SNIP
I did have some E mail exchanges with Klaus but he wasn't willing to admit any actual figures which is why I came over here. His answer to my question as to: what sort of advance 2200 rpm and 20" would give? was to 'read the manual, it's all there'. SNIP
Reading Klaus’ manual, it appears that for a standard 25 degree BTDC (mag) engine Klaus’ ignition could go as far as ~43 degrees. I suspect however that in practical cruise it would not be that advance, so I’d
guess something around 36 degrees. Excerpts:
“Engines Normally Timed at 25 degrees BTDC
(Leading Magnet Installed At 45 degrees Before TDC):
These are usually engines with compression ratios less than 8.7:1.
- At idle the timing display should indicate 40o ± 2o when the manifold pressure hose is connected and 21o ± 2o when disconnected.”
These imply a timing advance range of 19-22 degrees. Comparing to a fixed mag set at 25 degrees this yields:
- At idle timing is ~21 degrees BTDC
- Most advance condition is timing at ~43 degrees BTDC
What is unknown is the RPM relationship with timing. Considering the timing range at idle with/without manifold line connected perhaps there is no RPM to timing curve input. Don’t know.
I refer you back to the nice work over the last few years on timing effects on our engines. Boiling them all down, for a parallel valve Lycoming engine I believe 9 degrees of total advance (so 25-34 degrees BTDC) is the practical limit that can be used to get a bump in engine efficiency up high. Any more than that you tend to get higher CHTs and no additional power. That 9 degrees would be a low MP.
I do have personal experience on a new RV-7 with dual Plasma III ignitions. The engine had ~100 hours on it with the (new) owner fighting continuous high CHT problems. He was flying full rich and low power in an attempt to keep CHTs below 420. A buddy and I went to look. We verified the boxes timed per the install manual then put a timing light on the engine. The timing was right at 42 degrees (both boxes) and this was independent of RPM or manifold pressure. The boxes got sent back to Klaus and repaired.
My recommendation:
- Verify timing at idle with a timing light (MP line removed). Ignore what the box is telling you.
- If the ignitions check out with the timing light, experiment with limiting timing to something closer to 34 degrees. The timing pot may help but you may need adjust the initial timing set point as well. This should be done in small steps to evaluate progress (or lack of progress).
Carl