Avstar Aircraft of Washington, Inc.

10415 172nd St. E., Hangar A1
Puyallup, WA  98374
office (253)770-9964
or (253)770-0120
email:  avstarair@att.net

05-23-2004 Ask Mike! Archive
Leaning the Continental IO-470

Hello Mike,

I am trying to get a definitive answer as to leaning the continental IO-470, please, tell me, lean of peak? rich of peak? how many degrees so?
Thanks Mike



This is the question of the ages.  This is also an opinion; just like belly-buttons, everyone has one, and they are all different.  First, let me state that I do not have my own experience to draw from, just what I've discussed with my customers, and read / heard from the experts (Braley, etc.).

You don't want to be at peak.  This is, obviously, the hottest, with the pitfalls that surround it.  Being ROP is better power, and if you typically operating above 65% power, you need to be at least 50 degrees ROP on the leanest cylinder (the fuel helps cool the engine).  Below 65%, LOP is acceptable, but you want to have the richest cylinder 50 degrees LOP, and the leanest no more than 150 LOP.

To accomplish this properly, you need 5 things; 3 of which you have, but I'm not sure of the fourth or fifth.

1  The patience to make the fine adjustments.
2  Engine baffling that will keep from giving hot spots.
3  Gamijectors
4  I don't recall, do you have a vernier mixture control for making the fine adjustments?
5  Does your EGT give you immediate report of a cylinder going LOP, or does it just scan?

I would recommend upgrading your EGT to a graphic display type, so you can see all of what's happening, (all EGT and CHT readings) if you desire LOP operation.

Some folks I've discussed this with swear you also need a digital fuel flow gauge, but this would only assist in making the initial lean.  As you have analog Tach and MAP gauges, you can only set those components of the power setting within a needles width, so your analog FF gauge will get you to the same ballpark.

Proper LOP operation will save some fuel, and understandably will save cylinder wear because of cooler operation, no excess fuel to wash away lubrication, less combustion deposits, etc.

I don't know if I answered you, or just gave you some thing else to throw in your soup to stir up.

Gear Green,