M20K power settings / Numbers

[Alan Fox]

I am just putting a K model back into annual , First non test flight will be a 600 mile trip , in the 16000 foot range , It has old school engine temp gages , Intercooler , and Merlyn...  digital fuel flow , and digital temp on the intercooler , Took it for a short test flight ,  Had no problem making and holding 40 inches of MP ,  What are good settings / fuel flows , I havent owned a turbo in many years , and the last was a P210.... Thanks in advance , 

[PeteMc]

I do not have the Intercooler, so others may additional info.  But the numbers in the POH are a good start.  But realize you can extrapolate the numbers beyond what the POH shows since the Merlyn will give you additional MP as you go up.  The POH was based on the fixed "bolt" set wastegate and when you reached around 13K (from memory) the turbo would start to fall off.  So the POH will stop at various altitudes based on the performance with the Fixed Wastegate. With the Merlyn you had more boost up to max altitude, so you can just figure out the settings at higher altitudes.  (e.g. The POH stops with 31.7" at 12,000 ft @ 2400 RPM (75%), but the Merlyn will give you much more boost beyond 12K.)

And if you use ForeFlight, I've found their numbers in the available profiles are only for Best Economy.  So if you plan to fly Best Power, be careful of the fuel calculations FF gives you.  You may get a bit of a "pucker factor" when FF tells you the leg you planned is fine and you're looking at minimal fuel as you near your destination.  I find that if I'm not flying Lean of Peak (which FF also has no numbers for), I need to really increase the expected fuel flow.  I really don't like to turn the Turbo at the manuals "max" temp, I've talk to too many mechanics that say it just burns up the Turbo to lean it that hot.  So if Rich of Peak I'm more in the Pest Power range.

 

[N231BN]

Do you have the flight manual supplement for the intercooler installation?

[Z W]

Should be something like:

Cruise Climb: 32" MP 2500 RPM full rich (if you use this, many just do full power climbs to altitude, myself included)
Best speed cruise: 28" MP 2500 RPM, lean to peak TIT about 11.5-12GPH or 13.5 GPH ROP
Economy cruise: 26" MP 2400 RPM, lean to peak TIT or leaner, 10ish GPH
Descent: slowly reduce power to 20" MP, 2300 RPM, cowl flaps closed to maintain CHTs.  Hold until gear down.  Will also give you 100KIAS for approaches in level flight.
Gear down / pattern: 16" MAP should give you +/- 500 FPM descent at pattern speeds

[231LV]

Don't run an intercooled turbo at 40 MP, you are overboosting the engine. My typical max climb power is limited to 37 inches due to intercooling. Usually, I cruise at 10 gph running the engine LOP. Hottest CHT's are around 320 unless I am in the higher teens where the turbo is really working and glowing cherry red...then I can see 365-375 on the hottest. Enjoy your K...it is a great traveling machine!

[Phil EF]

There should be a Flight Manual Supplement and a placard for the intercooler power setting limitations  and fuel flows. 
Most intercoolers have a MP limit of 36” for T.O.  
Continental has a 20 second limit for overboost.  

[Red Leader]

If you can pull 40" of manifold pressure, your induction system is not adjusted correctly. With the TurboPlus, you should be limited to 36" - mine is.

[jlunseth]

 

[jlunseth]

We just had a couple of threads on this. You might want to look at them.

You should not operate an intercooled TSIO360 at 40”. That is an overboost. The purpose of the intercooler is to cool the induction air after it leaves the turbocharger, making it denser than a non-intercooled engine. About 37” is as high as you should go and 36” works fine too. You should have gotten a chart for the intercooler. The pilot uses the chart to adjust the power setting, starting with the settings for the factory (nonintercooled) engine, using the “differential temperature.” The differential temp is the drop in temp from the Compressor Discharge Temperature to the Induction Air Temp. The intercooler was supplied with a gauge that reads out that diff temp. The result is a substantially lower MP to create a given %HP than what is in the POH. Sounds complicated I suppose, but it is not really, after awhile you come up with some settings that work for you. 

[Q The Engineer]

FYI