DIYPNP Fan Control

[ZenitramNaes]

Hello all,

I'm curious to if anyone could shed some light on what exactly has to be done in order to be able to use this output. I have a Bosch 55 pin DIYPNP in my e34. I've swapped in one of those Volvo electric fans with a 80/88C temp switch on the radiator, but it still doesn't seem to be turning on soon enough.

To remedy this, I'd like to be able to wire the fan controls via megasquirt and see if that would help.

I understand I'm being a bit vague, but ultimately I would like to see setups from other users that have accomplished this or know the correct steps in order to achieve this. Most everything I find on the web for diypnp are for the Miatas.

If need be, feel free to ask any questions about my setup, ect if it helps clarify the answer I'm looking for.

Thanks,

-Sean

[Jaxx_]

I don't run the PNP setup, but you can control a relay to turn on the fan by going low output (ground output). You could also do going high (12V+) if you needed to for some odd reason... You need to pick a pin on the 55 pin connector that is free, and use a pin controlled by MS to turn on according to your settings--such as temp > 70C.

here's some info on mapped pins for MS2: http://msextra.com/doc/ms2extra/MS2-...htm#ms2options

you can use this documentation concerning outputs here:

http://msextra.com/doc/ms2extra/spareports.html

I hope this helps, the DIYPNP should have some outputs available if you haven't used them already. Make sure to add a free wheel diode if the relay doesn't have it.

[ZenitramNaes]

Thank you for the information. Most of that went over my head, though. I did build my own unit, but I'm more of a visual learner. I'll have to read through the links you posted a couple more times in hopes of a better understanding.

Again, thank you.

[Jaxx_]

Thank you for the information. Most of that went over my head, though. I did build my own unit, but I'm more of a visual learner. I'll have to read through the links you posted a couple more times in hopes of a better understanding.

Again, thank you.

no worries. I totally understand--I was at that point when I began my build. You'll get used to it, some of the terminology is what makes it more confusing than it needs to be.

Basically, you need to setup a portion of your prototyping area to a relay control, and then wire it up according to the schematic shown. You will then have relay control that you can decide the activation points... Thus giving you the ability to turn on/off a fan relay according to coolant temperature.

[CorvallisBMW]

Alternatively if you didn't have your heart set on controlling it through the DIYPNP system, you could use a standalone programmable fan controller. Spal makes one as an example: http://www.spal-usa.com/fans/automat...es/fanpwm.html

[Northern]

Am I missing something? Why not do the same as this?

[Jaxx_]

Am I missing something? Why not do the same as this?

because you can program it to meet two conditions instead of just one. for example, if TPS < 50% then activate the fan above 190F, otherwise leave it off. It makes sense if your conditions will soon be useless, such as if you're driving down the road and the fan is on. What's the point if you're already doing 15mph+? You can create any two conditions you want.

[CorvallisBMW]

Seems like a lot of hassle for zero gain. Running the electric fan doesn't hurt anything, I don't see a beneficial reason for over-constraining its operating variables.

As long as your temps are set right (thermostat temp set lower than fan switch temp) your fan won't come on unless it needs to be on. It's also very desirable to have your fan on whenever the engine is too hot, regardless of load. If you're stuck in traffic and it begins to get too hot, you don't want it shutting off the second you pass 15mph, you want it to stay on and cool the engine back to the proper temp and then shut off,

[Jaxx_]

Seems like a lot of hassle for zero gain. Running the electric fan doesn't hurt anything, I don't see a beneficial reason for over-constraining its operating variables.

As long as your temps are set right (thermostat temp set lower than fan switch temp) your fan won't come on unless it needs to be on. It's also very desirable to have your fan on whenever the engine is too hot, regardless of load. If you're stuck in traffic and it begins to get too hot, you don't want it shutting off the second you pass 15mph, you want it to stay on and cool the engine back to the proper temp and then shut off,

I mean, it causes more load on the alternator which can effect idle. Afterall, we are talking about ~30 amps here. I don't think it's a big deal either, but as I said, a fan is useless once you're moving.

I believe you also missed the point that megasquirt has hysteresis control. I guess you could do that with two probes and a few relays as a logic gate, but what a fucking mess. This feature alone (irrelevant to additional logic) is a much better implementation of temperature control than a temperature switch.


edit: oh yeah, $90 for a SPAL controller is ridiculous when the megasquirt implementation is going to cost less than $5 in parts.

[redsubdivisions]

Am I missing something? Why not do the same as this?

+1. I did this and it works perfect.

[LowR3V'in]

That spal thing is pretty sweet because it uses pwm.
You can start it off slow so there's no huge voltage drop with the on/off cycles.
It could stay on really low and smoothly go on full speed.

Megasquirt, you can't do that without building a huge circuit on a different board.
Here's my circuit bottom left and use the stock relay for the fan.



The fan would cause a huge spike so I had to add another ground strap on the block. Newer cars I notice use pwm for the a/c fan probably for the same reason.

[ZenitramNaes]

Thanks for the photo Low, I'm sure I'll get around to adding this eventually and my future self thanks you. If I have any questions I'll reference this thread and ask any additional questions.

[ZenitramNaes]

So more than a year later, I'm coming back to this thread to post some more questions I have and to share a bit of information I've learned.

So I've completed the building the circuit in the proto area.

Kit available from: http://www.diyautotune.com/catalog/m...ans-p-126.html

How mine looks


Underneath


Visual learners look here.


So essentially what I'm confused on where I go from here. I don't understand what JSO or D9 is since most of the info I find on the relay mod is for MSII users using the v3.57 board or something different than the DIYPNP 1.5v board I have. Also WLED is already being used for spark output C for my wasted spark setup.

TL ; DR What is the equivalent of JSO and D9 on the DIYPNP 1.5v board?

So of course any information is appreciated.

[ZenitramNaes]

D9=12v source JSO=programmable output.

Got everything wired up but fan is staying continuously grounded. Will update once I figure out why.

[ZenitramNaes]

Ditched the proto area setup and linked PAO directly to relay 1 IN and relay 1 OUT to my db15 connector to my external fan relay, fyi for future reference.