Forcing Air into the Engine Compartment, Engine Cooling ??? Options

[Rand]

I'm late to the game so flame me. #1 You cannot force air into a type 4. No, I don't mean you can't turbo one, because that you can. But you cannot force air into an engine bay and hope for results. Duh, it takes a pressured chamber.

You can direct cooler air perhaps. But it's been measured before.

I love it when new people try old things. One of these days, somebody's gonna make a breakthrough! But not if you are talking about air flow in a 914 engine bay.

Remember, it sucks. MUCH harder than you can blow. So bring cool air to the intake. Don't expect to pressurize it with "aero effects."

[wonkipop]

One point that some seem to be forgetting is that the air in the engine bay is usually pretty hot. Getting cool fresh air in there can only help.

Demick did some tests and found that air at the side of the engine bay was significantly cooler than air in the middle of the bay. He was able to drop his intake air temps by 10F or 20F by building a different intake snorkel, and he said he could get most of that benefit just by turning the stock air cleaner half around so the snorkel pointed off to the side of the bay.

Anecdotally, we have seen improvements in some cases. John Rogers (see some of his Tech Articles over on Pelican) put a deflector across the back of his roof panel, and saw cooler engine temperatures on his race car.

Charlie Davis looked into different cooling setups in terms of oil temp, and documented his attempts and findings here: https://members.rennlist.com/chuxter/TempTests.htm

--DD

interesting remarks and data.

all the type 3 and type 4 vws ran cold air induction intake via ducting.
no snorkel drawing engine bay air like 914s.

when type 3s went over to dual carbs in the mid 60s the engines ran cooler than the single carb 1500s. even the fuel and air intake has an effect on cylinder head temps and cylinder head valve train cooling in an air cooled engine. small effect admittedly but i understand significant enough to cure some of the overheating problems the early single carb versions of the 1500 pancake motor.

regarding @Highland measurement of the fan shroud temps after switch off.
the fan shroud gets very hot. its because its magnesium. the heat in the aluminium crankcase, iron cylinders etc flows into the magnesium and radiates from there. the fan shroud is basically a heat sink after switch off. heat flows from iron to aluminium to magnesium via conduction cascade. i'm not sure it means much for engine operation because as soon as air starts being blown through it, it cools very fast.
if you put your hand on the fan shroud just after switching off its in fact very cool.

i'm sure the fan shroud is the principle reason 914s suffered from so many hot start, fuel vaporization problems early on. that fan shroud sat there radiating intense heat right at the fuel pump and fuel lines after you parked your car. a great deal of the heat in the motor was drawn to the fan shroud and then lost through radiation from there.

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[emerygt350]

Having cooler air in the engine compartment can only be better, however,you should have an in and an out. I would suggest in on one side (ram) and then an out on the opposite (over the battery). One ram facing the air flow and the other getting pulled by the slip stream. Cycling the hot air out of the engine compartment will give you cooler air over the engine and cooler air into the intake. No need for any crazy physics or pressure differential equations. Fresh, cooler air, cycling through the engine bay is better than passive flow. That said, how much of a difference it makes? I dunno, give it a try and see. Easier than mounting a fan perhaps.

[emerygt350]

Dbl post