Cooling the car

[BadBong]

Thanks everyone for their input thus far. It sounds like wrapping the headers is a risky move.

It might be worth a try to reposition the intercooler and the aircon radiator so that the main radiator has more unobstructed airflow through it.

I’ve seen it in other vehicles where they form the shape of a horizontal ‘V’ directly behind the mouth of the front bumper. Has anyone seen this been done in an NB?

*Holding my breath on the cost of this… but I don’t want to leave the car as a ‘winter vehicle’. What’s the point of having an aircon if you can’t turn it on during summer…?

[Magpie]

http://clubroadster.net/vb_forum/58-forced-induction/65885-v-mount-setup.html#post1365582

I would look at the other suggestions first before the V thing. Contact NitroDann to discuss other solutions.

[davekmoore]

Of course it isn't always this simple but ultimately you're trying to get enough air to create a cooling effect by penetrating 4 things that are otherwise trying to stop it.

1. Intercooler, which is stopping flow to the
2. Air con radiator which is stopping flow to the
3. Coolant radiator, and yours is extra thick, meaning the air struggles to get through it and
4. Under-bonnet air pressure, which pushes back against incoming air and makes it harder still for incoming air to get through 1-3.

Adding more intake scoops will add to 4 and reduce flow. The existing air inlet area is plenty big enough.

Blocking off the holes where the fog lights were will allow more flow by slightly reducing under bonnet pressures.

The wool tuft test on your bonnet vent will soon show you if it's allowing more air in instead of venting pressure.

If you have to keep the air con radiator you might find you still need bonnet vents. These ones will allegedly reduce pressures by 50%: http://www.miataturbo.net/group-buys-me ... buy-80427/ and may be available elsewhere by now. Or, because I've given up on having air con my Mad Max bonnet is available!

Sealing around 1-3 will ensure air has no choice but to flow through them if you've dealt with 4.

[bruce]

I don't agree that the mouth of an MX5 is pretty big. It's big enough to cool a stock motor, but once you mod the motor heaps, you notice the restriction. It is a tiny hole. Not that I'm advocating to mod it and ruin the cars looks.

[NitroDann]

This isnt true for reasons Ill elaborate on later tonight.

[SuperMazdaKart]

Might be worthwhile to try a non ethylene glycol non anti-freeze coolant. Such as Nulon's Ultra Cool which is a coolant suitable for motorsport use as it's not as slippery if spilt on a track & has a better heat transfer then glycol based coolants.

[A.Chen89]

Vic, have the tuner look at the coolant temp adjustment/fuel cranking when the car is pretty hot. Sounds like it just needs tweaking there to stop the stalling and fix your hot start.

[davekmoore]

This isnt true for reasons Ill elaborate on later tonight.

Baited breath, Dann.

[Lokiel]

I don't agree that the mouth of an MX5 is pretty big. It's big enough to cool a stock motor, but once you mod the motor heaps, you notice the restriction. It is a tiny hole. Not that I'm advocating to mod it and ruin the cars looks.

949racing's Crusher (N/A) actually reduced the size of the mouth:

- with dedicated ducting, they got "too much" cooling (water temperature too low) so reduced the size of the mouth
- the two round ducts either side are brake ducts

Note also that the mouth has a grille over it which actually restricts the maximum amount of air that could enter the mouth.

[NitroDann]

Alright so basically to cut a really long easily google-able story short, many people seem to want to expose the entire front of their radiator to front on airflow.
Like this.

(Yeah its an intercooler, but you get the point)



What we are trying to do is get all of the airflow through the radiator right? so we feed the radiator with a hole as big as it right? Wrong. The radiator is made of metal, its about 2/3rds metal, only a third of the frontal area of a radiator is actual gaps that air can pass through, and on top of this there is significant restriction through those holes because of non linear flow (turbulence).

This is a close up of a radiator, check it, about 2/3rds metal and only 1/3rd of its frontal area can flow air through it.



But surely a hole bigger than 1/3rd will help to force the air though? Again no. While the gaps for air are around 1/3rd, turbulence in those gaps between the fins is very high due to the high air speeds and the tiny gaps. Restriction is also caused intentionally because of these little things that are manufactured into the fins called turbulators.

See below



This is a stack of heat exchanger fins and as you can see, on the inside there is corrugations and those corrugations have micro sized slots in them to increase surface area and turbulence.

So why do we want turbulence? Surely linear flow would let more air through and get us better cooling? Again no. The huge airspeed jams the air through just fine despite the 'small' 1/3rd mouth
opening. What the turbulence does it mixes the air up as it passes through and ensures fresh molecules of air constantly hit the fin surface.

The greater difference in temperature between 2 molecules there is the faster heat is transferred. This is called 'Delta T'. This is why even though we only want our steak to be 55*C when its cooked it cooks a lot faster if the pan is red hot. Because the hotter the pan the greater the difference in temperature and it transfers that heat faster.
When the molecules of air pass through the radiator they warm up and start to transfer heat slower and the turbulators ensure the air bounces around and fresh, cold molecules hit the hot fins.

Many OEM cars have 1/3rd rule openings for example.
VX commodore


NSX


MX5


See crusher above for how small it can be with 200whp and a good cooling system.

And here are some more fast fast cars fronts.

Note: only the middle lower hole goes to the radiator.







What you do have to do is duct that 1/3rd hole to the radiator to make sure the radiator uses all the third.


Etc etc

Dann

[speed]

This is one if the many reasons I love this forum. Thankyou Dann for teaching me yet another valuable lesson

[Steampunk]

A mate pointed this out as a great example of big-horsepower/small-opening

[bruce]

The NSX and Maclaren have their motors in the back (thus a lot of the heat off the motor is not cooled via the front-they have ducts in the side of the car?).
That race car 5 is always travelling at speed. Sitting in city traffic I predict it would suffer.
But you have to consider, when you get the science right, a small opening works (ala stock MX5). When you muck around with a 5 as we have done, the science is not happening.

[NitroDann]

The engine block does not need air cooling.

The mouth being made bigger doesnt help at high speed, and for the same reason cannot help at low speed either.

Dann

[hks_kansei]

i'm with Dann here.

Engine blocks dont have air cooling (outside of Beetles and bikes), the closest you have is the sump which does get a little bit of air cooling, but I mean a little bit.

An easy way to see if something is using air to cool it is to look for fins, ie: excess surface area to get more air onto the item to cool it.

radiator has millions of tiny fins.
Motorbike engine has lots of fins on the block
MX5 engine has none, other than some small ones on the sump (which are more likely strengthening ribs than cooling fins)


Radiators also need the air to move at the right speed through them, too slow and the air isn't drawing the heat out enough, too fast and the air doesnt have a chance to absorb the heat to remove it.
Same with the coolant, fit a slow pump and the engine cooks before the coolant can cool it, too fast and it cooks because the coolant isn't having the heat drawn out of it in the radiator.