Surefly Before/After TAS and Mpg Data

[Ragsf15e]

Let me start by saying I'm not sure the data is clear enough to make any broad conclusions about the Surefly Mag on my M20F.  However, I'll post some graphs I made showing LOP TAS and LOP Mpg from before and after installation.  The "before" data are from speed runs from the last 3 years.  The "SF" data are all from this winter.  The power settings were all ~15 LOP except at very low (~6,000') where I needed to be a bit leaner.  The weights and CG aren't necessarily the same, so that may cause problems.  All the data is from my WAAS GPS, JPI 930 and 3 way speed runs to compute TAS.

My own conclusions - It starts almost like a car.  Runs smoother (slightly).  Could go deeper LOP if I wanted (fuel savings?).  And maybe, just maybe, the data indicates a few more knots when LOP at higher altitudes.  ROP looks just about like no change from before the SF Mag.

Thoughts?

LOP TAS vs Density Alt

lop TAS.pdf

 

LOP Mpg vs Density Altitude

lop mpg.pdf

 

ROP TAS

rop TAS.pdf

 

ROP Mpg

rop mpg.pdf

[McMooney]

You make me feel like a slacker, I should really keep better records.

 

I only really noticed it starts better and goes further LOP.  25 is easy. 

made it from KGTU to KDWH in 9 gallons sunday,  fuel flow meter read about 8.2gph the whole way

[Ragsf15e]

52 minutes ago, McMooney said:

You make me feel like a slacker, I should really keep better records.

 

I only really noticed it starts better and goes further LOP.  25 is easy. 

made it from KGTU to KDWH in 9 gallons sunday,  fuel flow meter read about 8.2gph the whole way

Yeah it’s definitely smoother lop.  I think you have to be pretty high altitude to see the benefits from advancing timing.  Not sure you’ll go that high on a short Texas leg like that, but try 10,500’ one day.  It’s definitely advanced timing there.

Also, if you’re going further lop than before, you might save fuel, but probably won’t be faster.  My speed runs were on the same lop setting (15 degrees).

Only thing I don’t like is my inability to do an inflight mag check without a bang/afterfire.

[MikeOH]

@Ragsf15e Curious about your methodology for establishing the error bars.

Thanks!

[McMooney]

1 hour ago, Ragsf15e said:

Yeah it’s definitely smoother lop.  I think you have to be pretty high altitude to see the benefits from advancing timing.  Not sure you’ll go that high on a short Texas leg like that, but try 10,500’ one day.  It’s definitely advanced timing there.

Also, if you’re going further lop than before, you might save fuel, but probably won’t be faster.  My speed runs were on the same lop setting (15 degrees).

Only thing I don’t like is my inability to do an inflight mag check without a bang/afterfire.

I was honestly trying to save all the $2.60 gas i could 8), not so much worried about speed.  plus in these times, the girl needs all the flying i can give her 

[MikeOH]

Just rebuilt both mags at annual this past January.  I thought briefly about an E-mag but went traditional.  This data based thread makes me feel like I didn't make a huge mistake; maybe gave up easy starting.  But, I've only had a couple of hard hot starts...never ran a battery down.  And, I've got my hot start procedure pretty dialed in, now

[McMooney]

my mags were coming up on 500 hrs, so i swapped 1 for the surefly just to be rid of the overhaul req.

unfortunately still have to overhaul the other 

[Ragsf15e]

1 hour ago, MikeOH said:

@Ragsf15e Curious about your methodology for establishing the error bars.

Thanks!

Mike, I wish I had a proper statistical method for figuring the error bars, but I don’t.  I do know that my gps GS will slowly fluctuate +\-2 knots or so over a couple minutes even if I’ve stabilized so I just picked that.

 Sorry I don’t have a better answer.

Rags

[Ragsf15e]

1 hour ago, McMooney said:

my mags were coming up on 500 hrs, so i swapped 1 for the surefly just to be rid of the overhaul req.

unfortunately still have to overhaul the other 

Same reason for my install.

[MikeOH]

Just now, Ragsf15e said:

Mike, I wish I had a proper statistical method for figuring the error bars, but I don’t.  I do know that my gps GS will slowly fluctuate +\-2 knots or so over a couple minutes even if I’ve stabilized so I just picked that.

 Sorry I don’t have a better answer.

Rags

Nothing wrong with that answer!

Thanks

[carusoam]

Great details Rags!

We need somebody with big data statistics capability.... 

Best regards,

-a-

[FloridaMan]

Says every job description from companies that don’t understand data. 

[wishboneash]

19 hours ago, Ragsf15e said:

Let me start by saying I'm not sure the data is clear enough to make any broad conclusions about the Surefly Mag on my M20F.  However, I'll post some graphs I made showing LOP TAS and LOP Mpg from before and after installation.  The "before" data are from speed runs from the last 3 years.  The "SF" data are all from this winter.  The power settings were all ~15 LOP except at very low (~6,000') where I needed to be a bit leaner.  The weights and CG aren't necessarily the same, so that may cause problems.  All the data is from my WAAS GPS, JPI 930 and 3 way speed runs to compute TAS.

My own conclusions - It starts almost like a car.  Runs smoother (slightly).  Could go deeper LOP if I wanted (fuel savings?).  And maybe, just maybe, the data indicates a few more knots when LOP at higher altitudes.  ROP looks just about like no change from before the SF Mag.

Thoughts?

 

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.

[Ragsf15e]

5 hours ago, 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.

Interesting, did you change the wiring so it starts on both mags?  Normally they only start on the left mag.

Ive had to get pretty high altitude to notice the tiny bit of speed difference, and it’s only lop.

[Andy95W]

15 minutes ago, Ragsf15e said:

 

Ive had to get pretty high altitude to notice the tiny bit of speed difference, and it’s only lop.

This makes me wonder if the variable timing is worth doing on a carbureted engine like in the M20C.  It would be a simpler installation as well without the MP hookup.

[Ragsf15e]

17 minutes ago, Andy95W said:

This makes me wonder if the variable timing is worth doing on a carbureted engine like in the M20C.  It would be a simpler installation as well without the MP hookup.

The MP hookup is pretty simple though.  The battery is more work unless you’ve got your battery in the front still.  

I can see your point if you’re not going to run lop, but it’s probably worth installing the MP just to see if it helps it run lop - doesn’t mean you have to fly like that all the time.  

[Bob - S50]

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.

Let me create an advance summary below:

RPM  2400  2500  2600  2700

MP

25"     0    0     0      0

23-25"  4.5  4.5   4.5    4.5

22-23"  9    9     9      9

21-22"  12   13.5  13.5   13.5

21"     12   13.5  15     16.5

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'+.

[Ragsf15e]

1 hour ago, 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.

Let me create an advance summary below:

RPM  2400  2500  2600  2700

MP

25"     0    0     0      0

23-25"  4.5  4.5   4.5    4.5

22-23"  9    9     9      9

21-22"  12   13.5  13.5   13.5

21"     12   13.5  15     16.5

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'+.

All my speed tests are done wide open throttle, ram on, 2500 rpm.  What you’re saying definitely makes sense.  I start to see the improvement (slight) above about 8000’ or so and it seems to increase with altitude.  I need more data to say it’s real though.

[carusoam]

Our 1930s tractor engines are so efficient... it is going to be hard to eke out a few percentage points more...

Running LOP is a big chunk of efficiency boost...  so is leaning in general...

This benefit is at the end of the burn cycle... get all the fuel burned before it exits the exhaust valve...

 

Getting the mixture started on Fire is at the beginning of the burn cycle...this is what the electronic mag seems to be doing well...

These two benefits also seem to be independent of each other...

They both try hard to get all the fuel burned before exiting the exhaust valve...

without starting the burn too quickly... as in setting the timing too far forwards...

 

With a better controlled burn... it would be great to take advantage of the advanced timing under lower power Settings...

The carb’s main challenge is uneven fuel/air mixtures going to each cylinder...

Aside from that... the operation of the O360 is expected to be improved as would an IO360...

Just... it can’t improve the wider GAMI spread any... this happens before the ignition system is involved...

It will be interesting to see how lean the O360 can go while using the electronic mag... is there an improvement....(?)

This will be an interesting observation...

Keep the data coming...

Best regards,

-a-

[Bentonck]

So this is basically a win/win?  Easier starting & better LOP operation?  Sign me up!

[aviatoreb]

32 minutes ago, Bentonck said:

So this is basically a win/win?  Easier starting & better LOP operation?  Sign me up!

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.

[carusoam]

3 hours ago, Bentonck said:

So this is basically a win/win?  Easier starting & better LOP operation?  Sign me up!

Just check the paperwork to see if your engine is on their list...

The number of engines has been increasing quickly...

PP thoughts only, not a mechanic...

Best regards,

-a-

[Bob_Belville]

And then there's the reliability factor. The EI has no 500 hours inspection... no moving parts. 

[Ragsf15e]

9 hours ago, Bentonck said:

So this is basically a win/win?  Easier starting & better LOP operation?  Sign me up!

With a turbo you can’t currently use the timing advance function, but yeah, it’s approved for most engines/airframes.  Maybe they’ll eventually get advanced timing on turbos?

[David Lloyd]

At least two reasons the advanced timing feature won't be approved for a turbo engine: the turbocharger increases the manifold pressure to where the SIM would not advance the timing anyway. More importantly, at high altitude if the SIM loses the manifold pressure reference it would see ambient pressure (low at high altitude) and would advance the timing.  A scenario that could involve getting new fixed timing mags to go with your new engine.  They explain this on the Surefly site, might require some digging.