All,
I am getting a high mag drop and rough running engine whenever I switch to one mag; it doesn't matter which one. I have a new Lyc O-360A3A built up by Penn Yann Aero with dual P-mags running auto plugs. First start was about a week ago. I just got around to doing a mag check a couple of days ago and have been having the problem every time I run a check. The engine was test run at Penn Yann and the test data record shows normal drops for mag tests at various RPM settings. Since it is new engine I am only able to run it for about 2 minutes before the CHT's get up to 300 deg. I always shut it down at this point.
Here is what I am doing:
Start engine and let idle at 1000 for 10 seconds or so
Increase RPM to 1500 (sometimes 1600)
Ground P-Lead on left mag
Note RPM drop of 300 plus and engine runs somewhat rough
Unground P-Lead on left mag and let engine settle at higher RPM
Ground P-Lead on right mag
Note RPM drop of 350 plus and engine runs somewhat rough
Here is what I have done so far:
Verified timing of P-mags (the first time I did this I found that the left mag was not timed properly (i.e. solid red light at TC) so I re-timed both mags and now get two greens)
Checked resistance of each ingnition wire. All seem to be near spec of 180 ohms per foot.
Removed and checked gap of each spark plug
Re-installed all plug wires on the plugs and P-mags and verified they were seated properly.
So, does anyone have any suggestions as to what to check next? I talked with Brad at Emag Air and he suggested several of the above checks. However, he also thinks that since both mags are behaving the same that it is unlikely an ignition problem. That makes sense to me. I am going to replace all 4 lower spark plugs (BR8ES) with brand new ones and see the problem changes. However, I thought I would go ahead and post this question to see what other ideas might pop up while I am doing that.
Thanks in advance.
I am getting a high mag drop and rough running engine whenever I switch to one mag; it doesn't matter which one. I have a new Lyc O-360A3A built up by Penn Yann Aero with dual P-mags running auto plugs. First start was about a week ago. I just got around to doing a mag check a couple of days ago and have been having the problem every time I run a check. The engine was test run at Penn Yann and the test data record shows normal drops for mag tests at various RPM settings. Since it is new engine I am only able to run it for about 2 minutes before the CHT's get up to 300 deg. I always shut it down at this point.
Here is what I am doing:
Start engine and let idle at 1000 for 10 seconds or so
Increase RPM to 1500 (sometimes 1600)
Ground P-Lead on left mag
Note RPM drop of 300 plus and engine runs somewhat rough
Unground P-Lead on left mag and let engine settle at higher RPM
Ground P-Lead on right mag
Note RPM drop of 350 plus and engine runs somewhat rough
Here is what I have done so far:
Verified timing of P-mags (the first time I did this I found that the left mag was not timed properly (i.e. solid red light at TC) so I re-timed both mags and now get two greens)
Checked resistance of each ingnition wire. All seem to be near spec of 180 ohms per foot.
Removed and checked gap of each spark plug
Re-installed all plug wires on the plugs and P-mags and verified they were seated properly.
So, does anyone have any suggestions as to what to check next? I talked with Brad at Emag Air and he suggested several of the above checks. However, he also thinks that since both mags are behaving the same that it is unlikely an ignition problem. That makes sense to me. I am going to replace all 4 lower spark plugs (BR8ES) with brand new ones and see the problem changes. However, I thought I would go ahead and post this question to see what other ideas might pop up while I am doing that.
Thanks in advance.