Got a curiosity question for the group.
I just ordered an oil cooler for my RV8. I selected a 10599R after studying the Stewart Warner performance charts:
http://www.oilcoolers.com/LCHX Specifications.pdf
Oil circulation for an angle valve engine is between 7 and 9 GPM. If I assume 7.3 lbs per gallon, that's roughly 50 to 65 lbs of oil per minute.
OK, look at the "Oil Side Pressure Drop" chart for a 8432R. They don't even rate the 8432R past 55 lbs per minute....and at 55 lbs you have an oil pressure drop of 15.5 psi. Compare the same chart for a 10599R. At 60 lbs per minute oil pressure drop is only about 5 psi.
The 8432R is a dual pass cooler. You would expect additional resistance to flow compared to a single pass 10599R, but 10 psi? It takes a lot of power to pump oil.....and it looks a bit short on flow capacity anyway.
Both coolers have the same air side pressure drop. Assume 5 inches water across the baffles and you have 27 lbs of air per minute.
Now go to "Calculated Heat Rejection". At 55 lbs/min oil flow (the maximum) and 27 lbs of air you can transfer about 400 BTU/min with an 8432R. At 60 lbs/min oil flow the 10599R will do 375 BTU/min. The difference is only a little over 6%, and 55 vs 60 oil flow rate is probably a fair comparison given the reduced oil flow resistance of the 10599R.
I found the charts surprising, and thus my question.
Why is the 8432R so popular? Am I missing something?
I just ordered an oil cooler for my RV8. I selected a 10599R after studying the Stewart Warner performance charts:
http://www.oilcoolers.com/LCHX Specifications.pdf
Oil circulation for an angle valve engine is between 7 and 9 GPM. If I assume 7.3 lbs per gallon, that's roughly 50 to 65 lbs of oil per minute.
OK, look at the "Oil Side Pressure Drop" chart for a 8432R. They don't even rate the 8432R past 55 lbs per minute....and at 55 lbs you have an oil pressure drop of 15.5 psi. Compare the same chart for a 10599R. At 60 lbs per minute oil pressure drop is only about 5 psi.
The 8432R is a dual pass cooler. You would expect additional resistance to flow compared to a single pass 10599R, but 10 psi? It takes a lot of power to pump oil.....and it looks a bit short on flow capacity anyway.
Both coolers have the same air side pressure drop. Assume 5 inches water across the baffles and you have 27 lbs of air per minute.
Now go to "Calculated Heat Rejection". At 55 lbs/min oil flow (the maximum) and 27 lbs of air you can transfer about 400 BTU/min with an 8432R. At 60 lbs/min oil flow the 10599R will do 375 BTU/min. The difference is only a little over 6%, and 55 vs 60 oil flow rate is probably a fair comparison given the reduced oil flow resistance of the 10599R.
I found the charts surprising, and thus my question.
Why is the 8432R so popular? Am I missing something?