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- Jun 14, 2017
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Hi all
I recently had overhauled cylinders and new NFS high compression pistons installed in my experimental O-200 powered cub. It has a closed cowl which is not designed very well. Not a PA11 cowl but I guess whoever built it, had that in mind.
I have always had oil temps in upper range of green arc (my green arc is marked from 110 -240F) and oil pressure in lower range of green arc (green arc marked from 20-50psi).
Since I wasnt ever able to develop full RPM for an O-200 (see other discussion here regarding props and high compression pistons), I was rarely revving more than 2450rpm whether full throttle or throttled back somewhat.
Now with new cylinders and pistons installed, instruction from AME was to fly WOT all the time with straight mineral oil to assist with the bedding of rings and cylinders. This now results in 2600rpm WOT in cruise. Still not as high as I would like, but about 100rpm better than I got before the high compression pistons.
The problem now is that flying at this power setting quickly pushes my oil temps to 240F and pressure drops to 16psi. Doing a gliding descent can get oil temp down to 205 and pressure back to around 22psi. (I fly from a fairly hot and high strip. 4750 elevation and even now in winter daytime temps are around 70F)
I am thinking that there might be a couple of factors at play:
1. The crude design of my cowl might not be cooling cylinders as efficiently as it could and thus causes high temps
2. Bottom end is starting to give notice
3. Oil pressure relief valve not set properly.
Is installing an oil cooler an option? (Like Steves Aircraft Okl Cooler or Airwolf Chiller)
Can I fly with cowl completely removed to check my suspicion of cowl creating high temps and subsequent low presures?
Can I set oil pressure relief upwards or is this a band aid / old wives tale?
What else can be the cause?
Any advice will be appreciated.
I recently had overhauled cylinders and new NFS high compression pistons installed in my experimental O-200 powered cub. It has a closed cowl which is not designed very well. Not a PA11 cowl but I guess whoever built it, had that in mind.
I have always had oil temps in upper range of green arc (my green arc is marked from 110 -240F) and oil pressure in lower range of green arc (green arc marked from 20-50psi).
Since I wasnt ever able to develop full RPM for an O-200 (see other discussion here regarding props and high compression pistons), I was rarely revving more than 2450rpm whether full throttle or throttled back somewhat.
Now with new cylinders and pistons installed, instruction from AME was to fly WOT all the time with straight mineral oil to assist with the bedding of rings and cylinders. This now results in 2600rpm WOT in cruise. Still not as high as I would like, but about 100rpm better than I got before the high compression pistons.
The problem now is that flying at this power setting quickly pushes my oil temps to 240F and pressure drops to 16psi. Doing a gliding descent can get oil temp down to 205 and pressure back to around 22psi. (I fly from a fairly hot and high strip. 4750 elevation and even now in winter daytime temps are around 70F)
I am thinking that there might be a couple of factors at play:
1. The crude design of my cowl might not be cooling cylinders as efficiently as it could and thus causes high temps
2. Bottom end is starting to give notice
3. Oil pressure relief valve not set properly.
Is installing an oil cooler an option? (Like Steves Aircraft Okl Cooler or Airwolf Chiller)
Can I fly with cowl completely removed to check my suspicion of cowl creating high temps and subsequent low presures?
Can I set oil pressure relief upwards or is this a band aid / old wives tale?
What else can be the cause?
Any advice will be appreciated.
