PWM cooling fan(s) control using ECM

[Lous69]

I am trying to figure out what would be required to set up Pulse Width Modulated cooling fan control using the E67 ECU that came with my LSA crate motor.

The ECU that GM Performance sells to go with the LSA crate engine (part number 19259293) comes set up for On/Off fan control. I would prefer PWM fan control.

Of course I could find a stand alone PWM fan controller and run it independent of the ECU but I would prefer to have the ECU control the fans using more inputs than just the engine temp. (Such as AC pressure and ambient temperature).

Here is what I am wondering:

Can I use the PWM fan control module (Part number 10377609) that is used in the ZR 1 Corvette which also uses the E67 ECU and drive it with a signal from my ECU just like the ZR 1 Corvette does?

I'm assuming I would need to find the correct pin on the ECU and add a wire. If so, I have no problem with doing that. Does anyone know which pin that is on the E67 ECU?

I think the Trailblazer SS also used the E67 ECU. It uses pin #64 for PWM control of the cooling fan clutch. Might that be the same one the ZR 1 uses to drive the PWM fan control module?

Would the algorithms for PWM cooling fan control already be in my ECU or would they be completely absent? If absent, could I have a tuner grab that subroutine from a ZR 1 Corvette program and install it into my ECU?

Thanks in advance for any words of wisdom.

[mikels]

Simple answer is, yes - you can control a PWM fan controller with GM E67 controller (or E38 or E40).

Wiring is fairly simple - just need to wire PWM output from controller (can find wiring mech's for Corvette online pretty easily).

Obviously calibration needs to be changed as well from what controller was delivered with. Crate engine is disrete output, and you need PWM. There are several variables that need to be changed to make this work properly (including PWM frequency).

Fan output duty cycle can then be calibrated based on these inputs:
-Engine coolant temp - from ECT sensor
-AC pressure (will need to add production pressure sensor and wire as well)
-Intake air temp - IAT sensor in MAF

You can also calibrate 'after run' on fan to keep fan running at lower level after hot shut-down to reduce heat soak.

HP Tuners allows access to all these variables.

Dave

Dave

[Lous69]

Originally Posted by mikels

Simple answer is, yes - you can control a PWM fan controller with GM E67 controller (or E38 or E40).

Wiring is fairly simple - just need to wire PWM output from controller (can find wiring mech's for Corvette online pretty easily).

Obviously calibration needs to be changed as well from what controller was delivered with. Crate engine is disrete output, and you need PWM. There are several variables that need to be changed to make this work properly (including PWM frequency).

Fan output duty cycle can then be calibrated based on these inputs:
-Engine coolant temp - from ECT sensor
-AC pressure (will need to add production pressure sensor and wire as well)
-Intake air temp - IAT sensor in MAF

You can also calibrate 'after run' on fan to keep fan running at lower level after hot shut-down to reduce heat soak.

HP Tuners allows access to all these variables.

Dave

Dave

Dave, Thank you very much for your reply. You've given me a new head of steam to figure out how to accomplish the mission.

If I understand your response it means I need to:

1.Buy the PWM fan control module used on all C6 Corvettes

2. Find a pin out diagram for the E67 ECM like the one that came with my LSA crate engine. Best bet would be the pinout for the C6 ZR1 corvette.

3. Find a wiring diagram for a ZR 1 C6 Corvette that shows the wiring between the E67 ECM and the PWM fan control module.

4. Add a wire from the PWM signal output pin on my E67 ECM and run it to the PWM fan control module.

5. Purchase AC pressure sensor used in the C6 corvette and install in my system.

6. Have my ECM programmed to provide the PWM output signals I prefer to the output pin I added the wire to.

Did I understand correctly?

Thanks again for your willingness to point me in the right direction.

[mikels]

Originally Posted by Lous69

1.Buy the PWM fan control module used on all C6 Corvettes

2. Find a pin out diagram for the E67 ECM like the one that came with my LSA crate engine. Best bet would be the pinout for the C6 ZR1 corvette.

3. Find a wiring diagram for a ZR 1 C6 Corvette that shows the wiring between the E67 ECM and the PWM fan control module.

4. Add a wire from the PWM signal output pin on my E67 ECM and run it to the PWM fan control module.

5. Purchase AC pressure sensor used in the C6 corvette and install in my system.

6. Have my ECM programmed to provide the PWM output signals I prefer to the output pin I added the wire to.

Just add step 5.5 - wire AC pressure sensor to ECM (which will also be on wiring mech for ZR1 Corvette) and you've got it.

Be sure to check origional crate engine harness - they run Fan 1 and Fan 2 output to fan relay - you need Fan 1 to go to PWM control module - and have fan power leads NOT running through relay - just a fuse.

Corvette fan (400 watt) pulls ~32 amps peak, so size fuse, wiring appropriately.

SRX fan (850 watt) we've used on Stielow's latest cars pulls ~65 amps peak.

Dave

[Lous69]

Originally Posted by mikels

Just add step 5.5 - wire AC pressure sensor to ECM (which will also be on wiring mech for ZR1 Corvette) and you've got it.

Be sure to check origional crate engine harness - they run Fan 1 and Fan 2 output to fan relay - you need Fan 1 to go to PWM control module - and have fan power leads NOT running through relay - just a fuse.

Corvette fan (400 watt) pulls ~32 amps peak, so size fuse, wiring appropriately.

SRX fan (850 watt) we've used on Stielow's latest cars pulls ~65 amps peak.

Dave

Thank you very much for your advice Dave.

I'm curious if you would know this:

Does the software subroutine to drive a cooling fan PWM output signal already exist in the E67 ECM that came with my LSA crate motor such that it just needs to be turned on after we add the wires mentioned above or will we need to first install a program or "operating system" from a ZR1 application then modify that program with a tune for my LSA motor?

I'm wondering if the later approach would also require turning off a lot of other subroutines that the ZR1 application program or "operating system" will be looking for.

Thanks again for sharing your knowledge with the rest of us.
Lou

[mikels]

Algorithm for PWM fan control is already in your software - just need to select 'PWM fan control' instead of 'descrete fan control' - then set calibrations to how you want fan to operate (% duty cycle based on ECT, AC pressure, IAT).

Dave

[carbuff]

Question of ignorance here, looking for a little education...

Can you use a PWM fan controller on any cooling fan, or does the fan need to be designed to handle the fast on/off switch of the PWM? In other words, would you burn-out a normal fan if using a PWM controller on it?

I haven't looked, but I'm now wondering if anyone makes an aftermarket PWM fan controller. I think the idea here is interesting, but at least from the GM implementation, it's not just a simple aftermarket conversion...

[mikels]

Originally Posted by carbuff

Question of ignorance here, looking for a little education...

Can you use a PWM fan controller on any cooling fan, or does the fan need to be designed to handle the fast on/off switch of the PWM? In other words, would you burn-out a normal fan if using a PWM controller on it?

I haven't looked, but I'm now wondering if anyone makes an aftermarket PWM fan controller. I think the idea here is interesting, but at least from the GM implementation, it's not just a simple aftermarket conversion...

The high frequency signal goes to the control module - not the fan motor directly. This causes output voltage of controller to be reduced (proportional to PWM signal). So long as fan motor can run at lower voltage levels, should not be an issue.

There are a couple aftermarket PWM fan controllers but I have no experience with them.

Dave

[Lous69]

Thanks for your continued sharing of knowledge Dave. It REALLY HELPS.

Since I am using a 2nd Gen Camaro radiator set up made by C&R that has two large fans, I plan to use two of the GM PWM fan control modules.

My thinking is that GM validated those modules for the current draw of just one C6 Corvette fan. Since I have two fans, it seems safest to use two modules vs. "hoping" one module will be able to handle the current draw of two fans.

I know that probably sounds like overkill but hey, I'm an engineer. It's in my blood.

Of course, my plan presumes that I can send the PWM signal from the E67 ECM to both fan modules.

Do you suppose that will be a problem?
Would you happen to know what the frequency and voltage amplitude of the PWM signal from the E67 ECM is?

Oddly enough, the toughest part of my plan appears to be sourcing the connectors that plug into the GM Fan control module. Best
I can tell, the only way you can buy those connectors from GM is as part of an entire C6 fan assembly whch lists for over $400!

If anyone knows where those connectors can be purchased separately I would appreciate them giving me a hint or clue.

I may have to connect wires to the module tabs and then pot the end of the module, effectively converting it to a pigtail version.

Thanks again Dave.

[parsonsj]

I'm glad I started reading this thread! Very very interesting, and far superior to what I did on my last project which was to use a relay to override and run the fans with pressure monitoring via a trinary switch.

Just to clarify (for me, anyway ) : the E67 in the LSA crate motor offering from GM (pn 19259293) can monitor the A/C line pressure and turn on the fans? Does it do that with PWM support (just running the fan enough to keep the high side pressure to certain number)? Or does it do that by running the fans full speed until the high side pressure drops below a threshold?

And all the while, it's keeping track of the coolant temp and running the fans appropriately for that too?

Sweet!