Power for an engine bay fan?

[routier1642]

I want to fit an engine bay fan in my VZ Adventra.

I know little about car electrics.

What's the easiest way to wire it in?
It may need to pull 4A or so.

 

[Big-Al]

4amps is not very much. what sort of fan is it and what do you want to do with it?

 

[routier1642]

I haven't picked the fan yet.

I'm doing experiments to improve the airflow through the engine bay, mainly to cool the intake system.

I've been working on passive cooling that works when the car is moving, like ventilation holes and partial ducts, but the measured temperature of the intake air builds up rapidly whenever the car is at rest.
Short of putting vents in the bonnet, which would only help a little when stationary anyway, I can't see a solution other than a fan.

I know that the energy put into the fan may not be returned by the small gains of colder air. I know that.
But I'm not going to give up on the idea without trying it.

So - where can I plug it in??

 

[acarmody]

Directly to the battery and switched on via relay tied to something that only turns on accessories is the easiest.

 

[PIR4TE]

Mate I did some research into cooler IATs because of MaFless wandering like a drunk in the sun sucking in 70° over the radiator around town heres one of the threads you might be interested in.
I packed in the investigation when I realised that the best solution was ethanol (e85) not only its cooling properties and manifold pressure effects but E85's resistance to knocking allowed it to withstand intake air temperatures all the way up to 130°C, and spark timing of 30° bTDC before knocking.
In other words induction and combustion are vastly improved and hardly dependent on IATs at all, except below 0°C.
Here's some good reading, http://dspace.mit.edu/bitstream/handle/1721.1/59952/676953430.pdf see bottom of Page 39 and summary on page 51.
Simply change your fuel pump (~$150), swap injectors and get a flex fuel sensor (~$150). You can DIY tune using either software or pay a lad with a lappy either way is about $500 to calibrate and optimize.
112 RON, 40% less carbon and up to 50¢ a litre cheaper than 98.