Mixture Rich or Best for ground ops

[DCarlton]

On 11/24/2021 at 6:37 AM, Marc_B said:

https://www.advancedpilot.com/articles.php?action=article&articleid=1844
 

came across this last night looking at APS. As @201er mentioned, Deakin suggests leaning enough that it would stumble if you forgot to enrichen on takeoff roll.

This was useful.  I warmed up at 1100-1200 and let my oil come up to 100 deg before I pulled out of parking today, and paid more attention to my taxi RPMs (keeping it between 1000-1200; although it takes a little more to get moving).  I leaned during taxi and I let the plane run lean a bit before I shut it down.  It was good to get back to some of those basics.  Thanks for posting.  

Edited November 27, 2021 by DCarlton

[Pilot boy]

On 11/23/2021 at 11:47 PM, DCarlton said:

So you use the engine monitor to find LOP at run up RPMs, then do the mag check and look for the uniform EGT increase?  I typically operate 300 feet above sea level and don't do much leaning on the ground.  I need to improve my SOP.

You should definitely be leaning.  Your engine will probably improve over time as you clean up the plugs lol.  I lean aggressively in my E at 1200 MSL and after a year of ownership the engine runs better than ever.  As soon as I land and cross the hold lines I’m leaning way back etc.  

I also like the technique after run up to lean it aggressively as then you really know when you add power for takeoff that you didn’t enrich the mixture.

[DCarlton]

2 hours ago, Pilot boy said:

You should definitely be leaning.  Your engine will probably improve over time as you clean up the plugs lol.  I lean aggressively in my E at 1200 MSL and after a year of ownership the engine runs better than ever.  As soon as I land and cross the hold lines I’m leaning way back etc.  

I also like the technique after run up to lean it aggressively as then you really know when you add power for takeoff that you didn’t enrich the mixture.

I tried leaning aggressively today to convince myself I'd always get a shudder when I advance the throttle.  It works.  However, I'll probably continue in most cases to lean for DA in the run up (ROP) and leave it there until I take off... unless I'm waiting for a long time.  But lots of good tips.

[Pilot boy]

On 11/26/2021 at 11:05 PM, DCarlton said:

I tried leaning aggressively today to convince myself I'd always get a shudder when I advance the throttle.  It works.  However, I'll probably continue in most cases to lean for DA in the run up (ROP) and leave it there until I take off... unless I'm waiting for a long time.  But lots of good tips.

  My only concern here would be that you may take off without max power someday when you forget to enrich from ROP.  It will happen at some point though I guess if you catch it on takeoff that the MP and RPMs aren’t topped out you’d know then...hopefully not on a short field.

[carusoam]

If you have a FF gauge…

RPM, MP, and FF are a quick glance as the T/O roll starts to unwind…. If you have all three, you have max power… (compare to book values at your local altitude.)

They are easy to see without much looking away from the centerline…

If you don’t have all three (showing book values for expected BHP%)… max power isn’t going to be there either…

 

My O360 was a lead factory… I assumed that was normal… it may have been one or two cylinders were running richer than the other two….

FF distribution for carbs is designed around WOT… not so much around idle speeds….

Best regards,

-a-

[DCarlton]

1 hour ago, Pilot boy said:

  My only concern here would be that you may take off without max power someday when you forget to enrich from ROP.  It will happen at some point though I guess if you catch it on takeoff that the MP and RPMs aren’t topped out you’d know then...hopefully not on a short field.

My terminology is probably a little off.  I rarely take off without the mixture full rich unless high DA is involved.  I need to revisit the best procedure to lean for high DA now that I have an engine monitor.  Usually I lean until it runs rough, put a turn or two on it until it smooths out, then add another turn or two just to feel good about the setting.  I haven't operated at a 5000+ foot airport in a long time. 

[A64Pilot]

Fuel flow is the thing to look at when throttle reaches full, then RPM maybe, but if fuel flow isn’t right, abort and figure out why.

 

[tmo]

FWIW, the thing I watch for when throttle approaches full is MP, way too easy to exceed 40". I watch FF as I advance the throttle, yes, as well as RPM, but MP is my main focus as far as engine parameters go.

My point is that different engines will have different things to look for.

[RobertGary1]

On 11/28/2021 at 7:52 PM, Pilot boy said:

  My only concern here would be that you may take off without max power someday when you forget to enrich from ROP.  It will happen at some point though I guess if you catch it on takeoff that the MP and RPMs aren’t topped out you’d know then...hopefully not on a short field.

Sounds like you’re not leaning enough. Shouldn’t be able to get more than 1500 rpm at full throttle when leaned on the ground. If you need more power temporarily enriched then back to ground lean. 

[Hank]

4 hours ago, RobertGary1 said:

Sounds like you’re not leaning enough. Shouldn’t be able to get more than 1500 rpm at full throttle when leaned on the ground. If you need more power temporarily enriched then back to ground lean. 

Exactly! I have to enrichen to taxi uphill . . . . Ain't gonna takeoff, it'll drown and cut off!

[bmcconnaha]

mixture lean enough on the ground that and power addition will cause a stumble.  no danger of taking off lean if you do that.  give it a a turn or two for the run up.  run up at 1700-1800, look for a rise in each cylinder EGT on each mag, lightly cycle the prop a time or two depending on temp (no need to deep cycle it), and then back to 1000rpm and leaned where you cant add any throttle without a stumble.  wont foul plugs that way

[Pilot boy]

On 11/28/2021 at 11:45 PM, DCarlton said:

My terminology is probably a little off.  I rarely take off without the mixture full rich unless high DA is involved.  I need to revisit the best procedure to lean for high DA now that I have an engine monitor.  Usually I lean until it runs rough, put a turn or two on it until it smooths out, then add another turn or two just to feel good about the setting.  I haven't operated at a 5000+ foot airport in a long time. 

I don’t think This leaning technique would get you a guarantee of max power unless you do the leaning while at full throttle.  You will not be able to tell if the engine is getting all the fuel it needs to produce max power if you’re adjusting it at like 1800 rpms etc.  you might mistakenly leave it too lean as the engine needs much more fuel when you put the throttle at full demand for takeoff.

[NM Mooney]

Sorry if this hasn't been covered, but hasn't anybody installed a modern AFR gauge instead of feeling about in the dark re: mixture?  It takes all of a half-hour to drill and dimple the pipe, weld on a bung, and wiring these gauges is a snap.  I think there are leftover accessory switches to run the minuscule current to the gauge (and heated sensor).  Very precise, and they're not expensive these days. 

The only requirement with most broad band sensors is that they're mounted 18" (along the flow, not as the crow flies) from the exhaust port (and angled slightly off horizontal), so, you could just stick one somewhere in the Mooney's exhaust pipe...?

Edited December 5, 2021 by NM Mooney

[Culver LFA]

An O2 sensor is going to have a very short life in a leaded environment

[Ragsf15e]

On 11/28/2021 at 10:45 PM, DCarlton said:

My terminology is probably a little off.  I rarely take off without the mixture full rich unless high DA is involved.  I need to revisit the best procedure to lean for high DA now that I have an engine monitor.  Usually I lean until it runs rough, put a turn or two on it until it smooths out, then add another turn or two just to feel good about the setting.  I haven't operated at a 5000+ foot airport in a long time. 

Nothing wrong with setting your high DA mixture during runup but there’s a (slightly) better technique that you can use during takeoff roll if you have egts on all cylinders.  It’s called target egt and you can find several MS threads on it.

Basically you know your sea level full power, full rich egt (should be about 1200 on io-360), then you lean to that value for your high DA takeoff roll and climb. You can also lean in any climb to that same target value.  Obviously you don’t want to heat up your cylinders, but I think you’ll find the target egt method works well.  On my F model I lean for 1220 egt as I climb or during takeoff roll if high DA.

[DCarlton]

4 minutes ago, Ragsf15e said:

Nothing wrong with setting your high DA mixture during runup but there’s a (slightly) better technique that you can use during takeoff roll if you have egts on all cylinders.  It’s called target egt and you can find several MS threads on it.

Basically you know your sea level full power, full rich egt (should be about 1200 on io-360), then you lean to that value for your high DA takeoff roll and climb. You can also lean in any climb to that same target value.  Obviously you don’t want to heat up your cylinders, but I think you’ll find the target egt method works well.  On my F model I lean for 1220 egt as I climb or during takeoff roll if high DA.

Interesting.  Haven't read or had anyone explain that but it makes sense.  I'll try it.  Thanks. 

Edited December 6, 2021 by DCarlton

[MikeOH]

@Ragsf15e

What are you seeing for fuel flow at take-off power and 1220 EGT?

Mine is around 1330 with 16.5 gph and I'm beginining to wonder if that is atypical.

[Ragsf15e]

2 minutes ago, MikeOH said:

@Ragsf15e

What are you seeing for fuel flow at take-off power and 1220 EGT?

Mine is around 1330 with 16.5 gph and I'm beginining to wonder if that is atypical.

Interesting, are you at sea level?  That’s low ff and high egt.  You should have ~18gph during t/o roll.  I’m at 2000’ (although DA today was basically sea level) and I’m full rich, 18ish.  Low 1200s is common egts, but there is variability in engines and egt probe placement.  However with that ff, I’d say you could be in for an adjustment.  Probably help keep your CHTs cooler during takeoff and initial climb.  Although I bet egts are around 1220 by the time you hit 2000’.

[Ragsf15e]

28 minutes ago, DCarlton said:

Interesting.  Haven't read or had anyone explain that but it makes sense.  I'll try it.  Thanks. 

No problem, it’s worth trying.  I use it all the time in the climb.  If you need to lean for high DA takeoff, It’s a little tough to adjust during the takeoff roll with everything going on, but it’s doable.  Not my invention, there’s plenty of reading on it, but it works for me.

[MikeOH]

10 minutes ago, Ragsf15e said:

Interesting, are you at sea level?  That’s low ff and high egt.  You should have ~18gph during t/o roll.  I’m at 2000’ (although DA today was basically sea level) and I’m full rich, 18ish.  Low 1200s is common egts, but there is variability in engines and egt probe placement.  However with that ff, I’d say you could be in for an adjustment.  Probably help keep your CHTs cooler during takeoff and initial climb.  Although I bet egts are around 1220 by the time you hit 2000’.

I'm at 1014 MSL; DA typically a little over 2000'.  And, EGT does start to drop pretty quickly.  However, my #2 CHT always runs high, especially in the summer.

[Ragsf15e]

15 minutes ago, MikeOH said:

I'm at 1014 MSL; DA typically a little over 2000'.  And, EGT does start to drop pretty quickly.  However, my #2 CHT always runs high, especially in the summer.

Need more FF!

Im no mechanic so I’m not sure how that’s adjusted, but there’s probably a procedure and standards in the maintenance manual.

[NM Mooney]

3 hours ago, Culver LFA said:

An O2 sensor is going to have a very short life in a leaded environment

Ah, there you have it...  How silly of me. 

BTW - I see that the FAA has a committee hard at work on developing lead-free avgas, as reported here.  I guess it's a bit mystifying to me, since high-torque and high-horsepower auto engines have been successfully running lead-free gas for so long now, and the compression ratio of the Lycoming in the '63 M20C isn't all that high at 8.7:1.  Heck, my mid '80s air-sucker 911 was running 9.3:1 CR burning unleaded premium with no detonation... 

Anyway, thanks for the response. 

[jaylw314]

11 minutes ago, Ragsf15e said:

Need more FF!

Im no mechanic so I’m not sure how that’s adjusted, but there’s probably a procedure and standards in the maintenance manual.

AFAIK the fuel metering device for the IO-360 is not field adjustable for full power fuel flow.  IIRC, there are a couple threads where people have attempted to get them repair/overhauled.  The talk about adjusting the full power fuel flow is more relevant for Continentals like the TSIO-360

I get about 16.0 gph, which I thought sounded low, but I've never had a problem with high CHT's or any sign the engine isn't rich enough at full power (if anything, I struggle to keep my temps high enough).  

[Ragsf15e]

1 minute ago, jaylw314 said:

AFAIK the fuel metering device for the IO-360 is not field adjustable for full power fuel flow.  IIRC, there are a couple threads where people have attempted to get them repair/overhauled.  The talk about adjusting the full power fuel flow is more relevant for Continentals like the TSIO-360

I get about 16.0 gph, which I thought sounded low, but I've never had a problem with high CHT's or any sign the engine isn't rich enough at full power (if anything, I struggle to keep my temps high enough).  

Maybe 16ish is ok?  I think there are some threads around here where people discussed this but I’m not sure there was a perfect resolution?

[Ragsf15e]

2 minutes ago, Ragsf15e said:

Maybe 16ish is ok?  I think there are some threads around here where people discussed this but I’m not sure there was a perfect resolution?

this is a perfect thread on it. Get down about 8 posts to @kortopates description with Saavy data.