trip was 4500 to 5000 miles long.

ISSPRO makes a post turbo gauge for those who want to use them. I just use a regular one.

Jim

 

I have had the pyro pre turbo on all three of the trucks I had/have. No problems with any probe failures, Urban legend.

I work on many stationary engines with pyrometers mounted pre-turbo as well as per cylinder and never heard of any failures of the pyros causing problems even after failed head components.

I would go pre turbo and be rest assured you have accurate data.

J-eh

 

is there a difference between a pre and post-turbo thermocouple?

 

I just moved my sendor from post-turbo to pre-turbo and you wouldn't believe the difference!!! The gauge reacts so much quicker now its amazing. Trust me, there is a big difference between the two locations.

 

i was wondering if there is a difference between the parts. i mean, is a thermocouple a thermocouple? or is there one manufactured for post-turbo and one for pre-turbo.

 

I have had mine pre-turbo for 12 years now. I haven't had a problem. I would also think if there was a problem with pre-turbo we would hear about it. But I haven't.
Dean

 

The thermocouples are the same, i.e.: there is only one thermocouple, regardless of where you choose to mount it.

 

If you are overly concerned contact ISSPRO, they make a high temp probe, I am not positive about the temperature measurement ranges, but the TC itself is made out of a material that handles extreme heat better. Possibly tungsten or inconel.

 

These are good points too. The money you spend on the gauge helps out. You would want a probe that is rated for diesel service and of a good quality as with anything I guess. If you get the el-cheapo probe, you may run into problems.

If you look at the probes from Isspro or Autometer they are pretty heavily made and durable.

 

The main difference in the Isspro Pre and post turbo is not the thermocouple. As stated, a thermocouple is a thermocople, in regards to pre or post turbo. The difference is the color coding on the gauge. The post turbo gauge has the red line, so to speak, at a lower temperature than the pre turbo. I have mine installed pre turbo.

Darrin

 

AFAIK, all the thermocouples marketed for this application are type K (chromel/alumel). The housings (Inconel or other similar high temp alloys) are designed to handle the temperature range of the thermocouple.

Mine is pre-turbo, as I'm interested in the temperature of the exhaust coming out of the cylinders and into the turbo's turbine section, not the temperature of the exhaust coming out of the turbocharger (which matters absolutely nothing to me.)

Rusty