Surefly Before/After TAS and Mpg Data

[Hank]

On 4/28/2020 at 7:29 PM, Bob - S50 said:

Somebody over on the Cessna forum posted the timing schedule for the Surefly.  Since you are talking about increase in speed, I assume we are talking about cruise power settings.  Let's say 2400 RPM or higher.  Assuming you have an engine timed to 20 BTDC and if I read it correctly, there is zero advance until your MP is below 25".  That's about 4000 - 5000'.  Higher if you are using RAM.

. . .

Also, for lower power settings, it appears you will never get any advance with RPM below 1600.  It also appears that the maximum advance increases by 1.5 degrees for every 100 increase in RPM.  And as you can see you get the most advance (benefit?) at high RPM and low MP.  That makes sense because both of those conditions tend to cause the peak pressure to move further past TDC.

So to see much increase in efficiency I would expect you need to be cruising up around 8000'+.

isn't that where we all fly our Moopneys anyway? The only time I'm lower is on short hops; even the 40-min flight to KFFC on a Spruce run, I'm generally at least 7500 outbound / 6500 on the return.

[wishboneash]

On 4/28/2020 at 10:40 AM, wishboneash said:

I have a very similar experience. I get the engine to start on the first crank now. I see a 10-20 rpm drop on the mag check on the Surefly. I don't see much difference in speeds except it is runs LOP better. I switched out the right mag with the Surefly and overhauled the left mag.

I believe there's a jumper you can remove in the starter switch to enable the right mag (Surefly in this case) to be used while starting. I have yet to check the LOP operations above 8,000 ft to check performance.

[Bob - S50]

2 hours ago, Hank said:

isn't that where we all fly our Moopneys anyway? The only time I'm lower is on short hops; even the 40-min flight to KFFC on a Spruce run, I'm generally at least 7500 outbound / 6500 on the return.

Not me.  Up to 300 miles I don't save any gas by going high and I only save a couple minutes (no wind).  I pick my  altitude based on terrain, then ride, and finally wind.  For flights under an hour I usually fly somewhere between 3500 and 5500.

[aviatoreb]

Total cost = sum of all the costs that matter to me.

fuel cost = cost 1

comfort = cost 2

safety = cost 3 - and for me this may mean flying higher than fuel optimal - eg over mountains.  I have been doing this for years, and 2 years ago - that practice saved my bacon.  I had a engine out emergency and flying high gave me options and it worked out to a lovely runway landing.  Luck by design.

So just like I purchase insurance which has a dollar cost.  I fly higher than minimal for fuel savings, and I am happy with the investment.  I fly to ten thousand feet when crossing my local mountains to Burlington on a 25 min flight when there are 4000 ft routes (around the peaks) which will work.

Total cost = cost 1 + cost 2 + cost 3 > cost 1 alone.  But it is total cost that matters to me.

Edited May 2, 2020 by aviatoreb

[Browncbr1]

It seems to me that the typical sweet spot DA for peak and LOP operations of the surefly is about 2k’ higher than conventional mags..   does that ring true to you guys?    

[Ragsf15e]

12 hours ago, Browncbr1 said:

It seems to me that the typical sweet spot DA for peak and LOP operations of the surefly is about 2k’ higher than conventional mags..   does that ring true to you guys?    

Seems reasonable.  
 

I don’t really know where the sweet spot is for traditional mags - just need to be lop enough to stay out of the “red box”/ detonation when you’re at low altitude and high power.

However, the SF does seem to make more of a difference at altitudes where I was use to losing power and speed more rapidly as I leaned.  Say above 8500 or so.

Funny thing is I did all those lop speed runs and graphs, but I typically fly ROP to get the 5 extra knots because I’ve got two 4 year old terrorists in the backseat!

[carusoam]

Mr. Brown,

See if you can help me understand what you mean by sweet spot... and how the SureFly changes it...

There are a couple of things going on at the same time...
 

How are we defining the sweet spot for LOP operations...?

For an NA engine...

0) Avoiding the red box/fin defined by 65% bhp... is generally above 8k’... check your engine chart in your POH to see what altitude that is...  MP @65% bhp...

1) There is a sweet spot for power vs. drag... aka best speed... near 8k’ msl.... below is more power, above is less drag...

2) For deep LOP operations lower than 8k’ is better... how deep do you want to go, 90dF?  Lower is better to go deeper LOP...

3) Effects of a cleaner spark, compliments of a SureFly mag, or is this related to the mag’s advanced timing?

4) At what MP does the timing advance..?  More of a direct question of a set point and how the device works... still not a sweet spot...

5) The Mag won’t know where the mixture knob is... with somebody else paying for fuel... ROP may be the sweet spot for high speed ops...

6) I’m a fan of being very high (altitude = safety)... just short of O2 altitudes... WOT... and cool CHTs... and very slightly LOP... that would be the sweet spot for me...

7) I would be looking forward to having an electronic mag with a stronger spark to improve the fuel burn...

8) Following up with adjusting the timing further BTDC... is great the lower the MP is...(engine safety)

9) Sweet spot sort of implies going higher or lower, something gets worse...

10) The sweet spot for NA planes is around 8k’ because MP is still good and drag isn’t that bad... higher, the power drops out... lower the drag increases...

11) for most power LOP... 

• First be flying LOP...
• WOT... for max power available...
• Adjust mixture to allow the most fuel to be burned, yet not wasted by any cylinder going ROP...
• Select timing to be as advanced as the engine allows... following the Airframe manufacturer’s recommendation, or STC...

12) So... I don’t think we’re discussing a ‘sweet spot’ as much as we are discussing an MP to be avoided while experimenting with LOP safely...   Or what MP allows the mag timing shift...

Always share JPI data so other people can share what you are seeing...

PP thoughts only, not a mechanic... probing for more detail.

Best regards,

-a-

 

[Browncbr1]

10 hours ago, carusoam said:

Mr. Brown,

See if you can help me understand what you mean by sweet spot... and how the SureFly changes it...

There are a couple of things going on at the same time...
 

How are we defining the sweet spot for LOP operations...?

For an NA engine...

0) Avoiding the red box/fin defined by 65% bhp... is generally above 8k’... check your engine chart in your POH to see what altitude that is...  MP @65% bhp...

1) There is a sweet spot for power vs. drag... aka best speed... near 8k’ msl.... below is more power, above is less drag...

2) For deep LOP operations lower than 8k’ is better... how deep do you want to go, 90dF?  Lower is better to go deeper LOP...

3) Effects of a cleaner spark, compliments of a SureFly mag, or is this related to the mag’s advanced timing?

4) At what MP does the timing advance..?  More of a direct question of a set point and how the device works... still not a sweet spot...

5) The Mag won’t know where the mixture knob is... with somebody else paying for fuel... ROP may be the sweet spot for high speed ops...

6) I’m a fan of being very high (altitude = safety)... just short of O2 altitudes... WOT... and cool CHTs... and very slightly LOP... that would be the sweet spot for me...

7) I would be looking forward to having an electronic mag with a stronger spark to improve the fuel burn...

8) Following up with adjusting the timing further BTDC... is great the lower the MP is...(engine safety)

9) Sweet spot sort of implies going higher or lower, something gets worse...

10) The sweet spot for NA planes is around 8k’ because MP is still good and drag isn’t that bad... higher, the power drops out... lower the drag increases...

11) for most power LOP... 

• First be flying LOP...
• WOT... for max power available...
• Adjust mixture to allow the most fuel to be burned, yet not wasted by any cylinder going ROP...
• Select timing to be as advanced as the engine allows... following the Airframe manufacturer’s recommendation, or STC...

12) So... I don’t think we’re discussing a ‘sweet spot’ as much as we are discussing an MP to be avoided while experimenting with LOP safely...   Or what MP allows the mag timing shift...

Always share JPI data so other people can share what you are seeing...

PP thoughts only, not a mechanic... probing for more detail.

Best regards,

-a-

 

Good point.  Sorry I didn’t share my idea of sweet spot.   For my F with the top prop, I have found that I get best TAS at 65% leaned to 0-10 LOP between 8-10k feet.   I always pick 9k if more than 45 minutes enroute.  In the hot summer, I’ll just make sure 10k doesn’t get too high DA for a headache, which often means I go at 8k if not over terrain.     I’ve flown my F at 12k once before and fuel burn was less, but I had to increase rpm to maintain TAS..  after a short while, the higher rpm starts pounding my head.   There is the oxygen issue too, but even down low, I don’t run higher rpm except for climb.  100rom makes a big difference in noise level.

I always climb to where WOT gives me 21-23”...  and I set rpm 2450-2300 respectively to maintain key number of ~46.   I target to run my richest cylinder (#1) right at peak. See attached picture, 152ktas at 9000...  look at JPI settings with cool temps.

I see TAS drop off pretty quick with these power settings below 7k.   At 6k, my F is 5-10kts slower at the same power setting, which means I have to run it harder to get the same TAS.  

So, I was thinking my sweet spot is 8-10k feet with my slick mags at 25DBTDC, but sounds like it might be more like 10-12k feet with surefly???

Edited May 3, 2020 by Browncbr1

[Browncbr1]

I was just killing time on my phone today sitting outside..  I visited aircraft spruce to see if any deals are going on and the first thing that came up was 15% off on surefly ignition systems.    So I just bought one figuring it will go on at August annual when my mags are right at 500hrs.   What the heck, bought a new Concorde axc too! Happy birthday to myself!

[podair]

I fly my M20F pretty much exactly the same way as Mr Brown... mine is probably a tad slower but solid 140ktas... stock 1967 F with harzell 3 blade.

I use the Mooney to fly to our house in France on a regular basis from the UK, and tend to always fly the same route/altitude. My typical route is around 350nm, of which 30min over water from UK to France or when I was living in Spain over mountains, so I tend to like to fly relatively high. 

Over the last dozen years and 1200hrs I also find that the ideal is 8k-9k feet leaned at 33litres (8.75 gal/h) at peak/slightly lop giving me 145kts, map around 22 and 2500 rpm (46 key number). Very often fly at 10k due to the airway structure here and 32 litres (8.5) there gives me 143kt, map dropping to 21 (with boost on) . I have O2 so sometimes fly higher due to weather and it is pretty happy 12-13k and slightly higher, but at the cost of some speed where I'd struggle to get over 140kt tas for 30-31 litres. So roughly 1litre (.25 gal) for 2k feet. Double the litre/hour and you get % hp. These numbers are so consistent that I was once getting 5kt less and wondered what was wrong. Turns out the step had not retracted as the tube to the vacuum had come loose.

I could lean probably a tad more LOP but it quickly sounds a bit unhappy. Will look into the Surefly next time the mag inspection comes up, the Electroair is also an option.

[Will_TX]

On 4/30/2020 at 2:42 PM, aviatoreb said:

In my case, in my engine, the surefly has been night and day regarding LOP ops.  Lean of peak was simply not a reasonable option for me before, and now it seems to be a terrific option.  It was a night and day change of how my engine seems to behave.  This new option is still new for me but I seem to be able to run nicely, and very cool, and smooth across a wide range of settings saving between roughly 3 to 4 gallons per hour depending on the setting.  Very pleased.

We recently added the Surefly to our 1967 F model.  We are still experimenting with LOP operating which we were very hesitant to try before.   At altitude  running 100 ROP it seems our cylinders & oil temps are elevated more than usual and enriching the mixture running extra rich doesn't seem to help with cooling like it used to.   Running ~50 LOP the engine seems to be much happier.   The cylinders were at least 20-30 degrees cooler and oil Temps 25-35 degrees cooler.   The engine ran smoothly & we reduced fuel burn in cruise to 7 GPH at 12000 ft.  Flew non stop 5 hours from Northern Kansas to the Houston Texas area and burned only 40 gallons of our 64 on board!  We do have a JPI engine monitor to monitor each cylinder,  each EGT, and precise fuel flow.  

Like I said we are still getting used to it,  but I'm really excited about the fuel savings and efficiency. 

Oh and it starts like a car now even on those intermediate hot starts.  Yes we had it wired to start on both the Surefly and magneto.

[carusoam]

Welcome aboard Will…

You might try to find a more recent thread for the latest in Surefly discussions…

And some older threads for the basics of LOP….  

Either way….  M20F, Surefly, and LOP… go perfect together…

When you get a chance… add some data and a pic to your avatar area…

Best regards,

-a-

[Ragsf15e]

40 minutes ago, Will_TX said:

We recently added the Surefly to our 1967 F model.  We are still experimenting with LOP operating which we were very hesitant to try before.   At altitude  running 100 ROP it seems our cylinders & oil temps are elevated more than usual and enriching the mixture running extra rich doesn't seem to help with cooling like it used to.   Running ~50 LOP the engine seems to be much happier.   The cylinders were at least 20-30 degrees cooler and oil Temps 25-35 degrees cooler.   The engine ran smoothly & we reduced fuel burn in cruise to 7 GPH at 12000 ft.  Flew non stop 5 hours from Northern Kansas to the Houston Texas area and burned only 40 gallons of our 64 on board!  We do have a JPI engine monitor to monitor each cylinder,  each EGT, and precise fuel flow.  

Like I said we are still getting used to it,  but I'm really excited about the fuel savings and efficiency. 

Oh and it starts like a car now even on those intermediate hot starts.  Yes we had it wired to start on both the Surefly and magneto.

Good to hear it’s mostly working well for you.  I haven’t had much trouble ROP or LOP keeping the engine cool enough until it was super hot in the NW last week, then I had about as you described.  Typically 100 ROP is about 10 degrees hotter chts than before which is just fine.  I’d recommend looking at your baffles and making sure they are in good shape.