Turbo guys...question

[KLRDMD]

Quote: danb35

LOP ops at the same MP/RPM settings will yield less power than ROP ops (at the mixtures typically used).  However, with a turbo, you can add a couple of inches of MP to restore the lost power, and still be burning less fuel (and running cooler).  With a non-turbo engine, you can't add any more throttle in most cases.

 

[jlunseth]

Yeah, I didn't see a drop in MP when I leaned LOP, there was just a noticeable reduction in power and speed.  It had occurred to me that the next step would be to try to push the MP up to make up for the loss of power, but the plane is in annual right now so my experimentation has been interrupted.  I have also noticed that the TSIO-360-LB can be a little finicky about allowing LOP leaning.  Sometimes it works, other times I either see an unacceptably high TIT during the leaning process, or I get the engine leaned out and a couple minutes later the TIT is going too high.  I have also been told that LOP at 75% is not a good idea in the 360, works ok in the bigger bore engines, LOP should be limited to 65% in the 360.  That is not appealing to me, go to 65%, lean LOP, and then have the power go down from there.  Saving GPH is no good if the aircraft speed drops so low that you are not saving MPG. 

Let me get the plane back, I will play with this a little, and then maybe we can have another discussion on it.

[KLRDMD]

Quote: jlunseth

Yeah, I didn't see a drop in MP when I leaned LOP, there was just a noticeable reduction in power and speed.  It had occurred to me that the next step would be to try to push the MP up to make up for the loss of power, but the plane is in annual right now so my experimentation has been interrupted.  I have also noticed that the TSIO-360-LB can be a little finicky about allowing LOP leaning.  Sometimes it works, other times I either see an unacceptably high TIT during the leaning process, or I get the engine leaned out and a couple minutes later the TIT is going too high.  I have also been told that LOP at 75% is not a good idea in the 360, works ok in the bigger bore engines, LOP should be limited to 65% in the 360.  That is not appealing to me, go to 65%, lean LOP, and then have the power go down from there.  Saving GPH is no good if the aircraft speed drops so low that you are not saving MPG. 

Let me get the plane back, I will play with this a little, and then maybe we can have another discussion on it.

[KLRDMD]

Quote: JimR

"I figure 75º LOP on the one monitored cylinder means all cylinders are at least 20º LOP"

How do you figure this, Ken?  Thanks.  Very insightful discussion.

[jlunseth]

Quote: KLRDM

65% power is 65% power, whether ROP or LOP. 75% power is 75% power, whether ROP or LOP. If you're comfortable running your engine at 75% power ROP, you should be comfortable running it at 75% power when LOP. If you only run it at 65% power ROP, then it makes sense that you only want to run 65% power when LOP. Does that seem logical to you ?

75% power is a specific airspeed, whether ROP or LOP - doesn't matter, 75% power is the same airspeed either way. Of course the same for 65%. If you lost airspeed, you were running a lower % power, that's the way it has to work. Percent power when LOP is 100% a function of fuel flow. MP, RPM, etc. are all absolutely meaningless. Fuel flow IS % power when LOP.

[KLRDMD]

Quote: jlunseth

On the first paragraph above, no, I am afraid it doesn't seem logical to me.  Or rather, it doesn't seem logical in the way pilots learn to set %HP, which is MP and RPM. The problem is that in a POH, a particular percent power is "defined" as a specific MP setting and a specific RPM, with the engine running ROP (at least in the older manuals like mine).  So 32" and 2500 may be 75% per the manual, but when you start leaning LOP those settings do not give you 75% any longer.

Percent power means percent of rated maximum HP.  Mine is 210, but lets say 200 to make it simple.  If I am running my 200 HP engine at 75% the output is 150 HP.  So let's say I am at 75% and leaned ROP, and I decide I want to go LOP.  Without touching the throttle, I start to lean the engine out.  What I am doing is reducing the amount of fuel going in to the engine, and it is fuel which provides the energy to develop those 150 HP.  ROP, I have more fuel going in than the engine can really use, so the engine is producing its max. power for that throttle setting, which in this case is 150 HP.  When I lean LOP, leaving the throttle alone, I reach a point where I am actually reducing the HP.  The engine is getting plenty of air, but not enough fuel (energy) to produce 150HP any longer, so I am no longer at 75%, even though I  haven't touched the throttle.

My point is that 75% is 75%, yes, in terms of percent HP, but not in terms of the throttle and RPM settings we are all accustomed to as creating 75%.  You can't set the throttle and mixture to get 75% when you are ROP, and then expect that you can lean LOP from there and still get 75% with the same throttle setting you had when you were ROP.  That is why the logical next step is to open (increase) the throttle a little.  I think. 

So we are probably saying the same thing, because I agree with the statement in the last paragraph that fuel flow is % power when LOP.  When you are already LOP and you move the mixture knob in or out, you are actually changing the %HP.

As for the advice I have heard to not push the LB above 65% when LOP, I think the concern is temperatures, not HP output.  I can't explain that one, because I am not the person giving the advice, I am just passing on what I have been told.  I am going to experiment with it myself and see what happens.

[KLRDMD]

Quote: JimR

[FlyingAggie]

One of the first upgrades I am planning for my new bird is sending the operator to the Advance Pilot Seminars, which Scott/KSMoonaic has highly encouraged.

Alan

Quote: JimR

Thanks, Ken.  Your experience and intuition are good enough for me.  I've been learning all that I can for a couple of years now about LOP operations and especially the APS theories and teachings.

Jim

[KLRDMD]

Quote: FlyingAggie

[FlyingAggie]

And miss out on experiencing the beauty and luxury of Ada, OK?

I'll have to see if they still have online courses.

Alan

Quote: KLRDMD

[jlunseth]

Last I looked,they don't have a course scheduled in beautiful Ada, maybe later in the year.

[Kwixdraw]

Not to divert the thread but somewhere in all of this isn't there an issue of the pressurized mags working properly at high altitudes?  Seems like I read something in a book by the guy that owns SkyRanch ( is it John Schwaner or something like that?) that there were some problems with proper ignition due to the thinner atmosphere causing erratic spark timing. Just trying to understand the whole turbo ops picture since I may want one someday.

[Magnum]

For the power setting (ROP or LOP) get a EDM800 or 830. Walter Atkinson told me that the guys from Advanced Pilot Seminars worked out the algorithm for JPI and and it indicates correct (ROP AND LOP). IMHO it uses OAT, RPM and MP while ROP and FF while LOP.

If a intercooler is installed the OAT probe could be mounted in the induction duct for the EDM to show correct HP. But I don't know if that really works.

[jlunseth]

I am getting the 930 which does have the capability to display differential temp., i.e. the difference between the Compressor Discharge Temp. and the Induction Air Temp.  I believe the ability to measure and display that temp. is part of the STC for the Turboplus, in any event Turboplus provided a Diff. Temp. Gauge that went in when my intercooler was installed in '02.  The only thing I am not quite buying about the JPI units is the percent HP display.  That is just an algorithm, and it appears to be based on throttle settings.  They input the information from your POH to build the algorithm, and the POH assumes ROP leaning.  So if you have an MP of 32" and an RPM of 2500 and your manual says that equals 75% HP, the unit displays 75%.  But as we have just discussed, if you are LOP those throttle and RPM settings do not necessarily equal 75%, so the percent HP display likely won't be accurate in LOP mode. 

Other than that, the unit looks really great and I am looking forward to flying it.

Thanks for the great discussion, this flying a turbo is interesting and there is alot to try to understand. 

[Magnum]

Quote: jlunseth

...  They input the information from your POH to build the algorithm, and the POH assumes ROP leaning.  So if you have an MP of 32" and an RPM of 2500 and your manual says that equals 75% HP, the unit displays 75%.  But as we have just discussed, if you are LOP those throttle and RPM settings do not necessarily equal 75%, so the percent HP display likely won't be accurate in LOP mode. ...

[KSMooniac]

I believe APS still offers the online version of the course, but IMO if there is any possible way to attend the live seminar, it is *very* well worth the effort.  I'm an engineer and probably could have learned quite a bit from the online self-study, but there is tremendous value in the live course, especially seeing the engine test stand in operation and watching the concepts demonstrated in real-time.  There are significant question-answer sessions that are tremendously beneficial too.  I learned more in 2.5 days there than in many engineering courses.

Beautiful Ada is, well, small-town OK.  Not that there is anything wrong with that.  I stayed in a nice new Holiday Inn Express.  Food is catered to the class, and there are two dinners out in town.  No rental car is needed, as they help with the transportation, too.  Typically they'll have a class in the May or June time frame, and another in the fall sometime.

[KSMooniac]

Jim, regarding Ken's ability to know all of his cylinders are safely LOP from his single EGT instrument...that is one of the gems from the class that you'll learn why running an engine LOP w/o a monitor is actually wiser than running one ROP w/o a monitor!

As mentioned above, when LOP power is directly related to fuel flow.  Moving the mixture either direction changes the power output.  Think of our IO-360's as four separate engines running in formation...if they each make the same amount of power, then it will be smooth and relatively balanced.  If one (or more) is making more or less power than the others, then there will be an imbalance and you'll feel it.  Causes for the imbalance could be a weak plug, clogged injector, induction leak, etc. and you'll feel immediately that something is amiss.

Running ROP, the opposite is true.  You can move across the mixture range quite a bit and not appreciably change the power output.  So, you could be flying along at 100 or 150 ROP and get some debris into one injector and effectively lean that one cylinder to 20 or 40 ROP and you won't feel a thing.  However, that is the worst mixture setting to be at, and you'll be really abusing that one cylinder with higher heat and pressures.  Without a monitor, you'd never know it was happening, either.  If flying LOP, you'd notice it immediately.

Since Ken only has a single EGT, he knows when he is LOP in that one cylinder.  By leaning to 30+ LOP *and* having a smooth running engine, he knows the other 3 jugs are very close to the one with the EGT reading.

[jlunseth]

Well, here is the potential problem.  And I am talking about my engine only, I don't know about anyone else's.  Don't ask me why cause I can't explain it, but if everything is not just right once the engine has been leaned, either to ROP or LOP, the engine tends to fall back towards the bottom of the curve.  In other words, ROP the fuel flow goes up and the engine is too ROP.  The temps are running cooler than you want them, but at least you are not burning the engine up.  But when this happens LOP, the engine goes back towards the peak, and sometimes the temps at peak are hotter than the way the engine should run, particulary TIT which I have seen go to the "peak plus" setting that is allowed only for very short durations in my manual.  Conditions in the engine and in the atmosphere seem to need to be more stable to stabily run LOP than ROP.

[KSMooniac]

It sounds like you might be experiencing the "bootstrapping" problem that is common for the TSIO-360.  Ken might be able to shed some light on the issue.

I've not flown a 231 so I don't have any relevant experience with it.  From what I've been able to surmise from reading the various forums, the TSIO-360 is quite finicky, and some can get them to run great LOP and others can't.  This comes from Turbo Arrow and Seneca drivers as well as 231/252 folks.  The APS guys confirm it as well.

[seebruce]

Very interesting topic. I bought a 231 about 2 months ago and am still trying to get the feel for it. My plane has a EDM700, Gami injectors and intercooler. I've been experimenting with LOP and this discussion has helped me greatly. I was out  doing some practice approaches running LOP. I was running 2300 rpm, 27 in mp, burning 8.6 gph and indicating 125kts. My TIT was 1554 and the hottest cylinder was 324. I'm in PA and it was about 0c.I have attached the fuel flow vs. horsepower chart for the TSIO-360LB. Am I correct in my assumption that according to the fuel flow I was at 124 hp or about 60%.

 

[seebruce]

Attachment didn't work. How do you add an attachment?

[KLRDMD]

Quote: JimR

All of this having been said, I am almost exclusively running LOP now when I'm just sight seeing, which makes up a substantial percentage of my flying.  I've also run LOP in a few cross countries when it was just me aboard and I wasn't in a hurry.  All at 55% to 60% power.  The improvement in efficiency is remarkable compared to having to run around at 100 degrees ROP or more, which is what I typically do when I want more than 60% power.      

[KLRDMD]

Quote: JimR

[KLRDMD]

Quote: JimR

[KLRDMD]

Quote: JimR