[Walt Fricke]

Gordon - good point. I know that a restriction raises pressure - think of the thumb over the end of a garden hose. What I don't know is what the effect of a fairly minor restriction at just one point in a longish (relative to the restriction) line is. Is flow reduced at the discharge end by the restriction no matter how far away? If the pump can just build higher pressure before the restriction, does its effect go away? How does the drag from the wall of a tube affect things?

Recalling my Carroll Smith, I remember that for the cooling air ideally you want to have the inlet duct smaller than the cooler area, and the exit tuct slightly larger than the inlet. The idea here is to have the incoming cooling air expand and thus slow down as it passes through the cooler. This makes the heat transfer more efficient as the air lingers longer, so to speak, to take up more heat. Up to some limit, no doubt. I suppose that some similar thermodynamic is at work with the flow of oil? If it zips through too fast, is the heat loss side of things less efficient?

Maybe someone who took thermodynamics in engine school and remembers it can educate the rest of us.

On my first Mazda cooler I had a heck of a time wrenching on the fittings with the spoiler in place and the brake ducting, which as a pro for a 12 over a 16. But if it works, I see a -16 as pretty much an economic decision. Marginal cost and marginal gain may be down in the noise here.