Been some debate around what drives nozzle flow for things like chain sprays and piston cooling jets...came across the following curves, so thought it might be fun to spend a lazy Saturday morning with Bernoulli and my new chart, along with some very good HTHS versus Oil Pressure data to see where it went.
Here's the correction curve for nozzles with viscosity, at constant pressure...calculate your flow using the appropriate equations, and apply the corrector...clearly viscosity changes the rate of flow through the nozzles...pick the 41 psi line, and you can clearly see that a 10cst oil flows 20% less than the theoretical, versus a 20cst flowing 40% less than a fluid with now viscosity effect...so at a constant 41psi, a 10cst oil would flow 33% more massflow than a 20cst oil (0.8/0.6).
However, next line up (172psi), clearly the lines are WAY closer together...both flow a lot more than the 41psi line, and the difference between them is 0.9/0.8, or 12.5%.
Which brings into topic another correction curve, this one isoviscosity lines versus pressure.
Can see clearly that at the range of oil pressures that are suitable for engine operation (say 50 to 100psi), there's literally no difference (there IS, but it's tiny) between the 5 and 10cst lines. There's no 20cst line, and given the exponential spacing, I'll decree that in the range 50-100psi, the correction is 0.95, nearly nothing but it's there.
So we've got the two curves, flow correction at constant pressure, and flow correction at constant viscosity.
But we KNOW that pressure in an engine changes with viscosity, and we have at hand some very comprehensive and handy data produced by CATERHAM, demonstrating that there is a strong correlation between HTHS and operating oil pressure...it's good research.
So I used those figures, and the corrections to get a theoretical spray volume for a 1.5mm orifice. the "95C correction" is to correct for density at the stated 95C test temperature
And tried the same model for if there was a 10psi poppet valve in the circuit which some do...
Given that the KV DOES influence flow by the tiniest bit, I'm still fixated on using the lowest KV100 for the HTHS.
Take for example M1 racing 0W50, with a 3.8 HTHS and 17.2 KV100, would develop the oil pressure (motive for squirter volume) of Redline 10W30, but have the flow correction of 17.2 cst, same as the M1 15W50...would have less piston cooling than the 15W50, AND the 10W30...
Here's the correction curve for nozzles with viscosity, at constant pressure...calculate your flow using the appropriate equations, and apply the corrector...clearly viscosity changes the rate of flow through the nozzles...pick the 41 psi line, and you can clearly see that a 10cst oil flows 20% less than the theoretical, versus a 20cst flowing 40% less than a fluid with now viscosity effect...so at a constant 41psi, a 10cst oil would flow 33% more massflow than a 20cst oil (0.8/0.6).
However, next line up (172psi), clearly the lines are WAY closer together...both flow a lot more than the 41psi line, and the difference between them is 0.9/0.8, or 12.5%.
Which brings into topic another correction curve, this one isoviscosity lines versus pressure.
Can see clearly that at the range of oil pressures that are suitable for engine operation (say 50 to 100psi), there's literally no difference (there IS, but it's tiny) between the 5 and 10cst lines. There's no 20cst line, and given the exponential spacing, I'll decree that in the range 50-100psi, the correction is 0.95, nearly nothing but it's there.
So we've got the two curves, flow correction at constant pressure, and flow correction at constant viscosity.
But we KNOW that pressure in an engine changes with viscosity, and we have at hand some very comprehensive and handy data produced by CATERHAM, demonstrating that there is a strong correlation between HTHS and operating oil pressure...it's good research.
So I used those figures, and the corrections to get a theoretical spray volume for a 1.5mm orifice. the "95C correction" is to correct for density at the stated 95C test temperature
And tried the same model for if there was a 10psi poppet valve in the circuit which some do...
Given that the KV DOES influence flow by the tiniest bit, I'm still fixated on using the lowest KV100 for the HTHS.
Take for example M1 racing 0W50, with a 3.8 HTHS and 17.2 KV100, would develop the oil pressure (motive for squirter volume) of Redline 10W30, but have the flow correction of 17.2 cst, same as the M1 15W50...would have less piston cooling than the 15W50, AND the 10W30...