front mounted oil cooler, line size Options

[mtrotter]

so, for a type 4, if I run a 38 mm pump, i can get away with -12 lines. I guess time will tell.

[Brian_Boss]

Pressure is not created by a pump, pressure is created by restrictions downstream of the pump.

I agree. The point I was trying to make is that the pressure is only increased upstream of the restriction. Where you care about pressure in a motor (internal oil passages/bearings) is downstream of the cooler lines.

Look at the fuel pressure regulator in your (fuel injected) car.
Look at the oil pressure regulators in your engine case.
Look at the expansion valve on your A/C.
Look at most recirculating hydraulic systems.

In each of these cases, the high pressure is upstream of the restriction.

Think about the reason you instinctively put your thumb over the end of a water hose to make it spray by raising the pressure in the hose.

OK, say the faucet is the oil pump and your thumb is the main bearing clearance. I you put a kink in the middle of the hose, will the water spray further? I don't think so.

If -10 lines would make more pressure in the engine than -12, why wouldn't -8 or -6 be even better?

[John]

-10 or -12 lines will work with a TIV motor with a high volume oil pump just fine. The most restrictive spot on most of these front oil cooler setups is the pancake oil filter adapter and the associated fittings. That is where I have seen the smallest orifaces in these setups.

There may be some pressure loss due to line size, but real world experience shows that any pressure loss due to line size appears to be made up by running cooler (higher viscosity) oil through the engine (which raises the oil pressure).

When we ran with a TIV in the track car with a front mounted cooler, we used -12 lines because that was what was recommended by other 914 guys 19 years ago. We had no oil related problems in the time that we ran the car in that configuration. (2 drivers, track only car).

If I was going to recommend line size, I would go with -12 line.