AeroVee Performance (Cold Air Induction)

[Bryan Cotton]

After the mixture tweak, the EGT runs around 1390F during takeoff and climb, at full rich, so about perfect. Lower density altitude may push that over the 1400F redline - but we are getting warmer too. OAT was about 36F this morning. It is a little too rich at idle. When I shut down in the mixture rich position, the rpm surges a little before it dies. I've never had that before although from other discussions on the forum it is pretty common. So I think I'll leave it for now and see where it goes as we head into spring.

[Bryan Cotton]

We flew 4.4 hours today and it's definitely too lean at high power settings. I'm going to try the 2.5 needle. We have the 2.0 in currently.

[Bryan Cotton]

The 2.5 needle is installed. As soon as the air filter is installed I'm going to try a ground run. I did add some sealing to the air filter shroud.

flap closed.png (548.11 KiB) Viewed 3801 times

This is installed so the flap will open and prevent high pressure, or if a bird flies into the intake and blocks the scat tube then it will flap in and let the engine suck air from under the cowl.

flap open.png (468.59 KiB) Viewed 3801 times

[Bryan Cotton]

It took about 3 adjustments, 1/4 turn lean each time to get it to run well on the ground. Next step flight test.

[Bryan Cotton]

Flight test results: still too rich. At full rich the engine was not happy at all. Leaned out and it smoothed out. But in a full power climb I was having a hard time adjusting the mixture so the engine was happy and the EGTs were below 1400F. I'm going to try another 1/4 turn lean.

[BobDz]

Appreciate your research Bryan. Very valuable and useful information.

[bvolcko38]

How much ram air pressure do yo think you are getting, if any?

[Bryan Cotton]

How much ram air pressure do yo think you are getting, if any?

Hopefully none. Lots of leaks in the air filter shroud and the rubber strip is free to flap open. Mostly I'm shooting for fresh air.

[Bryan Cotton]

I flew today, after my latest adjustment and it seems pretty good. One odd thing though. The EGT that is generally the highest is going to about 1450F in the climb, while the other ones are pretty cold. I'm seeing 1100-1200 on the cool ones and the closest one is a little over 1300F. If I enrichen the mixture so that the high EGT drops below 1400F, the engine runs poorly like it is slobberingly rich. I pull it a little leaner and it smooths out. I am not sure I believe the data. Next time I have the cowl off I am going to swap some EGT probes around. Very easy to do as I have a terminal block where they plug in.

I think by the next oil change I'm going to go 1/8 turn leaner. The fact that it is too rich with the mixture all the way in, even in cool temps (it was about 40) means it will only be richer as we roll into summer. Regarding single digits (F) and below zero, I can revisit that next year.

I know others have chased unbalanced EGTs before. Mine have never been balanced, but not this unbalanced.

[BobDz]

Just out of curiosity Bryan, what's the location of the hot cylinder?