I've had mixed results with electric fans, but the D3 goes to a electric fan setup, and while replacing my fan clutch on the D2 S8 I have now, I ran without any fan for a few hours in the winter, and it was not only so much more QUIET, but there was absolutely more power off the line that I noticed, and when the new fan clutch was put in, it was noisy, and cut down on power that I can feel. (After a few seconds, you can't tell, but off the line, in traffic, you notice it.)

Just the noise reduction is a nice benefit, and I'd be willing to think it would improve fuel economy on long drives too.

I've also considered this on my S8.
Remind me, does the S8's radiator have a thermoswitch? I've replaced the damn thing when I bought the car 10 months ago and can't for the life of me remember if it had one!
I know my B5's radiator does...
If I was to go down the thermofan route, I would want an independent circuit from the aircon auxiliary fan, and the ideal trigger is a cooler temperature switch.

Previous to my B5, I had a Holden VR Berlina efi V8. I fitted this with a twin thermofan setup using a radiator mounted thermoswitch (with relays etc). The (indicated) fuel consumption on highway cycle went from roughly 25mpg (US) to nearly 28mpg. Harder to calculate with local driving, but there was an improvement.
Economy gains wasn't my main motivation though, the engine became much freer revving and had more noticable off-the-line performance. They say an engine fan (which in the VR's case was a 5kg steel monster!) is worth 5hp...

See post # 5 here >>

https://www.audiworld.com/forums/sho...4#post24523814

Ah that's interesting!
Thanks Sam.

So it could be quite simple to wire, using the auxiliary fan's power wires as either feed or trigger for a relay. Though the relay idea limits the two speed action...
I had no idea the thermoswitch had two temperature settings. I still don't recall the thermoswitch in the radiator though - forgetting things at the grand old age of 38 ;)