Aircooled VW South Africa

I noticed there is some type 4 topics going around I found this pic on the net and would like to know what you type 4 gurus think about it

I think it can work if the fan can supply enough cfm.

From what I could find on the net the std beetle fan produces

Looks like ~1700-1800 CFM with a doghouse fan and std pulley, assuming no slippage, 5000 crank RPM.

A good 12" electric fan can produce:

Electric Fan, Single, 12 in. Diameter, Reversible, 2,300 cfm, Black, Plastic, Kit

if you do more probing into that car, you will find it isnt a street driven car, but is used for short course "auto cross" events.

Big problem is air pressure. The standard type 4 fan pumps 800 litre per second at 4600 rpm, (vw's spec). This is at a relatively high pressure, to get this much air to flow past the small gaps between the cooling fins. Aircooled vw engines needs lots of cooling air pressure.

A typical electric radiator fan is not designed to work against that kind of back pressure. Those designed for that kind of pressure needs plenty energy. More than the alternator can supply.

Other problem is efficiency. The typical automotive alternator's efficiency can be as low as 50% at full load. More a type of "cost effective domestic" class design. Look at how relatively thin it's stator wiring is, (often under 2mm), compared to say house wiring rated at 55-100 amps. An alternator relies on lots of cooling air to prevent that thin wiring from burning out. Like a domestic vacuum cleaner, that generates more waste heat than mechanical power...

Add to that the losses of the electric fan.

Best efficiency is by direct mechanical drive.

Watercooled cars use electric fans because:
1) Many of them have transverse engines and it is difficult and expensive to change mechanical shaft drive through 90 degs. (think some early Peugeots tried this with a loong belt and lots of pulleys). Most heavy duty longitudinally engine mounted bakkies and 4x4's still use mechanical fan drive.
2) ease of regulating cooling by changing fan speed.
3) radiators designed for electric fans are of low air restriction, large surface area type.

The beetle and type four takes about 4 hp to turn the stock fan there is just no way to get 4hp from 12v
Armand

Dawie wrote:Big problem is air pressure. The standard type 4 fan pumps 800 litre per second at 4600 rpm, (vw's spec). This is at a relatively high pressure, to get this much air to flow past the small gaps between the cooling fins. Aircooled vw engines needs lots of cooling air pressure.

A typical electric radiator fan is not designed to work against that kind of back pressure. Those designed for that kind of pressure needs plenty energy. More than the alternator can supply.

This is obviously why a turbo is not electric either, you can't get decent pressure from the limited resources & space in a car..
(And when I say a turbo I mean the turbine is not an electric fan)

This is obviously why a turbo is not electric either

Electric assisted turbo prototype

Electrically "assisted" being the operative word. That "assistance" is probably about reducing turbo lag, but you can see the turbio is still exhaust driven because the electric drive alone can't power the turbo at full power.

You are correct. It is only assisted to reduce lag.

If they clever, the waste under no boost conditions can turn that thing into a generator.....

Rgrds

or if they are even more clever, they can install a turbine that is way too large and use it to regulate boost pressure by using it as a generator.
Kers system?

Except for the loss of power due to exhaust back pressure.

4hp is 250A at 12 Volts. That's kinda heavy...