M20E Performance / POH numbers

[The Other Red Baron]

On my recent XC to/from Colorado I had a lot of time to stare at the gauges and compare what I was seeing on the gauges with the manual.  At 10k 2500RPM 21" GPH is 11.2gal and TAS is 181/185 depending on weight with the note "BEST POWER MIXTURE." I of course lean it out and I was only seeing 9GPH which isn't even on the chart at 2500RPM.  I'm just doing the old lean till rough then enrichen a bit technique because when I've tried to truly run LOP 25+deg I just don't like the sound coming out of the engine.  It runs but it doesn't sound happy.

My question to the crowd is in these situations can I look at gal/hour on the charts and use those numbers to get a better estimate of TAS or does it all just get thrown out the window and I have to find my own TAS at different levels/power for future flight planning? For example at 10K 2400RPM 18" we get closer @ 9.3GPH and TAS 162/166.

[Skydancer2992]

MPH or knots?

[The Other Red Baron]

MPH in ye ole '65 POH

[Skydancer2992]

I was thinking if knots, there must be a lot of speed mods on that plane.

 

[The Other Red Baron]

I wish!  We calculated the TAS one day while shooting approaches and it was making book numbers but I probably hadn't leaned it out much.  I had to find something interesting to do over Kansas the other day so I dug out the POH and noticed how far off my numbers were from the book in cruise. 

[carusoam]

Torb,

I like the idea of discussing engine ops...

But it’s hard to get past, “it runs, but doesn’t sound happy...”
 

There has got to be a way to become familiar enough with the fact based instrumentation you have... to get away from running the engine based on feelings...

What does a happy sounding engine sound like?

Of course... there are things about engine ops... when they feel bad... it’s because something has gone wrong...
 

Add to that...

Were you trying to graph data that says if I burn this much gas, I will go this fast, and cover this much distance?

I’m sure this can be done... but the super computer, data crunching, weather gathering, DA calculating machinery probably isn’t available while in flight...  

leaning by feeling is just too crude...  That is why we got engine monitors... then we can discuss how lean you went... was it 2 or 5°F LOP... power drops off so much by going a few degrees LOP...

technically an engine monitor isn’t needed for that either... but the monitor will verify that all cylinders are operating the same way...

Sounds like a great flight...

See if you can post your engine monitor’s data...

PP thoughts only, not a data hound...

Best regards,

-a-

[The Other Red Baron]

Happy = Sounds smooth (as a 4 cyl can sound)

Not happy = Sounds like a Krylon spray paint can

I've seen other people on here mention how running LOP may not sound the smoothest, but it doesn't inspire confidence in the wife...

Yeah I'm just trying to figure out how to get my long XC flight planning a bit more accurate.  It wasn't drastically off considering getting vectored around a bit, but just shooting for more accuracy.

I'll get that data this weekend.

 

edit: Flymac's initial post sums up what I'm trying to convey, but I have no idea about our GAMI spread honestly. 

 

Edited October 3, 2020 by The Other Red Baron
added link

[Ragsf15e]

6 hours ago, The Other Red Baron said:

On my recent XC to/from Colorado I had a lot of time to stare at the gauges and compare what I was seeing on the gauges with the manual.  At 10k 2500RPM 21" GPH is 11.2gal and TAS is 181/185 depending on weight with the note "BEST POWER MIXTURE." I of course lean it out and I was only seeing 9GPH which isn't even on the chart at 2500RPM.  I'm just doing the old lean till rough then enrichen a bit technique because when I've tried to truly run LOP 25+deg I just don't like the sound coming out of the engine.  It runs but it doesn't sound happy.

My question to the crowd is in these situations can I look at gal/hour on the charts and use those numbers to get a better estimate of TAS or does it all just get thrown out the window and I have to find my own TAS at different levels/power for future flight planning? For example at 10K 2400RPM 18" we get closer @ 9.3GPH and TAS 162/166.

I think you’re probably leaner than the book numbers.  At 10k, my 68 poh says lean to 80rich of peak which isn’t great but probably not gonna hurt anything at that altitude.  Do you have an engine monitor that you could use to set 100 rich of peak?  At 100 rop, you can compare that to the poh with like rpm and you should be in the ballpark.

Based on the way you describe lean until rough and then back to smooth, I’d say you were right around peak egt.  The speed and fuel seems about right too.

An engine monitor with 4xegts is worth 1,000 internet guesses though...