Just got this from ropeyracing

[Petrus]

So does the "stock" car not have the electric fan under the louvres?

No.
It has a metal tray.

[H1GRM]

I wonder how good the fan is at actually dispersing the heat.

[lgriffiths]

Hûh???

If you mean absorbing heat than no; it has no mass; just sheet metal.

Heat soak is when things you're trying to keep cool soak up heat from something hot when its not moving as there's no airflow to keep it cool. After a hard drive, things are pretty toasty in that engine-bay.

[Petrus]

So what I thought.
So no, no mass.

Btw, the engine room gets less hot than you would expect; léss than the front engine layout; there is a topic about that ;-)

It appéars to get a lot hotter because when you open the lid or are even behind the car, you feel the heat of the cat and muffler and yes those dó get hot, hotter than the traditional layout.
The engine however is in front of that, cooled by water ánd enveloped by a stream of fresh, cool ambient air from both side intakes.
When under load, so when exhaust/cat get hót, that airflow takes the heat immediately out the back; góne.
Only when hardly moving or stopped, do the muffle/hat radiate heat to the engine but that is per definition unloaded so not an issue.

[Joesson]

I wonder how good the fan is at actually dispersing the heat.

iirc @Ardent has a fan on the engine lid of his turbo.

[lgriffiths]

So what I thought.
So no, no mass.

Adding mass would make heat soak worse  as it would get up to temp when moving, then radiate the stored heat when your not moving.

To reduce heat soak you want to have a way for heat to get out, might not be for this at all, just a thought.

[Ardent]

I wonder how good the fan is at actually dispersing the heat.

iirc @Ardent has a fan on the engine lid of his turbo.

@H1GRM
Good enough. Wearing shorts as often as I can, this is how I discovered which way the fan works. I got out after a drive, heat was enough to kick the fan in and could feel the warm air around my legs. I was surprised as imiagined the fan would suck the warm out the top, but in fact blows the ambient air in, which then exits down, sides and rear. like when you are moving.

[1979scotte]

So does the "stock" car not have the electric fan under the louvres?

No that's a tte turbo extra.
Sucks air into the engine bay.

[H1GRM]

@s12vea sucks air in or hot air out?

[Petrus]

I was surprised as imiagined the fan would suck the warm out the top, but in fact blows the ambient air in, which then exits down, sides and rear. like when you are moving.

Indeed surprising and .... questionable:
1. When on the move, the louvres are in a turbulent, lower pressure drag area behind the hood.
2. The side vents take in air.
3. Sucking in aire from a low pressure area, into the engine room, raising the pressure, has less air coming in the side vents...
4. When not on the move the natural tendency for hot air is to ríse and going wíth the flow generally more effective than going against it.
5. I don´t get it.

On an NA though, a fan set up is contraproductive. It hampers flow when not blowing, is needless extra weight, sapping the battery thus engine and an extra complication potentially causing problems.
There is nothing better that natural air circulation; like thermosyphon; like gravity; the default is that it works.



On an u

[Carolyn]

When I saw Ardent's fan set-up, I thought the blowing down was weird.

Then I looked at where the heat was (the turbo and it's manifold), and where the potential heat soak is and blowing down made sense.

On my supercharger car, I've set the fan to blow up.  That's because the exhaust sits above the supercharger and it's ducting.

One has to remember that 'on the move' might well mean crawling along in traffic(or sitting still at the lights/junction etc.), when the side vents aren't doing much.

[shnazzle]

Air doesn't "flow" over the grill at the back. It tumbles all over and around it. Especially at speed.
Hood up, the airflow actually seems to come back towards the rear window and towards the passenger side (driver's side for you Petrus). I've noticed this tons of times in the rain at speed. The water pulls almost horizontally across the windscreen. Not downwards and towards the back of the car.
Hood down, you'll notice that if your wind deflector is up and it's a bit on the loose side, at high speed it actually folds inwards towards the interior. Mine's not THAT loose, so the force is quite big on it.

When I had my TTE banana spoiler, it didn't do this. Not sure what that means as I'm no airflow expert.

Easily sorted with an experiment with some strips of paper and tape I guess. Drive around and see if the strips just dance around like mad and fly off the car or whether they lie flat against the engine lid at speed.

In any case, I'm almost certain that next to no air "flows" in via the grill. The only evidence I've seen of any "flow" is nearer the sides. On a rainy day on a dirty car, you can see streaks on the lleft and right sides of the engine lid. I've seen someone put vents there. That makes more sense.

[s12vea]

@s12vea sucks air in or hot air out?

Sucks air in

[Petrus]

Air doesn't "flow" over the grill at the back. It tumbles all over and around it. Especially at speed.
...
In any case, I'm almost certain that next to no air "flows" in via the grill.[ /quote]

Hence my reasoning that sucking the air oút of the engine is the most logical:
- low pressure/turbulence above the louvres
- side entering air
- laws of nature: hot air rises

Even at low/no speed it seems odd to go against the flow, literally.

It´s the way it is though; the TTE fan sucks. Euh, sucks air ín ;-)

The spoilers.... that is a bit more complicated and depending on which one we are talking about. The TTE, TRD, ducktail and after market wing all have different effects, following the same principles ofcourse.

p.s. had a look on the web; kew TOM´s did something to this effect.

And here it is:



They put scoops facing forward, besides the top and two entries on either side of the rear lid. Can´t see wheather is has a fan in the chamber, blowing down, but it should.
Now, this is not proof of anythng ofcourse; just an illustration of what TOM´s did.

[Ardent]

Just to add another small variable.
Remember the fan only kicks in at a certain temp. It's not on all the time.
If you are moving it generally doesn't, It has, but rare.

We all seem to agree on the general normal air flow. The fan only kicks in and generates some, when there isn't.

Whether it is air or water flow.
Looking at the lovers and trays underneath. They line up rather nicely with rounded edge of the back box heat shield. I don't believe that is by accident. Equally the slim rear vent.

On the subject of air flow/turbulence. Driving along today windows down so air flow all over the place.
Then zap kapow, a wasp entered stage left and smacked itself into the rev counter binnicle face first and stayed there the rest of the ride. Dazed and confused.