Is the electrical fan conversion any good?

[Jan Pedersen]

According to this guy: http://hachiroku.net/forums/showthread.php?t=17462
An electrical fan will free up 6 whp!!! It does seem quite optimistic though...

[NoHachi]

If you believe it takes 8 fullgrown horses to spin that tiny little fan there..

Like you said.. a bit optimistic..I think he's missing a zero and a dot in that figure.

[jondee86]

The fan absorbed power that is stated, occurs at around 7,500 rpm
engine speed. The fan is overdriven. I don't have the measurements
to hand, but I'd guess by about 30%. In round figures this will give a
fan speed of 10,000 rpm.

Now, the Fan Laws say that the power absorbed by a fan varies as the
cube of the rpm. So, even in the absence of any data on airflow or
pressure, I have no difficulty in believing that the OEM fan could absorb
8 hp. Dyno testing is probably more demanding than actual road use,
as there will be less airflow thru the radiator from the external cooling
fans. And the viscous coupling tightens up as it gets hotter.

Having said that, I still use the viscous fan for everyday driving, but I
do take it off for circuit racing For a dedicated race car I would use
an electric fan and thermostatic switch.

Cheers... jondee86

[heshan]

8whp??? Now this is something I really didn't expect such a huge gain.. probably not so much on a stock engine..

[NoHachi]

jondee86 Wrote:Now, the Fan Laws say that the power absorbed by a fan varies as the
cube of the rpm. So, even in the absence of any data on airflow or
pressure, I have no difficulty in believing that the OEM fan could absorb
8 hp. Dyno testing is probably more demanding than actual road use,
as there will be less airflow thru the radiator from the external cooling
fans. And the viscous coupling tightens up as it gets hotter.

I've been taking a look at fan related websites..for example:
http://www.engineeringtoolbox.com/fans-e...d_197.html

If I punch in some numbers, say 1500CFM =~2000m2/h at any pressure rise (usually negligable in cars) I come up with an "ideal "power consumption of between 0.04 and 1.00 kWatt.. more or less in line with what I expected..

You have to punch in some crazy numbers to explain an 8hp drain. For example:
- that the fan has to work against a pressure difference of more then 2Bar (usually in a car, the pressure tends to work in your advantage..the little fan certainly isn't able to bring underhood pressures to anything remotely positive...wish it could though..cheap boost!)
- the fan is pushing more then 10.000m3/h..or around 6000CFM! (for reference..big block V8 dragster fans..designed for short and heavy loads in circle track and dragracing push around 3000CFM.)
- some very poor efficiency numbers..only possible if toyota got the design completely wrong..

Would love to see some some fan-law calculations to see in which ballpark they end up.. My feeling is that its between 0 and 1 hp (@crank).

Look at it from another perspective..an electric fan replacing the OEM fan would have to pull similar numbers.. lets say its about 50% more efficient (huge!) then it would be close to a 4kW current draw.. any idea how long the combination of alternator and battery would sustain that? (stock alternator =~ 1kW).

[jondee86]

I don't think it is as complicated as that The Fan Laws state that the
absorbed power is proportional to the cube of the speed. If we assume
that the stock fan absorbs 100 Watts @ 1000 rpm, then @ 5000 rpm it
will absorb 12.5 kW.

These figures are simply to illustrate the point. I have no idea how much
slip there is in the viscous coupling, so cannot say if it runs even close to
the pulley speed under load. Nor do I know how much air it shifts. What
I do know is that a small bathroom extract fan will absorb 60 - 100 Watts
against negligible resistance.

So, as I said earlier, to me it is quite plausible that the engine driven
fan can absorb the level of power demonstrated on the dyno test.
Electrically driven cooling fans only need to shift air when the car is stuck
in traffic. At other times the movement of the car will provide sufficient
airflow thru the radiator.

The engine driven fan responds to the leaving air temperature from the
radiator. In low airspeed, high load situations (such as on a dyno), it will
be working hard.

Cheers... jondee86

[Gnugfur]

jondee86 Wrote:So, as I said earlier, to me it is quite plausible that the engine driven
fan can absorb the level of power demonstrated on the dyno test.
Electrically driven cooling fans only need to shift air when the car is stuck
in traffic. At other times the movement of the car will provide sufficient
airflow thru the radiator.

Hey

I agree with everything else. But i want to add something here.
With proper fan control like a ECU management system. You are able to control when the fans should activate. You could even do that with a turn knob if you tune its voltage right.

Anyway, we ran a 550bhp 200sx S14 on a small track that we got here and it overheated after one lap. Changed its thermostat, it improved. But after mounting up dual fans that ran constantly when we did laps we never had a problem with overheating.

[jondee86]

Gnugfur Wrote:Anyway, we ran a 550bhp 200sx S14 on a small track
that we got here and it overheated after one lap. Changed its thermostat, it improved. But after mounting up dual fans that ran constantly when we did laps we never had a problem with overheating.

No mystery here !! The cooling system is essentially a water to air heat
exchanger. For the engine temperature to remain stable, the heat gain to
the water from combustion etc, must equal the heat lost to the air.

In any race car the cooling system must be rated to handle the heat load
from the engine. In your case, the cooling system was inadequate for the
power output on a low (road) speed track. You increased the airflow (and
therefore the heat rejection) by installing two fans. On a faster track, one
fan would probably have been enough

Cheers... jondee86

[Gnugfur]

jondee86 Wrote:

Gnugfur Wrote:Anyway, we ran a 550bhp 200sx S14 on a small track
that we got here and it overheated after one lap. Changed its thermostat, it improved. But after mounting up dual fans that ran constantly when we did laps we never had a problem with overheating.

No mystery here !! The cooling system is essentially a water to air heat
exchanger. For the engine temperature to remain stable, the heat gain to
the water from combustion etc, must equal the heat lost to the air.

In any race car the cooling system must be rated to handle the heat load
from the engine. In your case, the cooling system was inadequate for the
power output on a low (road) speed track. You increased the airflow (and
therefore the heat rejection) by installing two fans. On a faster track, one
fan would probably have been enough

Cheers... jondee86

You are most correct good sir.

Its a very small track indeed. Made for gokarts. So you're hardly ever up in any high speeds at all.

[harkes]

I used a fan from a CarinaE 1,8 - fits perfectly

- Harkes