Originally Posted by
Clearedtoreenter
Data from a TIO540
Will run 35-40F LOP smooth as silk, after that: vibes in undies.
That's pretty normal for NA engines. Why won't they run leaner? The fuel atomization and vaporization is not as good as in turbos that will run as far as 120dF LOP quite smoothly.
Originally Posted by
Clearedtoreenter
I like TIT around 1500.... I find it hard to believe running TIT 1600+ and significantly higher EGT's is going to increase my TBO from my Lycoming approved ROP.
The question is, "Why do you
'feel' that way?" EGT/TIT are not in any way related to engine longevity. The only issue is the exhaust plumbing or turbo, but both of those components can easily handle 1650dF all day long. It's only when EGT gets above about 1700-1750 that the metal of the exhaust plumbing begins to suffer. The turbo is designed to operate at 1650dF continuously.
The issues in longevity are two-fold: 1) controlling heat, and 2) controlling pressure. Both of these are moderated when LOP. The difference between heat and pressure at Best power and at 50dF LOP are significant. Very significant. Two engines, one ROP and one LOP AT THE SAME HP, will have the LOP engine running much cooler and under far less stress.
An optimal LOP setting (NA) results in a loss of only about 3 knots TAS for a savings of 3 gph in a 285-300 HP engine. That's a 20% fuel savings for a 2% loss of airspeed. If you are losing more speed than that, you are leaner than optimal. If you take one vector from ATC, you've eaten up that speed difference! Turbos are different. They can actually produce more HP LOP than ROP if one is controlling CHTs. That means that I can go faster on less fuel and have the engine operate under less stress.
It may be worthwhile to ask, "if Lycoming really felt that their 'approved' ROP methodology was best, why is their new FADEC-type engine set up to run LOP?"
There are well over 400 million flight hours of hard data which supports the above comments.