Farmboy
MEMBER
Middlebury, VT
As I've been working on theoretical solutions to a high oil temp issue myself, I've considered a number of thoughts in this thread. Pressure differential is definitely the root baseline, which of course probably creates velocity with a higher pressure delta, and therefore more cooling. But it's based on pressure as the man said.
Not that this will help anyone in this thread regarding plenums, but without a differential test set, one of my first goals was to ensure that my current exit opening and chin spoiler is helping the air leave the lower cowl, and not encouraging it to enter, as if were not a low pressure area.
I taped on some tuffs and clamped my old go pro on the gear to see if I could get an idea of the airflow. You'll see better after about the 6 min mark, as the sunlight doesn't help and I didn't have a closer mounting location. I also taped a short row of tuffs behind the carb air box (it's a PA-11-90).
For the most part the tuffs show as expected. Airflow off the chin spoiler streams on by, and airflow at the edges seem good.
Couple interesting things that I don't truly know the value of yet -
- The leftmost tuff on the row behind the airbox is constantly turbulent and/or some other direction.
- The tuffs in the middle quite often are steaming outwards (sideways), as if the air is somehow being pushed left and right from the center mark. The right side is a little turbulent due to the short exhaust stacks stuck there, which I plan to extend an inch or two.
Anyhow, it was a simple first look today to start down the road of getting good "exhaust" air, which is part of creating the best pressure differential I can. I may add lower cowl louver vents, and I also may look at adding some nose bowl opening enhancements, to help capture more air and drive it into the upper cowl.
Video quality is not great by today's standards - I suggest viewing full screen on a computer to get any value from it.
Not that this will help anyone in this thread regarding plenums, but without a differential test set, one of my first goals was to ensure that my current exit opening and chin spoiler is helping the air leave the lower cowl, and not encouraging it to enter, as if were not a low pressure area.
I taped on some tuffs and clamped my old go pro on the gear to see if I could get an idea of the airflow. You'll see better after about the 6 min mark, as the sunlight doesn't help and I didn't have a closer mounting location. I also taped a short row of tuffs behind the carb air box (it's a PA-11-90).
For the most part the tuffs show as expected. Airflow off the chin spoiler streams on by, and airflow at the edges seem good.
Couple interesting things that I don't truly know the value of yet -
- The leftmost tuff on the row behind the airbox is constantly turbulent and/or some other direction.
- The tuffs in the middle quite often are steaming outwards (sideways), as if the air is somehow being pushed left and right from the center mark. The right side is a little turbulent due to the short exhaust stacks stuck there, which I plan to extend an inch or two.
Anyhow, it was a simple first look today to start down the road of getting good "exhaust" air, which is part of creating the best pressure differential I can. I may add lower cowl louver vents, and I also may look at adding some nose bowl opening enhancements, to help capture more air and drive it into the upper cowl.
Video quality is not great by today's standards - I suggest viewing full screen on a computer to get any value from it.