PWM cooling fan(s) control using ECM

[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

[carbuff]

Andrew,

Question: when driving down the road normally, won't the fan spin due to airflow through the radiator? I'm curious how much more the motors spin the fans at 5% vs. what air passing through it would be?

That would take some math to figure out I assume, but I am curious.

[GregWeld]

Originally Posted by carbuff

Andrew,

Question: when driving down the road normally, won't the fan spin due to airflow through the radiator? I'm curious how much more the motors spin the fans at 5% vs. what air passing through it would be?

That would take some math to figure out I assume, but I am curious.

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

[andrewb70]

Originally Posted by GregWeld

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

Precisely. See my comment above.

Andrew

[130fe]

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

[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).