What Did You Do With Your Aux Cooling System

[Kevin Means]

As we plan our mods to our M1083, I was wondering what others did with their auxiliary cooling fan/radiator that's located between the frame rales. It sits pretty high above the 2nd set of rails. If we install a third set of rails to mount the box, the fan looks like it's going to be pretty close to the bottom of the box. It seems like an afterthought, judging by the way it's mounted (clamped to the upper C rail) Did you relocate yours, or leave it in place?

Kevin

 

[aw113sgte]

Not sure your exact setup, but my m1096 has the cooler mounted lower with some angle steel. Used some kydex (plastic) to allow for flex and prevent metal to metal contact.

 

[ckouba]

Mounted my 1088 vertical trans cooler between the frame rails. Pic in my build thread, was super simple and only required new hoses. I put new fans on (much lower profile) as well though to gain some clearance for airflow. No issues in 10k+ miles.

 

[GeneralDisorder]

How heavy you planning on being?

Especially if you are going to ECO hubs and your cooling system is now twice the size it needs to be and your engine/transmission is turning half its RPM and making significantly less heat.......

All that is to say you can simply delete the whole mess and just run like the 4x4 trucks that didn't come with the aux cooler. You don't need it especially with quality synthetic ATF, and you especially don't need it with ECO hubs. Just more junk to fail. Toss it overboard is my vote.

 

[Ronmar]

What General said
You are probably never going to get to the weight and conditions that aux cooler was intended to deal with. Your system has the same heat exchanger all the other trucks have, you can simply plumb the trans out and in direct to the cooler by removing the thermal mixer, and the fin cooler and fans...

 

[Kevin Means]

Interesting (the idea of tossing it) We did purchase the Eco Hubs, but haven't installed them yet. I was wondering if the RPM change would make a difference in cooling. I did read through your build thread ckouba. It's been very helpful.
Thanks again. You guys are great help.

Kevin

 

[GeneralDisorder]

Interesting (the idea of tossing it) We did purchase the Eco Hubs, but haven't installed them yet. I was wondering if the RPM change would make a difference in cooling. I did read through your build thread ckouba. It's been very helpful.
Thanks again. You guys are great help.

Kevin

It makes a HUGE difference in cooling - it might as well be doubling your cooling system. Read through the ECO hubs thread. When I installed the first set (besides Mike's prototype) in my 2008 M1079 A1R and did a mileage test run my radiator fan literally never turned on while the lighter (empty) 1078 cargo that was tailing me was running it's radiator fan every two minutes. The additional 3.5 mpg of fuel consumption is going mostly to just making heat with the engine so far past it's torque/efficiency peak.

AND you need to stop whatever else you are doing and INSTALL THE ECO HUBS. They change the game so much you NEED to experience what the new game is like before you proceed with the rest of your build. It can/will change your direction on things.

 

[aw113sgte]

It makes a HUGE difference in cooling - it might as well be doubling your cooling system. Read through the ECO hubs thread. When I installed the first set (besides Mike's prototype) in my 2008 M1079 A1R and did a mileage test run my radiator fan literally never turned on while the lighter (empty) 1078 cargo that was tailing me was running it's radiator fan every two minutes. The additional 3.5 mpg of fuel consumption is going mostly to just making heat with the engine so far past it's torque/efficiency peak.

AND you need to stop whatever else you are doing and INSTALL THE ECO HUBS. They change the game so much you NEED to experience what the new game is like before you proceed with the rest of your build. It can/will change your direction on things.

Was 70f this weekend, 6x6 weighing 30400lbs, had the fan turn on twice in 2 hrs driving, and there are some steep hills here (minutes of WOT). C7 with eco hubs.
Fan turned on about 20 times the day prior for the same trip at 50f, but had the cold weather shield on.

 

[GeneralDisorder]

Was 70f this weekend, 6x6 weighing 30400lbs, had the fan turn on twice in 2 hrs driving, and there are some steep hills here (minutes of WOT). C7 with eco hubs.
Fan turned on about 20 times the day prior for the same trip at 50f, but had the cold weather shield on.

Are you running the aux trans cooler? I doubt it would matter.

 

[Ronmar]

Driving a diesel around above the peak torque RPM is like driving with an exhaust brake on due to all the added pumping losses. You burn a bunch of extra fuel and create a bunch of added engine heat to overcome those pumping loads Then there is the added losses from the 6 gearboxes at the hubs...

You will like the hubs, I have not heard of anyone who has not...

 

[GeneralDisorder]

Driving a diesel around above the peak torque RPM is like driving with an exhaust brake on due to all the added pumping losses. You burn a bunch of extra fuel and create a bunch of added engine heat to overcome those pumping loads Then there is the added losses from the 6 gearboxes at the hubs...

You will like the hubs, I have not heard of anyone who has not...

Not to mention the losses due to driving above ~50-55 mph which become overwhelmingly significant the faster you go.

 

[aw113sgte]

Are you running the aux trans cooler? I doubt it would matter.

I am. No idea if it makes a difference. Not like there is any air flow through it without the fan so only advantage would be a little help to cool down faster when the fan kicks in.

That said, I have had the fans kick on well before 200f coolant temp, when pulling a hill in second...guessing there is a trans temp switch causing that.

 

[Ronmar]

I am. No idea if it makes a difference. Not like there is any air flow through it without the fan so only advantage would be a little help to cool down faster when the fan kicks in.

That said, I have had the fans kick on well before 200f coolant temp, when pulling a hill in second...guessing there is a trans temp switch causing that.

What truck and engine? As far as I have seen the aux cooling fan relay is piggybacked off of the engin cooling fan circuit. On the A0, triggered by the 205F coolant switch in the upper rad pipe. On the A1 controlled by the ECU engine temp fan setting.

there is a thermostatic bypass valve that decides when it sends fluid out to the aux cooler. Not sure what temp that thermostat starts to open… You would have to put a temp sensor on the line out to the cooler to see if it is sending any fluid out there, the fan runs regardless…

 

[aw113sgte]

What truck and engine? As far as I have seen the aux cooling fan relay is piggybacked off of the engin cooling fan circuit. On the A0, triggered by the 205F coolant switch in the upper rad pipe. On the A1 controlled by the ECU engine temp fan setting.

there is a thermostatic bypass valve that decides when it sends fluid out to the aux cooler. Not sure what temp that thermostat starts to open… You would have to put a temp sensor on the line out to the cooler to see if it is sending any fluid out there, the fan runs regardless…

M1096 C7.
Under high load conditions in low gear (trans not locked?) it will switch on fans well before the 205f coolant mark. Wish we had a trans temp gauge. (yes both engine and trans fans are activated at the same time).

 

[Ronmar]

Yea I am not sure what engine temp the ECU is programmed for. General surely knows. I am planning on connecting my trans temp and engine temp senders to the oil sample ports near the trans cooler And on the engine oil cooler. Don”t have a need for the oil sample ports.

this won’t tell you if the diverter is sending any oil to the aux cooler though…

 

[GeneralDisorder]

Yea I am not sure what engine temp the ECU is programmed for. General surely knows. I am planning on connecting my trans temp and engine temp senders to the oil sample ports near the trans cooler And on the engine oil cooler. Don”t have a need for the oil sample ports.

this won’t tell you if the diverter is sending any oil to the aux cooler though…

Radiator fan ECU temp is 205. Thermostats are 190 though I have seen some 180's as well. And I don't have any rhyme or reason to that other than were all CAT branded.

I don't believe the engine computer knows or cares what gear you are in. I have not seen any indication (that I can recall) that the ECU is aware of the selected gear although I can't rule out that there may be some functionality I'm not aware of that would let it change cooling system operation via some external input or even knowing what the reported gear is or some other indication from the communication bus but again I have no evidence of that and have not experienced the low gear change in cooling system behavior but I don't use 1st gear much at my weight and my radiator fan almost never runs with ECO hubs so I would have to devise some kind of test routine.

 

[aw113sgte]

I have it kick on well before 205f coolant temp when pulling a steep grade in second. I don't know the exact grade but the truck with 330hp will barely accelerate under full throttle. If I go a little faster and it's in 3rd it usually doesn't kick on until 205f. Makes me think it's seeing higher trans temps with a non locked condition.

 

[GeneralDisorder]

Hhhhmmm need to review the schematics. Maybe there's some trans temp over-ride on the later MTV.....

 

[aw113sgte]

Might be over the data bus as well. Not that it really matters.

 

[GeneralDisorder]

Might be over the data bus as well. Not that it really matters.

I don't think so because that doesn't seem to be a thing on the 4x4 trucks without the aux cooling system. If it was a databus thing then the ECU would be doing it on all of them since they all use the same ECU programing other than HP/TQ and they definitely all use the same TCU with no changes to programming at all. Also that should be a setting that can be changed inside the ECU that controls the fan and I'm pretty familiar with all the settings and haven't run across any settings even remotely like that.

And I've run all of the C7 military maps including the M-ATV 370 HP map and I haven't seen anything like that in the settings. I was thinking an external relay being commanded by the TCU that overrides the ECU fan control.