Maybe the hell hole is just the poor over heated car trying to cool itself.

Superhawk996 is right on. The most important thing is that engine tin is well sealed and there is no pressure loss from the high pressure area which is the area between the cylinders and the engine tin. Air leaks can occur around the spark plugs and through the holes that are present for the spark plug cable holders and any other holes or joints. These unsealed holes will rob the cylinders of the high pressure cooling air that the fan has forced in.

right on @PCH
and @Superhawk996

there is a fan in there...........
and it doesn't want to be sucking in anything hot, or blowing anything hot where its not supposed to be, because....... its a pretty good fan. and its supposed to be a ducted cooling system, there is nothing passive about it.

At the last hillclimb event 10 days ago, it rained (well, it is the UK). I had a pair of GoPros fitted, one facing to the rear, allowing me to watch the way the water droplets moved as the car picked up speed. Those on the decklid were drawn forward towards the grill but those on the panel ahead of the grill remained pretty well static except when cornering. Max speed on the hill around 70mph.

https://youtu.be/shsi-iYdO-8

Even though my scoop experiments to date have been yielded poor results, I felt like I should give an update; mostly cause all the input I received was useful in trying to improve what already is adequate cooling.

Based on your input I put thermocouples at the fan inlet and between the tin and engine where the stock CHT is.

Today the ambient temperature was about 75F. I ran with and without the scoop. My fan inlet temperature was about 100F and the CHT ran between 110 to 120F depending upon rpm.

With the engine off and parked in my garage the temperature started to climb. I didn't watch it till the temperature rise reversed, but the fan probe (basically engine compartment) got to 135 F and the probe by the CHT got to about 270F. I took a mini leaf blower and blew into my scoop getting my fan probe to drop about 15F (to about 120F); and yes, it did rise back to 135F after I removed the leaf blower.

The scoop I used was resigned for better flow and directed air to the fan, but I think it still lacks efficiency and capacity to make a difference. Those side vents are awfully small for 914's fan compacity and based on some of the comments it seems the air flow from the vents to the fan are poor.

Oh well, back to the drawing board.

Click to view attachmentClick to view attachment

I disagree. I would call these excellent results. Okay, so the result wasn't what we hoped, but you had an idea and tested it with actual data! How rare is that?!! My hat is off to you for providing useful data to build on. Thank you.

The fan will only move a fixed amount of air, or CFM
Adding air won’t change what the fan can push.

Adding flaps underneath, like the factory did, creates more suction which helps the fan work better.

This is an oil cooled car, air assisted.
If you live in a hot climate, I would focus on oil cooling.

Consider the newer Boxster and 911 with split coolers up front underneath each headlight,
Look at the real estate you can get under those areas with a two row or three row cooler, then add “finned” tubing to route the oil up and back, and best the tubing inside the outer rocker cover.

You would be amazed how adding oil cooling, and like Mark said, adding the additional oil capacity, will dramatically help cool the motor.

the fact that you're gathering and analyzing the data!

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

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."

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.

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.

Dbl post