PWM fan or E30 fan with stock wiring?

[NvE30]

Is it better to use a PWM electric fan or just use stock e30 fan with stock wiring with Hi/Lo speed relays?

[R3Z3N]

Advantage to the PWM fan is threefold: better heat management dependent on speed and temperature, less shock load the the system as the fan switches on and off, more power at wide open throttle as the fan will turn off to not draw alternator power.

Here is the full version of how the PWM fan works

[Northern]

less shock load the the system as the fan switches on and off

I think this is the big one for me. I use the Merc switch with aux fan wiring, and there's a definite idle dip/light dimming when the fan kicks in.
Not really a problem, but it's something that's recently started to annoy me more.

[TobyB]

The only real down side to the E46 system is that the pwm fan's a known weak spot.

It's certainly very elegant.

t

[nando]

You can control any fan with PWM - including the stock E30 fan. the PWM module can be removed from any E46 fan, and you can wire that to whatever fan you want to use.

Personally, I got tired of the fan switch because it switched on/off constantly and was very noticeable. I'd definitely do PWM if I had the choice.

[ba114]

Clutch fan FTW

[R3Z3N]

Clutch fan FTW

No clutch fan for S54 swaps...... not enough room.

[nando]

Or N52s, which never had a clutch fan to begin with.

I mean, the clutch fan definitely cost my M20 some power. and I had plans to put the electric fan back in with a PWM controller to avoid the harsh on/off switching... but, it's slow either way, so I just never bothered.