O-360 LOP Ops

[0TreeLemur]

Late November flight after getting the Hartzell Top Prop re-painted for the second time.  The factory primer wouldn't hold it on.

Three plus hour leg at 6500', severe clear and smooth, somewhere over Kansas.

The new prop paint seems to have thrown the balance off, so I run at 2500 rpm 'cause it feels smoother.

Bored.   At 2500 rpm I have a fair bit of throttle plate engaged to keep the power at 75%.  Hmmm, that creates a lot of intake turbulence.  Wonder if I can run this carbureted fire-snortin' beast lean of peak?

Yes!    It ran about 30F LOP and it was smooth with just an occasional burble.  20% reduction in ff for a 8-10% reduction in power that cost us about 7 kias.  

Proof:

[A64Pilot]

Carbureted motors can of course be run LOP, just not all are smooth doing so.

Some have found that a little carb heat helps in mixture distribution as another trick.

What will irritate you is it may run smooth today LOP and not tomorrow, obviously something changed

Edited December 9, 2021 by A64Pilot

[Hank]

Mine would not run smoothly LOP, even with partial throttle a d varying carb heat. Then my carb heat flapper joint failed in flight. With it properly repaired, I can run 15-20° LOP but don't because my speed falls off much faster than Lemur's. And I don't have the pretty graphs.

[Ragsf15e]

13 hours ago, 0TreeLemur said:

Late November flight after getting the Hartzell Top Prop re-painted for the second time.  The factory primer wouldn't hold it on.

Three plus hour leg at 6500', severe clear and smooth, somewhere over Kansas.

The new prop paint seems to have thrown the balance off, so I run at 2500 rpm 'cause it feels smoother.

Bored.   At 2500 rpm I have a fair bit of throttle plate engaged to keep the power at 75%.  Hmmm, that creates a lot of intake turbulence.  Wonder if I can run this carbureted fire-snortin' beast lean of peak?

Yes!    It ran about 30F LOP and it was smooth with just an occasional burble.  20% reduction in ff for a 8-10% reduction in power that cost us about 7 kias.  

Proof:

Could you then increase mp to get back a few knots since you had it pulled back?

[jaylw314]

Notice all your CHT's went down when you leaned except for CHT#2, so that's probably your richest cylinder.  That'd be the one to watch if you try it again

[DXB]

14 hours ago, 0TreeLemur said:

Late November flight after getting the Hartzell Top Prop re-painted for the second time.  The factory primer wouldn't hold it on.

Three plus hour leg at 6500', severe clear and smooth, somewhere over Kansas.

The new prop paint seems to have thrown the balance off, so I run at 2500 rpm 'cause it feels smoother.

Bored.   At 2500 rpm I have a fair bit of throttle plate engaged to keep the power at 75%.  Hmmm, that creates a lot of intake turbulence.  Wonder if I can run this carbureted fire-snortin' beast lean of peak?

Yes!    It ran about 30F LOP and it was smooth with just an occasional burble.  20% reduction in ff for a 8-10% reduction in power that cost us about 7 kias.  

Proof:

This leaves me confused - bear with me if I'm reading it entirely wrong and I have a misconception that needs to be corrected.  The segment from ~2:15-2:30 is when you have reduced fuel flow (~8gph), but at least 3 of 4 EGTs are above the previous baseline, suggesting you're still ROP.   What doesn't make sense to me is that 3 CHTs drop during that segment, which shouldn't happen until you're pretty far LOP.  What am I missing?

 

[Ragsf15e]

50 minutes ago, DXB said:

This leaves me confused - bear with me if I'm reading it entirely wrong and I have a misconception that needs to be corrected.  The segment from ~2:15-2:30 is when you have reduced fuel flow (~8gph), but at least 3 of 4 EGTs are above the previous baseline, suggesting you're still ROP.   What doesn't make sense to me is that 3 CHTs drop during that segment, which shouldn't happen until you're pretty far LOP.  What am I missing?

 

I didn’t watch to see where it peaks, but 30d lop DOES have higher egts than 100d rop.  Does that explain your difference?

[0TreeLemur]

8 hours ago, Ragsf15e said:

Could you then increase mp to get back a few knots since you had it pulled back?

Didn't think of that.  I was just really surprised to get it to run smooth LOP.  That might make it run rougher by decreasing the turbulence in the intake manifold

[DXB]

8 hours ago, Ragsf15e said:

I didn’t watch to see where it peaks, but 30d lop DOES have higher egts than 100d rop.  Does that explain your difference?

yes that's true good point - the data display may not be granular enough to capture passing though peak EGT