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For those of you that run EGT thermocouple probes with your turbocharged rotaries, how deep into the exhaust manifold do you center the probe? I'm getting some conflicting info from the internet on that question - some say to center the probe tip smack in the center of the exhaust runner, regardless of normally aspirated or turbo applications. But I've found others (see screenshot below from Haltech's website that says go no deeper than 6mm in for turbo/boosted applications. Which is correct an why? I've got one of Howard Coleman's new exhaust manifolds coming for my FD, and I want to get the EGT installation right!
Could be the same logic as with wideband sensors. Innovate wants you to install it so just the tip of the sensor is in the stream while it seems everyone else provides a bung so that the sensor is a fair but in the stream.
It could have something to do with overheating the sensor which is ironic because heating thr sensor is the whole point. I think the best answer for this one is to defer to manufacturer of the sensor. I really don't think it matters either way honestly
I think it really depends on the manufacturer .
for example this below tells you maximum insertion depth.
The sensorconnection sensors are great and reasonably priced
They also carry 3/16" sensors. for our case, a 1/4" is preferred. the 3/16" dont last but i have used the 3/16" sensors for temperatures where the temperature is not as high (differential and transmission).
I bias towards the '6mm' depth rule they've got pictured be it turbocharged or NA. Unless you're running 3/16 sensors (they can deform relatively quickly at high rotary EGTs and full depth like in the first example) the most important thing to do is make sure each sensor is at the same depth.
" the most important thing to do is make sure each sensor is at the same depth."
sensor placement is important from both an absolute and relative aspect.
absolute because you want to know the real temp coming out of the motor. the closer to the motor the better as the stream cools as it heads off to drive the turbine.
relative because you want to know if there is a temperature delta between the front and rear rotors.
mine are placed about an inch and a half from the flange and are in areas of similar flow. i routinely see around 10 F diff at max power.
one item, while we are on the subject, is the SENSOR. i had been running EGT sensors since 2003 and they lasted generally less than 2 years. around 2021 Rick Lawler's wonderful EGT Technologies introduced their Super (X) Sensors. they were designed for Top Fuel and are on most nitro rigs today including Brittany Force. if you think the rotary is tough on sensors... . my Super X were installed 2021 and are perfect.
but, but, if they are bombproof they must be slow.
i log EGTs at 500 Hz.
here's a save that is approx one second. case closed on slow.
to find them you have to go to EGT Technologies site and the Catalog. here's a few tips:
"EGT Suggestion's Choosing the Proper EGT Sensor
#1 LifeSpan-Larger the sensor diameter longer it lives! Yes! The 1/4” has 4x the life of 1/8” sensor. #2 Reaction Time – The smaller the sensor the Faster is reacts to Temperature changes in the pipe. The same is said for Exposed tip sensors which have faster reaction that closed tip. #3 Open or Closed Tip - We Suggest Open Tips for Racing and occasional street use and Closed tip for street use and any applications that use conventional engine oils or high sufur fuels like diesel. #4 Wire Length- Sensor wire can be shortened if required however if you need to lengthen you MUST use Type K thermocouple wire and Type K connectors. Do not use copper connectors any other alloy which will change resistance values. You can use solder if its directly at the instruments connection. #5 Mounting Hardware– Do not use brass on exhaust sensors, these will blow out of the pipe. We prefer weld-on style in Mild steel on Naturally aspirated engines, Stainless Steel on Boosted or Nitrous Motor’s #6 Sensor Sizing– Picking the correct sensor is critical to data collection, We recommend 1/8” sensors for naturally aspirated engines that need extremely fast data like dynamometers, or testing facilities. The 3/16” is used in Naturally aspirated engines with minor power adders like 250hp shot of nitrous. The 1/4” Sensors are a MUST in Turbocharged, Supercharged or Rotary Engines. #7 Sensor Placement– Sensor’s only needs to be installed 1/4”-3/8” into the exhaust stream. Install probe 4” from the exhaust valve centerline (4 stroke)"
