[ERushing]

Has anyone tried reducing airflow through #3 and #4 cylinders on an IO-540 to increase pressure in the upper cowling to improve cooling on #5 & #6?

I'm considering a fiberglass/ RTV layup over a portion of the upper #3 & #4 cylinders to block a bit of the flow through the fins on those cylinders, also blocking the gaps between the forward, middle and aft cylinders. My #3 & #4 run about 40 degrees cooler than #5 & #6, not surprising on an IO-540. My baffling is well sealed and I have a "bump" built into the #5 baffle allowing air to pass through to the lower fins. Just looking to optimize a bit more.

Stupid idea? Worth a try?

Thanks!

 

[Kyle Boatright]

Has anyone tried reducing airflow through #3 and #4 cylinders on an IO-540 to increase pressure in the upper cowling to improve cooling on #5 & #6?

I'm considering a fiberglass/ RTV layup over a portion of the upper #3 & #4 cylinders to block a bit of the flow through the fins on those cylinders, also blocking the gaps between the forward, middle and aft cylinders. My #3 & #4 run about 40 degrees cooler than #5 & #6, not surprising on an IO-540. My baffling is well sealed and I have a "bump" built into the #5 baffle allowing air to pass through to the lower fins. Just looking to optimize a bit more.

Stupid idea? Worth a try?

Thanks!

ED, I think you'd do better to throttle the airflow around those cylinders by extending the inner-cylinder baffles to reduce the gap under the cylinders. Placing a fin blocker on top of the cylinders isn't going to reduce airflow out of the plenum, but it is going to block most of the airflow to the fins along the top of the cylinders, potentially creating a hot spot.

 

[BobTurner]

40 deg (F?) seems like a substantial cht difference. Have you checked that all cylinders are running at the same mixture ratio? (Can #5 and 6 be running a little closer to peak egt than the others?)

 

[ERushing]

40 deg (F?) seems like a substantial cht difference. Have you checked that all cylinders are running at the same mixture ratio? (Can #5 and 6 be running a little closer to peak egt than the others?)

Yes. I'm pretty close. I've been tuning my injector restrictors. But I'm peaking within in 0.4 gph at this point.

#6 loses a lot of cooling because of the oil cooler duct. I wish I would have bumped out my #5 bump just a bit more. That probably would have helped too.