Dbro172
Well Known Member
I recently installed a single PMAG, replacing a slick impulse mag; leaving one Impulse and one PMAG, on an O-320. Installation was easy, pulling new wires through the firewall fittings was the toughest part, also had to switch my RPM sensor from my right magneto to the left magneto, requiring me to pull the left magneto, which was an adventure...
Initial results seem to be a bit smoother operation and definitely higher CHTs and lower EGTs. Previously I worked very hard to get my CHTs to mid 300's while the EGTS were running in the mid 1400's. First flight with PMAG, highest CHT was back around 400 with EGT's in the 1350's at 65% power. I re-timed the PMAG to 2 degrees ATDC which dropped highest CHT to 380's at 65% power and 390's - 400 at 75% power. I was leed to believe the slick mag would be rendered useless with the added PMAG but at cruise It still runs better on both mags vs. the PMAG alone. RPM drops at runup are similar between both mags. I grounded the PMAG to an engine case accessory bolt (vac pump cover I believe).
At 7500' I was able to get smooth operation running one cylinder 50 degrees LOP, which dropped that cylinder temp (#4, hottest) in line with the others. When it comes to (trying to) run LOP on a carb, is it OK to run one cylinder LOP while others might be at peak still, or even 100 ROP? Will it get smoother by adding a second PMAG (installed breaker and pulled wire for second PMAG at this time)
Problem with a carb is it really only gets best cooling and fuel distribution with the throttle at WOT, or slightly backed off and in my plane I need to be 10,000'+ to run WOT. Usually from 6500 to 8500 I'm still backed off the wall a good inch or so.
Anyway, just looking for some advice for setting up and operating PMAG(s) with a carb.
Initial results seem to be a bit smoother operation and definitely higher CHTs and lower EGTs. Previously I worked very hard to get my CHTs to mid 300's while the EGTS were running in the mid 1400's. First flight with PMAG, highest CHT was back around 400 with EGT's in the 1350's at 65% power. I re-timed the PMAG to 2 degrees ATDC which dropped highest CHT to 380's at 65% power and 390's - 400 at 75% power. I was leed to believe the slick mag would be rendered useless with the added PMAG but at cruise It still runs better on both mags vs. the PMAG alone. RPM drops at runup are similar between both mags. I grounded the PMAG to an engine case accessory bolt (vac pump cover I believe).
At 7500' I was able to get smooth operation running one cylinder 50 degrees LOP, which dropped that cylinder temp (#4, hottest) in line with the others. When it comes to (trying to) run LOP on a carb, is it OK to run one cylinder LOP while others might be at peak still, or even 100 ROP? Will it get smoother by adding a second PMAG (installed breaker and pulled wire for second PMAG at this time)
Problem with a carb is it really only gets best cooling and fuel distribution with the throttle at WOT, or slightly backed off and in my plane I need to be 10,000'+ to run WOT. Usually from 6500 to 8500 I'm still backed off the wall a good inch or so.
Anyway, just looking for some advice for setting up and operating PMAG(s) with a carb.