If I missed it in this thread, apologies. What is your engine monitor reporting for fuel flow at the low RPM just as the engine starts to die?
DJ
It doesn't actually die, just #1/2 go "cold" with EGT of 600 or so implying poor or no combustion. Rest of cylinders fire on just fine. But fuel flow at 700-800 RPM is in the 2.5gph range
Basically, the flow divided purpose is to shut off fuel flow when pressure drops below a set point so it would give you a good idle cut off. Since EGT is an indicator of fuel mixture and mixture is predicated on air flow and fuel. That's why the potential exists for possible Val ve issues. If the same group did, both motors just adds a adfitionall factor for troubleshooting.
While possibly far-fetched in your case. In my massive reading library, I did come across a case of lousy running lthat eventually was traced to a poor casting with slag in the induction cast spyder on top of the engine. Caused crappy flow to one cyl. That was some very involved, troubled shooting.
Since it looks like your fuel flow and your timing are dead nuts. I think we almost have to look for a mechanical reason. One more deep thought is if you have good records on the overhaulverify exactly what cam was put in and which lifters were installed. I know on the 520 series. They make different versions and can be easily intermix, with some interesting operational problems.
Carl
looks like cam is PN 643069; lifters are 653906 (?) writing is hard to discern. Signature shop. Would confirm on Continental but online Illustrated Parts Catalog is broken- apparently they had a cyber attack that crashed their US operations out of Alabama.
It doesn't actually die, just #1/2 go "cold" with EGT of 600 or so implying poor or no combustion. Rest of cylinders fire on just fine. But fuel flow at 700-800 RPM is in the 2.5gph range
Mine has run very rough / died when FF went below 2.1 GPH. TCM tech support said the fuel manifold (spider) has a minimum pressure (FF) in order to stay open and that's why I asked. I vaguely recall a couple of cylinders at much lower EGT when starting up at low RPM. I know this isn't moving you towards a solution though maybe the 'not only me' data is useful.
I did manage to find in all my reading material, the hi flow lifters have to be used with certain valve/guide combos, so this may not be a issue on your engine. However, back in the 80's tcm did modify flow dividers on 520 series ( as i was reading) for improved flow when hot and idle. This was my impetus for checking your dividers, and perhaps see if there is a upgrade or change that can be applied to your engines. ( im stabbing they may have changed others too. ) I'm also assuming there is no oil fouling on plug of each engine. Carl
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It doesn't actually die, just #1/2 go "cold" with EGT of 600 or so implying poor or no combustion. Rest of cylinders fire on just fine. But fuel flow at 700-800 RPM is in the 2.5gph range
looks like cam is PN 643069; lifters are 653906 (?) writing is hard to discern. Signature shop. Would confirm on Continental but online Illustrated Parts Catalog is broken- apparently they had a cyber attack that crashed their US operations out of Alabama.
Mine has run very rough / died when FF went below 2.1 GPH. TCM tech support said the fuel manifold (spider) has a minimum pressure (FF) in order to stay open and that's why I asked. I vaguely recall a couple of cylinders at much lower EGT when starting up at low RPM. I know this isn't moving you towards a solution though maybe the 'not only me' data is useful.
DJ
T, what do you see for MP at idles?
carl
48 yrs A/P IA DAL aircraft inspector. 172N
I did manage to find in all my reading material, the hi flow lifters have to be used with certain valve/guide combos, so this may not be a issue on your engine. However, back in the 80's tcm did modify flow dividers on 520 series ( as i was reading) for improved flow when hot and idle. This was my impetus for checking your dividers, and perhaps see if there is a upgrade or change that can be applied to your engines. ( im stabbing they may have changed others too. ) I'm also assuming there is no oil fouling on plug of each engine. Carl
48 yrs A/P IA DAL aircraft inspector. 172N