reasonable M20J speeds

[dominikos]

Folks,

I picked my plane from the first annual and it feels slower. It makes RPM and MP, but it used to show/get higher IAS, at least per my recollection. In annual, there was some work done on the front landing gear but before I go bug A&P to check whether there is some extra drag, I wanted to check with you guys whether the numbers below are to be expected or should be investigated. It could be also weather related, when I dropped plane for annual, the temps were in high 70s. Now they are in mid 90s. And it is my first Texas summer of ownership, so don't have reference.

Unfortunately with the wet weather in TX, I was only able to run a 3-way speed test at 2,000 ft.

Here is what I got - 2000ft, 92F - corrected POH numbers for temperature. All my gauges are original, analog gauges.
cowl flaps open:
- 24/2400 - 139 kts - POH: 153 kts (adjusted for temp: ~ 150kts) - 11 kts difference
- 22/2200 - 127 kts - POH: 142 kts  (adjusted for temp: ~ 138kts) -  11 kts difference

cowl flaps closed:
- 22/2200 - 131 kts - POH: 142 kts  (adjusted for temp: ~ 138kts) -  7 kts difference

Do those speeds look right? 

Thanks, Dominik

[A64Pilot]

Where is your mixture, if LOP then I’d say you are about where I am as I run 22 squared often at 7 GPH and get 130 ish speeds, but faster if ROP.

But 24 squared if ROP then I am closer to 150 kts. 

WFO and ROP down low I’m at 168 kts. but also about 15-17 GPH keeping things cool.

 

I think we slow down in Summer

Edited June 30, 2021 by A64Pilot

[N201MKTurbo]

41 minutes ago, dominikos said:

Folks,

I picked my plane from the first annual and it feels slower. It makes RPM and MP, but it used to show/get higher IAS, at least per my recollection. In annual, there was some work done on the front landing gear but before I go bug A&P to check whether there is some extra drag, I wanted to check with you guys whether the numbers below are to be expected or should be investigated. It could be also weather related, when I dropped plane for annual, the temps were in high 70s. Now they are in mid 90s. And it is my first Texas summer of ownership, so don't have reference.

Unfortunately with the wet weather in TX, I was only able to run a 3-way speed test at 2,000 ft.

Here is what I got - 2000ft, 92F - corrected POH numbers for temperature. All my gauges are original, analog gauges.
cowl flaps open:
- 24/2400 - 139 kts - POH: 153 kts (adjusted for temp: ~ 150kts) - 11 kts difference
- 22/2200 - 127 kts - POH: 142 kts  (adjusted for temp: ~ 138kts) -  11 kts difference

cowl flaps closed:
- 22/2200 - 131 kts - POH: 142 kts  (adjusted for temp: ~ 138kts) -  7 kts difference

Do those speeds look right? 

Thanks, Dominik

Did they change the timing?

Are the gear doors hanging?

Did they "fix" the rigging?

My old F was faster than that.

[dominikos]

Just now, A64Pilot said:

Where is your mixture, if LOP then I’d say you are about where I am as I run 22 squared often at 7 GPH and get 130 ish speeds, but faster if ROP.

But 24 squared if ROP then yeah you should be closer to 150 kts 

I’m somewhere in between. Don’t have EIS, so I lean for somewhere between economy and best power mixture to 50 drop of peak EGT. I just looked at POH, their guidelines are in Fahrenheit, but EGT is in Celsius. Looks like I’m closer to best power mixture.

[dominikos]

11 minutes ago, N201MKTurbo said:

Did they change the timing?

Are the gear doors hanging?

Did they "fix" the rigging?

My old F was faster than that.

• dual magnetos were overhauled - they have not been for almost 1000 hours so it was about time
• I suspected front gear door but I don’t have ability to put it on jacks myself but did a video and nothing obvious shows up
• No, there was no adjustment to rigging - only lubricated controls

[Shadrach]

47 minutes ago, dominikos said:

Folks,

I picked my plane from the first annual and it feels slower. It makes RPM and MP, but it used to show/get higher IAS, at least per my recollection. In annual, there was some work done on the front landing gear but before I go bug A&P to check whether there is some extra drag, I wanted to check with you guys whether the numbers below are to be expected or should be investigated. It could be also weather related, when I dropped plane for annual, the temps were in high 70s. Now they are in mid 90s. And it is my first Texas summer of ownership, so don't have reference.

Unfortunately with the wet weather in TX, I was only able to run a 3-way speed test at 2,000 ft.

Here is what I got - 2000ft, 92F - corrected POH numbers for temperature. All my gauges are original, analog gauges.
cowl flaps open:
- 24/2400 - 139 kts - POH: 153 kts (adjusted for temp: ~ 150kts) - 11 kts difference
- 22/2200 - 127 kts - POH: 142 kts  (adjusted for temp: ~ 138kts) -  11 kts difference

cowl flaps closed:
- 22/2200 - 131 kts - POH: 142 kts  (adjusted for temp: ~ 138kts) -  7 kts difference

Do those speeds look right? 

Thanks, Dominik

I know it was a hot day but to add a little context, at 2000ft my very stock 67 F will indicate more than 150kts at 2500rpm and just about any mixture setting. In the winter it will indicate well into the yellow line approaching 160KIAS.  The corrected airspeed would be 2-3 mph less than indicated.

I think think the problem is not so much with book speeds but more with book power settings.   A 201 will certainly run 153kts and it will also run 24 squared.  Asking it to do both at 2000ft is probably not realistic.

[ArtVandelay]

What’s your fuel flows….I never cruise that low, so can’t tell you.

Get up to ~9000’, LOP ~9gph, and I expect ~150 knots.

Here in Florida with the hotter temperatures and higher humidity means numbers will always be less than book.

[Shadrach]

9 minutes ago, dominikos said:

I’m somewhere in between. Don’t have EIS, so I lean for somewhere between economy and best power mixture to 50 drop of peak EGT. I just looked at POH, their guidelines are in Fahrenheit, but EGT is in Celsius. Looks like I’m closer to best power mixture.

So you're running 50 ROP?  That should be generating as near to max speed as makes no difference. That is a very aggressive mixture setting at 2000ft.

[dominikos]

Just now, Shadrach said:

So you're running 50 ROP?  That should be generating as near to max speed as makes no difference. That is a very aggressive mixture setting at 2000ft.

 still learning, so happy to take pointers. What should that be? During transition, I was taught to lean it for 50 ROP as safe guidelines.

[A64Pilot]

If your lean of max temp, then your lean of peak.

Be careful leaning at high power,you can hurt things if not lean enough. Personally I won’t go LOP at high power and won’t even do a lean find. But then I enjoy the economy more than the speed, why 22 squared and 7 GPH is my favorite down low cruise, going for breakfast etc.

To make book speeds you have to be ROP, a lot of the magic of LOP isn’t so much LOP as it is reduced power.

To make book speeds you will likely need to run 725C and of course be ROP. One should never give absolute numbers but I bet 725 is safe, on the rich side of safe

 

[A64Pilot]

14 minutes ago, dominikos said:

 still learning, so happy to take pointers. What should that be? During transition, I was taught to lean it for 50 ROP as safe guidelines.

50 ROP is fine, but too hot for me at high power, it’s a good safe cruise mix though,a little richer won’t hurt, a little leaner could depending on power setting.

Look at your cruise charts, I pick 65% as a safe number, at that power or below you can’t hurt anything wit the red knob, above 75% and you can. Being risk adverse and knowing what motors cost I stay way safe, so if I’m wanting LOP that means I’m sacrificing speed for economy, so to further maximize economy I run at 65% cruise, which isn’t bad, it’s what my Maule and a C-182 cruise at, at higher power and fuel burn.

‘I downloaded an app called aircraft power that tells me percent power, I’ll attach a photo, at 22 squared your only at 55% power if ROP, less if LOP, so making 130 kts on 100 HP ain’t bad at all.

‘This app is apparently conservative compared to our cruise charts, it apparently says our power is higher than the charts, I don’t know why, but using the chart to stay below 75% is conservative.

On edit, if your going to cruise ROP and ROP is safe and has been done for a long time, err on the rich side, if you decide your at a training level to try LOP. do so only well below 75% and err on the lean side, running her as lean as she will run smoothly is safer then say 25f LOP.

As you don’t have a way to watch every cylinder EGT, if you decide to give LOP a try, do so only at lower power settings,that way if you have one cylinder that is much richer than the one with the probe, you can’t hurt anything.

 

Edited June 30, 2021 by A64Pilot

[Shadrach]

12 hours ago, dominikos said:

 still learning, so happy to take pointers. What should that be? During transition, I was taught to lean it for 50 ROP as safe guidelines.

For now, I would suggest that you only lean below 75% power and use either 100 rich of peak EGT (or richer if needed for cooling) on the leanest cylinder or Peak EGT on the richest cylinder.  Once  you've become comfortable with the airframe you can drink from the fire hose of engine management techniques and combustion science. 

Edited July 1, 2021 by Shadrach

[A64Pilot]

I believe he’s like me, only has stock instrumentation, and it’s marked in C for some reason. the smallest increment if memory is correct is 25C. 

25C = 77F

So if he is 50 degrees rich of peak on a stock gauge unless he’s converting to F, then he is 122 F ROP

If running ROP, a little extra fuel is a safety margin

[Shadrach]

3 minutes ago, A64Pilot said:

50 ROP is fine, but too hot for me at high power, it’s a good safe cruise mix though,a little richer won’t hurt, a little leaner could depending on power setting.

50 ROP is about the hottest mixture setting there is with regard to CHT.  Any significant movement leaner or richer will cause CHTs to drop.  40ROP may be slightly hotter but that mixture range is the one in which the cylinder is burning the most fuel at a point closest to TDC.  This does not mean it's not a viable mixture setting it just means that it is the hottest.

[Shadrach]

Just now, A64Pilot said:

I believe he’s like me, only has stock instrumentation, and it’s marked in C for some reason. the smallest increment if memory is correct is 25C. 

25C = 77F

So if he is 50 degrees rich of peak on a stock gauge unless he’s converting to F, then he is 122 F ROP

If running ROP, a little extra fuel is a safety margin

Did not catch the scale being used. 50C ROP is a much kinder place to be than 50F ROP.

[A64Pilot]

1 minute ago, Shadrach said:

Did not catch the scale being used. 50C ROP is a much kinder place to be than 50F ROP.

He may be converting though.

 

On edit, problem with recommending a set EGT is it’s a sliding scale, there are low power settings where peak is entirely correct and power setting thst it will cause damage guaranteed.

 

Edited June 30, 2021 by A64Pilot

[Shadrach]

40 minutes ago, dominikos said:

I’m somewhere in between. Don’t have EIS, so I lean for somewhere between economy and best power mixture to 50 drop of peak EGT. I just looked at POH, their guidelines are in Fahrenheit, but EGT is in Celsius. Looks like I’m closer to best power mixture.

So if indeed you are closer to best power, your plane is on the slow side of the spectrum. Probably better to do some testing at altitude using a 3 way gps run.  http://www.csgnetwork.com/tasgpscalc.html

[Shadrach]

1 minute ago, A64Pilot said:

He may be converting though.

He did mention that he was actually closer to best power, he just didn't post the number. Misfire on my part.

Edited June 30, 2021 by Shadrach

[dominikos]

6 minutes ago, Shadrach said:

Did not catch the scale being used. 50C ROP is a much kinder place to be than 50F ROP.

Here is my EGT instrument, I aim for 725 C. I tried converting but that’s challenging with Fahrenheit so sticked to Celsius.

 

 

[dominikos]

10 minutes ago, Shadrach said:

So if indeed you are closer to best power, your plane is on the slow side of the spectrum. Probably better to do some testing at altitude using a 3 way gps run.  http://www.csgnetwork.com/tasgpscalc.html

I did 3way test at 2,000. The plan is to run another test at 4,000 or 6,000 ft weather permitting. 

Frustrated with the weather because the plane feels slower but I have no way to confirm 

[Shadrach]

On 6/30/2021 at 10:40 AM, dominikos said:

Here is my EGT instrument, I aim for 725 C. I tried converting but that’s challenging with Fahrenheit so sticked to Celsius.

 

 

The problem is not that it is in C, the problem is that the scale is in increments of 25. It needs to be finer. increments of 20 or even better 10. Ideally you would slowly lean to peak EGT and then set 40C richer.  There is also the problem of that being just one cylinder of 4 and having no idea where the other 3 are.  Tech has com a long way since then. If I were you, I would prioritize an engine monitor soon.

Edited July 2, 2021 by Shadrach

[PT20J]

There’s the old fashioned way of leaning for max speed. Takes patience, smooth air and you have to hold altitude precisely. Easier with an autopilot.

The problem with comparing speeds is that seldom is a complete set of data supplied: pressure altitude, OAT, rpm, MAP, mixture, fuel flow, IAS. And, then there is the problem of the accuracy of old instruments. 

But if your plane seems different after maintenance, it may well be. There should be logbook entries so you know what was done. Sometime, as someone mentioned, the timing gets set wrong, This should show up during a mag check.

Skip

[A64Pilot]

This is a dangerous statement as aircraft and conditions differ, but my airplane is way safe at 725C, and it’s awfully close to best power.

‘If you pull back to 75% or less and slowly lean to peak, you may get to 800C or close to it, or at least I can get close. However peak is a function of conditions and cylinder compression, one reason why cylinders will peak at different temps is slightly different compression ratios, low compression motors will peak at higher temps.

Engine monitors are nice and good for troubleshooting, but they aren’t as necessary as many woud have you believe. Your airplane has flown for how long without one?

When I have the excess money floating around I’ll install an EI UBG-16 myself. based on I know the people and know I can get great support if needed.

‘At 75% or higher, be rich, best power or richer. I define normal cruise as a power setting at or below 75%, once below 75%,  you can pretty much do anything you want to with the mixture, you can’t hurt the motor, it’s not making enough heat to hurt itself. I like 65% or lower to add an unnecessary safety margin.

Only time I’m above 75% is takeoff and climb, I never cruise above it for engine longevity.

[Hank]

2 hours ago, A64Pilot said:

I believe he’s like me, only has stock instrumentation, and it’s marked in C for some reason. the smallest increment if memory is correct is 25C. 

25C = 77F

So if he is 50 degrees rich of peak on a stock gauge unless he’s converting to F, then he is 122 F ROP

If running ROP, a little extra fuel is a safety margin

It doesn't work that way. Yes, when the thermometer points at 25ºC, that's the same as 77ºF. But ROP / LOP is a difference in two temperatures, so you have to remember:

Mathematically, 1ºC = 1.8ºF

If he's running 50ºC ROP, that's 90ºF ROP. Going the other way, 50ºF ROP = 28ºC ROP.

And I would ignore the whole 725ºC EGT, as no two engines show the same actual EGT number due to slight differences in installation. Move the sensor 1/8" and the number will change a lot. Converting, 725ºC = 1337ºF, so your EGT sensor is mounted differently than mine, a little further from the cylinder.

Two things matter with EGT:  what is the peak temperature? how far below peak are you running [LOP or ROP]?

I always check my peak temperature, it tends to wander around from one flight to another due to temperature, humidity, air pressure, density altitude and phase of the moon. It's often 1500ºF, but sometimes 1525ºF, so I run 1450-1475º depending on where the actual peak is on each flight.

[dominikos]

my peak is around 775 C, quite consistently, hence, I always aim for 725C when leaning. as Shadrach pointed, with current instrumentation, I don’t have granular view - my temps reads are within 10-15C