this is good advice and also you want to check your thread depth because npt thread is tapered and you do not want to bottom out the probe to the manifold. since it is tapered it seals on the threads itself and if you bottom out the probe it will be sticking too far into the pipe and will not seal correctly. so dont put the whole tap in so it will thread in and out freely like a normal tap would

 

I am about to take on this task as well. I have a HOG Performance Pyrometer and teh temperature probe is about 1.5" long. Is this normal? It would seem to me that with all of the care we go to to get the airflow into and out of the engine quicker and smoother that a probe that size would cause some turbulence???

 

What is the best way to properly get the thread depth for a proper seat? I'm installing an autometer pyro probe soon. What is the correct thread for this as well. 1/8 NPT?

 

I would assume that 1/8" NPT is standard for all brands of thermocouples.
Thread depth is never standard with NPT. You must drill and tap in a little ways and then test fit the fitting that you are going to use. If it looks good then you are done. If it's too tight then you must cut the threads another turn of the tap. Repeat until you can get it no more than halfway in without using a wrench.

 

Make sure you use the proper size drill for the tap. I didn't have the number drill so used the closest fraction drill. Broke the tap off in the manifold. Was able to finally back it out but was sweating profusely during the process. Stupid move considering where I was working.

 

you need a .339 drill which is an "R" drill. it is important to use the right size drill because if it is too tight the tap will break and if it is too loose the pyro will not seal correctly. also make sure you get the tap started straight once you have your hole drilled

 

I found the right sized tap (1/8" - 27) in town at Sears, but could not find the bit locally. I ordered the size R bit online from www.drillsandtaps.com You can also get the tap there, if you couldn't tell by the name of the site.

 

Thanks Kwik....so what your saying is, for proper depth, the threads of the probe need to be so that it is tight w/o bottoming out? Maybe with a couple of threads still showing on the probe itself when tight?

Got my "r" bit ordered!!

 

yes because it actually seals on the threads wothout bottoming out. on mine about 3/4 of the threads are into the manifold with 1/4 showing. you want the tip of the thremocouple in the center of the exhaust flow.

 

What Muktown said.

 

I have talked to more peaple that say to mount the pyro sensor after the turbo because the sensor deteriorates and falls apart. Turbo probably wouldn't like to pass that. Has anyone else tread the instructions to there gauge kit.

 

The instructions that came with the guage do say to mount it post turbo. However, your most accurate readings will come from a pre turbo mount. Also, I have never heard of anyone who has a probe mounted pre turbo in a PSD that has had the probe break off.

 

True statement indeed 4X4 which brings up an interesting scenario. There are alot of guys swaying members to place there probe pre-turbo when in fact it will be subjected to temperatures as high as 1,000-1300 degrees for extended periods of time quite frankly much longer than 2-3 minutes for sure. Yet some of these same guys have posted that they wouldn't use certain glow plugs in there engines due to the fact the they fear overheating and melting tips breaking off causing possible engine damage. I submit the question that if there is that much concern on the tip of a glow plug that is only exposed to these temperatures for a 2-3 minute cycle and are designed for this exact application why aren't they concerned about the same type of tip in the exhaust manifold that is exposed to these temperatures sometimes for hours on long trips or under heavy loads or during towing? Are pryo/egt temp probes made that much more superior to glow plug tips? I would guess not, therefore mounting the egt probe post-turbo would completely eliminate the chance of engine failure from tip melting/breakage with the only downside being you will just need to find your "safe temperature cushion range". The flip side being pre turbo with an accurate reading and constantly wondering if/when the egt probe is going to break. It's all personal preference but if a guy is that concerned with tip melting/breakage he should go with post turbo placement. Post turbo temp readings eventually come down to individual vehicles as each one is modded or setup differently than others so it is difficult to compare that one guys vehicle only sees 100 degree post turbo drop off while another may see 300 degree drop off.

 

i wouldnt be too concerned about a pryo probe melting and breaking off because i believe they are made on inconel which is a very heat resistant metal and has to get well above 1200 degrees to even begin to start melting. i dont think there is anything to worry about. i havent heard of anyone having it break off

 

what is a safe range for a post turbo pyro? there's no way im willing to risk my 10k engine with metal shavings and the possibility of my the probe breaking off due to the heat.