Advancing the timing to 28° from 25° in a A4M

smartanthony

I have a '76 Archer II and noticed a performance decrease from 28° magneto timing to the engine stamped 25°.... is there more benefits than harm going back to 28°...?

Scott Sherer

Hi, first things first. What does the engine owners maintenance manual say to set it at? That should be the definitive source. While you're looking that up, I'll send this to our A&P, Erich Rempert for his comments. Please stand by.

smartanthony

Thanks Scott, standing by....oh, BTW, the snowblower/tug is awesome...may employ the great idea...

Scott Sherer

I agree totally. What a novel and unique approach to tugging our airplanes. Of course, if you live in Florida it might not work so well, lol. Have a great weekend!

smartanthony

You as well, thanks Scott...Florida some day, for now just south of Madison, Wisconsin...Tony

Scott Sherer

MSN? Really? I'm just south of Milwaukee at BUU! We're neighbors!

smartanthony

Burlington..? 7WI5...Brooklyn/Syvrud, just south of Oregon, 3100' grass airstrip...Wag-Aero has some great stuff...

Scott Sherer

Yes they do. I'm at the home of Knots2U. I could spend all of my money there, lol Have a great weekend!

Scott Sherer

SmartAnthony
Here are comments from our A&P, Erich Rempert:

28* is not legal or recommend. However 3* is not an outrageous amount of timing to be out of spec either. Many mechanics would not choose to adjust the timing if it was off 3*, but it really depends on the application.

A turbo supercharged engine with the timing advanced 3would be a potential problem I'd address, the possibility of detonation and catastrophic engine failure is too high to leave it. If it were 3 retarded it would be safe but performance would suffer perhaps by 10-20hp.

On a J-3 cub with an A-65, I'd set the timing where it ran best...

I suppose your "eye" is best when it comes to your airplane...

(But I wouldn't adjust my eyes much more)

-Erich

smartanthony

Erich, thanks for the information, but could you please tell me why at 25° (recommended) it's smoother but seemingly, I lost the (rocket) power...thanks, Tony

Scott Sherer

Hi Tony,
Erich does mention above that with 28 degrees you have the possibility of detonation or catastrophic engine failure but you also gain 10 to 20 HP. With it turned back to 25 degrees, the engine is smooth and safe but at the cost of 10 to 20 HP. The extra HP aren't normal and you're overdriving the engine, causing you the potential of losing it.

smartanthony

Good morning Scott, thanks for reiterating what Erich had said...it is more smooth and safe, I just miss the noticeable power loss...maybe down the road a PA -28R -201T would be a good idea.
Tony

Scott Sherer

Hi Tony,
I just purchased a PA-28R-201T. I'm very happy with it.

Safe flying!