Dual Electroair Ignitions Poor Idle

[Walt]

With the manifold pressure disconnected I would "assume" the timing should go to 25 deg (this would be equivelent to full throttle).

[David-aviator]

I had a similar problem with 2 mags.

The symptoms were very poor idle and even a quit sometimes at less than 1000 rpm.

The cause was the FI system. Fuel flow would not drop below 2 gph at idle. The FI system has an idle feature that should drop to about 1 gph. It was not doing that. Don at AFP fixed it.

If you have fuel flow indication, check it at idle.

[Sid Lambert]

Depends on the generation ElectroAir. I have the older system but with a mag housing pickup. It idles around 15-18 degrees and it only advances above 25 BTDC at high altitude and low RPM. I would expect a rough idle at 15-18 BTDC timing.

[jbasol]

That's correct, with the sensors disconnected it fixes the timing at 25deg. Electroair does not set up any RPM based advance. They set a fixed timing of 25deg and then advance the timing based on manifold pressure. To me this seems like they're missing part of the equation to optimum ignition timing, but I found it didn't pay to argue the point with them, they only tell me: "we have thousands of these out there that don't exhibit this behavior".

The engine idles sooooo smooth at 25deg, I'm inclined to change the timing curve to idle it there. But I saw Klaus runs 35deg at idle with the Lightspeed as well, so it gave me pause to contemplate why my engine doesn't seem to like that.

-John

[Mile High Relic]

Isn't the whole point of electronic ignition to advance the timing at high speed/high power settings? I can't seem to wrap my head around advancing the timing to 35deg BTDC at idle. Isn't that backwards?

The E-mag installation documentation (I realize we're talking Electroair here) has a graphical representation of the advance curve, and they use 20-25 deg at idle and up to 39deg at high RPM.

[jbasol]

Exactly! In every auto engine I've ever dealt with, Idle is around 15-18deg BTDC, and it advances as rpm increases.

I doubt there is much to be gained from such an advance at Idle, so I won't be terribly worried if I have to make some changes to what Electroair has for a curve, but I'm still perplexed on why it worked at one point, but now doesn't.

-John

[rocketbob]

Originally Posted by Dennis_I

Is it running at 35degres BTDC at idle?

should be around 35 at full power and 5-15 at idle on a electronic system with a programmed ignition curve

This is incorrect. At full power timing is 25 degrees, and this is not unique to the electroair.

[Phlyan Pan]

It is possible for an air leak to show up under vacuum that would not show up under pressure.

Just a thought.

[Dennis_I]

just an example of a "normal" timing curve...

[Sid Lambert]

I think electronic ignition confuses too many people.

In a perfect world the EI will have the same timing as the mag at idle (25 BTDC on most of our engines), it would have the same timing as the mag at full power (25 BTDC on most of our engines) BUT it would advance once the engine is under lighter loads such as economy cruise at altitude (6K and above).

Linking the timing to RPM alone is asking for the engine to give up. Linking the timing to just the MAP is also not good. The 2 have to work together.

Surely most of you guys have seen the inside of a pre-electronic ignition distributor in a car/truck? It has a vacuum (MAP) hook-up and weights on springs that work together to advance the timing when the car is cruising down the road. Read, engine under light load.

The same principals apply to the EI in our airplanes. Some vendors go a step above and change the baseline curve for different situations but it all goes back to advance the timing ONLY when the engine is under a light load.