Uneven EGT's

[Rotodyne]

Since purchasing my Onex I have put around 100 hours on the Aerovee and during that time when leaned at cruise the left cylinders EGT's have been consistently 150-200 degrees higher than the right cylinders. I have rebuilt the top end during that time and the inlet manifolds have been of several times so I was sure this wasn't due to an intake manifold leak.

I remembered some time in the past reading a post on this forum where someone had a similar issue that was fixed by rotating the AeroInjector (AeroCarb) a few degrees. I also contacted Sonex about my issue and they told me "The AeroCarb should be aligned with the engine so the throttle slide moves forward and backward, not side to side".

I took a look at my installation and noted that the AeroInjector was rotated a few, may 10 degrees to the right, so I loosened the clamps and turned it to the left, maybe 5 degrees past straight, so a total turn of 15 degrees turn. Since making this change the left cylinder EGT's are now much closer to the right with only a 50-100 degree spread. The engine is also running considerably smoother and producing more power.

Just thought I would share this as it may help someone else.

Happy flying!

[AlexZ]

Did you try switching the EGT sensors frome sides? My left sensor gave 80 degrees C higher temp. After switching sides the right side is higher, although not as much.

If I understand correctly I have to turn the Aerocarb a few degrees to the right to get lower EGT at the right side?

[GraemeSmith]

I also spent a bit of time carefully reapplying the CHT probes so they were in the same relative place on each cylinder and that their contact area was as near identical as I could make them AND the wiring routed away from the heads and fins so the length of the wire was not influenced by that heat. And I got a lot more sense and uniformity out of the CHT's. So I would try something similar for the EGT probes.

[Rotodyne]

Did you try switching the EGT sensors frome sides? My left sensor gave 80 degrees C higher temp. After switching sides the right side is higher, although not as much.

If I understand correctly I have to turn the Aerocarb a few degrees to the right to get lower EGT at the right side?

I didn't switch the sensors as the differences in EGT's mirrored the differences I was seeing in CHT's, so to me it was pretty clear I had a mixture issue rather than a sensor issue.
I don't know if in your case turning the Aerocarb to the right will give you lower EGT's on the right, but what is clear is that in my case a small rotation had a considerable effect. I will probably experiment further in the future but for now I'm very happy with the result and wishing I'd tried it a years ago.

[lutorm]

The absolute value of the EGT isn't particularly meaningful since it depends on position in the exhaust pipe, distance from the exhaust value, the routing of the exhaust pipe, etc. What is meaningful is the change in EGT when you change the mixture.

Personally, I wouldn't care if the EGTs were uneven unless I've confirmed that peak EGT for the different cylinders also happens at very different mixtures. If they all go up and down together, everything's fine.

See Mike Bush's "EGT and CHT" webinar at https://youtu.be/fqe9j74qMdk.

[Rotodyne]

The absolute value of the EGT isn't particularly meaningful since it depends on position in the exhaust pipe, distance from the exhaust value, the routing of the exhaust pipe, etc. What is meaningful is the change in EGT when you change the mixture.

Personally, I wouldn't care if the EGTs were uneven unless I've confirmed that peak EGT for the different cylinders also happens at very different mixtures. If they all go up and down together, everything's fine.

See Mike Bush's "EGT and CHT" webinar at https://youtu.be/fqe9j74qMdk.

Hi Luutorm, thanks for the webinar link, very informative and makes me think I may have been misunderstanding the issue. That said the small rotation of the AeroIjector still caused a significant reduction in EGT spread between cylinders, and importantly a noticeably smoother running engine.

[Rynoth]

Just to state the obvious (and since this is the Aerovee forum), I think that for the Aerovee Turbo rotating the aeroinjector would be irrelevant to even fuel delivery. The turbo compressor spins it all up anyways.