TMann,
Well, I've just finished spending who knows how many months (years) trying to get my oil temps down only to finally discover the problem was a defective oil cooler. It appears that the only oil cooling was from the oil/water exchanger. While it was too high for comfort, especially during summer, it did cool the oil well enough to keep me flying throughout the Texas summer. After just recently discovering the defective cooler, I replaced it with a Modine of similar size & style and flew it for the first time today. WOW! What a difference, possibly enough to remove the oil/water exchanger altogether (more testing is requried). Addimitedly, the OAT was in the mid 40's, the return oil temp was down in the 150*F range, when it had been around 210 - 240*F. On today's flight, in cruise configuration, the coolant was 165-170 with cowl flap closed.
Also, it appears that Lynn Hannover is correct (big surprise) about the best horsepower being produced at around 160*F oil temp. I saw an extra 11 knots IAS today over my typical cruise speeds. I'm sure it wasn't just my imagination as the fuel flow was also higher. (Gotta take the bad with the good.)
So, if you want to go fast(er), work on reducing those oil temps.
Mark S.
On Sat, Dec 19, 2009 at 10:29 AM, Thomas Mann <tmann@n200lz.com> wrote:
Mark,
I’m going to investigate that further but first look seems like a winner if it can handle the BTU loads (which does not seem like an issue.
I like the idea of a single scoop as well as a single radiator if it can be done. I’m thinking airflow here.
The P-51 scoop is supposed to create enough thrust as a result of the heated expanding air jetting out the back to cancel out 90%+ of the drag created. I never could get my head around the whole ram-jet theory but that’s the basis.
The other benefit I see here is the comment provided earlier about the optimum oil and coolant temp being closer to the 180F range, both of which I could control with my coolant thermostat.
Like I say, I have time to work these things out.
T Mann
Have you considered using a Laminova type oil/water exchanger? They're relatively light, compact, work well, and come in a variety of sizes.
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