I have headers on my 2056 and no heat. What are people doing wit the outlets on the Fan/Blower housing at the bottom of the engine?

1) Leave them open and let them blow. NO HE or Tubes and such any more

2) Close off the blower outlets on the housing?

NOTE: this is not the aux electric blower that turns on with the heater in the engine bay


this was an older topic but I’m not finding with me search criteria

Either leave them open or block them off from the inside. Blocking them from the outside disrupts the air flow as it is trying to blow air into a dead end. Keep in mind that air normally flows thru them at all times even when the heat is off.

I have an old housing, it would be fun to reshape the inside to delete the outputs, but I would not have any way to measure the results? and NOT pulling it at this time to play
One would guess that it will make more flow if done correctly?


IF its better flow and better cooling? Is more flow/ faster flow better cooling?

Some one must have done this before this thread?

Rarely.

The problem is that airflow isn’t the dominant factor - it’s the extremely limited ability of air to cool vs a liquid like water. The dominant factor in air cooling is the temperature differential between the ambient air and the engine.

Here’s a chart of the heat transfer coefficient of air (Hc) vs air velocity
Click to view attachment


You’ll notice it (Hc) gets flatter as air velocity increases. You can do the thought experiment that if you were able to achieve a sky high velocity; the cooling would diminish because the cooling air would be moving so fast, it wouldn’t even have time to pick up heat from the head because of the short time the air is exposed to the head, and the poor thermal conductivity of the air itself.

So unless you’re starting low on the curve with very slow airflow, the gains diminish as velocity increases due in part to the compressibility of air. Meaning it’s taking a bigger and bigger fan to increase air velocity with more HP being required to drive the bigger fan.

I don’t have the airflow velocity numbers for the T4 engine (could be measured) but I’d be willing to bet that Porsche engineers optimized the airflow vs HP consumption. As a result, trying to move the operating point by increasing air velocity will only net you diminishing returns.

maybe i am not understanding but it seems that if we dont need the air from the impeller to push air into the HE, that if you remove those and just block off the bottom of the fan housing that more air would flow then over the top of the motor, its got to go somewhere, i have wondered about that for a while. i know the much of the cooling of the motor is from the oil circulating a pulling heat out internally but over hthe cylinders and heads, more air for certainly is necessary and helpful, now maybe not as much as we would like but less air going out the bottom of that allowing for more air directed over the cylinders i would thing would help especially on hot humid days of the south.

1

Matt

here is a view from the inside to block off the bottom outlets;


Click to view attachment

Not that simple.

Blocking off the lower outlets will increase static pressure that the fan sees.

There is a basic relation ship between airflow volume and static pressure. As static pressure increases, airflow decreases.

Below is a typical centrifugal fan curve vs static pressure. If we start at lower static pressure (yellow) line and increase the static pressure by constricting the airflow, you’ll see that the curves now cross at a lower airflow volume (red).

The exact result would depend on the specifics of the T4 motor fan curve and exactly how much the static pressure increases by blocking off the lower outlets.

Only thing I would say is, someday play to just run headers as well for accessibility etc, since I only drive on summer days. I think leaving them open would have a small advantage do to others saying they are always moving air. I would like to see something to stop the potential of mice building a nest in the open cavity, scene, mesh etc.

If I had heat exchangers, I would run the fan outlets just to cool the HEs and increase primary tube life. I'd leave the exits open if I was not using them for heat to the interior.

There is no downside to reducing the exhaust temps IMO.

I'd KILL for a sheet metal encased down tubes with forced cooling on all of my turbo builds. It's the ONLY way to properly cool stupid hot turbo exhaust.

On a turbo Miata this type of cooling set up would negate the need for transmission tunnel heat shielding.

Unshielded, a turbo Miata can melt your shoes!