My 914 is running a 2056 build, never really had a problem with overheating but I decided it couldn’t hurt to help pull some fresh air into the engine compartment towards the cooling system, Especially if it only cost me $30.98. I have my rain tray removed and the rough part was finding a small enough cooling fan to fit under the lid! I found this one on EBAY for $30.98 shipped. It’s a 12V 80W 7” Slim Reversible Electric Radiator Cooling Auto Fan Push. Hooked up a hot and ground where it only comes on when the keys on and it works great! Just used cable ties to attach it to the wire mesh. I will have to watch my temp gauge to see if it actually drops my temp any. EBAY #183643285998. Not as good as a oil cooling adapter system but I cain’t see where it can hurt anything. Have a great day

Pics

Nice work!

Thanks, appreciate the comment! Have a great day, enjoy your 914.

If you live in a dry country area, or don't drive in the rain, your OK.

No rain tray without some kind of rain hat air cleaner cover is a little dangerous, as you could get rain in the carbs and hydrolock your engine. This is why the PMO watershields are so popular for 6 cyl engines.

Very true! I keep a precut piece of plexiglass with me just in case I’m caught in the rain, which fits over my engine cover. Attaches with 4 magnets.

I respect your work, so please don't be offended. But that little electric fan doesn't do anything. The fan on the engine is a thousand times stronger. If you have any heat issues, there's something else wrong.

Wondering if this set up also helps as a cold air intake. Remember this research? https://members.rennlist.com/demick/coldair.html

Maybe but a 914 gets hot when it is idling @ traffic lights because the fan speed is slow ,an otherwise healthy well tuned engine gets cooled fine when its running along,if the fan moves enough air it could help with cooling but depends on HOW much it moves,the 914 fan moves 300cfm max that's a lot of air.
Besides if people didn't try stuff we would have no development of "improvement' parts for our cars,you only need to look @ the many vendors on here that have done just that.

I've considered doing this not to cool the engine while running but to help cool down the engine once I stop and turn the engine off. Thought about a 10 minute timer. 7" Fans on Amazon show 1350 CFM and one has 1730 CFM, alot higher then I expected.

The small fan will have minimal impact. Engine fan not quite 1000 times stronger literally but the thought process is correct. The engine fan air is forced directly across the cylinders and MORE importantly the oil cooler.

Unfortunately even though these engines are called air cooled, they are largely oil cooled. Not only by the oil cooler but also by oil in contact with the engine case. This is why there are fins on the bottom of the engine case even though those fins are not touched by the cooling air coming from the crank driven fan.

Air has a terrible inability to remove heat from objects. The ability to transfer heat is reflected by a materials heat transfer coefficient. Air has a very low coefficient. This is offset by having a huge surface area of cylinder fins and head fins to increase the effective area cooled by this low heat transfer coefficient of air.

Liquids like water or in the 914's case, OIL have a far higher heat transfer coefficient. Actually an order of magnitude higher (10X). Oil flowing in the oil cooler could actually be two orders of magnitude higher (100X) depending on the conditions of the air (humid vs. dry, air velocity, etc.). Compare the numbers for oil flowing in tubes (i.e. the oil cooler) vs. gasses in free convection.

See table of heat transfer coefficients below.

Click to view attachment

For many engines that are running hot, the oil cooler can be found to be obstructed and/or the cooling flaps have been disabled or worse removed.

For more info:
https://www.engineeringtoolbox.com/convecti...sfer-d_430.html

Like other post I just posted, I don't mean this as an offense. I agree completely that experimentation and development improves the breed but the experimentation should generally be backed by physics and engineering first principles.

I say this because there are a number of unscrupulous vendors out there. However, I'm thinking more of the improve your fuel economy by 100% by attaching our special rare earth magnet to your fuel line variety than any specific vendor that supports this forum!

As stated already, basically zero effect on a running engine. Would have more effect on a non runing engine (after shut down) but only if the direction was changed to pull hot air out of the engine compartment.

Never hurts to try!

I’ll apologize in advance. I’m an engineer and love to debate for the sport of it.

Exactly what problem is being solved by cooling the engine after shutdown?

Does it justify the weight, complexity and cost of the fan?

I’m partial to the Colin Chapman school of weight management. Less weight = better. 2000 lb vehicles don’t happen by accident or by adding on unnecessary stuff.

It really isn’t a matter of just try. The engineering works or it doesn’t.

A fan like that OP picture is very ineffective without a shroud covering the rest of the grille opening. You will essentially get recirculating around the edges of the small fan shroud that kills the efficiency of the electric fan. Covering the grille to improve the efficiency of the fan would destroy the normal convection that otherwise cools the engine after shutdown.

Additional consequences;
Running the fan post shutdown draws down your battery.
Alternator then has to work harder after restart to charge the battery
That added alternator load puts more load on engine and then engine runs hotter (trivial amount)
That added load from alternator robs fuel economy and creates more emissions at startup (May or may not be trivial depending on your point of view)

Sorry I just can’t help myself. The point being we don’t have to just try it to work through the effects. Even if someone wants to try, you have 1/2 of the instrumentation needed to do the science projects. Use the cylinder head temperature sensor, measure resistance change over time with the fan on and the fan off. Plot results and let the data decide.

I am easily swayed by sound data.

Oh boy, double sorry guys!

Yes it will help to cool the engine when shut down. But I'd surmise that the effect is negligible in the long run. Once the engine is shut down it's technically cooling at a much larger differential. You feel the heat radiating out, but the engine has a boundary layer of air that is not not moving in the fan area and fins. If you actually needed cooling, a fan that directs air through the normal cooling path is 20x more effective than ambient air movement.

There is a natural cooling of the motor by design. Warm air rises drawing heat upward from the engine. In theory the air under the car (ground) is cooler, so it can be drawn up as the air above rises.

In short, if it makes you feel better great, but the down side is more electrical load when the charging system is off, as well as a new electric circuit that you have created Directly off the battery with a timer switch would be best.

I guess the question is why is it running hot? Do you have an oversize displacement that creates more heat?

I have a 72 with an external oil cooler (mounted under the car) that is stock except that. It was a Reno car for most of it's life. I like this approach best as it keeps the car cooler to begin with. Additional capacity for volume and heat exchange are your friend.

Slight add: technically the temperature differential between cooling air and the engine hasn’t changed after shutdown. You also go from forced convection (more effective) to natural convection.

What has changed is that you’ve cut off the heat INPUT. That is, the engine is no longer burning fuel and having 85% of that fuel energy wasted as heat generation.

OR you can use a set of THESE:
Click to view attachment

Great responses, back to the drawing board Thanks

Not to be picking nits here but all that hot oil is still cooled down by air. That's how oil coolers work.
Heck, even your water cooled car is still cooled by moving *air* over the radiator.

Yes, both oil and water are much more efficient in removing heat from an engine case/heads/etc, no question here. But the final heat dissipation is still done by air.

You’re good. I concede that point that air does the final heat removal from the oil cooler is by air.

Many just overlook how important that little oil cooler is. It may look small but it is very effective and very important to 914 cooling.

FYI - many modern engines now use oil to water coolers (Ex: turbo cooling). No air involved. That is until the water is cooled and again I’ll concede that the final heat transfer to environment is by air. But riddle me this. . . Then why don’t we call all ICE engines and even EV's with liquid cooled batteries . . . Wait for it. . . Air cooled?

Quick anecdote on cooling power of oil to aluminum case heat transfer.

When in college, and participating in Formula SAE, many teams took typical motor of the time, liquid cooled Honda CBR 600, and mounted the engine directly behind the occupant seat mid engine style with little if any real airflow getting to it. Recycled the factory CBR radiator thinking the cooling problem was taken care of (assuming stock HP).

Wrong. Overheating results.

Why? In part, because of lost the cooling of the engine case being exposed to the air stream like it was on the motorcycle (even though partially behind fairings on the bike).

Bottom line: Don't discount the radiation and convection cooling of that aluminum case filled with hot oil.

Are those tie-wraps holding the fan? They'll dry out & crack in no time from the heat.

Right on!

I used tie wraps when I first installed it but now I’ve metal strips. thanks

Yeah im not sure why your fixing a problem that doesn't exist


I did like the idea of having the fan run for a bit
After turning the car off



But if its cooler engine your after a front mounted oil cooler will be the best .

And if i was going to try to force air in thru the grill
Id setup a roof or side scoop /snorkle that would ram air into the engine compartment via ram air (at speed of course) but routed to the carbs not just to circulate air

I used to worry about that, but I found that zero load on the engine at idle more than compensates for the fan speed. The heat factor ramps way up under load. I used to worry about that until I ran head temp gauges and saw that a moving car does not run cooler than an idling car. I'd be curious what you've actually been able to measure.

I totally love to see people experiment! Sorry if that came across wrong.

TheLogo just a thought, you might be on to something there in reference to rigging up a ram air system directed towards the carbs air filters! The only performance aspect that can be guaranteed is that the air entering through the ram air system is at the ambient (outside) air temperature. From that aspect, Routing the air from these locations reduces the stagnant pressure head as the vehicle is pushed through the air. Additionally it also delivers air at the lowest temperature possible.
Something you must consider and deal with is pressure equalization between the fuel bowl and the amount of air fed to the venturis. If this is not taken into account, the mixture leans out as speed increases. You need to make sure the fuel bowl vent tubes experience the same pressurized air that is feeding the venturis.

Apologies for jumping on the dissing bandwagon, but without a baffle or some ducting much of the air will just go around the outside of the fan and back in the front again.

Sorry. 8(

I agree about the baffle or ducting directly into the engine fan.

I see what you mean
I guess to really take advantage a old 911 type airbox
Would be better to route the air then right down the carb
Throat


But now im thinking keeping the engine compartment cooler not for engine temp but for cooler ambient air temp for the intake