Alternate engine cooling setup Options

[Superhawk996]

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. (IMG:style_emoticons/default/happy11.gif)

[windforfun]

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

[windforfun]

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.

(IMG:style_emoticons/default/agree.gif)

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.



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

Right on!

[9144me2enjoy]

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

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

[thelogo]

Yeah im not sure why your fixing a problem that doesn't exist (IMG:style_emoticons/default/screwy.gif)


I did like the idea of having the fan run for a bit
After turning the car off (IMG:style_emoticons/default/pray.gif)



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

[Rand]

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.

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 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.

[9144me2enjoy]

Yeah im not sure why your fixing a problem that doesn't exist (IMG:style_emoticons/default/screwy.gif)


I did like the idea of having the fan run for a bit
After turning the car off (IMG:style_emoticons/default/pray.gif)



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

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.

[mikesmith]

Pics

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(

[9144me2enjoy]

Pics

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.

[thelogo]

Yeah im not sure why your fixing a problem that doesn't exist (IMG:style_emoticons/default/screwy.gif)


I did like the idea of having the fan run for a bit
After turning the car off (IMG:style_emoticons/default/pray.gif)



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

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.

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 (IMG:style_emoticons/default/poke.gif)


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