hindsight2020
Final Approach
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- Apr 3, 2010
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hindsight2020
New-to-me 28R-200 still at annual, hope to get it back by the end of the week/start of the next one. IO-360-C1C (angle valve 200hp). AP found the mag timing at 25* instead of the 20* as stamped on the engine plate. These engines come in both timing varieties and there have been Lyco SIs in the past which have called for retarding timing to 20*. Be that as it may, there it is stamped at 20*
I'm getting a little anxy because I know this means a reduction of engine performance, though it provides an increase in detonation margins, lower CHTs and theoretically easier starting.
My normal running parameters are exclusively at 55-65% power WOT and 2400RPM, 6k-14k msl. I never run 75% in cruise; only gain 3-4 knots for an additional GPH and I can't get 75% power at 2400 anyways at the altitudes I like cruising at (higher the better).
Should I expect any substantial decrease in cruise speed after annual? A 4-5 knot loss at 65% would constitute a substantial loss to me. I'd also be ****ed if this thing starts running hella rough above 10k. Currently it leans very well at altitude and as opposed to the theoretical difficulty an injected engine would have with an advanced timing, I haven't suffered any starting problems on mine on 25*.
Is 5* timing between 20-25 range really something that's going to be noticeable at all by me, or are we talking about the loss of a couple HP on takeoff at the top end RPM/power combo where the performance loss would be manifested? Cube root power rule leads me to believe I shouldn't see jack squat in cruise performance change, but interested in hearing y'alls experience. Thanks!
I'm getting a little anxy because I know this means a reduction of engine performance, though it provides an increase in detonation margins, lower CHTs and theoretically easier starting.
My normal running parameters are exclusively at 55-65% power WOT and 2400RPM, 6k-14k msl. I never run 75% in cruise; only gain 3-4 knots for an additional GPH and I can't get 75% power at 2400 anyways at the altitudes I like cruising at (higher the better).
Should I expect any substantial decrease in cruise speed after annual? A 4-5 knot loss at 65% would constitute a substantial loss to me. I'd also be ****ed if this thing starts running hella rough above 10k. Currently it leans very well at altitude and as opposed to the theoretical difficulty an injected engine would have with an advanced timing, I haven't suffered any starting problems on mine on 25*.
Is 5* timing between 20-25 range really something that's going to be noticeable at all by me, or are we talking about the loss of a couple HP on takeoff at the top end RPM/power combo where the performance loss would be manifested? Cube root power rule leads me to believe I shouldn't see jack squat in cruise performance change, but interested in hearing y'alls experience. Thanks!