Fuel Burn - New Owner With Questions

[jpusser]

Just bought a 62 c model and wanted to get thoughts on a few things.  Every where I researched said the c would burn about 9 gph but I can't get it below 11gph.  I normally fly at 055 or 065.  Any Ideas?

I have a little surge in the prop on take off but it is fine after a few min.

The oil temp is the only guage in the garwin cluster that doesn't work.  Any ideas would be great.

Also I get a fuel smell after landing, but that is the only time.  Can't find any stains.  It has bladders.

Fuel Pressure Likes to go above redline sometimes, especially with pump on

Plane flys great and runs good, I would just like to work out some of the quirks.

Thanks

 

[carusoam]

jpusser,

How are you measuring fuel flow in your in your 62C?  fuel flow monitor? If it is based on refilling the tank at the end of a flight, did you account for high fuel flow during take-off/climb?

How are you leaning to get best fuel flow?  Are you using the ships' EGT or do you have a better monitor?

Best regards,

-a-

[skyking]

Hi Jpusser: You should be at about 9.5 gallons with that engine etc.

I would go out and do a flight with full tanks and fill up again after you get back. The fuel monitor may be out of whack.

Use one tank for run up , take off etc. then switch tanks and fly for an hour. When you get back measure the fuel in the tank you used for cruise ( the tank used for climb out etc will burn more than 9.5 and may be as high as 12-13). That should give you a close number to your actual burn rate.

[scottfromiowa]

You are of course heavier with more fuel.  If you are only flying two hours having more than 30-35 gallons of fuel on board will reduce performance including fuel burn.  I have fuel measuring sticks and I sump the tanks before each flight.  What RPM and manifold pressure are you flying?  What are the hours on the engine/prop?  If you lean to engine roughness and then enrich slightly to smooth engine you are likely lean of peak or at peak.  The How do you lean question by Carusoam is key...good luck with your Mooney.  You are NOT going to see 9GPH without going higher and leaning/reducing MP.  My 66 M20E POH says 2350RPM and 22.0HG to achieve 9.1GPH...I bought Mooney to go fast so down low (5,000 feet) I'm burning 11.5GPH at 25 squared.  At 7,000 POH says 10.5.  That is about right for my Mooney.  A gallon of fuel to fly 150 knots and get there quicker...hopefully burning LESS fuel doing it.  Unless you are sacrificing speed (fine if your local/in no hurry) you are NOT going to see 9GPH without doing above...

[Hank]

Quote: jpusser

Just bought a 62 c model and wanted to get thoughts on a few things.  Every where I researched said the c would burn about 9 gph but I can't get it below 11gph.  I normally fly at 055 or 065.  Any Ideas?

[KLRDMD]

Quote: Hank

[scottfromiowa]

Ken,

With respect...Stop with the anti 50 degrees ROP "warnings, caviots, ;<) signs etc.  The planes are rated to fly with this internal temp/pressure to TBO.  There is NOTHING prohibiting this operation.  I/We understand how you feel about this setting.  I find it to be a good balance between performance and economy and my cylinder temps are all 350 or below.  In my M20E I am FINE with this setting...

[danb35]

Quote: scottfromiowa

I/We understand how you feel about this setting.

[scottfromiowa]

Dan:

I have read and read and read Ken's comments and warnings to those who decide to run at 50 degrees rich of peak, that is what I am refering too regarding feelings, nothing more than feelings....  I get it.  Pressure is highest there.  I get it.  Might possibly prevent my engine from getting to 3,000 hours.  I get it.  What else have ya got?

[scottfromiowa]

Science and fact says the earth is getting warmer.  It's the why/how and what will change this...if anything (man does) that makes me take exception...but that's another topic for another forum.

[KSMooniac]

Actually, there is data that shows the earth getting cooler since 1998.    

ROP/LOP and what the temps and pressures are at 50 ROP are much easier to debate than climate change since there is bonefied data that is known to all, and can be measured.  Lycoming and TCM (and the airframers) have a huge dis-incentive to re-write their op specs because it becomes a tantamount admission to publishing bad info long ago, which could expose them to lawsuits, or even reset the 18 year liability term that was limited by the '94 legislation.

[scottfromiowa]

I've never been much of a conspiracy theorist.  I choose NOT to believe that an OEM engine company that is focused on improvement, would not modify practices that would see more success with their product by its users.

[scottfromiowa]

I don't mind debate, but like politics I get sick of the same commercial over and over again.

[DaV8or]

Being a new owner, I too have wrestled with the where do you put the engine controls and who do you believe dilemma. I found solace in the fact that almost everyone agrees that if you run your engine at 65%, you pretty much can't hurt your engine, so put the mixture where ever you like. For now, I'm choosing 100 ROP until I can grill some more people on the subject. I still get 10gph and that's OK.

[KLRDMD]

Quote: scottfromiowa

With respect...Stop with the anti 50 degrees ROP "warnings, caviots, ;<) signs etc.  The planes are rated to fly with this internal temp/pressure to TBO.  There is NOTHING prohibiting this operation.  I/We understand how you feel about this setting.  I find it to be a good balance between performance and economy and my cylinder temps are all 350 or below.  In my M20E I am FINE with this setting...

[jpusser]

The fuel burn is calculated only by filling the tank.  The mixture is set by leaning to rough and then back in till smoth.  The engine has about 1900 hrs with 700 since toh. I generally set the prop at 2500 and throttle to the wall at 4500 or above. I am averaging 11 gal on 3 hr trips not around the pattern. I am going to add an egt and fuel computer soon.

Any ideas on the other questions?

A note to others please leave your differances to your post or qestions. 

[carusoam]

Jpusser,

Check your POH for the chart of fuel flow vs. manifold pressure (MP) at your chosen rpm.

I am thinking that the 9gph that you researched is at a reduced power setting.

the 11gph that you are experiencing is related to a higher power setting (full throttle, 2500 rpm, at 5,500 ft).

What does your POH say?

My M20C experience showed that I would measure/calculate slightly less than 10gph at full throttle, 2400 rpm at 11,500 ft.  This was using the similar leaning technique and fuel measurement that you have described.  Start, taxi and Climbing were on other tank and removed from the calculation.

You will find that power setting can greatly increase your fuel flow rate.  With this set-up, it is diificult to to accurately measure fuel flow while flying.  Fuel flow gauges have become very popular in recent years.

See the following authoritive article:

http://www.mooneypilots.com/mapalog/M20C%20Evaluation/M20C_Evaluation_Report.html

"the M20C should always give true airspeeds between 142 and 146 knots below 8000 feet and right at 140 knots nearing 10000 feet. Fuel burn rates at 50 degrees rich of peak should be right at 11.5 gallons per hour down low and 9.5 gallons per hour up high. Remember, these numbers are for the most efficient cruise power setting - full throttle, 2500 RPM, leaned to peak plus 50 degrees rich, cowl flaps closed."

Best regards,

-a-

[scottfromiowa]

Ken,

I have read all the discussion on the MAPA site regarding LOP.  I enjoy the read.  I DON'T disagree with the benefits of LOP operation.  I have tried to educate myself.  I thank you and others for this.  It's the continued "warnings" about flying 50 ROP that I take exception too.  When I drive my car I rarely accelerate hard from the light and tach the RPM to yellow, but my car can do this and it's fun sometimes...

Original POH's had VERY LITTLE guidance regarding mixture settings with regard to power...as there were not multi-probe EGT Cylinder devices being sold in the 60's.  Instead of debating can someone just give me a graph at different altitudes (5,000; 7,000; 10,000)  that shows Peak, 50 LOP, 50 ROP, 100 ROP with horsepower, fuel burn, exhaust temp and MP? IO-360 engine.

Thanks

Original poster-As Carusoam says...and I said: at that power setting and RPM at that altitude you are NOT going to see 9.0GPH in your Mooney.  Check out your POH.  I leaned the same way you are and found that (when I got a multi probe device) I was between 50 and 100 LOP.  I had to enrich quite a bit to achieve PEAK and more to get ROP.  I am still learning too.  Sorry for the thread creep and discussion...

[DanM20C]

Quote: jpusser

The fuel burn is calculated only by filling the tank.  The mixture is set by leaning to rough and then back in till smoth.  The engine has about 1900 hrs with 700 since toh. I generally set the prop at 2500 and throttle to the wall at 4500 or above. I am averaging 11 gal on 3 hr trips not around the pattern. I am going to add an egt and fuel computer soon.

Any ideas on the other questions?

A note to others please leave your differances to your post or qestions. 

[DaV8or]

Quote: jpusser

The fuel burn is calculated only by filling the tank.  The mixture is set by leaning to rough and then back in till smoth.  The engine has about 1900 hrs with 700 since toh. I generally set the prop at 2500 and throttle to the wall at 4500 or above. I am averaging 11 gal on 3 hr trips not around the pattern. I am going to add an egt and fuel computer soon.

Any ideas on the other questions?

A note to others please leave your differances to your post or qestions. 

[MARZ]

My first real trip with my 67 F was from Texas to Wisconsin this year - I stopped halfway in Missouri for a planned bio break and fuel.  The first fuel stop averaged out around 12 gph.  

Knowing we should be getting better the second half we paid more attention to the throttle setting - instead of firewalling the throttle we retarded it to where the indicated MP just started to decline at altitude, leaned till rough and enrichened (EGT was inop at the time)   ran at 2400 rpm.  The second fill up gave us an average in the upper 9's 

I have the exacts logged but this is pretty close..

[planebones]

Have someone run an optical tachometer on your plane (can buy one at Aircraft spruce).  If your tach is reading slow you will be very impressed with your ol' Mooney's speed but will be burning lots of fuel.  Your Man. pressure guage should read barometric pressure minus one inch for each 1000' above sea level (more or less) when sitting on the ground engine off....If it is way off from that you may be pulling more pressure than the guage reads and thus more fuel burn....My  plane reads 75RPM slow....I placard it and adjust accordingly...I live at high altitude and always fly above 10k density alt.  & still seem to burn and average of 9gph..Ken McCune  A&P/IA   65 M20-C  N7851V