Surefly electronic ignition

[Timberwolf]

Dan, you do bring up good points and point towards the gains on a parallel valve engine. Research seems to be lacking in the angle valve department from my research as to optimal timing values. I have sds cpi and believe my total advance with the LOP switch is set around 27-28 degrees. It seemed to be diminishing returns after that. Have you done any testing on the angle valve to determine good baseline settings for those systems capable of utilizing such a curve?

[Toobuilder]

Since you have CPI, you can use the LOP functions as a safe "flight test development" switch. Simply start at a known conservative advance setting on the basic curve (switch off), then add +1 degree to the LOP window and activate the switch. It the airplane picks up speed, add another degree, compare... Rinse/repeat until you see the speed peak, then drop off. The advance value that corresponds with peak speed is your "optimized" advance. The cool thing is that if the engine does something you don't like, just turn off the switch to instantly bail out of the test and get back to a known safe condition.

Finding the optimum value for cruise flight should take all of 20 minutes. Will give you something to do on your next long cross country.

[DanH]

Originally Posted by Toobuilder

Let's make sure the readership understands the proper context of "practical limit".

In the context of this thread, it would be 38 BTDC, the Surefly maximum.

But point taken: It's impossible to create a canned curve with enough breadth to handle every possible use case. And the larger the canned curve, the higher the probability that someone with an edge case is going to get stung by a dangerous condition.

Ok, so quit arguing against an absolutely safe alternative, one requiring no deep knowledge or test pilot skills...fixed timing at standard Lycoming values.

But you have to go to Ross to buy one.

A system with dual, in-flight switchable user-configured advance maps? No, you don't have to go to Ross, nor spend anywhere near as much money. However, here we're discussing Surefly.

[DanH]

Originally Posted by Timberwolf

....my total advance with the LOP switch is set around 27-28 degrees. It seemed to be diminishing returns after that.

Your observation matches mine, and Marvin McGraw's; sweet spot about 28 degrees.

The angle valve requires less advance. Given all the 390's going into 14's these days, it is why I object to canned advance maps based on parallel valve observations.

For example, the Surefly max is 38 BTDC at low manifold pressure. I've flown my IO-390 with advance pushed to 35 BTDC at 16,500, and found it wrong as a soup sandwich, slow and hot. 38 would be serious abuse.

[Toobuilder]

Originally Posted by DanH

Ok, so quit arguing against an absolutely safe alternative, one requiring no deep knowledge or test pilot skills...fixed timing at standard Lycoming values...

I agree that there are some pilots who should not ever be allowed to touch the mixture or propeller controls, but to suggest that tweaking ignition timing in flight requires the skills of a test pilot is quite a stretch. It's certainly not something to be taken lightly and the hardware makes a big difference, but it's not any harder than LOP ops.

I understand the desire to "protect the children" on this forum, but let's try avoid fearmongering.

[Tommy123]

What is obvious from these comments is that the internet experts haven’t bothered to look at the Surefly timing schedule. It is dependent on RPM AND MP. It would take extreme conditions for it to get to 38 BTDC.
We live in a time when your opinion outweighs the facts sad situation. I think it would be a good idea to identify your credentials when making these claims. Anecdotal information is useless.
This is why I no longer frequent this forum, gross misinformation.
The one about fasteners where one guy started claiming the metal being held together is a factor in shear was outstanding, thanks for the guy that was a structural engineer for debunking that.
That people confidently proclaim as truth things they barely understand is why a lot of info here and on many forums is useless.
As someone with over 40 years in aerospace as a airline mechanic, technical writer (translating engineering into English) working closely with engineers and as a freelance consultant and building the X47B prototype many “facts” I see make me cringe.
I really fear for a new to aviation builder that follows some of the “ facts” posted here.
There are some gems though, such as Walt but there are more than a few who should just keep silent, especially the ones who’s replies start with “I don’t know but.,,”
Thanks toVan for designing a idiot proof airplane.
Don’t bother critiquing me with your “expertise” I’m out of here.

[DanH]

Originally Posted by Tommy123

What is obvious from these comments is that the internet experts haven?t bothered to look at the Surefly timing schedule. It is dependent on RPM AND MP. It would take extreme conditions for it to get to 38 BTDC.

2700 RPM at any altitude over 9000. Not extreme for a fixed pitch RV.

As someone with over 40 years in aerospace as a airline mechanic, technical writer (translating engineering into English) working closely with engineers and as a freelance consultant and building the X47B prototype many ?facts? I see make me cringe.

Seriously Tom, ranting helps no one. If you have useful information to share, I'm sure your contribution would be appreciated.

[az_gila]

Originally Posted by DanH

2700 RPM at any altitude over 9000. Not extreme for a fixed pitch RV.
.....

To be more precise for a standard Lycoming, it appears to be 36.5 degrees at 2700 rpm

https://docs.wixstatic.com/ugd/712b8...40a99b37e8.pdf

[pecanflyboy]

Sounds like you guys have it all figured out. I look forward to the development of your product and its introduction to the market. I?m sure it will be perfect and there will be no criticism on this forum as a result of all your hard work. I can?t imagine someone undermining your success with strong opinions or speculation. Good luck!

[DanH]

Originally Posted by az_gila

To be more precise for a standard Lycoming, it appears to be 36.5 degrees at 2700 rpm

Thanks Gil. Good catch.

Originally Posted by pecanflyboy

However, it will advance up to 38 degrees once your are in the detonation safe zone below 25" manifold pressure.

From post #5. http://www.vansairforce.com/communit...11&postcount=5

Originally Posted by pecanflyboy

Sounds like you guys have it all figured out.

Nope. Set us straight. Is your "high compression IO-360" parallel or angle valve? Fixed pitch or constant speed?