More information about Surefly SIM electronic ignition

[svyolo]

That also explains the new prop. How do you like the new prop so far?

[Battson]

That also explains the new prop. How do you like the new prop so far?

....and the new wing skins and rudder.... never do things by halves!

Composite props are hard to compared with metal props. Chalk and cheese.

Advantages I notice straight away:

• They spin up and down RPM much more quickly, and so accelerate the aircraft faster as a result
• They act as a better brake too. Pushing the blue knob full forward at 20" MAP means you're left leaning on your safety belt as the plane slows down.
• I find I need more power on short finals too, or the plane drops in hard. This is a good tool to have in the bag.
• The lighter weight means there is a lot less vibration too, smoother ride for sure. I really notice that.
• The aesthetic lines of a composite prop look better every single time too, for me. The designers can do more with the materials.
• It might be slightly quieter too, hard to notice though.

On the other hand, everyone flying backcountry hates the gravel rash on composite props. I know plenty of guys who are struggling with it or have faced big prop repair bills. Same goes for me, I am fearful of what gravel will do.
They are probably a bit more of a speed brake if the engine fails. But that is hardly a consideration.

[svyolo]

Sounds like you made a lot of changes simultaneously, making it hard to see the difference one change made, like the tips. I think all of us appreciate the time you take to write it all up. I was shopping Maules and 185's a bit, and realized I was going to be beating the @#%$ out of whatever I flew. I absolutely wanted to be able to fix it, and make changes myself.

Thanks for your input.

[Paul_Millner]

{Mogas} is more volatile than 100LL, and risks detonation if running an aggressive advance tailored for 100LL

We're mixing apples and oranges a bit... winter time mogas can be more volatile than avgas, summertime is about the same nowadays. But volatility only speaks to the ease with which a fuel vaporizes... it doesn't tell us about detonation resistance.

Octane number tells us about detonation resistance, but it is complicated by using different systems for mogas and avgas octanes. If you take "pump octane" from the Texaco station and subtract five, that gets you pretty close to aviation octane. So that 93 AKI or (R+M)/2 premium you can buy along the Gulf Coast is really 88 aviation octane, compared to the 100LL specification of 100... and 100LL usually tests at about 102, 'cause the oil companies don't want problems with off-spec avgas and all the liability that entails. Big difference!

[Paul_Millner]

In the 60s mo-gas was filled with lead. It was not uncommon to go through a spark-plug every weekend (just a few hours of running time). I carried a 5-gal can with me and when I went flying; I would often bring a can of 100LL home with me for my snowmobile. It did wonders for my spark-plug bill.

There was no 100LL in the 1960's... it came on the scene about 1980. By that time, mogas lead was headed down from 3 to 4 grams per gallon (just like 100/130) to fractional grams/gallon by the end of the decade. Lead went away in mogas in the early '90's.

[bergy]

Maybe it wasn't 100 LL, but came out of the pump at the FBOs, cost nearly twice as much as the cut-rate mogas I had been using, and my sparkplugs lasted 3 times as long.
Thanks for the correction.

[Battson]

As my battery has aged, I noticed that starting got harder on cold mornings, but more frustratingly - kickbacks have become more common. I assumed this is related to the SureFly SIM units as will explain, but maybe not. I will explain. I am sharing this information in case it helps others.

I had issues with the Skytech LS series starter having trouble pushing through the first blade of compression. I’d sometimes even let the starter push the first cylinder part way through compression, release the starter, and then re-engage once the cylinder bled off the compression. I have been advised this issue has nothing to do with timing or advance, which I have also checked. I felt it was likely an issue caused by a softening battery plus high compressions (still high 70s / 80) struggling to beat the safety "timeout" in the SIM which I mentioned above in this thread. However I may have that wrong...

The technical detail comes straight from Surefly's technical department:

It has everything to do with how much the starter is robbing the battery of voltage during the start. As the engine approaches TDC, the SureFly SIM charges the coils in preparation to fire. If the starter robs the Surefly of voltage below its minimum operation voltage (8.5 V DC measured at the starter) during this charging process, the SureFly will shut down and will no longer contain the charge in the coils. This charge will sometimes dissipate as and early spark before TDC which will cause a kickback.

This was a revelation for me, as we measure voltage at the bus usually. Who knows what it's doing at the starter.

The Skytech LS starter should spin the prop briskly and easily through compression. If it is not, the troubleshooting approach is measuring the voltage drop at the starter lug when the starter is engaged. If it drops below 10 V DC you have an issue, such as:

1. Bad starter?

2. Bad battery cell - or old battery in my case...

3. Poor starter ground…I am advised this is by far the most common issue. How to troubleshoot that issue:
First, remove the starter and make sure there is not paint or corrosion on the mounting boss or the starter flange. Many engines come with this surface painted. This is critical as the starter grounds to the engine through this mounting surface. Second, check the engine ground to the airframe. It should be a heavy cable or braid from and unpainted/uncorroded engine bolt (not the engine mount bolts) to an unpainted/uncorroded airframe bolt. Not a clamp.

I haven't fully solved this issue yet. However, I bet a stronger electrical circuit and new battery are going to get me 80% of the way there.

[Bdflies]

That "low voltage causing premature spark" is kinda alarming. As pilots, we have lots of opportunities to abuse our engines, but premature (before TDC while cranking) is really tough on it! I bet your starter isn't very happy with that, either.
You'd think that the Surefly folks would have a preventative system in place.

[Battson]

I note that several of these 'features' may not be present in the Emag system.

[schu]

The lithium batteries have a higher resting voltage. Are you using one of those?

[Battson]

Yes that's true. However I am using the Oddessey PC680-MJ (lead gel).

I guess its worth noting that Li batteries offer a wide range of advantages, such as better voltage performance - especially in the cold, vastly more cycles (10x as many), lighter weight, deeper discharge, and longer shelf life. The disadvantages people typically cite are much greater cost, perceived "fire risk", and requirement for an internal BMS.

I have no qualms saying it's the cost which puts me off Getting 5 years from a lead battery is heaps, the Li battery would have to last 20 years to break even. We'll be lucky if the whole engine isn't battery powered by then...

[jaredyates]

The p-mag units let the prop turn for a short moment before sending the first spark, but perhaps yours is supposed to be doing that too. Being that you have ruled out dirty connections, the consensus in the Aeroelectric camp is that if your battery is having a hard time cranking, it is probably far beyond being able to provide a healthy reserve in the event of an alternator failure. Why not just replace it? Or capacity check it to find out.

[Battson]

Yes, replacing the battery and upgrading the electrical connections is also part of the plan.