I need a little advice in installing a pyrometer bung, or where to tap a hole for the pyrometer probe on my 2001 Cummins. I am just in the process of fitting up a 4 inch stainless exhaust from a bunch of bits I picked up on Ebay. I am using the Banks Power Elbow and TOP Pipe to start the system. It looks like I might be able to drill and tap a hole in a boss cast into the elbow. Does anyone know if that is recommended? I was also thinking about welding a bung to the top pipe just below the elbow. I do not have the pyrometer yet but was planning on using Autometer gauges and probe. Any advice out there?

Joe

 

It's a 50/50 split, Joe. Some will say put the bung in the pipe to get a reading from all cylinders. Some will say put it in the rear part of the manifold because cyl 6 is the most common cyl to drop. I put mine in the manifold using a 1/4 NPT to 1/8 NPT reduction bushing because the manifold isn't deep enough and the probe will bottom out if you drill the manifold to 1/8 NPT. The red bushing gives the extra height so this won't happen. The manifold will give a truer reading. If you put it in the pipe, you need to add about 250* to the reading.

So read the replies that you get, maybe do a search on here and make the decision that makes the most sense to you.

 

Welcome to the site Joe,
I tapped mine into the exhaust manifold (pre-turbo) and I think we would find that there may be more than 50% that install pre-turbo (just a guess). Here's an idea,,,,
Click on and then type PYRO into the search box. This will show gallery pictures of where different folks have installed their pyro probes.
This may give you some helpful info also.

 

Joe, I've always been post-turbo and when I got the power elbow I installed it on the boss. Most guys are going pre-turbo which I would have done too if I'd found this site 3 months ago.

 

Install it Pre-turbo and then you can be sure of what you are getting into. The 250°F rule sorta works for full speed RPM and stock fueling, but not at low RPM and full fuel. So if you want to take a slide rule with you to make sure you are on the curve that is your choice.

Pre turbo in the manifold is my suggestion..PDR Pyro install instructions.

 

Thanks for the tips on location, sounds like pre turbo is a better location for accurate temp readings. Any helpful advice on the drilling/tapping process. I would be worried about metal chips fying through the turbo if I don't be careful. Would you remove the turbo prior to tapping so that the manifold can be vacuumed or cleaned out?

Joe

 

coat your drill bit and tap in grease, clean off often and regrease. You will catch almost all the shavings. then you can dip a small magnet in the hole after or a magnetized screwdriver to clean up. This kind of cast iron is very easy to drill and tap. Totally opposite end of the spectrum from T1 high carbon steel and the stainless family.

 

put it pre turbo.There are 2 passages in the 24V manifold, I used the rear one,drill it right in the center of the hump,and once you go thru slip a small magnet down and pick up the shavings.Do not leave it running and drill it,god forbid the drill bit snaps off,it will lunch your turbo instantly.Ive drilled about 30 of them,and snapped 2 drill bits,it does happen occasionally. The small amount of chips that go past the turbo on the first start are nothing,they blow past the wheel before it even gets going.Ive never damaged any turbos doing it this way.Post turbo readings are estimates,they are only good for cooling down(hooking to a turbo timer).If you want to guess your EGTS,and have delayed response to actual EGT,put it post,if you want actual readings ppre turbo is the only way.

 

Undo the bolts to the turbo, place a piece of cardboard between the turbo and the maniforld, drill and tap the hole, start the truck to blow the shavings out, remove the cardboard and tighten the bolts for the turbo ... all finished and no screwing around with grease and no fear of damaging your turbo. Don't listen to anyone who says you won't damage your turbo, if the chance is there, you'll be sobbing having to dish out the cash. Let them experiment on their own turbos.

 

What a complete waste of time,your suggestion is like removing the engine to change the oil.One of those tiny chips ruining a turbo that is just getting moving? The same turbo wheel endures 100,000RPM at 1500+degrees ,(i can only imagine the centrifical forces at the outside of the wheel)thousands of heat cycles,while basically being torched ,glowing red,and you think a 1/32" chip of metal is going to hurt it as it goes by it while its cool,(and strong)and not spinning? Your taking more of a chance of getting something in there by unbolting the turbo (or breaking a studd)than you are by drilling it in place.
Joe,do it however you want,but like I said ive done over 30 of them,and never had a single issue,and i have friends who have done as many without an issue.This while job,start to finish takes all of 5-10 minutes to mark,drill,pencil magnet,tap,pencil magnet and install fitting.

 

Hey..Just put one in the other day..use a brand new drill bit..a good one..also, when you tap the threads..if you do at all..run the tap a little past the middle (of the tap)..makes for a nice clean thread..the hardest part is gettin' started..I used the magnet in the hole trick..worked fine..if you do screw something in..use a little anti-seize on it..things get hot!...you may want to remove it one day..

 

Oh yeah..put it in the manifold..easier to hold the drill straight and all that..at least 3/4's of an inch up from where the turbo bolts to the manifold and right in the middle of it..also get true readings...probes and gauges are VERY SENSITVE...

 

The way people worry about getting chips in the turbo makes me think they feel they are drilling into the intake portion of the turbo.
I've done at least fifty pyros and do nothing special at all, no grease or magnets, just drill and tap.
First time you start the engine they will blow right out the exhaust.

 

To keep the chips out of a turbo, I take off the intake boot and hold the compressor wheel retaining nut with a socket and breaker bar while someone starts it up. Cat and Cummins want dealer techs to pre-lube new turbos this way.

 

Pardon?