Engine surges when leaned?
- Thread starter zzfriend
- Start date
What do you consider low altitude?
zzfriend
New Member
Less than a thousand feet msl.
I don't typically try to lean at anything less than 3,000' MSL.
Ak Kurt
Well-Known Member
Scott,
You should always (below 75% power) lean, even below 3000'. You are missing out on some great fuel economy as well as loading your engine up with carbon and other combustion by-products when you do not lean.
Kurt
I'll have to recheck where I got that recommendation from. I'm sure I've read somewhere that leaning below 3,000 is not good....but, I could be wrong.
Jerry Cain
Member
You may be remembering that you should not lean below 5000 feet (or probably you remember 3000 feet) during takeoff and climbout in order to maitain maximum engine cooling. If you are just cruising, it would pay to lean for best economy at any altitude. AT low altitudes you probably won't be able to lean very much compared to high altitudes.
FLHusky
Active Member
As A student the 1970's I was told that leaning below 3K was not "necessary." Gas was cheap. Today it is necessary.
Altitude is a part of the equation in that we are looking for efficient burn (stoichiometric) which takes into consideration air density. I am not a chemist, but EGT is a derivative of efficient burn so adjustment to that at any altitude seems to make sense.
Altitude is a part of the equation in that we are looking for efficient burn (stoichiometric) which takes into consideration air density. I am not a chemist, but EGT is a derivative of efficient burn so adjustment to that at any altitude seems to make sense.
Surging
The key is to not lean above 75 % power, I believe. Above 5000 feet density altitude, these engines won't make 75% power, so it's always safe to lean above that DA.
I agree that at normal cruise power settings, below 75 % power, I always lean, regardless of altitude.
Do you have an MT prop? That may be part of the surging, as the governor hunts for its target rpm.
Mike
The key is to not lean above 75 % power, I believe. Above 5000 feet density altitude, these engines won't make 75% power, so it's always safe to lean above that DA.
I agree that at normal cruise power settings, below 75 % power, I always lean, regardless of altitude.
Do you have an MT prop? That may be part of the surging, as the governor hunts for its target rpm.
Mike
zzfriend
New Member
Thanks, Mike,
I can be cruising at 23/23, and when I lean to less than 9.5 gph, it starts surging, the leaner it gets, the wider the surge range. MT prop. If that's normal for the MT, I'll accept it, but if not, I think it must be a wrong size jet in the carburetor. Does one need the heavy prop to lean way back?
Z
I can be cruising at 23/23, and when I lean to less than 9.5 gph, it starts surging, the leaner it gets, the wider the surge range. MT prop. If that's normal for the MT, I'll accept it, but if not, I think it must be a wrong size jet in the carburetor. Does one need the heavy prop to lean way back?
Z
Snowbirdxx
Well-Known Member
Surging
Z
Try this: remove the airfilterelement for one flight and try to lean then.
TomD
Z
Try this: remove the airfilterelement for one flight and try to lean then.
TomD
Snowbirdxx
Well-Known Member
I fly mine with only a SS mesh instead of the filterelement, since I never land on dust / sand. I can lean it all the way to lean of peak without surging, but with the foam in it will do that. MT equipped.
Tomd
Tomd
