Leaning engines using Mike Busch Method

[Skybrd]

I got a interesting article from Sports Aviation December 2012, written by Mike Busch commentary. It's called Red Box Red Fin and about leaning engines. One thing he brought up was using LOP won't hurt anything and to try it. He also stated that EGT is not as important as CHT and to keep out of the red box stay under 400 degrees. I liked his commentary but wondered why he didn't comment about detonation. Have any of you read this article and might want to comment if his writings are good or bad. If a person leans to keep cyl head temps under 380 but leans too far won't it cause detonation? Another question is it ok to run LOP while breaking in a engine. This article says it not good to run 50 degrees ROP during cruise but LOP is ok.

[Jeff_S]

Yes, Mike Busch is a very credible source of information and most folks at least respect his opinion, even if they don't follow it completely.  I found the red fin an interesting twist on the whole LOP/ROP operations debate, and a bit easier to follow as a model, although practically speaking it portrays about the same info as the Red Box concept of the GAMI guys.

 

I am hoping you didn't really mean to start up the whole ROP/LOP debate again, though, with this thread. Surely you have searched and found the other threads that cover this ad nauseum. If not, and you really want to read about it, the Search button is your friend.

[aviatoreb]

I am hoping you didn't really mean to start up the whole ROP/LOP debate again, though, with this thread. Surely you have searched and found the other threads that cover this ad nauseum. If not, and you really want to read about it, the Search button is your friend.

 

Don't worry - we aren't worried about LOP/ROP running long anymore.  Just don't ask about Camguard since that is lively these days.

[PTK]

If you keep your CHT's under 400 your chances of detonation are next to nil. So LOP and use CHT as guide if want to go faster than best economy. Control power with mixture up to 380 max on CHT.

https://www.savvymx.com/index.php/resources/webinar

[jetdriven]

I disagree with Busch on this. You cannot just lean to 380 and run.  That said, detonation on an IO-360 is near impossible at 75% power and below, and difficult above that power setting.  Lean it to 25 LOP, and if the FF is above 10.0 GPH, lean it to that.  If any cylinder exceeds 380 (or 400 as you prefer), lean a little more. Thts conservative, easy, and it works.

[201er]

What do you guys think about running at/above 400CHT at below 65% power (namely when it's hot or high)? Some say below 65/60% to set mixture wherever, but does this matter if CHTs are high? Pressure is low at that setting which is why I wonder if CHT matters as much.

[NotarPilot]

My understanding is that below 65% you can set the mixture wherever which means you can have the EGTs pretty much wherever (i.e. at peak EGT if you want).  Obviously you wouldn't want to run full rich because you risk fouled spark plugs but I think it means you could run 50 ROP, at peak EGT or LOP and not have an issue with pressure being too high.

 

I have watched Mike Busch's webinars on EGT and CHT and the one about leaning, several times, and his big thing is keeping the CHTs low.  High CHTs are what your engine doesn't like.  If you haven't seen the webinars I highly recommend you take the time to watch them.  Mike pretty much says his personal redline is 400 CHT but ideally he keeps CHTs at 380 or less.  If he hits 400 CHT then be does something immediately to get CHTs back down.  He also explains how aluminum loses it's strength the higher the temps and shows graphs to explain how much tensile strength they lose at those high temps around 400F.  He also explains very well on how he leans.  What I find very interesting is the fact that he's got around 3600 hours on his engines without overhauling them.  200% of TBO sounds like he's doing something right.

 

I have pretty much adopted his method of leaning and running my engine to the best of my understanding.

[PTK]

What do you guys think about running at/above 400CHT at below 65% power (namely when it's hot or high)? Some say below 65/60% to set mixture wherever, but does this matter if CHTs are high? Pressure is low at that setting which is why I wonder if CHT matters as much.

CHT matters the most. Being a "temperature" it is the archenemy of our aluminum cylinder heads. Aluminum has a finite life anyway, in terms of fatigue cycles and it's only a matter of time before they will crack and fail. Keeping the CHT's cooler will delay this natural tendency of aluminum. Also high heat risks head/barrel separation.

CHT is not an exact indicator of cpp but it's what we have. We do need to judiciously adjust target CHT up or down a little according to conditions. Up when hot/high down when cold.

[PTK]

I disagree with Busch on this. You cannot just lean to 380 and run. That said, detonation on an IO-360 is near impossible at 75% power and below, and difficult above that power setting. Lean it to 25 LOP, and if the FF is above 10.0 GPH, lean it to that. If any cylinder exceeds 380 (or 400 as you prefer), lean a little more. Thts conservative, easy, and it works.

Byron I'm a fairly new lop convert. Just so I understand you correctly, are you saying lean to ff of 10 gph and tweek from there? I think Busch's reasoning is to pull the cylinders to the lean side fairly quickly to minimize any time spent around peak or rop "red box". He is not saying just lean to a certain CHT. what he is saying, and I agree with his logic, is pull all cylinders to lop. Then decide if you want to run best economy or a little faster based on fuel reserves. If you have sufficient reserves then can richen using CHT as guide. He doesn't bother locating peak. Reason I ask is because 10 gph is essentially peak. There are times one will want to run at best economy which is deep lop or a little faster.

[fantom]

You cannot just lean to 380 and run. 

 

Just to be certain, can you please elaborate....

[marks]

I have a question. I do well LOP and often cruise at 8.3 gph at 7,500 ft. but my CHT often falls so low it goes just under 300. Is it OK to operate below the green at 280 degrees or lower?

[201er]

JimR, what kind of RPM are you using with that and how many degrees LOP?

[PTK]

I have a question. I do well LOP and often cruise at 8.3 gph at 7,500 ft. but my CHT often falls so low it goes just under 300. Is it OK to operate below the green at 280 degrees or lower?

Marks, with CHT's under 300 deg you run the risk of lead fouling. Lead scavenging is a function of sufficient CHT and ethylene dibromide (C2H4Br2) in the fuel. If your plugs show lead deposits then your CHT's are low.

http://www.avweb.com/news/maint/182849-1.html

[201er]

MooneyPilot and JimR, what about higher? The other day I was cruising at 11,000ft to take advantage of winds aloft and I just couldn't find a good place to run my mixture. I obviously wanted maximum fuel efficiency, low speed (to take advantage of tailwind longer), and good cooling. But since my IAS was only about 110 KIAS (despite 130-140KTAS), cooling was terrible! I was getting 400CHT on hottest cylinder and had to trail the cowl flaps. Also the engine was very rough LOP so I had to keep it around peak to run steady. Fuel flow was around 8GPH and prop at 2300RPM, WOT (~19"). I wanted to make fuel flow lower but couldn't since leaning further wasn't an option. Any suggestions?

[201er]

Try higher RPM next time, Mike.  It'll increase your available power at high altitude and my understanding is that it should lower your CHTs.  I just fly at peak up high when I'm going for efficiency, which is most of the time.  I rarely get a chance to do it, though, because my wife and/or kids are usually with me and they start complaining about feeling bad due to the altitude above about 8500 feet. 

 

Jim

Go even higher! Eventually you'll get high enough that they won't be able to complain

 

As for higher RPM, I was trying to be more efficient and use less gas. Increasing RPM increased fuel flow. I understand that you are trying to imply increasing RPM and then going further LOP for cooling... but like I said it was running rough LOP at any setting so I couldn't go LOP enough to get the coolness....

[aviatoreb]

I think that Mike Busch is right about this but I'm not sure where exactly the line should be drawn. 

 

 

Jim

 

Hi Jim, (Ribbing aside about double blind studies and statistics...  :-)

 

I really like the concept too - pressure creates heat and heat is damaging as is pressure so temperature alone indicates heat and pressure.  But:

 

And all, here is some writing by Busch:

http://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning_198162-1.html

he said:

"

I lean so that the CHT of my hottest-running cylinder does not exceed a pre-established target value. That target depends on the aircraft and to some extent the OAT, but for most legacy aircraft (Beech, Cessna, Mooney, Piper, etc.) and most OATs, a target of about 380°F works well. (For more recently-designed aircraft like the Cirrus SR22 or Diamond DA42, with their superior engine-cooling systems, 350°F is a better number.) At unusually cold OATs, the target figure should be lowered a bit.

 

"

 

So which is it?  What is the magic number - 380? 350?  It can't be something in between?  If you have one of those airplanes with excellent cooling due to modern duct work, and the key number for pressure reasons 350CHT should be the target but you lean to 380CHT as your target, then you are running too much pressure and leaning incorrectly even according to Busch.  He names SR22 and DA42 as such airplanes (but aren't DA42's mostly fadec diesels except for a very few IO360s), but take for example the rocket.  I find that it has fabulous cooling, meaning if I run it hot to 380 then I am probably leaned badly.  So then according to Busch do I lean then to 350?  Or something in between 360?  Or maybe 340 because my airplane is even better cooled?  My point is that this while I agree with the magic number concept, the number surely depends on engine and install in various models.  No doubt he has done very very well in his particular engine and airplane.

 

By the way, Deakins wrote somewhere (I couldn't find it) a counter position to Busch's leaning strategy for this very reason - but I couldn't find it this evening. He further points out that on an especially cool day, that he can run especially high pressures if you simply use target CHT method - so lower it "a little"....but then is this easier than the "old fashioned" lean to deg relative to peak EGT for power setting?

 

It sure is a simple method, but I wish I had the rocket magic number.  And a table of OAT corrections.

[KSMooniac]

My dad used to fly high enough to make my brother and me pass out!      (usually in the 10k range in our '65 C)

 

201er, if your plane won't run smoothly LOP far enough to keep things cool, then I suggest to find out why and fix that problem!  Up that high you could run WOT at peak and 2700 RPM and be fine, presuming your fuel and air ratios are nicely balanced as they should be.  If it gets hot, then lean a little bit until below 380 dF.

[KSMooniac]

eb, you're flirting with the reason to NOT use CHT as a mixture setting.  The short answer is that CHT varies with OAT, density altitude (mass of air available for cooling) and of course power/mixture settings.  We MUST use EGT as a proxy for controlling the intra-cylinder pressures (ICP) which can get too high, especially in a turbo application.  We have no way (today) of directly sensing and displaying these ICPs which is why we use the EGT (or TIT) measurements.  Changing the mixture changes the power and most importantly affects the timing and magnitude of the peak ICP.  The peak ICP is what loads the cylinder, piston, crank, valves, etc. and if this value is too high, then it can lead to a premature failure, especially if coupled with high CHT.  It can also lead to detonation at high CHT.  

 

The danger with leaning to a CHT is that on a cold day we could be generating very high ICPs yet have a CHT below the target number of 400 or 380 or whatever you chose, and you'd have no way to know it unless you were aware of the EGT/TIT setting relative to peak.  It won't necessarily crater your engine immediately, but it is not a good place to leave it!  The 380 dF number is a good target for a continuous setting in climb or cruise and is more useful on the warmer days when setting a cruise power setting of 15 dF LOP, for example, your CHT might creep above that target even though your ICPs are in check.  The best reaction would be to lean a little further LOP to reduce CHT (and power a bit).  In the winter, it is likely fine to lean to a target EGT or fuel flow to get your power setting of choice and just be happy with lower CHTs than we get in the summer... you shouldn't lean to get them UP to 380 because you'll likely put the ICPs into the infamous red box.

 

EDIT:  I just re-read your question and would add that your magic number should be a cruise power setting at a given MP and RPM and then leaned to whatever setting you choose, outside of the red box.  If your turbo engine runs great LOP (hopefully so) then I would suggest something like 80% power and 70-80 dF LOP if you can do it.  That should be somewhere around 17.8 GPH.  (305 hp * 0.80 / 13.7)  That is far enough LOP to keep you out of the red box and a very fast and efficient power setting.  If you run ROP then I'd suggest 100 dF ROP at 75% power according to your POH, which is probably 20+ GPH and slower than the LOP power setting I suggested.     If your CHTs in either case are more than 380 dF, then you should lean a little more or enrichen a little more, respectively.

[KSMooniac]

Jim raised a good point I forgot to mention... once you truly understand the hows and whys of mixture management, then you can quickly and easily lean to a fuel flow setting and be done, then simply monitor your temps and fine-tune if necessary, or note when something goes awry (from a spark plug getting wonky, plugged injector, induction leak, whatever).  

 

Now is also a good time for me to add my monthly endorsement of the Advanced Pilot Seminars too!  Hands-down they offer the BEST way to learn all about engine management and trouble-shooting with a highly refined and efficient presentation of what is some difficult and dry material.  I learned more there than in many semester-long engineering courses!

[jetdriven]

Byron I'm a fairly new lop convert. Just so I understand you correctly, are you saying lean to ff of 10 gph and tweek from there? I think Busch's reasoning is to pull the cylinders to the lean side fairly quickly to minimize any time spent around peak or rop "red box". He is not saying just lean to a certain CHT. what he is saying, and I agree with his logic, is pull all cylinders to lop. Then decide if you want to run best economy or a little faster based on fuel reserves. If you have sufficient reserves then can richen using CHT as guide. He doesn't bother locating peak. Reason I ask is because 10 gph is essentially peak. There are times one will want to run at best economy which is deep lop or a little faster.

 

CHT is also a function of IAS and OAT.  Super cold days you may not be able to exceed 380 CHT at peak at sea level and full throttle.  You know ICP are above a safe, certified level, but the CHT doesn't tell you this. It is not a problem in NA aircraft above 4000-5000 feet. It IS a problem in turbocharged aircraft at any altitude.

 

What I am saying is lean to something around 25 degrees F LOP on your richest cylinder.  THEN, IF you FF is above 10.0 GPH, lean to 10.0 GPH.  This keeps you below 75% power.   Wait, there's more.  THEN, IF any CHT exceeds 380 or 400, depending on your religion, if it is night time, if Cindy is expecting another baby, lean a little further to keep the CHT below your 380 or 400F  trigger.  You can use CHT 380 as a guide to good leaning in warm weather  and at moderate altitude, but you can't set the mixture with it.   It is the long-term trend.  Not the parameter to set mixture with.  IF you are already established LOP, or if you are above 5000 feet, and you see 385 CHT, sure, lean a bit more. But at least you know where you are at to begin with.

[jetdriven]

MooneyPilot and JimR, what about higher? The other day I was cruising at 11,000ft to take advantage of winds aloft and I just couldn't find a good place to run my mixture. I obviously wanted maximum fuel efficiency, low speed (to take advantage of tailwind longer), and good cooling. But since my IAS was only about 110 KIAS (despite 130-140KTAS), cooling was terrible! I was getting 400CHT on hottest cylinder and had to trail the cowl flaps. Also the engine was very rough LOP so I had to keep it around peak to run steady. Fuel flow was around 8GPH and prop at 2300RPM, WOT (~19"). I wanted to make fuel flow lower but couldn't since leaning further wasn't an option. Any suggestions?

 

Like Jim, I have noticed a higher RPM setting will cool the engine at higher altitudes such as 11,000 feet. (really, at all altitudes, everything else constant)  The air is too thin there to cool the engine and I routinely see 380 CHT there. Leaning further results in unacceptable speed loss, and loss in NMPG.  However, raising RPM to 2600 or even 2700 RPM will lower cylinder pressure and lower the CHT a few degrees.  Also, I have learned to live with seeing a 380 continuous number on the engine monitor. It may be a case of "normalization of deviance" or "requirement creep", but often we cannot keep some cylinders below 380 in cruise.  We are already pushing 30-40 LOP and any leaner results in a tremor under the cowl. Now we never see 400, but I am learning to live with 380 if it is stable.  Lycoming says keep your engine under 435 in cruise and 65% power and below for long engine life. Redline CHT is 475.  I an beginning to yield on 380, but not 400 at this time.

[aviatoreb]

eb, you're flirting with the reason to NOT use CHT as a mixture setting.  The short answer is that CHT varies with OAT...The danger with leaning to a CHT is that on a cold day we could be generating very high ICPs yet have a CHT below the target number of 400 or 380 or whatever you chose,

 

EDIT:  I just re-read your question and would add that your magic number should be a cruise power setting at a given MP and RPM and then leaned to whatever setting you choose, outside of the red box.  If your turbo engine runs great LOP (hopefully so) then I would suggest something like 80% power and 70-80 dF LOP if you can do it.  That should be somewhere around 17.8 GPH.  (305 hp * 0.80 / 13.7)  That is far enough LOP to keep you out of the red box and a very fast and efficient power setting.  If you run ROP then I'd suggest 100 dF ROP at 75% power according to your POH, which is probably 20+ GPH and slower than the LOP power setting I suggested.     If your CHTs in either case are more than 380 dF, then you should lean a little more or enrichen a little more, respectively.

 

Hi Scott, I paraphrased you.  I hope you don't mind.

 

I was indeed intending to suggest the dangers of leaning to CHT alone. 3 mitigating factors to consider which may make it a problem as several of us have outline:

1. Esp cold OAT.  I occasionally fly at 0F or lower.

2. Esp good cooling/baffling/airspeed. 

 

Even on a warm day, the POH ROP settings put my CHTs in the 360s.  On a cold day, the POH ROP settings put my CHTs in the 340s for the hottest. 330s if especially cold OAT.  So if I were to lean to CHT to 380 I think the ICPs (thanks - I forgot that phrase) would be through the roof. Even 350 CHT on the coldest of days may make for too high for design ICPs.  Remember also that in a fast cruise in this airplane, there is a lot of airflow.

 

3.  The issue is especially dire and more prone to a catastrophic error in the case of a turbo airplane.

 

So main thing - be especially careful being sure what you are doing in a turbo on a cold day... I am file away the information as interesting that CHTs are a necessary but not sufficient condition to good engine health and longevity.  But I don't do the Busch method otherwise.

 

By the way, ICPs aside, is it fair to say that it is impossible to make a detonation even even in a turbo airplane if the CHTs are very low like 340?  So at least do I have that bugaboo not to worry abut.

 

As for your discussion of the joys of 80% LOP ops.  I have not managed that.  My TiT seems to be the limiting factor here in my particular install (as I have written before).  70-72% LOP is the highest I have run LOP. Tit creeps to 1600-1620 there which makes me uncomfortable.  I do not know what TiT would be for 80% but extrapolating suggests >1650 the TiT redline.  I have read on the Cessna 340 forum (they use the same engine) and a number of folks do in fact run the TSIO520NB exactly like that with no worry.  But the most I run LOP is 65% which allows me TiT in the 1570-80 range.  Call me a LOP whimp.  Its a shame too since I would looooove to run 80% power.  It is already like a bat out of hell at 76% power (recommended cruise on the POH chart, but at a whopping 22gph - yes I do this sometimes when I have a reason to get there quickly - it is fun to hot rod around like a bat out of hell sometimes too - like a 20 min flight with a friend there is not a great difference in total fuel burned whether at 72% or 76% over 20 min rop).  I do have a feeling that there is a way to run this plane at 80% at LOP but I have not found it yet.  BTW, yes my injectors are balanced to 0.3gph and we have really cleaned up the induction system so it is smooth at seemingly all settings until very severe LOP.

[aviatoreb]

Your fire breathing turbo charged engine and Northern operating environment are entirely different than mine, though, so all bets are off.   Scott is right, of course.  Lean based on EGTs, or in your case, TIT, I guess, and make adjustments from there to control CHTs, making allowances for atmospheric conditions. 

 

Agreed.  0F OAT + turbo fire breather - I do it the EGT, TIT way.  CHTs I observe but since they are rarely even close to scary high I mostly never need to worry about it.

 

Thanks for spelling my name correctly!  Few people do.

 

On cold days, I like to climb at 88% (per POH and full fuel) cruise climb after initial climb and I do so with cowl flaps closed which allows faster cruise climb of up to 150IAS and still fpm>1000.  This works closed cowl flaps and nice CHT if OAT is ~<25F or so.

[carusoam]

EB,

Fuel injector balance is 50% of the solution. Balanced intake runners would be the other 50%...

The IO550 has nice curved, near identical geometries to each cylinder.

Does the rocket have a similar intake design as the 550?

Any possibility of adding such a system?

Best regards,

-a-

[aviatoreb]

EB,

Fuel injector balance is 50% of the solution. Balanced intake runners would be the other 50%...

The IO550 has nice curved, near identical geometries to each cylinder.

Does the rocket have a similar intake design as the 550?

Any possibility of adding such a system?

Best regards,

-a-

 

I don't know anything about the intake geometries.  ANyone else?  For all I know I do.  So that is what makes the IO550 so famously awesome for LOPsOps?

 

I can say this....surely there must be no possible way to substantially alter the intake geometry, even for the better, without an STC in a certified airplane.  Too bad.