engine management, red box questions

[rbridges]

I'm a little confused on a few things, and I know some of these questions are going to sound dumb.  I have an engine monitor, and basically all I've ever done is try to keep CHT under 380, oil temp under 210 regardless of altitude.

 

I did some research on the "red box" and they give relative ROP #'s for % power ranges.  I guess 100% power is based on full manifold pressure at sea level?  so 65% would be 29.92*0.65?

 

To find out peak CHT, do you just lean it back and see how high the temps go up?  I've always been leery to do that b/c I felt it was hard on the engine.  Is there a # people use for certain engines, or is it pretty variable for each setup?

 

 

Obviously, I have an o-360.  What values are you using and how do you setup for cruise at various altitudes?  Input from anyone is appreciated, but I run ROP so those would be most helpful.

[Jeff_S]

Well, there is a wealth of information in various threads already posted on this forum so you would be wise to do some searches on the LOP/ROP topics and read through them. But to try answering a few of your questions...

 

First, percept power is a factor of RPM and MP and Fuel Flow, so your simplified approach is definitely NOT the way to determine this. Your POH should give you various ranges for power level settings based on the factors noted in this sentence, so a good place to start is studying those.

 

However, I never pay attention to percent power myself, preferring instead to use the generally recommended technique of leaving throttle wide open (WOT), reducing RPM to a cruise setting you like (2400-2550 for me) and then leaning to the appropriate setting. The way to do this is with your engine monitor. You don't say which one you've got, so I'll assume a JPI 700 as a baseline. Also, you don't say whether or not it has the specific LOP Lean Find mode. It should if it has the correct software.

 

But the way to find peak EGT (not CHT, by the way...they all work by measuring EGT) is to set up your engine as I've described above and then follow the instructions with your engine monitor.  As a non-fuel injected engine you may have trouble getting to LOP without undue roughness, but you may not...it depends on how well your carb is adjusted among other things.

[rbridges]

thanks, Jeff.  I have a UBG16 engine monitor.  ok, that makes sense about % power.  I knew that was a dumb question.  

 

anyway, I end up cruising very similar to your method.  I usually go WOT, 2400 rpm and lean.  It's how far I lean that comes into question.  I wanted to make sure i was not in the red box according to the articles I was reading.

[Marauder]

thanks, Jeff.  I have a UBG16 engine monitor.  ok, that makes sense about % power.  I knew that was a dumb question.  

 

anyway, I end up cruising very similar to your method.  I usually go WOT, 2400 rpm and lean.  It's how far I lean that comes into question.  I wanted to make sure i was not in the red box according to the articles I was reading.

 

 

Here is an article that might help you out: http://www.avweb.com/news/pelican/182583-1.html?redirected=1

[Cruiser]

I'm a little confused on a few things, and I know some of these questions are going to sound dumb.  I have an engine monitor, and basically all I've ever done is try to keep CHT under 380, oil temp under 210 regardless of altitude. 

 

I did some research on the "red box" and they give relative ROP #'s for % power ranges.  I guess 100% power is based on full manifold pressure at sea level?  so 65% would be 29.92*0.65?

I would use your POH for determining approximate %power for your aircraft.

 

To find out peak CHT, do you just lean it back and see how high the temps go up?  I've always been leery to do that b/c I felt it was hard on the engine.  Is there a # people use for certain engines, or is it pretty variable for each setup?

the Lycoming O-360 series peaks pretty much around 1500°F it could be a little lower or slightly higher but 1500 -1525 would be a good estimate. This is going to change based on altitude since your MP well vary. If you want to be precise, you just have to lean to peak then enrich the mixture from there.

 

Obviously, I have an o-360.  What values are you using and how do you setup for cruise at various altitudes?  Input from anyone is appreciated, but I run ROP so those would be most helpful.

Use the leaning procedure in climb to maintain your EGT temp near the value you note during the takeoff run (ideally this would be at sea level) but should be near 1250-1300°F or approx. -250°F of peak.

[Hank]

Rob--

I generally start with Book settings, even though they are given every 2500', as a baseline. For instance, a short lunch run will often be at 3000 msl. The 2500' chart shows 23"/2300 to be 71.5% power at 50F (+1% foe each 10 degrees below that; -1% for each 10 degrees above). I climb to 3000 with all levers fully forward, level off, accelerate then pull the throttle back to 22", and it rises right to 23" as the prop comes back to 2300. Then I pull the mixture back and watch my EGT needle move right until it pauses and she starts to cough a little. Then I push it forward until the needle moves two lines back to the left, and verify over the next couple of minutes that it stays where I put it. There is some variation but this is often in the vicinity of 1450; your number may be quite different as I only have the factory single gauge.

For a longer trip such as to MLJ, I climb the same way, maybe leaning some, to 9000'. The book shows at 10,000 msl that WOT =20.2", and 2500 gives 71%. At 7500, 21"/2500 gives 72.1%. So after levelling off and accelerating, I reduce throttle enough to make the MP needle move (call it 20.5" at 9000), set 2500 and call it 71-72%. As long as OAT is above 3F, this should be safe. I generally target~70% to get good speed. Again this is often around 1450, although this high it is okay to run at peak if you want.

With my simple analog gauge, it only takes about 5 seconds to set the mixture. Flying a friend's F with a round, orange bar graph monitor, it easily too 15-20 seconds just to find peak. It pays to keep an eye on CHT while climbing, accelerating, setting power, verifying mixture and periodically afterwards.

[rbridges]

Here is an article that might help you out: http://www.avweb.com/news/pelican/182583-1.html?redirected=1

 

thanks everyone, this has been helpful.  I actually found that article, but it makes more sense after reading this thread.

[mooneyflyer]

I'm a little confused on a few things, and I know some of these questions are going to sound dumb.  I have an engine monitor, and basically all I've ever done is try to keep CHT under 380, oil temp under 210 regardless of altitude.

 

I did some research on the "red box" and they give relative ROP #'s for % power ranges.  I guess 100% power is based on full manifold pressure at sea level?  so 65% would be 29.92*0.65?

 

To find out peak CHT, do you just lean it back and see how high the temps go up?  I've always been leery to do that b/c I felt it was hard on the engine.  Is there a # people use for certain engines, or is it pretty variable for each setup?

 

 

Obviously, I have an o-360.  What values are you using and how do you setup for cruise at various altitudes?  Input from anyone is appreciated, but I run ROP so those would be most helpful.

 

Red Box is not about "peak" CHT, or peak EGT for that matter.  Red Box is about running your engine for maximum useful life.  Most of us were taught, and many POH indicate flying at 50-deg ROP.  This maximizes your ICP (Internal Cylinder Pressure), which is BAD for your engine.

 

Keeping CHTs below 380-deg is also an engine longetivity issue.  Prolonged operation above 380-deg actuall causes changes, not good, in the metalurgy/strength of your cylinders.

 

At 60% BHP, or lower, you can run your engine at any mixture setting (as long as its running smoothly).

 

Hope this helps a little... even tho my response is late to this thread.

[carusoam]

Nicely assessed mooneyflyer...

Everybody has different priorities, from engine manufacturer, to airframe manufacturer, to pilot, to pilot's financier...

Running ROP 50dF (EGTs) gives high ICP and great HP but can lead to higher CHTs and increased cylinder wear and the following expenses as well. Not unsafe for your health, but not friendly to you wallet either...

Understanding everyone's priorities is the key to understanding their advice.

Some people will afford an extra set of cylinders to go that much faster and others can run LOP at higher altitudes and go a little slower in a more wallet friendly mode or flop between the two depending how you feel that day...

Best regards,

-a-

[DS1980]

rbridges,

 

I am glad I am not the only one who is confused!!!

We're here to help. Do you have specific questions?

[PTK]

I have a couple questions related to this.

One for you carbureted guys who must run ROP.

Do carbureted engines see more exhaust valve and guide issues than injected ran LOP?

And for injected engines that were ran ROP long enough to the point of perhaps developing exhaust valve issues and then ran LOP do those issues have any tendency of clearing up? Have any of these ever been studied or quantified?

IOW, always wondered if LOP ops tend to clear up exhaust valve and guide crud buildup. As long as valve is not burned.

Seeking knowledge, lots of knowledge! More knowledge!

[carusoam]

My C stuck and bent a valve early in my ownership. Probably, aided by a couple of years sitting in the grass...prior.

CHTs seem to have been un controlled as well, without a decent JPI. Ship's gauge showed a redline deep into the very hot zone....

Minimal guidance from the minimal owner's manual.

The best info on how to operate it came from MAPA. There was no MS to ask follow-up questions...

Fortunately, things are more in the hands of the user now. Instrumentation including all CHTs, EGTs and FF and reliable OAT.

Overall, the R is just an upgraded C. It's only a step or two up the ladder.

Best regards,

-a-

[scottfromiowa]

"daver328"...NOPE

[DaV8or]

So guys running 50 ROP while they are getting performances are putting the greatest stress on their engines (In a conversation a couple months ago with an owner of a very nice M20B who told me about Mooneyspace, he referenced running 50 ROP as his standard practice - I wondered if he ever read the posts here?)

 

Don't be so tough on the guy. You can run 50 degrees ROP safely if you want to, just run at 65% HP, or less. The APS guys and Mike Busch will tell you that the "Red Box" is just rough guide line. It's not precision numbers to set the controls by and in fact the box was developed on big bore Continental engines, so the Red Box for your O-360 could be a little different. To my knowledge, the folks at GAMI and APS have never done any testing on small bore engines. Mike Busch says to just worry about CHT and stop worrying about the rest.

 

However, there is one thing that APS, Mike Busch, Lycoming, Continental and even your mechanic have in common. They all will tell you it is safe to run at 65% HP or less and if you do, your engine will last a long time. So I personally think percentage of HP a is more important thing to worry about than the Red Box. Maybe if I were air racing with high power settings down low, I would worry about settings in the Red Box.

 

I use the Target EGT method on climb out and then depending on altitude and mission for the day, I will go either LOP, or ROP in cruise. If I go ROP, you have to use the POH numbers, so I created an interpolated cheat sheet from the POH numbers showing power setting at each altitude for both 65% and 75% that I laminated and keep in the plane. If I go ROP and at 65% I usually go close to peak for economy. If I'm fighting a headwind, or trying to get home quicker, I might go 75% and 125 ROP. LOP HP percentage is determined by fuel flow. GHP x 15 / 200 gives you the percentage for an IO 360 engine. If you're like me and don't do math well in your head, you can do what I did. I fly with an iPad and I downloaded a free ap called Big Calculator. It turns the entire face of the iPad into a ten key calculator with really big buttons and really big numbers. Perfect for the cockpit.

[scottfromiowa]

Don't be so tough on the guy. You can run 50 degrees ROP safely if you want to, just run at 65% HP, or less. The APS guys and Mike Busch will tell you that the "Red Box" is just rough guide line. It's not precision numbers to set the controls by and in fact the box was developed on big bore Continental engines, so the Red Box for your O-360 could be a little different. To my knowledge, the folks at GAMI and APS have never done any testing on small bore engines. Mike Busch says to just worry about CHT and stop worrying about the rest.

 

However, there is one thing that APS, Mike Busch, Lycoming, Continental and even your mechanic have in common. They all will tell you it is safe to run at 65% HP or less and if you do, your engine will last a long time. So I personally think percentage of HP a is more important thing to worry about than the Red Box. Maybe if I were air racing with high power settings down low, I would worry about settings in the Red Box.

 

I use the Target EGT method on climb out and then depending on altitude and mission for the day, I will go either LOP, or ROP in cruise. If I go ROP, you have to use the POH numbers, so I created an interpolated cheat sheet from the POH numbers showing power setting at each altitude for both 65% and 75% that I laminated and keep in the plane. If I go ROP and at 65% I usually go close to peak for economy. If I'm fighting a headwind, or trying to get home quicker, I might go 75% and 125 ROP. LOP HP percentage is determined by fuel flow. GHP x 15 / 200 gives you the percentage for an IO 360 engine. If you're like me and don't do math well in your head, you can do what I did. I fly with an iPad and I downloaded a free ap called Big Calculator. It turns the entire face of the iPad into a ten key calculator with really big buttons and really big numbers. Perfect for the cockpit.

My pick for personal BEST OF 2013 post of the year. Good stuff Dave...REALLY GOOD

[scottfromiowa]

You can also get a G3 and have the power % provided with a turn of a knob. N.I.C.E....and easy.

[Bob - S50]

"LOP HP percentage is determined by fuel flow. GHP x 15 / 200 gives you the percentage for an IO 360 engine. If you're like me and don't do math well in your head, you can do what I did. I fly with an iPad and I downloaded a free ap called Big Calculator."

 

The MAPA Safety Foundation gives an easy way to calculate approximate power setting.  Add the MP in inches to the RPM in hundreds.  For example 23" + 2400 RPM = 47.  For the the J they say 47 is about 65% power.  44 = 55%, 50 = 75%.

 

For the C, E, and F I think the 'number' is 46.  43 = 55%, 46 = 65%, 49 = 75%

 

You can easily check this with your POH.  Just pick a few altitudes then see how much MP it takes at each RPM to get the power setting you are interested in.

[Earl]

"LOP HP percentage is determined by fuel flow. GHP x 15 / 200 gives you the percentage for an IO 360 engine. If you're like me and don't do math well in your head, you can do what I did. I fly with an iPad and I downloaded a free ap called Big Calculator."

 

The MAPA Safety Foundation gives an easy way to calculate approximate power setting.  Add the MP in inches to the RPM in hundreds.  For example 23" + 2400 RPM = 47.  For the the J they say 47 is about 65% power.  44 = 55%, 50 = 75%.

 

For the C, E, and F I think the 'number' is 46.  43 = 55%, 46 = 65%, 49 = 75%

 

You can easily check this with your POH.  Just pick a few altitudes then see how much MP it takes at each RPM to get the power setting you are interested in.

I had recently heard the same thing about adding MP and RPM and if it equals 47 you are about 65% power.  In my 252 if you go to the POH and add MP plus RPM at the various 65% settings it actually adds up to 48.  I have started to use the 47 number so I am sure I stay out of the red box.  What I have not figured out is how to determine 65% with WOT and then adjusting RPM.  Seems like I would need to really dial back the RPM to have both add up to 47 or 48.  Or does WOT only apply to normally aspirated planes?

[DS1980]

I appreciate your willingness to help guys, but that "confusion" remark was not in earnest.

I have learned quite a bit from you folks here on Mooneyspace. And I must say I "get it." I have listened to Mike Busch and seen the red box chart several times now. It's great information!

At apx. 40f ROP internal cylinder pressure is at it's greatest -which is hard on the engine. So guys running 50 ROP while they are getting performances are putting the greatest stress on their engines (In a conversation a couple months ago with an owner of a very nice M20B who told me about Mooneyspace, he referenced running 50 ROP as his standard practice - I wondered if he ever read the posts here?)

My owners manual,says run 100 ROP and as it turns out, yeah ... that's the best practice ... Us carb guys will probably never run LOP. That's the REALITY - we have carbs, we need to run 100 ROP ... So for us "C" guys it's 10-11 gph and 145-150 KTAS. (Yeah, it says use TAKEOFF FLAPS TOO! Scottfromiowa)

On the upside, we paid less to buy the straight valve carbureted engines; they are reported to be lower maintenance ... and less to overhaul ... on the downside, we have slightly higher burns and slightly slower speeds ...

Anytime Mike Busch thinks he can get my O-360A1D to run LOP, he is welcome to show me ... !

It's all really great information, but it's up to me to accept the reality and make the application. I DEFINITELY SHOULD NOT run 50 ROP, and I can't run Lop with a carb.

Should we have spent a little more to get into a E? Depends on how much you fly and what's your mission. Honestly an E looks pretty good now, but we've "made our bed!" Still happy with the C, but all the LOP discussions are meaningless to carb owners! Going to dance with the Mooney I brought to the dance!

(I'm ok with this, I may not run as fast or as efficient as fuel-injected Mooneys .. but this information may have prevented me from doing thousands of dollars of damage to our engine by operating it incorrectly? There's no bad news here ... I have definitely benefitted from understanding the "red box!")

Careful, these are some pretty blanket statements. There are carb engines in airplanes that will run LOP, it just seems to be on a per-airplane basis rather than being model specific. It may be true that your engine cannot run LOP, and there are some carb guys on here that cannot. But it's not correct to say that all carb guys are stuck at ROP.

 

Maybe use takeoff flaps with carb heat? Kidding.

[carusoam]

With a turbo, you are probably able to run up to a very high MP...

Swapping in a low rpm isn't going to be helpful, I don't think...

The "key numbers" model published by MAPA gives a different sum for each plane / engine cobination.

For the K252 for instance 65% HP = 49

The R 65% HP= 44

J = 47

And C = 46

The key number simplifies a few things, but you still need the chart...(initially)

Fortunately the chart is free when you take their class.

You can use your own POH to determine a proper sum for your engine and A/F combination.

Expect that the sum will be higher for TC'd planes compared to N/A ones. 231 and Bravo are the highest.

Best regards,

-a-

[Hank]

There are two suggestions for running our engines LOP. 1) Reduce throttle some, to cock the throttle body and induce turbulent flow through the carburetor. This improves fuel atomization and makes for a more uniform fuel-air mixture being sent to the cylinders. 2) Add some carb heat, it may take more than just a crack.

I have not had success with LOP at low altitude, and keep forgetting to try above 7000'. At 9-10K, I do sometimes run at peak but haven't noticed fuel savings at the pump, although I do notice running 5 mph slower.

[DS1980]

Hank, try to mess around with RPM as well. Maybe slowing down the engine will reduce the CCV, which is more pronounced LOP. Just a thought.

[pinerunner]

Hank, try to mess around with RPM as well. Maybe slowing down the engine will reduce the CCV, which is more pronounced LOP. Just a thought.

I really hope someone with a C model trys this, it makes sense that slowing the velocity in the intake system would give those fuel droplets more chance to evaporate before they split into four separate flows. In the mean time some of the stuff that Busch and Deakins discuss can be implemented on the carburated planes, like leaning for taxi. Many are doing that.

[Hank]

My SOP for ground ops is to lean a lot, typically 1/2-2/3 travel of the lever. I also lean like this on landing, after exiting the runway or turning around to back-taxi. I've never had trouble, except the one time in a Cessna when the engine quit and I coasted off the runway, primed several pumps, restarted and finished taxiing full rich.

Next time I'm out, I'll try LOP again at 2400, but realistically that's as low as I will cruise between WV and NC/GA.