231 power and engine settings

[panther1400]

I just started trying operate a turbo 360 LB new from continental and put about 10 hours on it before taking it to have a MVP 50 installed never leaned it too much or ran it over about 70% but my question the lower altitude setting bring the rpm so low it seems to me like that would be lugging the engine (like 2150rpm and 32mp?) what MP and RPM setting do you guys like for this engine?

[Parker_Woodruff]

I like the RPM around 2600 - typicall not less than 2500.

Can you get your engine to run lean of peak?

In my limited amount of flying since buying my M20K, I typically have run about 27" MP and 2600 RPM.  But now that it looks like my induction system has been cleaned up, I should be running well  over 30" and LOP (read lower temps) without difficulty.

[panther1400]

No lop yet my cht didn't work so I was scared of hurting engine with only a TIT but am very interested in running lop after MVP 50 install!

 

[jlunseth]

What is the configuration of your LB?  Do you have the Merlyn wastegate and Turboplus or other intercooler?  Or do you have the factory set up?  The intercooler, in particular, makes a significant difference in MP settings for a particular %HP.  Sorry if you have provided this before, I have forgotten.

32" and 2150 sounds too low to me.  The concept of "oversquare" is outmoded, but it is still true that too high an MP and too low an RPM can overwork the engine.  The only power settings in my POH (I have a 231 w/LB engine) with RPM's under 2200 are either low power, or low altitude, and mostly a combination of both.

If cruising about FL190, you should stick with higher RPM's, 2500 or higher.  Prop is losing efficiency up there.  Below that, pick an RPM at which the engine runs nice and smooth and then use MP to adjust to your particular desired %HP setting.  I typically cruise at 2450, my engine really likes that.

[FBCK]

I have a 231 with the auto waste gate and a Turbo plus intercooler and I run mine at 2600 rpm and 28 inchs (in cruise) and find the TIT is usally the limiting factor, I like it no higher thatn 1600.  My number 2 cylinder also require monitoring as it usually is up at 380 wihile the others are around 330. This is burning 13.2 gallons per hour, if I lean it down to 10.5 per hour I find I losing to much speed. (I'm a novice with this plane, only 30 hrs, so take all this with a grain of salt)

[ChrisH]

Intercooler+wastegate, and I find that mine likes to run LOP at 11.5-12.0pgh, 30", 2650 RPM, hot weather this config needs trail position to keep cool though, or TIT & CHT's get a bit too hot. Flight plan 175kts at anything above 10k, I usually like flying 10k+ for cooler/smoother ride and more options in an emergency.

Great thing about this is that with my Monroy tanks, I have 8hrs of endurance. I've never made it past 6 without wanting to be on the ground much more desperately than the plane. But it's nice to have plenty of reserve. 

 

[jlunseth]

Chris are you sure you are LOP?  Those settings look to me to be about peak.  They would be in my engine.  But these TSIO360's seem to be idiosyncratic, so I don't know that means anything. 

Advanced Pilot Seminars recommends at least 60 LOP in a turbo, or at least 125 ROP.  But not in between those two numbers. 

If you are truly LOP enough, you should see a significant drop in CHT's.

Peak is not Peak TIT and then back off from that, by the way, "Peak" when ROP, is when the first cylinder EGT peaks, then enrich from that point.  When LOP it is when the last cylinder EGT peaks, then go further lean from that point. Its about cylinder EGT, not TIT.  If you are using TIT, likely some cylinders are on one side of peak and some are on the other, and most or all are sitting right in the "red box."

[FBCK]

Chris I have the Monroy tanks as well, which currently are leaking ($11,500 fix for that one in the spring), you consider 30 inches to be 83% power and do you clib at full power with the mixture all the way in and at what full flow would you do your climb.  I think if I did full power my engine may melt down.

[ChrisH]

It's well LOP in my bird, gami's+JPI are doing the job well. Yes, all cylinders and TIT peak and start dropping somewhere near peak power at 14-16gph, I go through there pretty quick as the TIT's will quickly climb well above red-line during the 'pull'.  

LOP power at that fuel flow is <75%. 12.7hp/gph for a 7.5:1 compression ratio of the tsio360.

I've tried climbing LOP, and it just doesn't work that well for me to get the kinds of climb rates that ATC expects, and the cooling issues. I climb ROP, full mixture, generally 34" seeing fuel flows 20+gph.  I have all my jpi alarms set at 385 CHT, and generally don't get any alarms.

 

[jlunseth]

I also climb 100% HP and full rich.  Jack Napoli, one of the MAPA PPP instructors, tells me he does a cruise climb.  First he levels of at some altitude to allow the aircraft to gain speed.  Then pitches up and I think uses 34" and says he maintains 120 kts.  I have the JPI 930 and watch the displayed %HP, which is an algorithm, not a measurement, and no one other than JPI knows exactly what goes into the algorithm.  It is clear that some type of air temp does though, either OAT or IAT.  At any rate, one interesting thing from the displayed HP is that "100% HP" means a lower MP at high altitude.  36" is max at takeoff, and even that usually results in %HP slightly over 100 (but then, I think the algorithm is conservative).  Somewhere in the teens, full power will be in the 33+ inch range.  So I think Jack's "cruise climb" setting of 34 is probably 80-90%HP in the lower altitudes, and 100%HP in the upper reaches. 

You will see the same thing if you take the time to look at the POH tables and make the adjustments per the turboplus table, but the resulting MP settings with be slightly higher.

[FBCK]

Just one more question, when I run lean I find the fuel flow and hence the mp seem to vary even when I'm in level fight, when rich I can just set it and its stay the same anybody else experince such activity.

[kortopates]

Cris, believe you made a typo on the multiplier. In case others, newer to LOP read this, the correct multiplier is 13.7HP/Gal for our 7.5:1 cylinders to compute LOP fuel flow. Your 11.5 -12 gal/hr is right in the 75% to 78.6% with 78.6% also being the recommended max cruise pwr setting in the 252 POH - which makes it my goal as well because I don't want to give up on speed. Of course is based on the full turbo installation, which is approaching a 231 with the intercooler and wasetgate added. The 252 78.6% ROP fuel flow is 12.7-12.9 gal/hr at 2400/29" or a 53 power number with however you want to trade off MP for RPM. I generally prefer 2400/29" for the quieter ride and have done 2500/28" with no difference but in noise. But anywhere from 2400-2700RPM is recommended in the POH from cruising from SL to 28K at their recommended max cruise power. In fact, I’ll use 2400/29” for cruise and not worry about adjusting for altitude since from 10K to 28K the MP setting only varies within ½”. But below from SL to 10K it varies 1.5” but I never cruise that low unless its a real short or training flight. (Also with 2400 cruise RPM, I never have to touch the prop again till I go back to max RPM crossing the FAF intercepting GS with gear down and "gurgle" power to ride the GS down at 100-105kts.)

Like jlunseth, I climb at full power/full rich from take off to the flight levels. I learned long ago that is the coolest and most efficient way to operate the engine (from a temp/rate of climb perspective). The fuel pump is designed and set up to increase the mixture at full power and should be putting out 24-25 gal/hr there if set up properly. If you pull it back to 32-24” for a cruise climb, you’ll lose the benefit of that circuit and see the fuel flow drop way back and temperatures go up accordingly – in addition to slowing your climb. The engine just wasn’t set up to climb like that. I do use a cruise climb power setting when SOCAL gives us a limited climb of just  a couple thousand feet to a level off.

I would love to operate LOP at 78.6% power or even higher, but in past I could only smoothly – and barely – operate at about 60% power and I didn’t buy a turbo to fly slow or low. I really need to be able to run smoothly at 50+LOP at desired higher power setting and just won’t operate with TIT in excess of 1550’. I prefer closer to 1500F, and will always keep it leaned to at least 1500 regardless of the power setting to keep it warm, till enrichening for landing. Its already glowing red at 1550 as it is.

I am ready to collect some fresh data and see how LOP I can get smoothly at high power settings. I’ve overhauled/replaced my entire ignition system and hoping I’ll see some dramatic improvement next time I run the gami test – but we’ll see. One of the big pluses of the 252 is that its easy to manage tempertures ROP, but I'd like to improve fuel economy as much as I can without sacrificing speed. Judt flying high enough often enables 16mpg and sometime as much as 20mpg with a favorable winds. Our Mooneys are very efficient!

[ChrisH]

Yes, your 252 engine is much simplier than our 231 cousins. As mentioned elsewhere in the thread, with intercooler, you no longer can run your 231 at 40". The cooler, denser air increases hp vs. original, and thus you get as part of the upgrade a large complex matrix relating your new maximum manifold pressure based on cooling effectiveness of your new intercooler (digital readout included in cockpit for your math comfort). 

Add to this, that in our 231 we can't firewall the throttle either, and you get some of the most fun engine management in any mooney.  So, net, I climb at 34" which is less than all the figures in my tables that I'm likely to encounter and worry about traffic and flying and not table / engine management and dream of having the $'s to step up to a Rocket or Acclaim.

As for your TIT, you may want to try higher RPM settings to get lower TIT, at least for me, it seems that the extra strokes pushing air through the turbo makes it work less to maintain manifold pressure. Then again a dual turbo of an Acclaim would seem a better option there too.

Of course, I could be all wrong, and running my engine into an early grave. 

 

 

 

[Parker_Woodruff]

Paul,

Interesting notes on LOP in your 252.  I have managed a LOP climb in mine while keeping cyls under 380 or so.  Performance was 36" MP, 2650 or 2700 RPM, Fuel flow 13.2 (something like 86% power).  Climb rate with my 3-blade  was 900-950/minute on a hot Texas day.

However, I could only hold LOP through about 4000' then had to go ROP due to roughness.  Hopefully the induction fixes Don Maxwell is working on will change that situation.  And of course my plane is in the shop getting the Encore conversion, which might help the climb a bit.

[kortopates]

Cris, I flew a 231 with an intercooler for few hundred hours before I got my 252. It climbed at full power well within temperature limits. I can't remember exactly what MP I used as Max, as I no longer have the turbo plus matrix table you refer too, but I recall I used between 36-37" as a max setting. I certainly understand operating conservatively, but if you’re seeing high temperatures climbing above 34” and fear a melt down at full power your fuel pump could be out of adjustment. It's quite common to have the fuel pressure setting on the pump too low but if its properly set to Continentals SID-97-E, you should be seeing 24+ GPH at full power climbing with low TIT and CHTS. Per the SID, your LB is actually set a bit higher than my MB. I can’t recall exactly what my 231 climb temps where, but my 252 climb CHTs are <= 330 and TIT ~1400 in climb – full power and full rich.

Good suggestion on varying the RPM to see an effect on TIT. I’ll have to try that and see what kind of effect I get.

[kortopates]

Parker, I will be most interested to hear how the conversion unfolds and I am getting ready to started on mine. I had induction leaks when I first got mine but I learned things just loosen up normally and I am constantly tightening induction hose clamps every time the cowl is off. I am not sure climbing LOP is worth it given its only about 20 minutes or less of the flight doing nearly 1K/min at full power, but if I can ever get good results in cruise – sure I can see trying; could even save you about 3-4 gal for the climb if you could keep that up to 18K . But I would sure like to get there for the cruise portion of my flight!

Keep us posted on your Encore conversion. Is Don finding all the parts so far? Like the Encore gear doors?

[Parker_Woodruff]

Paul - I'm not aware of the gear door difference. We have all the parts except one counterweight in the rudder That Mooney is making- that is unless we need gear doors and Don hasn't told me about that!

[kortopates]

Parker, I don't have the drawing in front of me, but from memory the middle main doors have to have a larger bulge to fit around the double puck brakes replacing your current single puck brakes. Looking at the IPC, drawing 32-11-00 page 2 you'll note that item 19, Middle gear door, is a different part numbers for encore vice the 252. Maybe Don knows something about modifying your existing doors but I think the difference in the size of the bulge is substantial. In fact I've always wondered if the added drag from the doors was the cause of the speed loss from the conversion - hard to believe it could be all from just weight.