Wide open Throttle leaned to lower RPM

[Henning]

And some of us stuck behind O470s with crappy induction systems can't take the roughness that going much LOP causes.

Now with altitude the throttle does stay fwd.

There are ways to tune that out using carb heat.

 

[Skylane81E]

There are ways to tune that out using carb heat.

Helps, but only so much. Need to get an analyzer and start playing. Know a guy who gets 25 degree spread with out carb heat on his, makes me wanna have at mine.

 

[Henning]

Helps, but only so much. Need to get an analyzer and start playing. Know a guy who gets 25 degree spread with out carb heat on his, makes me wanna have at mine.

Also are you running WOT when you're going really lean? It makes a big difference in the plenum air flow. Remember, once you are LOP, your MP & RPM are no longer representative of your power, your airspeed and fuel flow is. You can be WOT & redline RPM and still only be at 65% power by fuel flow. Best way for you to know how much power you are making is to note your airspeed in the %Power table for your altitude.

 

[JohnAJohnson]

I read somewhere at lower altitudes you can set the throttle to a 75% power setting with best power mixture, then lean the RPM back to the desired power setting. Above 8000 ft leave it wide open and lean back to whatever power setting you want. I think that was in a Piper POH

Yep. From my 1984 Warrior Manual, Chapter 4.27 Cruising:

For Best Economy cruise, a simplified leaning procedure which consistently allows accurate achievement of best engine efficiency has been developed. Best Economy Cruise performance is obtained with the throttle fully open. To obtain a desired cruise power setting, set the throttle and mixture control full forward, then begin leaning the mixture. The RPM will increase slightly but will begin to decrease. Continue leaning until the desired cruise engine RPM is reached...

 

[bluerooster]

I've talked to a couple of 195 drivers who claim that they can achieve maximum fuel efficiancy, by leaning aggressively, and then adding carb heat.
I was even told of fuel burns in the neighborhood of 9gph, at cruise.
The only jakes that I'm familier with will gobble up about 100gal/3 hours /2=about 15gph. And that's "economy cruise".

 

[Henning]

I've talked to a couple of 195 drivers who claim that they can achieve maximum fuel efficiancy, by leaning aggressively, and then adding carb heat.
I was even told of fuel burns in the neighborhood of 9gph, at cruise.
The only jakes that I'm familier with will gobble up about 100gal/3 hours /2=about 15gph. And that's "economy cruise".

Depends on how slow you want to go. The carb heat helps vaporize the fuel which then spreads more evenly and runs smoother, it does cost you power though and allows you to lean even further losing more power yet. As power goes down so does fuel flow. Use airspeed to determine % power.

 

[ARFlyer]

http://www.langleyflyingschool.com/...ks/Cessna 152/Section 4 Normal Procedures.pdf


Page 4

Enroute Climb

1. Airspeed 70-80 KIAS
2. Throttle - WIDE OPEN
3. Mixture full RICH below 3000FT, lean for maximum RPM above 3000FT

My flight school FOM and aircraft checklist state this exact procedure. If your in a Piper then it is full throttle, prop set to 2500 and -100* LOP via the mixture. If your in a Maule it is 2500 via the throttle and leaned to roughness and turned three times. This is only for x/c and not for local area flying. They assume your doing maneuvers in the practice areas.

Now how often are the performance charts, piper only, or leaning procedure followed? Well by the black soot on the exhaust and cowlings not a lot. I can say its tough to clean off the aircraft!