Cruiser Posted July 19, 2018 Report Share Posted July 19, 2018 I did a LOP in flight mag test today because I noticed a slight (get your attention) vibration on my last flight when I pulled back the RPM at reaching cruise altitude. The roughness only lasted a couple seconds but I noticed it. today I climbed to 5500' over the airport and setup straight and level cruise at -70 LOP ( I wanted to get as lean as possible. I didn't pull it back further because I think my IO550G 310 HP Continental will quit before it starts getting too rough. Number 4 has been the richest cylinder lately. It use to be Number 5. Number 3 has been the highest EGT in cruise by about 40-50 °F when cylinder temp is low to mid 300s. attached is the relevant part of the JPI 830 graph for EGT. The first spike is the L mag. The second spike is the R mag. Any comments?? Opinions? Suggestions? Thanks to all that contribute. TomK Quote Link to comment Share on other sites More sharing options...
jackn Posted July 20, 2018 Report Share Posted July 20, 2018 Savvy has a nice tool. Free upload & hit the ‘M’. In my case it was clear it was the lower #5 was a little weak. Not to state the obvious, but when you turn the switch all to the left it’s selecting the right mag. Anyway, it looks like your upper #1&3 plugs may be fouled? Quote Link to comment Share on other sites More sharing options...
carusoam Posted July 20, 2018 Report Share Posted July 20, 2018 Inviting Paul @kortopates to join us here... Tom, I see EGT 1 & 3 are not playing fair while running on the right mag. Blue and red(?) (challenging to see the colors clearly on my iPad) That would indicate to me there are two spark plugs on that mag that may not be burning as much fuel as they can... Kind of like getting a higher peak while running on one mag... But in this case you get an even higher peak because the fuel isn’t converting as well as the other cylinders... Be on the lookout for champion spark plugs... Or leaning until the plugs clean themselves? Check those plugs for age, hours, type, manufacturer... position in the cylinder... next on the list... how old are the mags? I would think there would be three tall peaks if the mag wasn’t generating proper voltage... PP thoughts only, not a mechanic... In the past, I have been able to lean 90° LOP at low altitudes before the IO550(g) would just shut off.... great for fuel conversion, CHT control... but not so good for speed... I must have had a really good set of injectors... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
jaylw314 Posted July 20, 2018 Report Share Posted July 20, 2018 18 hours ago, Cruiser said: Any comments? ? Opinions? Suggestions? Thanks to all that contribute. I noticed you only ran one mag for about 20 seconds each. The suggestion is to run on one mag for the duration of about 10 data points. Was your data rate every two seconds? It doesn't look like that on your graph, but I know it's hard to tell on JPI's software. If there are bad sparks (whatever the cause), you should see either LOWER EGT's or unstable EGT's. If there was no spark, you'd see your EGT bottom out but you'd probably stop the test due to sphincter contractions anyway. I couldn't conceive of a way for your EGT's to INCREASE due to a bad spark on one mag. So the alternate explanation is that on the right mag, #1 and #3 have good sparks and all the other cylinders have bad sparks. It might also suggest a mag or harness problem if it's that many spark plugs. That'd be my take... Maybe retry the test while less LOP, maybe -20deg? If it's a weak spark problem, doing it less LOP might show you what the peaks should actually look like for comparison. Quote Link to comment Share on other sites More sharing options...
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