M20J cruise settings

[larrynimmo]

I am curious what settings others use for cruise...lately I’ve been using 2,450/24 square either 75rop getting close to 145k avg ground speed@ 11gph....or 25 lop getting 130k @7.4gph

these are at 2,000’ 45f

[carusoam]

Cruise at 2k’ Larry?  (Just checking)

I have fear of C152s...

Best regards,

-a-

[larrynimmo]

Just now, carusoam said:

Cruise at 2k’ Larry?

I have fear of C152s...

Best regards,

-a-

Most of my flights are under 50 nautical miles away...and some are in restrictive airspace.

when I fly greater distances then I do between 6k and 9k depending on winds

[201Steve]

TBH I kind of use what feels good and don’t really have a go to. I start pulling stuff back (not throttle if high enough) and find a sweet spot. It’s very scientific.  but...If too slow, start pushing things forward. If too much gas, pull stuff back.   If temps too low/high.... well, you get the idea. Each parameter is usually between 23-25 though. If impatient ROP. If feeling low stress, LOP. 
 

[toto]

I only ever use 2500rpm for cruise. If it's a normal cross country flight, it's always 2500+WOT. Simple as it gets. 

If I'm going any distance at a low altitude, I'm normally at 21" or less. But I don't particularly like going any distance at 2k unless it's in a PA-18

[EricJ]

I'm usually at 8k-10k feet, always wot/2500, usually 100 ROP.   Gives a reliable 150 kts at about ~10.2 gph.

 

[jetdriven]

Full throttle.  2500 rpm. 15-30 LOP

[PT20J]

Down low (2000 - 3000 MSL): 24 " and 2500 rpm. Fuel flow 9.5 gph about 20 F LOP

Higher (above 6000 MSL): WOT, 2500 rpm, peak EGT (compromise between range and speed).

I use 2500 rpm because Bob Kromer said that this was the most efficient speed for the McCauley prop. I don't have a map for the prop so I can't verify, but I figure Bob should know.

With a M20J, I have a little Lycoming 4-banger which is pretty efficient compared to a big bore Continental. So I figured I already pre-saved on fuel. I bought the Mooney to get places fast and efficiently and peak EGT seems a good tradeoff. 

Skip

[gacoon]

Full throttle, 2500rpm, if

[toto]

36 minutes ago, PT20J said:

I use 2500 rpm because Bob Kromer said that this was the most efficient speed for the McCauley prop. I don't have a map for the prop so I can't verify, but I figure Bob should know.

If Bob is the one who wrote (or performed) the MAPA evaluation for the J, then that's my source too

Pretty much everything I do with power settings is from MAPA guidance. 

[ZuluZulu]

I've been flying WOT/2550 RPM.  Typically cruising between 6500-9500'.  Sometimes overflying the Class B at 11500'.  Being reminded of Bob Kromer's advice upthread, I might try using 2500 RPM again, as I did for the first 25 hours.

Anyway, after using lean find and getting the same numbers enough times I simply lean to 12.0 GPH, which is 100º ROP, and that reliably delivers 155-160 KTAS according to the G5.  I've also used 10.5 GPH for "economy" cruise, which yielded about 145-150 KTAS if memory serves.  Much like @PT20J said, I like going fast.  

[ArtVandelay]

I'm usually at 8k-10k feet, always wot/2500, usually 100 ROP.   Gives a reliable 150 kts at about ~10.2 gph.
 

Same except I run LOP, so save ~1.5 gph.

[Ragsf15e]

13 hours ago, PT20J said:

Down low (2000 - 3000 MSL): 24 " and 2500 rpm. Fuel flow 9.5 gph about 20 F LOP

Higher (above 6000 MSL): WOT, 2500 rpm, peak EGT (compromise between range and speed).

I use 2500 rpm because Bob Kromer said that this was the most efficient speed for the McCauley prop. I don't have a map for the prop so I can't verify, but I figure Bob should know.

With a M20J, I have a little Lycoming 4-banger which is pretty efficient compared to a big bore Continental. So I figured I already pre-saved on fuel. I bought the Mooney to get places fast and efficiently and peak EGT seems a good tradeoff. 

Skip

I’ve used peak egt as well but usually up higher.  When you use it at ~6500’, what kind of CHT are you ending up with?  Are you leaning until all 4 are peaked and just leaving the richest one at peak so the others are slightly lop?  

I’d like to try that myself but don’t want to end up having a cylinder 25 rop or real hot.

[Derek]

I'm glad to see this thread. I am a relatively new Mooney pilot, had my '95 M20J for a year now and every single time I cruise I look at the cruise power chart on the sun visor and just dial in the power configuration % I want, usually 65%, with the lowest RPM listed for the altitude, and lean for best economy, as long as CHT stays down. If CHTs rise, I try to enrichen first before opening the cowl flaps.

I don't have go-to settings.

It seems like there are a lot of ways to go about this.

[EricJ]

7 hours ago, ArtVandelay said:

Same except I run LOP, so save ~1.5 gph.

I used to run LOP, but my plug fouling problems went away when I stopped, so I haven't gone back to it.   It does seem happier ROP.

[Ragsf15e]

44 minutes ago, EricJ said:

I used to run LOP, but my plug fouling problems went away when I stopped, so I haven't gone back to it.   It does seem happier ROP.

Was it running really cold CHTs lop?

[EricJ]

1 minute ago, Ragsf15e said:

Was it running really cold CHTs lop?

Cold enough, apparently.  I think that was ultimately the issue, which isn't a problem ROP.

[Ragsf15e]

1 hour ago, Derek said:

I'm glad to see this thread. I am a relatively new Mooney pilot, had my '95 M20J for a year now and every single time I cruise I look at the cruise power chart on the sun visor and just dial in the power configuration % I want, usually 65%, with the lowest RPM listed for the altitude, and lean for best economy, as long as CHT stays down. If CHTs rise, I try to enrichen first before opening the cowl flaps.

I don't have go-to settings.

It seems like there are a lot of ways to go about this.

If you have a good engine monitor with cht and egt for all cylinders as well as fuel flow, you can do better than the standard settings.  It all depends on what you’re looking for-speed, efficiency, noise reduction, low fuel flow (loiter), etc.  Additionally, you can keep your engine happy and healthy by keeping appropriate cylinder temps and your plugs lead free by proper leaning (usually on the ground).

Step one is having an engine monitor though.  Do you have one?

[ZuluZulu]

2 hours ago, Ragsf15e said:

I’ve used peak egt as well but usually up higher.  When you use it at ~6500’, what kind of CHT are you ending up with?  Are you leaning until all 4 are peaked and just leaving the richest one at peak so the others are slightly lop?  

I’d like to try that myself but don’t want to end up having a cylinder 25 rop or real hot.

I'm not @PT20J, but we both have MSEs and it sounds like I fly somewhat similarly so I'll add some data.  Using the settings I mentioned above, my CHTs in cruise with cowl flaps closed are usually about 355.  One is always a little cooler than the other three, around 335-350.  I try to keep them above 350º based on the final paragraph in this Mike Busch article.  I wasn't flying during the summer, but so far I've found it just about impossible to get them any higher than 370 no matter what I do.

ADDING: The only flights I had during summer were ferrying the plane home after purchase.  Found a few photos of the engine monitor from those flights: 354/354/361/353 (at 10.7 GPH), and another flight at 356/358/368/359 (at 10.5 GPH).  So it seems the same will be true next summer.

[Ragsf15e]

Just now, EricJ said:

Cold enough, apparently.  I think that was ultimately the issue, which isn't a problem ROP.

Yeah, mine will get pretty cold as well lop.  Especially at higher altitude, lower rpm and cold OAT.  My Surefly actually helped that a little and it stays in the 330f range lop now.

[Derek]

5 minutes ago, Ragsf15e said:

Step one is having an engine monitor though.  Do you have one?

Not yet.  Was waiting to get through 2 annuals. That's done now so I have confidence in the engine and airframe.

Next stop: avionics shop.

[gsxrpilot]

35 minutes ago, Derek said:

Not yet.  Was waiting to get through 2 annuals. That's done now so I have confidence in the engine and airframe.

Next stop: avionics shop.

An engine monitor is not Avionics. Any A&P can do that installation... at a lower hourly rate than the avionics shop.

[Ragsf15e]

8 minutes ago, gsxrpilot said:

An engine monitor is not Avionics. Any A&P can do that installation... at a lower hourly rate than the avionics shop.

I think that depends on the installation and the A&p.  Once they’re cutting out panel space and connecting to avionics (gps and audio alerts) some A&Ps will defer to an avionics shop.  For a simple, straightforward monitor I agree with you though.  Maybe cgr-30p?

[Tx_Aggie]

2500 rpm, wide open throttle, manage the cowl flaps and fuel flow (usually see 11.5 gph) for cht’s near and below 380 yields 155-160 ktas for me. 7-9k altitudes. 1980 M20J. 
 

When ambient OAT is really hot, ~70F+ and I’m at 5-7k I’ll run at 2400 rpm and usually see 155 ktas. 

[OR75]

23in/2400 rpm ... 9gal/hr 

nice and quiet