Not disagreeing with you MTV, I was just sharing the info that fixed my heating issues on climb out, info directly from Airplains—-who originally dis the conversion and set mine up

Consider checking the inter-cylinder baffles. They made a huge difference in CHT for me on my 205. Additionally, the pilot side rear baffle wall (the vertical aluminum section next to the dipstick) should be tight against the rear cylinder, and should be held forward with a spring loaded tensioner. That spring failed on mine, and it took a while to catch it. In flight, the air pressure would let the baffle flex open, and dump cooling air. As a result, my front and mid cylinders ran hotter, the rear ran cooler, and the air across the dipstick would slowly siphon oil. Perhaps a couple of tablespoons an hour, but it made a mess. I spent months trying to find a leak that wasn't really a leak, and messing around with the rubber part of the baffling trying to fix CHT.

This is what I’m getting at full power 25.7gph

Mechanics say its fine, but i feel like its not enough to keep the temps down

Also, they suggested retarding the timing to 20° instead of 22°
Are there any downsides or risks beside slight power loss?





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Find a new mechanic, seriously! Those fuel flows are waaaaaayyyy too low! Like MTV says, make sure you find someone who really knows how to set up fuel flows on these engines. A common mistake that was made in years past was setting fuel flows on a 550 to the same that the 520 that was just replaced was set too, this cooked a lot of cylinders before it was discovered.

Retarding the timing puts a band aid on one problem but creates another. Reducing timing will decrease power but will also increase EGT’s and increase the amount of combustion byproduct since less fuel is being burned before it is being exhausted out of the combustion chamber. More of this crud will adhere to the backside of the valves and contribute to valve related issues. Leave the timing where it is called for, it is a balance of temps between EGT and CHT.

Like others have said, baffling is critical. Be careful trimming the plate in front of the front cylinder down unless that cylinder is actually running hot. That plate’s purpose is to deflect more cool airflow up and over the front cylinder to help cool the rear cylinders.

Keep in mind, your 550 is producing more energy (power) than the 470 it replaces so naturally there will be more heat under the cowling, this makes proper baffling even more important.

Keep at it and report your findings so others can learn, good luck.

Kurt

G44 wrote:Find a new mechanic, seriously! Those fuel flows are waaaaaayyyy too low! Like MTV says, make sure you find someone who really knows how to set up fuel flows on these engines. A common mistake that was made in years past was setting fuel flows on a 550 to the same that the 520 that was just replaced was set too, this cooked a lot of cylinders before it was discovered.

Retarding the timing puts a band aid on one problem but creates another. Reducing timing will decrease power but will also increase EGT’s and increase the amount of combustion byproduct since less fuel is being burned before it is being exhausted out of the combustion chamber. More of this crud will adhere to the backside of the valves and contribute to valve related issues. Leave the timing where it is called for, it is a balance of temps between EGT and CHT.

Like others have said, baffling is critical. Be careful trimming the plate in front of the front cylinder down unless that cylinder is actually running hot. That plate’s purpose is to deflect more cool airflow up and over the front cylinder to help cool the rear cylinders.

Keep in mind, your 550 is producing more energy (power) than the 470 it replaces so naturally there will be more heat under the cowling, this makes proper baffling even more important.

Keep at it and report your findings so others can learn, good luck.

Kurt

Wow! Thanks for the detailed answer!

I also think the same way, mechanics sometimes won’t listen because they think you don’t know.
But I was pretty sure that fuel flow was not normal


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pabloecanales wrote:This is what I’m getting at full power 25.7gph

Mechanics say its fine, but i feel like its not enough to keep the temps down

Also, they suggested retarding the timing to 20° instead of 22°
Are there any downsides or risks beside slight power loss?





Sent from my iPhone using Tapatalk

Why is your full power setting only getting you 2500 RPM? Thats not right either. But the 25.7 is definitely to low.

As others have said, mechanics read the book that says 26.4-27.2 gph or whatever.

I've been dealing with this for years on IO-550 powered SR22's.

YOU NEED 29-30 GPH to keep it cool on initial climb.

My 185 with a 550 is no different.