P-Mags, A curve or B curve ?

tturner · #1 10-26-2011, 07:27 PM

I just install one P-mag on a factory stock o360-A1A and set it up with the A curve ( 34 deg max advance ). It is running very good on the A curve. Are any of you running on the B curve with this configuration and what differences have you noticed in performance versus the A curve.

petehowell · #2 10-26-2011, 07:52 PM

Hi Tommy,

I run a custom B curve (41 deg max advance) on my 0-320 RV-9A. My data shows that more advance yields better LOP ops, at the expense of hotter CHT on climb.

Running the A curve, I can't lean as far, but can climb as much as I want with no temp issues.

I choose to limit the summer climbs for better LOP ops most of the time. I have a switch in the cockpit to change curves when the engine is off.

N941WR · #3 10-26-2011, 07:59 PM

Is this a new engine or a newly OH'ed engine?

If so, run the "A" curve (jumper in) for the first 50 +/- hours. I recommend you plug the vacuum advance line for the first 15 hours so the P-mag acts like a fixed timing magneto. This will help you sort out possible cylinder cooling issues with a new engine installation.

After that, you can try the "B" curve and see what you get.

As Pete said, you can customize your "B" curve to suite your needs. This can be done with the free program provided on the Emag site. Or, if you buy a EICommander you can do it while the engine is running or in flight. Heck, you can even store multiple configurations and use the one that works best for you.

tturner · #4 10-26-2011, 08:25 PM

Bill

It is a new engine with 45 hours on it. Cylinder temps are still higher than I would like, 360 to 390 in cruse ROP, 320 to 360 LOP.

APACHE 56 · #5 10-27-2011, 06:03 AM

Quote:

Originally Posted by tturner

Bill

It is a new engine with 45 hours on it. Cylinder temps are still higher than I would like, 360 to 390 in cruse ROP, 320 to 360 LOP.

Tom,
I would think that you should expect somewhat higher cyl head temps (all other things being constant). If the electric ignitions work as advertised (i.e., more efficient operation) then more energy should remain in the cylinder as opposed to the exhaust stack.
It would be interesting to run an engine on mags then switch to electronic and compare the critical parameters; again standardinzed to a common condition.
The CYL head temps you presented don't seem to be all that bad.
Don

N941WR · #6 10-27-2011, 06:47 AM

Quote:

Originally Posted by APACHE 56

Tom,
I would think that you should expect somewhat higher cyl head temps (all other things being constant). If the electric ignitions work as advertised (i.e., more efficient operation) then more energy should remain in the cylinder as opposed to the exhaust stack.
It would be interesting to run an engine on mags then switch to electronic and compare the critical parameters; again standardinzed to a common condition.
The CYL head temps you presented don't seem to be all that bad.
Don

Well said. Those are good numbers.