Best gph?

[ryoder]

Looking through the 1965 M20C POH you can get about 6gph if you use 1800 RPM and 17 inches of mp. Is this realistic and can you really fly at this during a cross country flight? It certainly looks attractive to me as a new pilot used to flying slower 172s.

[Rwsavory]

You can, but you will not want to fly that slow for any length of time on a cross country. It will only take you a few flights to get used to the higher speed of the Mooney. Don't worry about it.

[1964-M20E]

fly it like you stole it.    GPH is part of the equation.  With the C you should be able to fly about 8-9GPH between 40 and 120 altitude and get pretty reasonable speeds and lay waste to someone flying a 172 burning 6 to 7 GPH

[N33GG]

Don't worry about GPH. Go fast and appreciate MPG.

[Andy95W]

I've tried 1800 and my engine really didn't like it much. Engines like smooth and mine wasn't.

Try flying at Carson speed, 1.32 x Vy, about 138 mph Indicated, and considered the best balance between speed and fuel burn. Works out to about 19" and 2400 rpm and very smooth.

[Hank]

Looking through the 1965 M20C POH you can get about 6gph if you use 1800 RPM and 17 inches of mp. Is this realistic and can you really fly at this during a cross country flight? It certainly looks attractive to me as a new pilot used to flying slower 172s.

The previous owner of my C flew to Myrtle Beach with friends in a 172. He beat them by about 1/4 of their flight time and used 10% les fuel. I don't like the control feel at low power settings like that. To go slow when needed, I generally set 2300 and whatever throttle is required; try ~17"/2300 instead to make Skyhawk speed. Or fly it like a Mooney.

[Lood]

The C should give you very close to 140kts, burning 9 odd gal/hr. That's almost 40kts faster than a C172 burning 6 gal/hr. If you do a 300nm cross country flight, the Mooney will take 2h10min and burn 19 odd gallons of fuel, while the C172 will take almost 3 hours and burn 18 gallons. Really not worth it to slow a Mooney down, because they're too efficient and economical.

Now, we haven't even started with flying that same Mooney LOP...

[jetdriven]

I havent seen a 172 that would burn 6 GPH, all the ones I ever saw burned at least 8 something, and sometimes near 10.

[ryoder]

Thanks for the Info. The Mooney poh says it can burn 5.9 at 1800 and 17mp. I just wondered if it would be bad for the engine. I actually like flying kind of slow to reduce noise and use less gas when just flying for fun. Here is an addon question. Do speed mods work down low in the speed range or just up near max cruise? The Mooney gets it's best range at this 5.9 fuel burn and can go 1000 statute miles with no reserve according to the poh.

[Guest]

I've done this before in both of my E models for no more than an hour, running 1900 RPM and 16-17" Hg. As long as the engine runs smoothly there is really no harm, save for not being able to get the oil hot enough to burn off moisture.

Mine would easily out run a 172/ Cherokee on 6 GPH as shown on the Shadin. If you just want to build time on low fuel cost it works well.

Adding to other comments, you do have to weigh out engine and maintenance costs by adding additional hours at the saving of fuel.

Clarence

[cbarry]

It really comes down to time between point A and point B. Reducing the power results in lowering the gph rate, but on most trips the total fuel burn will be negligible as compared to "cruise by design" settings (in other words, our aircraft design exudes efficiency from nose to tail--so use it).

[mikerocosm]

Below 9000', I run throttle wide open, lean to just-above-rough, and slow the prop to 1950 (how I wish that red band between 2100 and 2350 wasn't there!). I give up a couple of mph, but burn 7-8 gph, and still go almost 140 mph indicated, and it's a whole lot quieter. Above 9000', higher revs seem to be required. (And yes, I have a JPI EDM-700, and CHTs remain in the 290-330 range, depending on season.)

 

Good luck finding your sweet spots!

 

mws out

[orionflt]

I have been doing the same thing as mike, my speeds are still reasonable, my fuel burn is down, the aircraft is running smooth. I'm seeing almost no disadvantage to turning the RPM's down especially during high altitude cruise unless I have a strong head wind.

 

Brian

[carusoam]

Yes you can...

Fly a C slowly

Fly a C to maximize efficiency

Fly a C to build hours

Fly a C like a glider (use power to balance drag then go find a ridge and try soaring....)

Fly a C backwards. You will need a strong headwind.

I was young once. This made sense for what I was doing.

The C's carburetor is not that friendly with the less controlled distribution of fuel.

Lack of a JPI made it impossible to know how friendly the low power, low temperature is on the engine.

The C has some rpm / MP limitations to be aware of.

If you like to fly, the C is a great choice...

If you like to cover the ground quickly, the R is a big version of the C for near 10X the price, to not go 2X the speed....

It's good to be young,

-a-

[N33GG]

If you want to fly slow, buy an aircraft that likes to fly slow. Although you can fly slow in a Mooney, it is not what it was designed for. The wing and control surfaces like more airflow. It is not a pleasure to drag any aircraft slowly through the air that is designed for higher speed.

[Immelman]

Ok, I will be the dissent here...

My E flies nicely just barely lean of peak at 6gph, at varying prop speeds (2000 or 2400rpm, either way). I tend to get better speed at the lower RPM at low altitudes (close to Caron's speed, about 130mph indicated) when I operate this way at low altitude, i.e. close to sea level. The cylinders and oil are still warm enough to be healthy provided it is not a cold atmosphere in which case I would cruise with a higher power setting. If I am going somewhere any distance away, I will typically use more fuel/power... but for sight seeing or local flights where there is no destination, you can certainly enjoy C152 fuel burns at a higher speed in your mooney.

[ryoder]

Thanks guys. 150hp C172M economy is my goal since that is what I was planning on buying. Would speed mods help down low in speed? I like good fuel economy tat is why I drive a 2013 Corvette.

[Andy95W]

Thanks guys. 150hp C172M economy is my goal since that is what I was planning on buying. Would speed mods help down low in speed? I like good fuel economy tat is why I drive a 2013 Corvette.

Okay, so purely looking at numbers:

150 hp C172M = 110 kts. @7.5gph = 14.66 nm per gal

180 hp M20C = 145 kts. @ 10 gph = 14.5 nm per gal

Since I don't want to join CessnaSpace, I'll have to keep my M20C and go fast instead.

To answer your question about speed mods, I've bought lots of 'em. They're all good for something, but not necessarily speed. Wingtips look cool. Flap seals add climb rate. Cowl mods aid in engine cooling.

Since drag differential increases to the square of the speed (if I remember my physics classes), there will be less difference at low speed than high.

[Andy95W]

Okay, so I tried pulling my RPMs back to 1800-1900 today, and the engine was smoother than I remember it being. Noticeably quieter, too.

Does anyone know of any downside to running the engine that slow? My C seems to be really smooth between 2350 and 2450. Maybe I just feel weird about pulling the prop back to 1800.

[N201MKTurbo]

My turbo 201. LOP at 8 GPH and 140 KTS. 20.15 SMPG.

[Lood]

If I do some slow, leisure flying around the area where I stay, I leave the rpm at 2400 and just throttle back until I see 90mph indicated. Can't recall what the fuel flow is, but I think it's somewhere around 6 gal/hr. Like others, my engine also runs very smooth at 2400 rpm, although I haven't tried anything lower. In my Mooney, the most noise does seem to be wind noise and not so much engine or prop noise. Very noticeable and dependent on the speed I fly at.

[Hank]

Thanks guys. 150hp C172M economy is my goal since that is what I was planning on buying. Would speed mods help down low in speed? I like good fuel economy tat is why I drive a 2013 Corvette.

Even at our higher fuel flow, M20-C flies the same distance as a C-172, in less time, using less fuel. My wife and I went 2600+ nm with friends in a Skyhawk, carried some of their bags, left second (by up to a half hour), arrived first and used less fuel on every leg. We were typically 8500 msl, 2500, with the throttle backed off just enough to make the MP needle move, and leaned right to 50 ROP. (My carb won't do LOP, I've tried.)

I can slow down and match speed with a Skyhawk--start with 2300 and expect 16-17" and play with the throttle. Leaned out, of course--Full Rich is reserved for take offs and climbs only.

One of the nice things about flying is that you can go as fast as you are able. Most Corvettes won't beat a Honda by much on a long trip without lots of luck, lots of worry and a radar detector. But a Mooney will beat many other planes without a second thought. Want to go faster still? Get a different Mooney; TNs run 242 KIAS at altitude, which can be more than 300 knots groundspeed--just bring your checkbook to the table. There is a full assortment of prices and speeds in between.

[WardHolbrook]

Even at our higher fuel flow, M20-C flies the same distance as a C-172, in less time, using less fuel. My wife and I went 2600+ nm with friends in a Skyhawk, carried some of their bags, left second (by up to a half hour), arrived first and used less fuel on every leg. We were typically 8500 msl, 2500, with the throttle backed off just enough to make the MP needle move, and leaned right to 50 ROP. (My carb won't do LOP, I've tried.)

I can slow down and match speed with a Skyhawk--start with 2300 and expect 16-17" and play with the throttle. Leaned out, of course--Full Rich is reserved for take offs and climbs only.

One of the nice things about flying is that you can go as fast as you are able. Most Corvettes won't beat a Honda by much on a long trip without lots of luck, lots of worry and a radar detector. But a Mooney will beat many other planes without a second thought. Want to go faster still? Get a different Mooney; TNs run 242 KIAS at altitude, which can be more than 300 knots groundspeed--just bring your checkbook to the table. There is a full assortment of prices and speeds in between.

When you're flying from point A to point B, it's not about the cost per hour, it's all about cost per mile and sometimes it makes sense to look at cost per seat mile. Cessna 170s/172s are the poster children of successful aircraft designs. After all, they've built over 48,000 of them since 1948 with no end in sight, but there's a reason why Mooney's are so popular and keep rising from the ashes.  

[WardHolbrook]

Looking through the 1965 M20C POH you can get about 6gph if you use 1800 RPM and 17 inches of mp. Is this realistic and can you really fly at this during a cross country flight? It certainly looks attractive to me as a new pilot used to flying slower 172s.

You buy a Mooney for its speed and efficiency. I'll tell you what I tell guys that are getting into a jet cockpit for the first time - all that extra speed means in cruise is that it won't take quite so long for the waypoints to pass underneath your nose. Fly your new airplane the way it was meant to be flown - fast. Now, the difference will be when it comes time to slow down and configure for landing, but that's a training issue. Get a thorough checkout and do what it takes to maintain  your proficiency and fly the airplane the way it was meant to be flown. Enjoy your Mooney!  

[cliffy]

From point A to point B in my 64C I get 16 to 18 nautical miles per gallon. I like MPG as a cost planner. I typically use WOT and 2500 RPM and lean to just shy of peak EGT. Just did 5 hrs today at 12,500' and trued 137 kts. Had a conversation with Bill Wheat 3days ago and he agreed 135 to 140 kts is about right for a stock C model.

If I'm just tooling around the lake sightseeing it's 2500 and what ever MP gives me the speed I want, leaned to 100 short of peak just in case I need to add power in a hurry ( usually DAs of 7500 to 9000).