Where did you mount your EGT sensors?

[acam37]

We were going to install the EGT probes and the smoke oil injectors today but before we did we put the bottom cowl on to check for clearance. It appears the probe leads will rub the cowl if they go where we wanted to put them. Where is the best place to put these things? We are using 4 EGT and 2 smoke oil injectors.

[Bevan]

Not flying yet so I have nothing to say about how successful my EGT install will be, but... After much searching here and talking to other builders, I installed them all the exact same distance from the exhaust flange and in the same clock position on the pipe. This was done in attempt to have them read the same in terms of relative values. Considering each exhaust pipe has the first bend in a different position, spark plug access and cowl interference, mine ended up being mounted about 2.25 inches below the exhaust flange. According to what I had learned from others, the further from the flange the longer they will last, the closer they are, the more "responsive" they will be to changes going on in the cylinder. Not sure how true that is.

I would think that you would want the smoke oil injectors to be at least some or quite a bit aft of the EGT probes.

Bevan

[Scott Hersha]

My EGT probes are around 2", maybe a little more from the flange, like the previous poster and it works well. My smoke oil injectors are just a little below the EGT probes - maybe an inch or two - on cylinders #1 & #4. I have the Vetterman crossover exhaust and this gives the smoke oil a long hot ride through the pipe and exposure to two cylinder's exhaust heat (1 +2, & 4 + 3). This more completely burns the smoke oil in the pipe, and gives me excellent smoke without much residue on the belly.

[GeneL]

Ditto what Bevan said, I have flown with this setup on multiple planes and hundreds of hours. Smoke oil taps can be lower in the pipe since smoke oil doesn't "burn", it vaporizes.

[Mel]

Three important factors. As mentioned above.

Equal distance from flange. Closer = faster response, Farther = longer probe life.
Clearance from cowling.
Spark plug access.

[acam37]

I understand as to the distance issue, but I guess what I'm trying to ask is, on the -4 can how do people keep the leads from interfering with the cowl, since the exhaust pipes are so close to the cowl. On mine I only have a few inches of clearance. I though about just drilling the holes on the inboard side where they are facing the engine, if I can find a spot of equal distance on all.

[Mjuckes]

Arlie
I just mounted some on my -4. Same issue as you, I could not mount them @2" below the flange. Mine are 3.5" below the flange I had to angle them rearward. just keep them at a right angle to the gas flow. Have 5 hrs since install, all work well, and seem to be accurate. Peak at 1500 deg range. So I believe they are not to far from the flange. If you need pics I could pull the cowl and snap a few for you.

[acam37]

Mike, that would be great. Post some pictures.