[donaziza]

Could someone explain this to me. (I believe I got it off one of Mike Busch's Webinars)

It was about keeping your EGT's constant as you climb, the idea being to keep the mixture right, ie leaning it as you climb.I can't remember how that works.

If someone could help, I'd sure appreciate it.

Thanks:

 

[Jesse]

I don't know a specific rule, but I lean mine to he low 1300's as I climb. This keeps me well rich of peak for engine cooling but doesn't foul my plugs. On takeoff I usually see high 1100's to mid 1200's.

 

[Kevin Horton]

Could someone explain this to me. (I believe I got it off one of Mike Busch's Webinars)

It was about keeping your EGT's constant as you climb, the idea being to keep the mixture right, ie leaning it as you climb.I can't remember how that works.

If someone could help, I'd sure appreciate it.

Note your EGT during take-off, or as soon as possible after taking off. Lean as required during climb to keep the EGT equal to the value you noted during take-off.

I use this with my angle valve IO-360, and it has served me well all the way up to 18,000 ft.

 

[newtech]

I run 92 octane lead and ethanol free auto fuel in my O-360 A1A. Since there isn't any lead, is it as necessary to lean in a climb? I would think the only down side would be a higher fuel burn rate.

 

[Toobuilder]

I lean to best power EGT as soon as the wheels leave the ground, and maintain that value all the way up to about 7,000 feet, where I transition to cruise climb LOP.

 

[N427EF]

It's not about the lead.
Leaning in climb has more to do with efficiency than lead deposits.
You are simply loosing some power with an overly rich mixture as you climb
and at the same time burn money to boot.
So, no you don't need to lean but you definitely want to.
I too use the following leaning procedure in climb with 91 octane E10.

Note your EGT during take-off, or as soon as possible after taking off. Lean as required during climb to keep the EGT equal to the value you noted during take-off.

 

[DanH]

Could someone explain this to me. (I believe I got it off one of Mike Busch's Webinars)
It was about keeping your EGT's constant as you climb, the idea being to keep the mixture right, ie leaning it as you climb.I can't remember how that works.

Maybe Busch, maybe John Deakin.

John covered the subject in a Pelican's Perch article back in January 03. I suggest you do not read the article, as (1) it makes the subject far more complicated than necessary, (2) offers a great many target numbers which are not universal, and (3) centers actual operations advice around the basic Continental fuel delivery system, which is nothing like the FI found on the typical Lycoming/Lyclone in an RV (basic Continental meters fuel based on RPM, while Bendix/Precision/AFP meters based on mass airflow).

That said, there is a terrific illustration published as an addendum to that article; a Bonanza owner kindly made two climbs, one without leaning and one leaning for constant EGT. The basic operational concept is true for all, and is illustrated very well:

http://www.avweb.com/media/newspics/182093_second_and_third_climbs.jpg

The fundamental assumption underlying lean-in-the-climb is that full throttle fuel flow is sufficient to result in an EGT approximately 150~250 ROP. Which is better? You're read that debate here; some (including me) argue that 150 offers full rated power, while others feel 250 is mandatory for cooler CHT. Neither position is wrong, and most users, if within the range, are not going to change what they have in any case.

So yes, note EGT at 500~1000 feet, WOT, and maintain that target EGT in the climb. It is not necessary to be real fussy about maintaining an exact EGT value. KIS.

 

[rocketbob]

The fundamental assumption underlying lean-in-the-climb is that full throttle fuel flow is sufficient to result in an EGT approximately 150~250 ROP. Which is better? You're read that debate here; some (including me) argue that 150 offers full rated power, while others feel 250 is mandatory for cooler CHT.

I concur. What I've found is that at slightly rich of peak EGT in the climb is more than sufficient to keep the engine cool with good fuel distribution around 12.5 GPH. This I've discovered thru experimentation with the Rotec TBI. Climb CHT remains constant.

 

[skylor]

Leaning Lycoming's

Could someone explain this to me. (I believe I got it off one of Mike Busch's Webinars)

It was about keeping your EGT's constant as you climb, the idea being to keep the mixture right, ie leaning it as you climb.I can't remember how that works.

If someone could help, I'd sure appreciate it.

Thanks:

One thing to keep in mind is that much of Mike Busch's and John Deakin's writings are somewhat focused on operating fuel injected Continentals. A fundamental difference between the Continental fuel injection system and the Lycoming systems (Bendix/Precision or AFP) is that Continental's provide a fixed fuel flow for any given throttle position/RPM (excepting those with altitude compensating fuel pumps) meaning that they get richer and richer as air density decreases. The Lycoming systems on the other hand meter fuel flow based on throttle position and air mass-flow through the servo. This means that these injection systems automatically lean the mixture as air density decreases.

With that said (and as others have said) full throttle/full rich fuel flows are often higher than needed at less than full sea level air density thus even on Lycomings there is some benefit to leaning the mixture to a target EGT during climb at higher altitudes. Since I usually fly from sea level airports in warm weather (Southern California) I typically don't lean in climb until above 4 or 5 thousand feet for temperature control.

Skylor
RV-8

 

[JohnInReno]

Leaning Lycomings

I understand the concept of maintaining EGT, but no one seems to address the procedure when you are starting from 4,000 msl.

If I start at WOT and glance at the EGT when I get to 5,000 msl (1000agl), that is going to be way richer than someone flying from sea level.

 

[jimbo]

Note your EGT during take-off, or as soon as possible after taking off. Lean as required during climb to keep the EGT equal to the value you noted during take-off.

I use this with my angle valve IO-360, and it has served me well all the way up to 18,000 ft.

So does this also apply to a carbureted 0-320 as we'll? I remember the op manual saying climb out at full rich and WOT until reaching 6000 ft or so.

Jim

 

[Toobuilder]

Best power EGT is best power EGT.

Figure out what that value is for your engine and adjust mixture to match that value. Doesn't matter if you start your takeoff roll
at sea level or 10,000 feet.

 

[skylor]

Best a Power EGT

Best power EGT is best power EGT.

Figure out what that value is for your engine and adjust mixture to match that value. Doesn't matter if you start your takeoff roll
at sea level or 10,000 feet.

I disagree. Peak EGT temperature will drop with power. In other words, as altitude increases, the peak absolute EGT temperature drops. This is evident if you do a target EGT climb from sea level. At some point, leaning as altitude increases will no longer yield an increase in EGT, which means you've reached peak. For example, take off from sea level with a target of 1300F. As you climb through say 7 or 8 thousand, you might increase your target to 1400 or 1450 to get closer to best power, but as you go through 10 or 11 you'll find that you can no longer achieve 1450.

Skylor
RV-8

 

[Yen]

While doing this leaning would it be a good idea to keep an eye on CHT also. If the leaning is excessive you could run the risk of detonation and the earliest sign of that would be a big increase in CHT. Go back to full rich if there is any sign of detonation.

 

[BillL]

<snip> The Lycoming systems on the other hand meter fuel flow based on throttle position and air mass-flow through the servo. This means that these injection systems automatically lean the mixture as air density decreases. . . .

Skylor
RV-8

I need some help understanding this. Doesn't the AFP use a pressure drop across the servo to activate the fuel flow? How does it know the difference between 250 cfm flow at 1000 feet (WOT) and 6000 ft? How does it register density? Does it have an aneroid inside?

I am looking for theory of operation online too, but since you brought it up, maybe you could address this question.

Thanks

 

[rocketbob]

This means that these injection systems automatically lean the mixture as air density decreases.
Skylor
RV-8

Not quite...that is a rarely seen option with some RSA-5's but some RSA-10's have the automatic mixture unit attached.

The RSA-5's and knockoffs typically seen on RVs do not have this feature.

 

[Toobuilder]

I disagree. Peak EGT temperature will drop with power. In other words, as altitude increases, the peak absolute EGT temperature drops...

However, the sea level "best power" EGT does not move all that much below 7000 feet. If you wanted to be really on your game, then one could chart the best power EGT for every thousand feet, but I suspect that won't buy you much. Sticking with the sea level best power EGT and maintaining that all the way to cruise is much better than leaving the mixture full rich below 7500.

The point I'm intending to convey is that we don't have to make this hard. These engines flew fine with no EGT indication at all.

 

[DanH]

I am looking for theory of operation...

Bill, check your email.

 

[BillL]

Bill, check your email.

Thanks, Dan, that matches my memory of how this fuel injection system works from when I first learned it back in 1986. Memory is fallible though. Good to know I don't forget (some) technical things.

To the topic, the theory of operation is based on VOLUME of air through the servo, not MASS. The fuel pressure (to the spider) is based on pressure drop due to the VOLUME of air induced. This pressure goes to the fuel orifices that flow MASS based on the pressure.

So - air VOLUME is determines fuel MASS flow rate. Meaning, as one goes up in altitude, the richer the air/fuel ratio gets with the lower air mass flow, even as the engine continues to demand the same air VOLUME.

Richer? Bad? Well not necessarily, but the extra fuel does not participate in combustion, it simply evaporates and cools the process. In fact, after rich of peak occurs, it has been shown that alcohol, water etc (stuff that evaporates) will contribute to both cooling and what little extra power is produced from better thermodynamics.

So don't forget, as you are leaned at altitude the engine will QUIT when descending a significant amount if mixture is not adjusted.

 

[skylor]

RSA-5

Not quite...that is a rarely seen option with some RSA-5's but some RSA-10's have the automatic mixture unit attached.

The RSA-5's and knockoffs typically seen on RVs do not have this feature.

In this post, Mr. Rivera describes how the Bendix and AFP injection systems meter fuel base on Mass Air Flow:

http://www.vansairforce.com/community/showthread.php?p=864236#post864236

In my -8 with a stock factory Lycoming IO-360A1B6 if I takeoff at sea level and climb with all knobs forward (constant speed prop), my fuel flow clearly drops with increasing altitude, and the EGT's stay relatively constant telling me that the system is reducing fuel flow based on mass air flow. I'll post some data later today.

Skylor

 

[rocketbob]

Does your AFP unit have the egg shaped casting in the center? If so it has this feature. Most Bendix systems and the Silverhawk have the four exposed pitot tubes and do not automatically lean. I believe the egg shaped casting is called an automatic mixture aneroid and there are variations to it...some are internal and some are external.

 

[Toobuilder]

...So don't forget, as you are leaned at altitude the engine will QUIT when descending a significant amount if mixture is not adjusted...

Yes and no. This requires some elaboration. I typically run LOP and 10,500 to 11,500 enroute. During my descent, I manage only one lever - the throttle - to maintain 22-23 inches of MP. I usually don't touch the mixture until downwind or final. I've never had the engine give any hint it's going to quit.

OTOH, If you're asking it to maintain full throttle from altitude without touching the mixture, yes, I admit it will get very lean and likely quit as you descend.