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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Sun, Jun-18-2017, 04:33:10 PM   #261
Drewster
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Default Re: How to mount a Spal Electric fan to the stock shroud

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Originally Posted by BrockSamson View Post
I used to be an electronics technician. I think you guys are over complicating things.

We know the the aux fan comes on at 180f, and we know that aftermarket controllers are pretty unreliable. I used to use one on my old e36, it sucked.

So I think all we need to do is to run a relay in parallel with the aux fan power leads to run the main fan:
Amazon.com: OLS 40/30 Amp Waterproof Relay Switch Harness Set - 12V DC 5-Pin SPDT Automotive Relays 12 AWG Hot Wires: Automotive

and use one of these fuse blocks with a 25A or 30A fuse from the battery to the main fan:
Amazon.com: Blue Sea Systems Waterproof In-Line ATO/ATC Fuse Holder: Sports & Outdoors

This way we are not over loading the aux fan wiring and we are using our own 12AWG from the battery posts (extension) in the engine bay.

We are just taking the signal to the relay, dead simple and safe.

Also note: do not run the (-) fan wire to the battery, just find a close chassis ground with good connection

Here is a simple diagram, please excuse its ugliness I am away from a proper schematic program.
The relay wire colors may vary depending on brand.


Also, you could do one wire splice on black(+) on the AUX fan instead of using the brown(-) if you used a separate ground for the coil.


This is untested, but I intend to wire this up in a few weeks on my e46 M3.
Been there, done that, works great: http://www.m3forum.net/m3forum/showthread.php?t=533110
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Old Sun, Jun-18-2017, 04:44:51 PM   #262
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Default Re: How to mount a Spal Electric fan to the stock shroud

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Originally Posted by m2pc View Post
I'm not sure how well this will work... the aux fan on the E46 isn't simply wired to come on and off at specific temperatures, but it's a variable speed fan, controlled by the DME. Things like A/C operation affect its operation. IMHO it would be better to run a separate controller based strictly on coolant temperature.
Running a separate fan based on coolant temp is simply a drag on the alternator and thus the engine at high speed, where you're not moving any more air than the car is. Personally, I would just make a PWM controller (much cheaper) and tap into the green signal wire coming off of the DME to run in harmony with the AUX fan.. might even make one myself if I weren't already happy with the relay implementation.

Quote:
On the E36 it was easier because you could simply splice into the HIGH speed side of the fan (those aux fans were only 2 fixed speeds controlled by some relays). The E46 uses pulse width modulation (PWM) to variably control the fan speed. The brown and black wires at the fan are the modulated 12V signal. I'm guessing a relay here would probably buzz and chatter and turn the SPAL fan on full speed as soon as the aux fan came on even at a very slow speed.
The relay doesn't chatter. Relays naturally have something called "Hysteresis" meaning that the energy to engage them is greater than the energy where the internal field collapses and the armature breaks the circuit - otherwise circuits like the one in the e36 would chatter constantly due to contact bounce.

Quote:
The other side of the controller wouldn't be a place to splice either because there you have constant 12V and a connection to the CAN bus for the DME to communicate with it.
It isn't CAN - it's a simple high-side PWM signal

Quote:
Someone needs to come up with a modern, CAN-based solution that drives a SPAL fan by reading the actual coolant temp from the DME and responding accordingly. That way there's no need to tap external coolant sensors into the cooling path.

More info here: http://forum.e46fanatics.com/showthread.php?t=1041226
Again, coolant temp alone is a bad way to run the fan.
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Old Sun, Jun-18-2017, 04:48:55 PM   #263
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Default Re: How to mount a Spal Electric fan to the stock shroud

Quote:
Originally Posted by m2pc View Post
I'm not sure how well this will work... the aux fan on the E46 isn't simply wired to come on and off at specific temperatures, but it's a variable speed fan, controlled by the DME. Things like A/C operation affect its operation. IMHO it would be better to run a separate controller based strictly on coolant temperature.

On the E36 it was easier because you could simply splice into the HIGH speed side of the fan (those aux fans were only 2 fixed speeds controlled by some relays). The E46 uses pulse width modulation (PWM) to variably control the fan speed. The brown and black wires at the fan are the modulated 12V signal. I'm guessing a relay here would probably buzz and chatter and turn the SPAL fan on full speed as soon as the aux fan came on even at a very slow speed.

The other side of the controller wouldn't be a place to splice either because there you have constant 12V and a connection to the CAN bus for the DME to communicate with it.

Someone needs to come up with a modern, CAN-based solution that drives a SPAL fan by reading the actual coolant temp from the DME and responding accordingly. That way there's no need to tap external coolant sensors into the cooling path.

More info here: http://forum.e46fanatics.com/showthread.php?t=1041226
ahh, I didn't know it was PWM. Thank you for the reply. Saved me some future headaches

.....But Drewster runs his this way. His schematic is the same as mine. Except he triggers it off of the fan (-) brown wire.

Last edited by BrockSamson; Sun, Jun-18-2017 at 05:04:39 PM.
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Old Sun, Jun-18-2017, 04:56:43 PM   #264
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Default Re: How to mount a Spal Electric fan to the stock shroud

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Originally Posted by Drewster View Post
Been there, done that, works great: http://www.m3forum.net/m3forum/showthread.php?t=533110
Thanks Drewster! Looks like you did all the heavy lifting on this already!
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Old Sun, Jun-18-2017, 05:21:36 PM   #265
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Default Re: How to mount a Spal Electric fan to the stock shroud

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Originally Posted by BrockSamson View Post
ahh, I didn't know it was PWM. Thank you for the reply. Saved me some future headaches

.....But Drewster runs his this way. His schematic is the same as mine. Except he triggers it off of the fan (-) brown wire.
I believe (need to verify) that the fan has +12V constant on the black wire to it and the PWM is done on the brown (-) side.
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Old Sun, Jun-18-2017, 05:23:08 PM   #266
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Default Re: How to mount a Spal Electric fan to the stock shroud

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Originally Posted by m2pc View Post
I believe (need to verify) that the fan has +12V constant on the black wire to it and the PWM is done on the brown (-) side.
Correct - it's in that thread I linked.
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Old Sun, Jun-18-2017, 05:40:11 PM   #267
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Default Re: How to mount a Spal Electric fan to the stock shroud

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Originally Posted by BrockSamson View Post
Thanks Drewster! Looks like you did all the heavy lifting on this already!
No problem!

The difference in how I ran the relay trigger was to reduce the risk of a nasty short, as well as reduce the amount of splicing you need to do. The thought being that if you were to power the relay off of both wires, chafing or cutting the negative trigger wire to ground routes that high amperage fan circuit through a little ~20AWG wire. If I were to do my implementation over, I would put the fuse right off of the battery to protect both the fan and the relay.

Really, the biggest pain is getting to the aux fan and splicing that short little wire.

For ground, there's a good, beefy lug on the passenger side of the chassis, next to the splash shield mount. You just have to be sure to grind off any of the tan colored undercoat, as it is not conductive
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Old Mon, Jun-19-2017, 04:56:24 AM   #268
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Default Re: How to mount a Spal Electric fan to the stock shroud

Quote:
Originally Posted by Drewster View Post
Running a separate fan based on coolant temp is simply a drag on the alternator and thus the engine at high speed, where you're not moving any more air than the car is. Personally, I would just make a PWM controller (much cheaper) and tap into the green signal wire coming off of the DME to run in harmony with the AUX fan.. might even make one myself if I weren't already happy with the relay implementation.



The relay doesn't chatter. Relays naturally have something called "Hysteresis" meaning that the energy to engage them is greater than the energy where the internal field collapses and the armature breaks the circuit - otherwise circuits like the one in the e36 would chatter constantly due to contact bounce.



It isn't CAN - it's a simple high-side PWM signal
Sorry, I stand corrected! It's been awhile since I've tinkered with the electronics on these cars...


Quote:
Originally Posted by Drewster View Post
Again, coolant temp alone is a bad way to run the fan.
Interesting table in the post I linked to earlier:

Code:
F Eng Temp / %

120 / 0
122 / 30
158 / 40
176 / 65
185 / 83
194 / 100

MPH / Regulating Factor (1.0=full-on / 0=off)
0 / 1.0
31 / 1.0
62 / 1.0
74 / 0.5
86 / 0.0
124 / 0.0
Seems like your idea to "mirror" the aux fan PWM signal is a step in the right direction -- I just wonder how the A/C operation would affect this (I wouldn't want my main engine fan speed being affected by the climate control)? IIRC on the E36 simply engaging the A/C forced the AUX fan to run at one of the two speeds, to keep air flowing over the condenser even when the vehicle was not moving; I wonder how this works on the E46?

I wonder how well a small CAN-based controller that operated similar to how the DME does when controlling the PWM fan would work since engine coolant temp and MPH are both available on the bus?
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Old Mon, Jun-19-2017, 06:20:04 AM   #269
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Default Re: How to mount a Spal Electric fan to the stock shroud

Quote:
Originally Posted by m2pc View Post
Seems like your idea to "mirror" the aux fan PWM signal is a step in the right direction -- I just wonder how the A/C operation would affect this (I wouldn't want my main engine fan speed being affected by the climate control)? IIRC on the E36 simply engaging the A/C forced the AUX fan to run at one of the two speeds, to keep air flowing over the condenser even when the vehicle was not moving; I wonder how this works on the E46?

I wonder how well a small CAN-based controller that operated similar to how the DME does when controlling the PWM fan would work since engine coolant temp and MPH are both available on the bus?
I posted this on another forum a while back:

Quote:
Okay so I just dug through the assembly. This is how it works:

First the DME calculates the a fan speed from the radiator outlet temperature (KL_ELU_TKA). Then the DME checks the fan speed the IHKA is requesting via the CAN-bus (as mentioned, 15 possible values besides 0). It then compares the requested speeds, and will go with whichever is higher.

After determining the requested fanspeed (which can be anywhere from 0 - 100%), it is multiplied by the speed factor (KL_ELU_V). The final result is the speed DME will actually signal the fan to run at. While the stock software only uses 1.0, 0.5, and 0 as multipliers, you can pick anything in between

If any of the sensors or busses are misreading, there are other values/calculations the DME will assume

The possible AC-requested fan speeds are as shown below. I'm not sure what the logic in the climate control module looks like since I don't have a software dump of that.


The same basic scheme applies for cars with aux fans + mechanical fans and for cars with only electrical fans. Actual values may vary.
Attached Images
File Type: png BoTxccM.png (45.9 KB, 114 views)
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Last edited by terraphantm; Mon, Jun-19-2017 at 06:23:48 AM.
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Old Mon, Jun-19-2017, 02:51:35 PM   #270
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Default Re: How to mount a Spal Electric fan to the stock shroud

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Originally Posted by m2pc View Post
Sorry, I stand corrected! It's been awhile since I've tinkered with the electronics on these cars...

Seems like your idea to "mirror" the aux fan PWM signal is a step in the right direction -- I just wonder how the A/C operation would affect this (I wouldn't want my main engine fan speed being affected by the climate control)? IIRC on the E36 simply engaging the A/C forced the AUX fan to run at one of the two speeds, to keep air flowing over the condenser even when the vehicle was not moving; I wonder how this works on the E46?

I wonder how well a small CAN-based controller that operated similar to how the DME does when controlling the PWM fan would work since engine coolant temp and MPH are both available on the bus?
No worries! That's part of why I dug into it with an o-scope - there's lots of mis-information out there.

Personally I like having the IHKA command additional cooling to keep the AC operating efficiently. However, here in Texas AC is considered a critical component

The benefit of using the PWM signal to modulate the fan rather than engage a relay would be that when the fan is commanded on for the AC, it's only plodding at 50% power, rather than asking for all the engine fan can offer.
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Discussing How to mount a Spal Electric fan to the stock shroud in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)