Egt probe npt question
Senior User
Joined: Oct 2010
Posts: 259
Likes: 1
From: Powell, wy
I recently installed the same Hewitt gauge with the 1/4 npt. I started with a small pilot hole, and then used a unibit to get up to 7/16" ( if remember correctly). All I used was cutting oil on the bit, and no grease. From what I read, grease will cause issues with getting more shavings inside the manifold than without. Gravity and the design of the bit will help with removing most of the shavings. I held my shop vac hose next to the bit as I drilled to catch most of the shavings before they hit me. My gauge is very quick to respond.
It's a Van Gogh
Joined: Feb 2010
Posts: 7,812
Likes: 1,335
From: Elk Grove, CA
So after a short 3 day trip with the 5th wheel the egt needle would usually move 2-400* within a second of mashsing on the right pedal in the foothills of the Ozarks (zf6) The highest I could get it was 1050. I wasn't easy on it on purpose. Now to put in the ts 6 pos and see what all changes next week. If the 1/8 npt does have a faster response time I doubt I'd notice enough to care at this point. Thanks again
Since it has not been discussed and this looks like a good time; sustained 1250* is bad. A spike there or to 1350 is not a problem, but don't let it stay there long or something will melt. Increased airflow from higher revs will help keep it cool so don't hesitate to gear down. Lugging the engine with the pedal mashed is the recipe to make high EGTs.
Hotshot
Joined: Jul 2008
Posts: 12,782
Likes: 2,142
From: N.GA Mountains
Please tell everyone to stop worrying about the metal from drilling exhaust manifold. Drill it DRY, then pass a vacuum over the hole if it makes ya feel better. That little bit of metal dust will be gently pushed out the tailpipe at idle.
Id be waaaaay more concerned about some partially stuck, greasy bits hitting the turbine wheel while its spinning 30k rpms and HOT.
The pyro probe is measuring the exhaust 'gasses'. I don't see the probe/tap diameter making any difference.
The 1250* 'limit' is also based on the gas temp. It's gonna take awhile blowing 1250* air across those metal surfaces to see them get that hot and we have oil and coolant on the other side of all the 'hot' parts helping to keep them from melting. The sled pullers, etc might see 2200* going down the track and they don't melt things - but if you were at 1400* pulling the 3hr grade from Phoenix to Flagstaff in the middle of summer - you would probably do some damage.
That said, good tuning is the most critical part of the equation.
Id be waaaaay more concerned about some partially stuck, greasy bits hitting the turbine wheel while its spinning 30k rpms and HOT.
The pyro probe is measuring the exhaust 'gasses'. I don't see the probe/tap diameter making any difference.
The 1250* 'limit' is also based on the gas temp. It's gonna take awhile blowing 1250* air across those metal surfaces to see them get that hot and we have oil and coolant on the other side of all the 'hot' parts helping to keep them from melting. The sled pullers, etc might see 2200* going down the track and they don't melt things - but if you were at 1400* pulling the 3hr grade from Phoenix to Flagstaff in the middle of summer - you would probably do some damage.
That said, good tuning is the most critical part of the equation.
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mtgrzlyman
1999 - 2003 7.3L Power Stroke Diesel
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Aug 8, 2005 05:30 PM
