How do you lean...

[rdv]

[carusoam]

I suppose, somewhat to the right for most of us?

 

-a-

[Shadrach]

2 posts and already we've 2 of the most contentious subjects in the pilot community... Well done! I'll stay out of it...for now.

[sleepingsquirrel]

To the left, I'm left handed. Seriously though, with the red knob.

[fantom]

I try to trim most of the fat off.....

Too bad for all of us, Washington can't learn to do the same :-(

[jetdriven]

to 8.7 GPH for 65% power, and 9.9 for 75%.    that is it.  

 

[Shadrach]

rdv,

To answer your original question -  It depends... I use the following mixture settings for best performance, but with much consideration going to engine health and economy.  I cut and pasted this from my response to an older conversation I had elsewhere...

Taxi - Lean to roughness and increase until smooth - I also cycle the prop and check the mags in this configuration... I seldom use a "run up" RPM to make these checks unless I have a pilot (read CFI) in the plane that would be both uncomfortable with it or unable to accept the logic of doing it that way.  I want everyone to be comfy and confident, so I'll sacrifice my prop leading edges to avoid having a cockpit confrentaion.

Take off - Normaly full rich* If DA is ≥ 3000ft then I lean to target EGT on the richest cylinder which is about 1275-1300 on my plane or about 225-250 ROP...

Climb - Target EGT, see above... it just takes a slight twist about every 1000ft to keep richest cylinder's EGT ≤ 1300df.

Cruise - DAs of 150ft (low down the coast or river running) to 7500ft I'm LOP... I run ~55-65 Df LOP when down on the deck in level flight (maintaining CHT of <~370 on hot summer days and <~350 in the winter).  Degrees from peak on the lean side will decrease as cruise DA increases.  At 3000 I'm 35-40LOP working towards peak as I climb (which I usually get to around 7500-8500 DA) but holding CHTs in the earlier defined area. As I get into higher altitude ops, the surplus of air available for reasonable power settings LOP becomes an issue, so I often cruise at peak or around ~5df LOP in the 7000 - 9000 DA range. Higher than 10K and I run ROP as close to 75ROP as possible with CHTs in mind. 

[As an aside, I was very surprised at the speeds my old stock F was able to attain at DAs in the low 16,000s at 75ROP...]

Descent - I often maintain WOT ram air on and lean to reduce power. Normal descents are at 500-1000fpm. As I get within a few thousand feet of TPA I enrichen to target take off EGT-50 and leave it that way until touchdown...from that point on I typically use the throttle for power changes. The final lean to take off EGT mentioned above puts the mixture perfect for a full power go around in the rare case that it is needed, regardless of whether I'm landing at a 700ft or a 7000ft DA...

That is all...

Edit - Every few flights or so I will do a high power LOP mag check in descent to verify the health of my ignition system; it will show a problem long before the typical 1700rpm, full rich, ground run up will; it's a more strenuous test of the ignition systems capabilities... Bad plugs will sometimes only reveal themselves at high cylinder pressures and an inflight check will show it every time...

I know this all might read terribly complicated, but it's actually pretty simple in practice.

[jetdriven]

shadrach is right.  this is exactly what we do in the J.  We average 150 or so KTAS and 8.5-9 GPH

 

[rdv]

Thats too funny, you guys are hilarious. For some reason the body of my message didn't follow the title!

Anyways, what I meant by "how do you lean..." was what are some of the strategies used pilots for leaning in the climb and descent phase of flight. We have had many discussion about leaning in cruise, but not so much about the rest of the trip. Thanks for all your thoughts

Ross,

Above 3000' DA in the climb, how or why did you determine 225-250 DF to be target EGT temp?

Are you using balanced fuel injectors for smooth LOP operation?

 

Ryan

[Shadrach]

Quote: rdv

Ross,

Above 3000' DA in the climb, how or why did you determine 225-250 DF to be target EGT temp?

Are you using balanced fuel injectors for smooth LOP operation?

[Swingin]

I have an old (but functional) JPI scanner that will show me EGT or CHT for any of the cylinders - but only one at a time and you have to toggle over to which value you want displayed.  In my '67E, the #3 peaks last, and I set it around 1390 or 1400 in cruise (which is almost always above 10K here in Utah if I want to go anywhere other than west).  I also have a fuel-flow display on an antiquated totalizer that has proven to be quite accurate.  I usually set the fuel flow to 8.9GPH and cross-check it with the EGT.

For takeoff, almost always at high-DA, I start the roll full-rich (after a lean taxi of course) and then lean by feel until I feel the power top out - usually about 1/2" or so.  I try to climb rich enough to keep EGTs below 1300 until I'm ready to level off.

Clear as mud?

[rdv]

Ok, whats wrong with this picture:

Density alt-9600'

12 degrees c Outside air

133 KTAS

2400rpm

20inch manifold

190 degree f oil

peak egt:

1- 1486

2- 1501

3- 1486

4- 1468

 

100 degree rich of peak:

1-1370 cht-303

2-1411 cht-336

3-1402 cht-351

4-1360 cht-331

 

LOP

1-1422 cht-285

2-1436 cht-313

3-1422 cht-311

4-1409 cht-302

 

(jpi 700 analyzer)

 

[danb35]

Why do you think something's wrong with that picture?  At ~60 LOP, CHTs are cooler than at 100 ROP, which is exactly what I'd expect.

[jetdriven]

if you go further than 50 LOP, you are losing efficiency again.  Down below 4000' I do go leaner than that simply to keep power below 75%.   At 9600 density altitude, I would be between 20 LOP and peak depending on what speed I was getting.

[Shadrach]

Quote: rdv

Ok, whats wrong with this picture:

Density alt-9600'

12 degrees c Outside air

133 KTAS

2400rpm

20inch manifold

190 degree f oil

peak egt:

1- 1486

2- 1501

3- 1486

4- 1468

 

100 degree rich of peak:

1-1370 cht-303 =  = 116df ROP

2-1411 cht-336 =  = 90df ROP

3-1402 cht-351 =  = 84df ROP

4-1360 cht-331 =  = 108df ROP

weird yet unimportant coincidence is that you're not not 100 ROP on any cylinder, but that the average of all 4 is 99.5df ROP...

LOP

1-1422 cht-285 = 64df LOP

2-1436 cht-313 = 65df LOP

3-1422 cht-311 = 64df LOP

4-1409 cht-302 = 59df LOP

 

(jpi 700 analyzer)

 

[jetdriven]

you can clean the injectors overnight in acetone or hopppes #9 gun solvent it may tighten up the GAMI spread.  We took it furhter and swapped #1 and #4 now its a zero-.2  spread.

[Shadrach]

Jet, Am I missing the obvious here?  His numbers show that each cylinder is within a 6df spread from peak, while lean of stoic... How much closer can you get them??? Are you doubting the numbers?

[jetdriven]

Actually I have no idea of his GAMI spread because he did not list fuel flows at peak, only temperatures.  Ours had a .8 GPH spread, after cleaning and rearranging 1 and 4, it was either .2-0.   Im not sure which did it, but it happened.  What brough that comment out is yours saying that certain cylindfers typically run richer than others.  This can help that.

[Shadrach]

I've never bothered to do a GAMI spread in my bird as I do not have FF installed yet. However, using peak as a reference point, it appears his spread is almost 0.0, but only on the lean side. It seems a bit higher on the rich side. This makes me suspect that there's an issue with the data...