And, just as a side note, Lycoming specifically recommends AGAINST running MOST of their engines lean of peak. They have an interesting article posted on their web site that discusses their point, called "The New Old Leaning Procedure".

I'm not saying right or wrong, the guys in Twexas defend LOP with religious fervor, and I run LOP on some engines, but its not a bad idea to read what the folks who built your engine have to say.

MTV

Gunny,

One slight correction. FI gas engines don't inject fuel directly into the cylinder, but right before the intake valve. FI diesel engines do inject right into the cylinder (with a few exceptions).

Otherwise you are right on.

The EAA webinars on leaning provide lots of detailed technical data on the subject. They are long, but are worth watching. Their basic leaning seminar can be seen at: http://www.eaavideo.org/video.aspx?v=2274677932001. The advanced leaning seminar is available at: http://www.eaavideo.org/video.aspx?v=2534345030001. Both webinars are available for anyone to watch. You don't have to be an EAA member to view them. I recommend reviewing these sessions regardless of your viewpoint on the subject. Informed decisions require information, and these webinars provide lots of that.

Barnstormer wrote:Gunny,

One slight correction. FI gas engines don't inject fuel directly into the cylinder, but right before the intake valve. FI diesel engines do inject right into the cylinder (with a few exceptions).

Otherwise you are right on.

You are correct... right on to the intake valve.... thanks for the correction.

gunny

MTV-

Regarding your Hot #2 Cylinder.... for Continental engines the #2 always seems to run hotter than the rest.... GAMI makes a baffle piece that scoops more air over that cylinder... it works (but is STC'd only for the 520/550).

gunny

Gunny,

Sorry, it's a Lycoming, but thanks anyway.


MTV

You guys are right on here. Fly hound beat me to it. Mike Busch did an advanced leaning class a few weeks ago. It talks about LOP in carbureted engines and has lots of great info, some specific to the O-470.

I'll also add that the guys at Gami are great. My 205 had Gamis when I bought it, but the previous owner never did the Gami lean test to see if they were properly matched. My Gami Spread was .6 gph. When John-Paul at Gami heard that, he said, "Oh no, we can do better than that!" Three swapped nozzles later my spread was .2 gph! All my cylinders peak almost simultaneously. But it still wasn't running LOP smooth. The solution? Pull the throttle back 1/4" to 1/2" MP. That did the trick! It runs smoothly 60-70 degrees LOP, CHTs low to mid 300s, 130 mph TAS, and 9.7-10.3 gph. I couldn't be happier!

Experimented over the weekend with the partial carb heat technique. The 470-U didn't seem to run any better LOP with partial carb heat. Actually, temps are more even on both EGT/CHT without the carb heat. For some reason when I use partial carb heat #5 CHT runs a little hotter, around 365 instead of 345-350. I tried lots of different amounts of carb heat, and it does run ok like that, but no carb heat gives the most even temps. With no carb heat all cylinders are 285-330, except for #5 and it sits about 345-350. There is room for improvement on the baffling between oil cooler and #5 cylinder, so it may be possible to get her temps down with the others also.

Thanks again for everyone's input, really appreciate all the info.