Turbo vs NA

[Walter Atkinson]

Originally Posted by Ernie Martin

Make sure, however, that you understand the landscape. Do a Search on this Message Board for "lean of peak" and read the postings. Briefly, you want to have "balanced" injectors (read: GAMI injectors), engine monitoring with cylinder-by-cylinder EGT/CHT readings, the willingness and ability to understand and manage the leaning process, and preferably an engine no longer under warranty from an overhauler which prohibits LOP.

Understanding is always a good thing. Your engine is SUPPOSED to come with balanced F:A ratios as that is how it was designed. Unfortunately, many don't, hence the business opportunity for a company to produce an STC'd product that addresses that deficiency. No matter whether you operate ROP or LOP, the F:A ratios should be balanced for the engine to be a conforming engine. (a conforming engine is one which complies with the engineering design and the appropriate set-up.)

While engine monitors are very good ideas for a variety of reasons (I considered them mandatory), leaning isn't one of them. If you have balanced F:A ratios and the engine runs smoothly LOP, you do not need an engine monitor to properly or safely operate any engine LOP. If that were the case, literally hundreds of millions of flight hours of LOP mixture operation could not have been successfully accomplished. Those who have a thorough understanding of the issues appreciate that they need an engine monitor MUCH more when they operate ROP. There is no mixture setting that needs an engine monitor more than the mixture historically recommended by the OEMs. Go figure?

IMO, any overhauler who prohibits LOP operation should be asked why. It could be that the engine is not properly delivered (if it can't run smoothly LOP it is not a conforming engine), or the builder is poorly educated. In either case, I want to know what they know and don't know before buying their product. There are some shops which build very good engines who are truly clueless on how to operate them properly. If they deliver an engine that CANNOT be operated smoothly LOP, it is not a conforming engine. Period. For the money I spend on an overhaul, I darned sure expect it to be a conforming engine no matter how I plan to set the mixture.

YMMV.