Surefly Fired Spark Plugs Darker?

[A64Pilot]

Just now, N201MKTurbo said:

I hate to be a nit picker (well, maybe) but a hot plug causes pre-ignition not detonation. Pre-ignition may cause detonation.

Your correct, but both result in a destroyed piston. I believe it’s simply pre-ignition, not detonation

[Yetti]

14 minutes ago, A64Pilot said:

Don’t run a hotter plug, a hot plug can cause detonation. a cold plug will foul but cause no damage, so if anything err towards cold.

 

Simmer down.  Running a hotter plug was said in jest as there is probably not a hotter plug certified for the engine.

[N201MKTurbo]

11 minutes ago, A64Pilot said:

Your correct, but both result in a destroyed piston. I believe it’s simply pre-ignition, not detonation

Per-ignition can cause the fuel charge to ignite well ahead of when the spark would fire. This causes the fuel charge to burn and expand while the piston is still compressing. This can raise the cylinder pressure beyond the detonation pressure. The same as a severely advanced spark.

[Browncbr1]

Check that your surefly and mag are timed properly together.  Also, sureflys run best with gapping the plugs about twice as wide as regular mags.  ~.032”.  Some guys go way wider than that even.  
 

 

[Ragsf15e]

11 hours ago, Browncbr1 said:

Check that your surefly and mag are timed properly together.  Also, sureflys run best with gapping the plugs about twice as wide as regular mags.  ~.032”.  Some guys go way wider than that even.  
 

 

I think you’re on to something.  When we checked timings, mag was at 26 degrees, supposed to be at 20.  SF is set to 20.  Plugs are all gapped the same.  Between those two things you’re probably getting close.

[carusoam]

Some Mooney IO360s use 25° BTDC…

This timing gets a little better efficiency before letting the burning exhaust out of the valve….

The result is a higher CHT… comes along with that…

 

Some electronic mags initiate the flame front so nicely with their stronger spark…. It has a similar affect… the fuel is completing its burn better… before the valve opens….

Advancing the timing even more and going to 26° BTDC… that is going into an experimental area….

When bad stuff occurs inside the engine… it is often based on many environmental factors… Advancing the timing may not do it on its own… but, it is taking away the margin of safety that is built in…

 

What we can do to check timing normally….

A good run up and an engine monitor….

If you take your time allowing the EGTs to stabilize and stop climbing… you can compare the EGT graphs of one mag vs the other

When they are identical… so is their timing.  If one is taller than the other, the tall one is delayed… and more fuel is burning as it goes out the valve….

Comparing a regular mag with an electric one is hard to do… (for me)

PP thoughts only,

-a- 

[PT20J]

1 hour ago, Ragsf15e said:

I think you’re on to something.  When we checked timings, mag was at 26 degrees, supposed to be at 20.  SF is set to 20.  Plugs are all gapped the same.  Between those two things you’re probably getting close.

6 degrees off is a lot. Of course it’s possible someone incorrectly set it to 25 and it’s only one degree off. But if it really slipped 6 deg, I might IRAN the mag.

[Browncbr1]

13 hours ago, Ragsf15e said:

I think you’re on to something.  When we checked timings, mag was at 26 degrees, supposed to be at 20.  SF is set to 20.  Plugs are all gapped the same.  Between those two things you’re probably getting close.

From my experience, 20 degree timing causes all the problems you have.   The performance is noticeably less and plugs foul easily.   Go to 25 degrees and you will be happy.  26-27 is even better according to One MSC.  Do not use surefly advancing.  It’s a gimmick for people who want to fly low power at low DA.  If you fly over 5 or 6000 regularly, then the advancing will cause big problems in your climb above those altitudes.  
 

I’ve been happy with putting all surefly leads on bottom plugs and widen gaps to  .032-.034 with fixed 25 degree timing.  

Edited January 20, 2022 by Browncbr1

[Ragsf15e]

20 hours ago, PT20J said:

6 degrees off is a lot. Of course it’s possible someone incorrectly set it to 25 and it’s only one degree off. But if it really slipped 6 deg, I might IRAN the mag.

It did slip a lot, my IA said it was a lot too.  The mag was overhauled about 175 hours ago and he attributed it to the points wearing in.  Retimed it and good to go.  I’m gonna try to fly it tomorrow.  Much better than pulling and/putting in screws under the belly all day!

[Ragsf15e]

9 hours ago, Browncbr1 said:

From my experience, 20 degree timing causes all the problems you have.   The performance is noticeably less and plugs foul easily.   Go to 25 degrees and you will be happy.  26-27 is even better according to One MSC.  Do not use surefly advancing.  It’s a gimmick for people who want to fly low power at low DA.  If you fly over 5 or 6000 regularly, then the advancing will cause big problems in your climb above those altitudes.  
 

I’ve been happy with putting all surefly leads on bottom plugs and widen gaps to  .032-.034 with fixed 25 degree timing.  

I’m not sure if I agree with the SF causing problems above 6000’.  I’m always above 6,000’ and mine has been great.  I’ve had it as high as 15,500 in my na IO-360.  I agree there’s not much Performance gain, but I certainly haven’t noticed any cht or other issues.

[PT20J]

25 minutes ago, Ragsf15e said:

It did slip a lot, my IA said it was a lot too.  The mag was overhauled about 175 hours ago and he attributed it to the points wearing in.  Retimed it and good to go.  I’m gonna try to fly it tomorrow.  Much better than pulling and/putting in screws under the belly all day!

Maybe. But the mags are supposed to be designed so that the wear on different parts approximately cancels out. Also, there are two timings: mag to engine and internal (E-gap). If the points wear it will change the internal timing. You can get the spark to fire at the right crankshaft angle by bumping the engine to mag timing, but if the E-gap is off the spark will be weak. Did your IA reset the E-gap? 

I believe @EricJ has posted about his experience working on his own mags and may have some thoughts.

Skip

[Ragsf15e]

22 minutes ago, PT20J said:

Maybe. But the mags are supposed to be designed so that the wear on different parts approximately cancels out. Also, there are two timings: mag to engine and internal (E-gap). If the points wear it will change the internal timing. You can get the spark to fire at the right crankshaft angle by bumping the engine to mag timing, but if the E-gap is off the spark will be weak. Did your IA reset the E-gap? 

I believe @EricJ has posted about his experience working on his own mags and may have some thoughts.

Skip

Ill have to ask that when I see him tomorrow.  Thanks for the input!

[Ragsf15e]

25 minutes ago, PT20J said:

Maybe. But the mags are supposed to be designed so that the wear on different parts approximately cancels out. Also, there are two timings: mag to engine and internal (E-gap). If the points wear it will change the internal timing. You can get the spark to fire at the right crankshaft angle by bumping the engine to mag timing, but if the E-gap is off the spark will be weak. Did your IA reset the E-gap? 

I believe @EricJ has posted about his experience working on his own mags and may have some thoughts.

Skip

He did mention having to open it up, not sure if that means he did the internal?

[PT20J]

13 minutes ago, Ragsf15e said:

He did mention having to open it up, not sure if that means he did the internal?

If it is a Slick, I believe you need to open it to insert a tool to set the E-gap which I believe is actually an adjustment of the point gap. 

[EricJ]

19 hours ago, Ragsf15e said:

He did mention having to open it up, not sure if that means he did the internal?

Setting internal timing (e-gap) on a Slick is pretty easy if you have the little lock tool.   Even just initially setting timing you need to take the harness off to align the gear to #1 cyl, so he may have just been doing that, too.   Slicks are way easier to work on than Bendix mags, imho.   This does sound kinda strange, though.

 

[Ragsf15e]

4 hours ago, EricJ said:

Setting internal timing (e-gap) on a Slick is pretty easy if you have the little lock tool.   Even just initially setting timing you need to take the harness off to align the gear to #1 cyl, so he may have just been doing that, too.   Slicks are way easier to work on than Bendix mags, imho.   This does sound kinda strange, though.

 

So I spoke to him today.  Terminology may be slightly different, but I think he didn’t set the “internal” timing, just the mag to airplane timing.  He described it as the internal parts wearing in and him resetting the engine to mag timing to match that.  I’m only a lowly pilot, so I nodded and smiled and went flying.  It ran strong and smooth, mag check was even now before flight where previously it only dropped about 20rpm on the slick mag due to the timing being advanced.   Gami spread was 0.2ish at 10,500.  Annual is done in one week!  And I’ll keep an eye on the mag.