Variable ignition timing (100LL no longer available at RHV).

[JBrenneise]

Is there such a thing as a kit to add variable ignition timing for GA aircraft?

[KeithO]

Heading and subject asking 2 different questions ??
I'm assuming variable valve timing is out unless you install a Viking engine.

Ignition, there are different options available.
article in Kitplanes magazine on the different options.
https://www.kitplanes.com/electronic-ignitions-2/

[1001001]

Don't forget SDS:
http://www.sdsefi.com/aircraft.html

[abwaldal@gmail.com]

Go with SDS fuel and ignition, EM-5F system, and your worries are over.
I have an 0-360 8.5 compression ratio and I run Costco premium.
Yes I have the 6 port Andair valve for return lines to tanks and all SS/teflon lines.
Starts same cold or hot.
Problem solved.
My three cents worth Art

[rocketman1988]

Love my EFII System32!

[JBrenneise]

By ignition timing, I mean advancing or retarding the spark to compensate for lower octane fuel(s).

[KeithO]

If you mean flex fuel type capability (to adjust automatically based on onset of detonation) I am not sure anyone has that capability for air cooled engines. First of all the heads are too hot to mount regular knock sensors (designed for water cooled engines). Secondly I doubt that suitable locations for the knock sensors would be available.

I think any electronic ignition system would be set up for a particular fuel and thats it. For tuning, sensors and signal conditioning systems are available to be able to detect detonation very early (sending a signal out to a pair of headphones) with great sensitivity and the timing tables would then be adjusted accordingly and then locked.

[gasman]

Here is a system that will allow to match your timing to your situation..... http://www.sdsefi.com/cpi2.htm

[rv6ejguy]

With SDS CPI, CPI-2 or EM-5 systems, ignition timing is user programmable.

When burning 91 Mogas and using std compression ratios we normally retard timing at high MAP around 3-5 degrees so total timing might be around 20 degrees at 30 inches and then as MAP drops, we slowly bring more timing in so the full 25 deg is in at 25 inches and below. This is all automatic once programmed.

There will be a slight drop in takeoff power (around 6-7 hp on a 360) but cruise power and economy are unaffected above about 5000 MSL.

[airguy]

SDS is good stuff - I love it in my plane.