New Owner Questions - ROP/LOP & MP/RPM Settings

[johnggreen]

Richard,

I've been really busy lately and not spending much time on Mooneyspace.  I did not read all these posts quickly so I may repeat some things that have been said.  Still, here are a few brief comments.

1.  The Bravo POH is very complete with endurance, speed, and other charts, and I find it to be very accurate.  It will show that you get extra speed with altitude but very little additional range.

2.  I have taken the AP course and have this to say on LOP.  First, the only issue with where you run your engine from a durability standpoint is temperatures.  I have very good baffling, which is the key I think.  I simply don't have any problems with CHT's which raretly go over 330 at any setting.

3.  I have GAMI's and still LOP is a waste of time on my engine.  The lower fuel burns are matched with lower speeds.  Flying my engine LOP is a pain in the ass.  

4.  I use three settings for cruise  2400/30" and 2200/30", 2200/28".  I lean to 1650TIT or peak, which may come first at the lower settings.  At 2200'28" @ 15,000 I get 185 knots at 14-14.5 gallons depending on temp.  My CHT's will barely break 300 at that setting.  So, how do I improve on that?

5.  If I'm low and battling a head wind, I use the 2400/30 and still lean to 1650.

Again, in my dumb ass opinion, LOP or ROP makes little difference if you have acceptable temps.  

Jgreen

[helojunkie]

John - Thanks for the informaiton and power settings. Its good to see what the real world numbers look like so I can start to plot my performance. I am looking forward to the AP course to learn as much about my engine as I can!

[jlunseth]

Quote: testwest

If you are at 65% power, you should be able to pull the mixture through the peak TIT and get to the other side. Your TIT may exceed limits, momentarily. You should be able to get 50 deg LOP and your TIT will be back below limits. What is impressive is the drop in CHT due to the "spread out, slightly later" pressure profile in the cylinders.

Just a note so that the concept of LOP or ROP does not get confused.  All of the above is true, if you use the "pull through" method you will pull the mix thru peak TIT and TIT may exceed limits momentarily, but degrees ROP or LOP are not determined by relation to TIT.  They are determined by first cylinder to make peak EGT on the ROP side, or last cylinder to make peak EGT on the LOP side.  It is the degrees from peak EGT on that cylinder that determines how far ROP/LOP you are, not how far from peak TIT the engine is operating. 

[KSMooniac]

John's Bravo seems to be faster than most others that have been anecdotally documented here and elsewhere.  He is quite lucky in that regard!  I'm going to nit-pick in bold below based on my knowledge from the APS course and reading other bits of wisdom over the last 5 years.

Quote: johnggreen

2.  I have taken the AP course and have this to say on LOP.  First, the only issue with where you run your engine from a durability standpoint is temperatures.  Not true!  Equally important but not measured in our engines is the peak internal cylinder pressures.  Degrees ROP or LOP is a surrogate for this measurement, but reducing the peak pressures is conducive to long cylinder life.  If you're running 50 ROP in very cold OAT conditions, your CHT's could be fine but you could be beating the snot out of the cylinder, and you won't be able to measure it.

3.  I have GAMI's and still LOP is a waste of time on my engine.  The lower fuel burns are matched with lower speeds.  Flying my engine LOP is a pain in the ass.  Agree partially.  Anecdotally, running LOP on the Bravo engine might or might not work as some do, and some don't, and the experts have not been able to determine why that is.  Minimizing the GAMI spread is desirable even if you never fly LOP, but hi-power LOP ops offer many, many benefits.  75% power LOP will require more MP than 75% power ROP, but you'll end up at a measurably lower fuel flow and lower CHTs for equivalent speed.  Those are facts for all piston engines.  Turbos especially benefit since you can always increase MP to set 75% or even 85% power LOP if you wish, no matter what altitude you're at (below critical, anyway).  As a normally-aspirated owner, I can only wish to dial in more MP at altitude!

4.  I use three settings for cruise  2400/30" and 2200/30", 2200/28".  I lean to 1650TIT or peak, which may come first at the lower settings.  At 2200'28" @ 15,000 I get 185 knots at 14-14.5 gallons depending on temp.  My CHT's will barely break 300 at that setting.  So, how do I improve on that?

5.  If I'm low and battling a head wind, I use the 2400/30 and still lean to 1650.

Again, in my dumb ass opinion, LOP or ROP makes little difference if you have acceptable temps.  I'll always argue that LOP is a superior way to operate, especially if you have a turbo and then you don't have to suffer the speed loss that I do as a NA operator.  Hopefully your TIO-540 will be able to operate LOP.

Jgreen

[helojunkie]

Scott -

Thanks for the input, I am really looking forward to learning more about all of the LOP/ROP operations. There seems to be SOOOO many different opinions!

[KSMooniac]

Quote: helojunkie

Scott -

Thanks for the input, I am really looking forward to learning more about all of the LOP/ROP operations. There seems to be SOOOO many different opinions!

[helojunkie]

Scott - I have already downloaded his material, plus they are allowing me to take the online course free as a primer to the live course. Now July just needs to hurry up and get here!

[jetdriven]

Mike Busch's stuff, although not directly affiliated with APS, is good stuff too.  You wil be a qualified expert in no time.

http://www.avweb.com/news/savvyaviator/

 

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

[helojunkie]

Byron -

Another great resource! Thanks for pointing it out to me.

[johnggreen]

Scott,

I intentionally did not mention pressures as the discussion was getting pretty complicated already.  I don't necessarily disagree or agree with your point on internal pressures for the following rational.

The engine is designed to run within a range of temps and pressures.  Without getting into the actual pressures that are acceptable (largely because I don't have the techinical expertise to define or discuss them) if you are operating your engine within conservative parameters, I doubt seriously that it makes any difference.  Using temps as an example, you can operate the Bravo engine at over 400 CHT and be well within its operating "limits".  Mine operates at 330 and less.  Does that necessarily mean that 320 or 290 is "better" or that the engine will last longer at those lower temps?  

There are all kinds of wear taking place in the engine not related to cylinder temps or pressures that will require a TBO of 2,000 hours so if operating at 280 would indeed give you a 3,000 hour cylinder (which I doubt) what would be the point?

I'm certainly not disparaging anything you said and frankly, I may be wrong.  I will say that I think you can take this LOP business to extremes.  Well managed and maintained engines have been running TBO and longer way before anyone ever came up with the LOP concept.  I respect the guys at AP seminars, but I know that they make their living selling seminars and making a "critical" issue of every aspect of engine operation and tying that to a need for LOP is good for business.

I took the online course, and felt I got my money's worth.  That being said, I'm not going to get my diapers in a wad over every fractional tidbit of temps or combustion pressure that can be measured.

My engine just had a 6 month (semi-annual annual) compression check and all were 78 and 79 or 80.

Something is working quite well.

Jgreen

[KSMooniac]

 

I forgot about Mike Busch's wonderful writings and webinars.  They are excellent, and a lot of his work overlaps and complements APS.

John, I understand your position and approach to maintenance.  I'm not going to call you out on any of your operational practices and maintenance philosophies as you seem to have everything going well to keep you happy and confident in your engine (and entire plane for that matter).  I'm only trying to keep the ROP/LOP topics as clear as I can since it is *so* easy to muddy the waters.  

I'll stick up for APS/GAMI just a bit.  The seminars do cost a non-trivial amount of money, but compared to any other professional-level continuing ed class or college short course, etc, I think they are reasonable.  I think the seminar enterprise is complementary to the GAMI (and TATurbo) businesses, but it isn't an extended advertising vehicle.  All of the principals in the APS venture have or had day-jobs before they retired, and the seminars grew out of their discoveries when they got together to figure things out back in the early 90's.  I got the sense that they put the class together to fill a huge void in the education/training of pilots, owners and mechanics, and to that end they've succeeded.  I'm sure they have made money on it over the last ~15 years, but that doesn't cheapen any of their findings and teachings.  After 5 years of ownership I still say it was the best money I've spent as an owner.

Back to the science aspect briefly... I'm a structural engineer in the aircraft industry.  I don't do engineering work on piston engines, but understand the consequences of the temperature and pressure environments when it comes to the cylinders, pistons, rods, cranks and bearings.  Metal fatigues, and it fatigues faster at higher temps and higher loads (ie pressures) so anything we can do to reduce temps and peak pressures means that we have a better chance of a long fatigue life.  Yes, many engines (especially abused flight school engines) make TBO running ROP.  Many don't.  The knowledge from the APS recommendations, combined with judicious monitoring (via an engine monitor, oil analysis, etc.) and a conditional maintenance philosophy like Mike Busch preaches can really change the operational and especially the financial aspects of ownership with our engines.

For example, I'll use my IO-360 as an example since that is what I am most concerned with... I have a factory overhaul (that used new jugs) and am around 2000 hours on it right now.  I bought it with 1390 SMOH and had to "freshen" the jugs at 1650 SMOH due to low compression through the exhaust valves on two of them.  I decided to IRAN instead of a full top overhaul since I was on the back half of TBO, but the shop said the jugs looked great and would certainly be great candidates for overhaul instead of replacement when the time comes.  Anyway, I plan to keep flying until I get a good sign that it is time to tear the engine down, and the economics to run past TBO are compelling.  TBO is just a number guessed by the OEM from some statistical basis, and perhaps with just a bit of desire to sell more parts or engines sooner rather than later.  Back to the IO-360, new cylinders are single-source from Lycoming at ~$2000 each.  Overhauling my known-good cylinders should cost $700-$800 each, so if they are treated well such that they don't develop fatigue cracks from high pressures and temps, then I can save ~$5000 on the cost of my overhaul.  That is very significant to me!  Minimizing those peak pressures treats the rods, bolts, crank, bearings, case, etc. much better too, so that reduces the chances of case cracks and other maladies that lead to premature overhauls or component replacements.  

Then there is the fuel savings... for me without a turbo, I'm in the 1.0-1.5 GPH savings range, so with $6 fuel that yields $15,000 in savings over a 2000 hour run.  (Yes, I have to fly a bit slower than ROP, but there are still savings).  For you turbo guys, if you are able to run safely LOP, there is no speed penalty and an even greater fuel savings.  There is absolutely no downside for turbo LOP ops...the engine runs cooler, cleaner, and more efficient with no penalty!

BTW, the TAT Bonanza and TN-SR-22 guys are successfully running well past TBO.  I think they even mentioned they've got some 3000 hr runs out of those installations and when the engines were opened they still looked like new.  (there is a valve installation issue we've discussed in another thread that potentially throws a wrench in those plans sometimes)

That about exhausts what I feel like talking about tonight.  At the end of the day, the *best* course of action for any owner/operator is to get the education and then make your own decision about how to operate an engine instead of blindly following conventional wisdom, old wives tales, what your non-pilot mechanic told you to do, etc.  

 

[johnggreen]

Scott,

Again, I just don't see much room for us to disagree.  I suppose if LOP worked on my Bravo, I would use it.  I've tried it, multiple times, played with different approaches and it simply does nothing.

As for APS and GAMI, neither has to be sold to me.  I would not consider having an airplane without GAMI's whether I wanted to use LOP or not.

Now, if you really want to peak my interest, tell me why LOP works so well on a TN Continental and not worth a flip on a turbo Lycoming.

I will repeat my experience briefly.  LOP can be used on the Bravo, but the fall off in airspeed matches the fall off in fuel burn, maybe more and little difference in EGT's or CHT's.

Jgreen

[jetdriven]

John, the Continental engines love LOP, but I bet if you carefully log fuel burn, TAS, and EGT, you will find a 5-10% improvement in NMPG with LOP OPS. 

[johnggreen]

Byron,

When I have tried LOP in the Bravo, there is an incredibly fine line between getting my richest cylinder at least 50 degrees past peak and a rough running engine as well as the point where the power falls off the table.  I've recorded the "peaks" spread, talked to AP and GAMI and they say it is well within tolerance.

Also, my CHT's and EGT's seem to take quite a while to stabilize between each adjustment.  In short, it is a tedious pain in the ass.  I'm sitting there monkeying with mixture when I need to be flying the airplane.

10% fuel savings?  Not a chance!  I don't want to seem pompous, I am not, but that is such a minor fraction of the cost of flying my Bravo that I won't give it a second thought.

As I said in my previous post, once you are well within the operating parameters of the engine, I don't believe it makes any difference.  I have read nothing or seen anything in the AP seminar that would make me think otherwise.

To make a very simple comparison;  If I take a four foot long piece of 10" steel H pile and start hitting it with a ball pean hammer, I would probably have to hit it for a hundred years to bend it.  If I used a 22 oz. claw hammer, I would probably see no significant difference.  A 2000# pile driver drop hammer, yea two drops. Now you might know where  my life's experiences have centered.

OK, at 50 LOP, I get lower cylinder pressures than at 100 ROP.  So? At 75% power in my Bravo engine does it make ANY difference?  Perhaps, but other than a comparison of relative pressures and the charts showing the incredible rise in pressures that detonation causes, I've seen nothing to indicate that a properly managed engine will ever be damaged by the cylinder pressures caused by 100 ROP.

I'm all for LOP when it works and when it shows reasonable returns for the effort.  At this point, I don't think that applies to my engine.  If there is anyone out there who is getting good, predictable results on the TSIO-540, I would love to hear about it.  Maybe I am doing something wrong, but I'm not exactly a virgin to pilotage or engine management of any kind.

Not arguing, not saying that what you or Scott say is incorrect; it isn't.  I'm just saying that LOP isn't quite the all circumstance magical formula some profess it to be.

I will be quite happy to be proven wrong and that I can somehow SIGNIFICANTLY improve the efficiency and durability of the Bravo engine in any measurable way; opinions aside.

Jgreen

[Parker_Woodruff]

Quote: johnggreen

I'm just saying that LOP isn't quite the all circumstance magical formula some profess it to be.

I will be quite happy to be proven wrong and that I can somehow SIGNIFICANTLY improve the efficiency and durability of the Bravo engine in any measurable way; opinions aside.

Jgreen

[ChrisH]

I'm with Parker, I can fly my 231 at 75-80% power LOP at ~12gph with all temps cool. ROP for same power setting for my bird, to keep everything cool and be safe is more like 17gph. With $5-6 fuel, sure it's only $25-$30/hr....but, it's also the difference in range which often I'm more worried about.

 

Chris N1163D,  82 231

[KSMooniac]

Quote: johnggreen

Scott,

Again, I just don't see much room for us to disagree.  I suppose if LOP worked on my Bravo, I would use it.  I've tried it, multiple times, played with different approaches and it simply does nothing.

As for APS and GAMI, neither has to be sold to me.  I would not consider having an airplane without GAMI's whether I wanted to use LOP or not.

Now, if you really want to peak my interest, tell me why LOP works so well on a TN Continental and not worth a flip on a turbo Lycoming.

I will repeat my experience briefly.  LOP can be used on the Bravo, but the fall off in airspeed matches the fall off in fuel burn, maybe more and little difference in EGT's or CHT's.

Jgreen

[KSMooniac]

dp

[Parker_Woodruff]

Quote: KSMooniac

 

I believe so strongly in the benefits (financial and operational) that I don't want a plane that won't run LOP.  

[testwest]

Gents, let me throw out something....I am running two Lyc IO-540-S1A5s, turbonormalized by Aerostar/Machen (by the Aerostar TCDS, hence the possibly confusing lack of a "T" in front of the IO), in an Aerostar 601P. Basically, it is three M20J engines, TN, in very tight formation. One engine has GAMIs, the other does not. I have always been able to run the GAMI engine LOP, but the non-GAMI one was problematic and exhibited many of the same symptoms in terms of stabilizing, some roughness, high GAMI spread etc. , just as John Green describes.

And then.....

I discovered very high center electrode resistances in my Champion massive electrode spark plugs. There have been a number of posts on Beechtalk related to this issue, subsequent to the article I wrote for the Aerostar magazine on my discovery and the change I made....this change being installation of Tempest fine wire spark plugs. The different electrode design by Tempest is intended to be stable with respect to center electrode resistance in the long run.

Having made no other change, I can now run my non-GAMI engine much more consistently LOP with the new Tempest fine wire spark plugs. Now, one person's experience with one airplane is hardly a trend item that can be proffered as a sure-fire means to improving results when trying to go LOP. However, when our M20J comes out of the avionics shop, it will have an EDM-930 engine monitor and some old Champion spark plugs of unknown center electrode resistance. I intend to completely document that engine's parameters and characteristics, including LOP operations. Then, I'll change to the set of Tempest fine wires I have ready to install in that engine, and document the same parameters under the same flight conditions. If I notice an improvement similar to what I saw on the Aerostar, especially if the GAMI spread is positively changed by the spark plug change, I am fully prepared to go to GAMI/APS with a recommendation that operators make sure of the robustness of their spark plugs and related ignition systems prior to installing or modifying GAMIjectors.

So, Bravo guys, what kind of spark plugs do you run?

[KSMooniac]

Very good info, Norman!  Out of curiosity, what does the induction system look like on those IO-540s-S1A5s?  I'd love to see pics of that side-by-side with a Bravo engine.  What kind of mags are you running, and are they pressurized?

 

[testwest]

I'll send you a picture of the induction system, it is a thing of beauty. And they are non-pressurized Bendix mags!!

[testwest]

double post, sorry

[Parker_Woodruff]

Very cool, Norman!

[jlunseth]

Quote: testwest

I'll send you a picture of the induction system, it is a thing of beauty. And they are non-pressurized Bendix mags!!