PWM fan control?

[Jon K]

Just thinking aloud - one thing that bugs me sometimes is when my huge draw electric fans turn on (no mechanical fans on my car any longer). The draw is instantaneous so the ECU doesn't have a whole lot to work with - voltage correction maps working fine but this is a quick surge situation. Was thinking of picking up a PWM controller but was thinking it'd be more convenient if DTA could do it. Just thinking out loud!

I know Alex is prob tired of my thinking of crap lol

[Rob Stevens]

You could do it with an aux output but depends on the current you intend to present to the ecu.

I have seen a way of running 2 fans in series (6v) then using a relay network to switch them to parallel (12v) for full power. But I can't find the wiring diagram, and it uses 2 ecu outputs

[stevieturbo]

I dont think there would be any way for DTA to do it internally....

ie it cant handle the current and doesnt normally pulse that fast.

Even the Aux out's dont pulse particularly fast to try and use an SSR to then handle the current

If the firmware could be changed to allow the fan output to be a proper fast PWM signal....it would be a good upgrade.

There are various high current motor controllers out there that can do that part of the job, I'm just not savvy enough as to how to make the DTA control them !
Most seem to want a variable resistance as the high/low controller...a small few will accept a voltage input.

[Jon K]

You could do it with an aux output but depends on the current you intend to present to the ecu.

I have seen a way of running 2 fans in series (6v) then using a relay network to switch them to parallel (12v) for full power. But I can't find the wiring diagram, and it uses 2 ecu outputs

The current draw on my setup could be pretty high - higher than the ECU could handle natively. But perhaps a pair of solid state relays and a PWM output from the ECU?

[Alex DTA]

Aux out with PWM based on coolant temperature + solid state relay should work. Frequency is adjustable too.
Which aux outs do you have left?

[Jon K]

Aux out with PWM based on coolant temperature + solid state relay should work. Frequency is adjustable too.
Which aux outs do you have left?

I have to take inventory - I think you're right that this should work. I need to map out my I/O so I can recall more quickly whats free/not and what conflicts/doesn't.

[ignitionautosport]

Could use an OEM fan controller that outputs a nice voltage instead of pulsing with the pwm, have seen guys use them to power fuel pumps too these days and run a duty map for the fuel pump rpm vs boost.

[stevieturbo]

PWM'ing is far better for everything vs some sort of resistor based lower voltage.

But frequency's need to be high, I've seen most electronics type people say 10k or so although I know people have used lower.

[ignitionautosport]

Agreed, just apparently the OEM controllers must increase the freq or something to make the output smoother? It's a guess.

I don't argue with Crispeed

[stevieturbo]

Agreed, just apparently the OEM controllers must increase the freq or something to make the output smoother? It's a guess.

I don't argue with Crispeed

Oddly what he is suggesting is completely the opposite !! PWM'ing is far kinder to the motors than some sort of stable reduced voltage which is why it is always the preferred method of reducing a motors speed.

Although I'd nearly say the controller he is using is maybe actually PWM'ing the output rather than reducing voltage ? It would be odd these days for a manufacturer to go down the old route and then employing a controller of some sort to actually do it....well other than for cost reasons.

Whilst related to fuel pump control, great thread here. Max knows his shit


http://www.pistonheads.com/gassing/topic.asp?t=916550