Reducing to 25/2500

[Andy95W]

Just now, teejayevans said:

You don't have to do both, i reduce RPM, but throttle remains WO on climbs.

That's exactly what I meant by saying rpm backed off to something quieter in the climb.  Not for people on the ground, but for me.

[jetdriven]

4 hours ago, N1395W said:

Not trying to be argumentative, Ross, but I think the rationale is more about internal cylinder pressure in "saving" the engine, not about restricting air flow.

Less horsepower produced = less internal pressure = ?

For me, if I'm actually going somewhere, I fly exactly the same as Hank (and others). WOT, max rpm, mixture at target EGT, rpm backed off a little as I climb for slightly less noise.

For just sightseeing or fun, WOT/2700 to about 1000', throttle back to something quieter after that and gently coast up to about 1500 AGL, then about 18" and 2300-2400 rpm (wherever the engine feels smooth and happy) leaned out as far as I can and still keep the engine smooth, and always keeping CHTs below 380.

Sure, less internal pressure, but far below certified limits. IO-360s dont blow heads off barrels because they exceed some magical BMEP number, in fact, the only ones that have head separation are the rebuilt cylinders with untold hours on them, not first run, conforming factory cylinders.  Either way, do the compression tests, look for fin staining, and run the engine within certified limits.  Which is 29.92" MP at 59F, and 2700 RPM.

One more thing, above 4500 feet or so, 2700 RPM is LESS cylinder pressure than 2500, at all throttle settings. 

So be kind to your engine, run it at WOT, give it plenty of fuel and airspeed for cooling, and run it at 2700 RPM, so you can get to a higher altitude sooner... (less MP = less HP = less internal stresses, none of which are exceeding the certified margins, but anyways)

Edited May 4, 2016 by jetdriven

[Shadrach]

 

6 hours ago, N1395W said:

Not trying to be argumentative, Ross, but I think the rationale is more about internal cylinder pressure in "saving" the engine, not about restricting air flow.

Less horsepower produced = less internal pressure = ?

For me, if I'm actually going somewhere, I fly exactly the same as Hank (and others). WOT, max rpm, mixture at target EGT, rpm backed off a little as I climb for slightly less noise.

For just sightseeing or fun, WOT/2700 to about 1000', throttle back to something quieter after that and gently coast up to about 1500 AGL, then about 18" and 2300-2400 rpm (wherever the engine feels smooth and happy) leaned out as far as I can and still keep the engine smooth, and always keeping CHTs below 380.

Andy, I don't dissagree with you for continuous operations. Pull back if you wanna. I do this with the mixture with an injected engine. Not an option in May carbureted birds. However for climb (low speed, low airflow and high power), I think that most analysis will show that the less time you spend in the climb regime, the better.  When climbing in your C, do you see a reduction in CHTs at reduced throttle?  My cumulative CHTs tend to run hotter if I reduce power. That is to say, that CHTs take longer to heat up, but will be higher when I reach altitude (which also takes longer).

[Raptor05121]

Awesome notes guys, thanks.

[N33GG]

On 5/3/2016 at 7:31 AM, mooniac15u said:

Getting your complex endorsement isn't a checkride, it's a learning opportunity. You've read the POH and you know what it says. You are also aware that others use a different technique. Why not just ask your CFI about this?  Asking the question shows you have a deeper understanding of engine management than just memorizing what's in the POH. 

Let's see... imagine as a CFI I am requested to give a complex endorsement.  Therefore, by simple logic, the pilot has not yet even received a complex endorsement, and is likely low on the complex experience curve.  However, upon showing up for the complex endorsement flight, the pilot is going to show me he has a deeper understanding of engine management than just memorizing the POH, from reading forums on the web.  I'm not sure this would favorably impress me.  In fact, it might make me nervous and wanting to find out if there is anything flat wrong or dangerous in his head, that this pilot has picked up during his browsing, before I sign him off with my name in his log book.  It would likely extend the ride, at the very least.

I stand by my original statement.  Stick to the POH until you get the endorsement.  

again, just my two cents

[201er]

Just now, N33GG said:

Let's see... imagine as a CFI I am requested to give a complex endorsement. 

I stand by my original statement.  Stick to the POH until you get the endorsement.  

Probably a sensible idea, especially if it's an insecure instructor.

[jetdriven]

On May 3, 2016 at 9:21 AM, MyNameIsNobody said:

Yes, you are (broken record), but since you are playing "my song" feel free to groove the hell out of it.  When I fly I don't putter.  I bought the Mooney to fly cross country fast and efficient.  Whether climbing to 2000 of 10000 WOT gets you there more quickly with no penalty other than fuel flow.

It is safer (altitude is life), cooler (on the engine and the passengers as cooler air is higher) and faster.  This s a no-brainier, but "Max" for many (It's your engine etc comments) is just a hard concept for some to grasp.  This concept is a lot like LOP.  Some get it and some think bad dark thoughts.

WOT in climb is NOT "hard on the engine."  IT is BETTER for cooling.  Now leaning in climb...THAT has the potential to cause problems if not done properly.  

Enough Noobs and non-believers to make this resurface like a Crakken from the depths...

and to Mr. "Check ride"...I rode a tank and a generals rank when the Blitzkrieg reigned and the bodies stank.

I'd find an instructor who isn't still stuck in 1971.  I've been admonished for "burning up my engine" running it over square and LOP and even one who insisted the rudder turns the airplane. Flat turns, is the key, ailerons are a secondary control. His student didn't know what a VFR chart looked like it how to turn on an iPad not use the 430 "direct" feature.  I don't fly with those people anymore. 

Edited May 5, 2016 by jetdriven

[Shadrach]

19 hours ago, jetdriven said:

Sure, less internal pressure, but far below certified limits. IO-360s dont blow heads off barrels because they exceed some magical BMEP number, in fact, the only ones that have head separation are the rebuilt cylinders with untold hours on them, not first run, conforming factory cylinders.  Either way, do the compression tests, look for fin staining, and run the engine within certified limits.  Which is 29.92" MP at 59F, and 2700 RPM.

One more thing, above 4500 feet or so, 2700 RPM is LESS cylinder pressure than 2500, at all throttle settings. 

So be kind to your engine, run it at WOT, give it plenty of fuel and airspeed for cooling, and run it at 2700 RPM, so you can get to a higher altitude sooner... (less MP = less HP = less internal stresses, none of which are exceeding the certified margins, but anyways)

I need to be educated here. It was my assumption that ICP goes up with RPM reduction at any altitude.  If F/A ratio and therefore flame front speed remain relatively constant, slowing the piston down would seemingly shift the peak pressure closer to TDC increasing peak pressure and increasing CHTs. What am I missing?

[Andy95W]

18 hours ago, Shadrach said:

 

Andy, I don't dissagree with you for continuous operations. Pull back if you wanna. I do this with the mixture with an injected engine. Not an option in May carbureted birds. However for climb (low speed, low airflow and high power), I think that most analysis will show that the less time you spend in the climb regime, the better.  When climbing in your C, do you see a reduction in CHTs at reduced throttle?  My cumulative CHTs tend to run hotter if I reduce power. That is to say, that CHTs take longer to heat up, but will be higher when I reach altitude (which also takes longer).

My point was really about the somewhat odd-ball situations where you are only climbing to 1500' AGL, or about 2 minutes or less elapsed time when lightly loaded.  I throttle back just to relieve noise and vibration on myself since I'm just out for fun anyway.

Really enjoying the discussion, though.

[jetdriven]

6 hours ago, Shadrach said:

I need to be educated here. It was my assumption that ICP goes up with RPM reduction at any altitude.  If F/A ratio and therefore flame front speed remain relatively constant, slowing the piston down would seemingly shift the peak pressure closer to TDC increasing peak pressure and increasing CHTs. What am I missing?

Nothing...

[Shadrach]

10 hours ago, jetdriven said:

Nothing...

I was referring to your above "4500' feet or so" comment. Why does altitude matter?

[carusoam]

If adding an engine monitor...  Consider FF, carb temp and OAT for the C.

Best regards,

-a-

[Raptor05121]

23 minutes ago, daver328 said:

I have tried WOT and 2700 many times under many conditions the past three years and doing it that way makes CHTs WAY HOT, like 450° + every time. A carb O-360 does not necessarily act like an injected IO-360. 

Don't know why someone might think they know better than the brilliant engineers who designed the plane and wrote the procedures? I just follow the freakin book unless there is a good reason not to ... Those procedures seem to work best. Better than the forum geniuses procedures ... In my experience ...

From the reading I am getting at, WOT should run cooler CHT's due to the enrichment valve on the carb dumping more fuel to cool the heads. I plan to spend several days flying different profiles and see what I can come up with on mine.

Also, are you suggesting that I follow my POH that says keep engine at full rich for ALL operations except for above 5,000 feet? It also says I should fly at the 50*F ROP, which is highest CHTs and consequently, ICP (which we now know to be the exact opposite of true). Lycoming has switched their viewpoints in the past 40 years more than my girlfriend changes shoes in a day.

I'd trust that JPI-830 before anything written when Kennedy was in office on longevity...

[ArtVandelay]

More power requires more fuel burn which gives off more heat, and if climbing with reduced cooling, you're going to get hotter temperatures.

In 1960s they didn't have engine monitors, if you can keep your CHTs below 400 (I use 390 as warning level), go for it

My engine talks to me, at 2700 it sounds like it is working hard,at 2600 its a lot quieter.

[jetdriven]

On May 6, 2016 at 6:52 AM, Shadrach said:

I was referring to your above "4500' feet or so" comment. Why does altitude matter?

That's the most altitude you can are 25" mp full throttle. I changed the statement later to "at all throttle settings" so I'd guess the altitude part is not needed.  Perhaps this is clearer. At a given MP, cylinder pressure is lower at 2700 RPM  than 2500. 

[Cyril Gibb]

7 hours ago, daver328 said:

I am saying that doing what the geniuses on here say should be making cooler CHTs ... (WOT/2700) ...  Makes our CHT's go way hot. I tried it several times. 

 

What is your fuel flow at WOT ?

[DXB]

\

9 hours ago, daver328 said:

Pretty sure our 1965C Owners Manual specifically calls for 25/25. See photo attached ...

We also climb at 115-120 as recommended (see attached) yeah, like the book says. That work best. 

25/25 works best too. 

I have tried WOT and 2700 many times under many conditions the past three years and doing it that way makes CHTs WAY HOT, like 450° + every time. A carb O-360 does not necessarily act like an injected IO-360. 

Don't know why someone might think they know better than the brilliant engineers who designed the plane and wrote the procedures? I just follow the freakin book unless there is a good reason not to ... Those procedures seem to work best. Better than the forum geniuses procedures ... In my experience ...

(1965 M20C, LASAR COWL,MOD, POWERFLOW EXHAUST, CHALLENGER INTAKE, JPI EDM-830) 

 

16 hours ago, Skmoore63 said:

I've spent a year in my 65C playing with this, it has the Powerflow exhaust so there may be a fuel flow issue here. I also have the original gauges so the readings are very approximate. The bird will climb at WOT at lower altitudes at around 400-410 CHT, 25/2500 is about 380 CHT. The cool down when I reduce power is fairly quick (within 1 minute). From other posts on MooneySpace, this could be the problem with the carburetor jet being too small for the increased efficiency of the exhaust. But WOT climb definitely gets you up there quicker and usually by 3-4K' the temps are below 400. Going in for annual this month, may add an analyzer and see what's really happening in the engine room!

 

The carb'd planes have temp issues for sure. When I first got my C, CHTs were certainly a problem right after takeoff.  I was following my POH and pulled back to 26/26-ish early in climb, and this certainly correlated with a drop in CHTs.  But it also coincided with increasing speed and altitude, so I was unsure of any causal relationship.  Then I read multiple sources encouraging climb at WOT, 2700 so I did that.  It certainly didn't seem any cooler, maybe a bit hotter, but not running away out of control, so I kept doing it.  Now I've improved my baffling (still a work in progress - another story) and have a much better engine monitor with FF - it tells me I'm using 17.5ish gph at takeoff vs. the anticipated 18.2 in the POH.  Maybe the enrichment circuit wasn't working?  So then I fussed over this with my MSC at annual, ultimately agreed with them that my FF is essentially normal, and it wasn't worth pulling the carb to address. 

Bottom line- this topic remains a very fuzzy area for me, and the carb has some distinct issues. I do believe the folks who say following the POH gives better temps- Notably both quoted above have the Powerflow exhaust, yet another variable, but I seriously doubt if the 60's POHs should be treated as the final word on this particular issue.

Skmoore63- please report back your experience! 

[testwest]

OK, guys, lots of good information here, and some not so good, I am afraid. If you are in this discussion, please go find the threads on Vz that I initiated, and download and read the thesis, here:

http://www.openclip.net/Benchmark/IntroducingVz.pdf

A full power Target EGT climb at a speed about 1.3 times your published Vy will give the best combination of time to altitude and velocity-made-good to top of climb (which is a lateral down path point, not an altitude), engine performance and cooling, and fuel used to get there. If you want, you can reduce the RPM (only) a little bit to reduce noise in the cabin. A small reduction goes a long way. Even going back to 2650 from 2700 can make a pretty big difference in perceived sound. There is no need to adjust parameters other than target EGT for gross weight, winds, density altitude or anything else. If your airplane engine runs too hot at this condition, it is well outside its design spec for engine cooling, and repairs/adjustments  need to be made to the engine full power fuel flow, baffling, cowl flap rigging, or a combination of these.

Instructors who still insist on teaching "square" engine management are only perpetuating myths. Even the FAA has specifically addressed this poor practice in the Airplane Flying Handbook, FAA-H-8083-3A, Chapter 11, downloadable here:

https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/airplane_handbook/media/faa-h-8083-3a-5of7.pdf

I will go so far as to post the relevant paragraph and page number via a screen shot:

I will see if I can dig up the power chart from the Lycoming O-360 and IO-360 series airplanes.

By the way, most POHs are awful. See these posts, they are gems!

http://www.avweb.com/news/pelican/186015-1.html

http://www.avweb.com/news/pelican/186216-1.html

Edited May 8, 2016 by testwest
adding info

[testwest]

Found it in the Operator's Manual, Textron Lycoming Aircraft Engines, series O-360, IO-360 [etc], p/n 60297-12.

Page 3-37, Figure 3-21. "Sea Level and Altitude Performance IO-360-A, C [etc] series:

 

 

Key takeaways for this engine...WOT is permissible 2400 rpm and above. 2300/28" ok, and so is 2200/27". In my Aerostar I run 2200/26" (turbo normalized) on a Lyc IO-540-S1A5, which is basically 1.5 M20J engines, same compression ratio.

For Alex (Raptor05121) do what you need to get the complex endorsement, then find the version of the chart above applicable to your engine, and run it. Next BFR, if your CFI questions your practices, win a few beers (or a comp'ed checkride) using facts and data. Happy Mooneying!

 

[carusoam]

Nice chart, Norman!

I need to find the IO550 version of that.

Have you started the Ph.D. Thesis yet? 

Best regards,

-a-

[testwest]

Thanks, carusoam! Have not started the PhD yet, though. Kinda busy at work!!!

[Hector]

Short flight today from Jacksonville FL to St Augustine. Since I had this thread in my mind decided to do a quick test. I have a 67C with the O-360-A1D. OAT in the afternoon was 80 F. On my way down to SGJ I used WOTFR/2700RPM. Just to keep things simple immediately after takeoff I trimmed for 120 mph and climbed to 4000. Initial fuel flow was 17.8 gph and temp on hottest cylinder climbed to max of 401 and decreased to 380 by 3500 feet. On the return flight after takeoff I climbed at 26/2600 per my POH, full rich again (16.5 gph). I trimmed for 120 mph climb as before. Temps climbed to 400 and decreased to 377 by 3500 feet. Essentially, no difference in temperature only I gave up rate of climb. I don't know if 25/25 would have been different or if later in the summer when OAT here in Florida hits 97 F.

Sent from my iPhone using Tapatalk

[ryoder]

I used to do that but based on this site and the mapa doc here http://www.mooneypilots.com/mapalog/M20C%20Evaluation/M20C_Evaluation_Report.html plus my flight instructors advice I no longer do.  I have a 1000 foot checklist which includes shutting off fuel pump, dialing back the prop to 2600 and pitching for 120mph for better cooling.  I fly like this until I get to my altitude but monitor CHT closely and pitch down if it gets too warm.  I also start leaning once I hit 2000 feet even while still climbing.

 

I touch nothing on the engine until 1000 feet and call out "though one thousand" when I get there.

[bonal]

So this discussion leads me to ask how is it any different than all the fixed prop carb models that POH says WOT 2700 our engines are the same and full in governor is like the fixed pitch. We do have adjustability but are all these other models causing harm to their engines 

[Shadrach]

1 hour ago, bonal said:

So this discussion leads me to ask how is it any different than all the fixed prop carb models that POH says WOT 2700 our engines are the same and full in governor is like the fixed pitch. We do have adjustability but are all these other models causing harm to their engines 

Prop full forward is the same as having a fixed pitch climb prop.  Both are limiting engine speed with load (pitch).  Most folks that fly fixed pitch, carbureted aircraft have almost no engine instrumentation and are accustomed to it.  Ignorance is bliss.  From the well instrumented carbureted engines that I have seen, I theorize that most could use a bit more fuel at WOT.  I cannot wrap my head around some of the CHT numbers I see on these engines given that they are running lower compression ratios and less power.  If you O drivers were to look at the cowling on my IO, you'd swear it would over temp. It has a simple baffle seal dressed inward (toward the pressure) that rests against the top of the cowl...that's it and rarely runs more than 350 in climb.