PWM cooling fan(s) control using ECM

[130fe]

Justin, do you have a link to the kit you listed?

[4wheels]

Interesting data. Thanks for sharing it.

As you mentioned the 50 deg ambient you mention is a significant variable. So is load (speed, grade, weight, other drag etc.) along with overall engine efficiency (extreme example - a 8.0:1 compression engine with timing set to way below MBT spark is going to put a lot of extra heat into the cooling system). You likely wouldn't be controlling to those temperatures without a fan at 80 or 90 degrees ambient or if you were going up a hill or stuck is stop and go traffic with other vehicles around (less airflow, more heat).

But if you are trying to control to an engine coolant temperature I am not sure having ambient as part of your fan control strategy would help much. The feedback on the coolant temperature should do that. Most OEM's are controlling the coolant temperature/fan operation to above thermostat temperature. When you try to control the coolant temperature with the fans to a temperature around the same as the thermostat then it can get more complicated as the two can be working in phase and out of phase. The thermostat has a range of temperatures (starts to open vs fully open) and where it reads temperature may not be the same as the fans and the difference between the two varies depending on many other conditions.

Just some more variables for you to worry about....

Originally Posted by andrewb70

So........

I am not ashamed to admit that I might be slightly obsessed with the ability to control my fan speed.

Recently I had to add coolant to my system (I was running straight water in the summer) so that I don't hurt anything during the long WI winter. After adding the coolant (good to about -40 degrees) I noticed that the engine ran about 4-5 degrees hotter under previously noted conditions. This of course caused the fan to run faster per the table that I programmed.

So I decided to "retune" the table and just set it to work the best it can in my car. For me, "the best it can" is running the fan as slowly as possible, while maintaining a target temperature. But what is that target temperature? LOL

I know I have a stock thermostat which by all accounts is 187 degrees. Given that information I can turn off the fan and just watch what the temperature does under varying conditions (granted all of this is dependent on ambient temperature and ideal I would incorporate it into the fan control strategy for optimal results, but even GM doesn't do this...Didn't I say that I might be slightly obsessed?)

Driving normally around town (aka like grandma...top speed 35) the temperature never got above 191-192 (about 50 ambient). I then took it on the highway and cruising at a steady 75 mph the temp was stable between 194-195 degrees (all this with the fan off).

So I configured my table as follows at vehicle speed below 40mph...

Temp:fan %

194:5 (off)
200:10
210:20

Then it ramps in rather quickly (I don't recall the exact numbers). The fan basically never kicks on around town and temps is steady at 191-192.

For vehicle speed above 40mph I just configured the cells to be one value off, like this:

194:5
200:5
210:10

etc....again, ramping in quickly. Temp is steady at 194-195 without the fan.

I don't know if this is optimal in terms of thermal efficiency. Probably not because my engine seems to run cooler than it would in the donor vehicle (2009 Colorado pick-up). But in terms of my target goal (cycling the fan as little as possible) I think I succeeded.

Anyway, I thought I would share for anyone that cares.

Comments, questions, and opinions welcome.

Andrew

[4wheels]

With some of the newer high output fans the vehicle speed based fan disable strategy isn't used anymore. If the cooling is enough that the fans aren't needed then they turn off due to temperature anyway.

Originally Posted by GregWeld

Running down the road - the fan shouldn't be needed at all.

[4wheels]

I am doing some testing of a stand alone PWM fan controller for a manufacturer. Since this is a stand alone system it reads a separate coolant temperature sensor and can be used on any vehicle (doesn't have to have PWM fan control strategy in the ECM).

One question that has come up in my testing is what is this other sensor reading for temperature since it isn't the same as the other temperature sensors in the cooling system (not the same sensor and may or may not be in the same location in comparison to engine, pump, thermostat, radiator etc.).

If you were a potential customer for this type of product, would an output of temperature from a fan controller be of interest? For example I would like to see it output temperature as a 0-5 volt signal that I could read with a data acquisition system or even just a simple volt meter. Might even be able to drive a gauge with this output (depends on the gauge type).

Any feedback/ideas?

Thanks.

[andrewb70]

Originally Posted by 4wheels

I am doing some testing of a stand alone PWM fan controller for a manufacturer. Since this is a stand alone system it reads a separate coolant temperature sensor and can be used on any vehicle (doesn't have to have PWM fan control strategy in the ECM).

One question that has come up in my testing is what is this other sensor reading for temperature since it isn't the same as the other temperature sensors in the cooling system (not the same sensor and may or may not be in the same location in comparison to engine, pump, thermostat, radiator etc.).

If you were a potential customer for this type of product, would an output of temperature from a fan controller be of interest? For example I would like to see it output temperature as a 0-5 volt signal that I could read with a data acquisition system or even just a simple volt meter. Might even be able to drive a gauge with this output (depends on the gauge type).

Any feedback/ideas?

Thanks.

If you are targeting users that may not have EFI, then I see a benefit to having a "temp out." As you said, this can be used to drive a gauge in the dash. I think most temp gauges use a thermister style sensor so the output would need to be resistance.

Andrew

[mikels]

Originally Posted by GregWeld

Running down the road - the fan shouldn't be needed at all.

Not completely true - if running the fan creates more negative pressure on backside of cooling system stack, running fan will increase cooling.

For example - when Mark switched Red Devil to 850W fan from 400W, it resulted in ~10 F reduction in coolant and oil temps (oil-to-water oil cooler in radiator) when running on track - with average speeds well above what you typically run on street.

Keep in mind this is a very thick (~5-6") cooling stack as well (A/C condenser, ICHE, radiator)

So ability to create more negative pressure on backside of cooling stack resulted in more airflow across coolers - and more heat transfer as a result.

Dave

[GregWeld]

Originally Posted by mikels

Not completely true - if running the fan creates more negative pressure on backside of cooling system stack, running fan will increase cooling.

For example - when Mark switched Red Devil to 850W fan from 400W, it resulted in ~10 F reduction in coolant and oil temps (oil-to-water oil cooler in radiator) when running on track - with average speeds well above what you typically run on street.

Keep in mind this is a very thick (~5-6") cooling stack as well (A/C condenser, ICHE, radiator)

So ability to create more negative pressure on backside of cooling stack resulted in more airflow across coolers - and more heat transfer as a result.

Dave

Good info Dave.... and Yes - I can certainly see in a racing situation, and with that much horsepower creating additional heat that needs to be dispersed. I was referring to a normal freeway cruising situation where even my Semi truck rarely engages the fan (air engaged fan of ginormous proportions).

[GregWeld]

I found this info in an article written about the 2016 Cadillac ATS-V:




The enemy of a performance car - beyond speed cameras and over-zealous highway police - is heat, and Cadillac has left nothing to chance there. Every grille and vent has a purpose, and in fact the engineers had to get creative to accommodate every heat-exchanger they wanted to install.

So, there are eight heat-exchangers in total, along with an 850W cooling fan. Each of the “grillettes” - the lower side grilles - has an intercooler, linked with the main cooler for the engine. The auto transmission alone gets two coolers, one in the traditional place behind the grille, and another mounted flat on the underside, near the front, the only spot Caddy had left.

[parsonsj]

Originally Posted by 4wheels

Any feedback/ideas?

Yes, it would be awesome for such a standalone controller to also support an AC pressure sensor. All the fan controllers I've seen just turn on the fans to a set speed (usually 100%) with a 12V input signal when the AC is turned on.

[mikels]

Originally Posted by parsonsj

Yes, it would be awesome for such a standalone controller to also support an AC pressure sensor. All the fan controllers I've seen just turn on the fans to a set speed (usually 100%) with a 12V input signal when the AC is turned on.

This functionality is built into OEM control logic (E40, E38, E67, etc. with PWM fan control. There are cal's based on following:

• ECT
• Oil temp
• Trans temp
• IAT
• AC pressure

Way logic works is a % output based on each of these inputs - and highest request wins. In other words, if ECT is requesting 30%, but AC pressure is requesting 42%, fans are driven @ 42%.

Stand-alone controller would need provisions for a scaled 0-5V input based on AC pressure with a cal relating that pressure to a requested output. And same logic where highest request wins.

Dave