CAC lesson learned

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CAC lesson learned

July 22, 2018, 12:14:25 pm

With my recent conversion of the electronic hydraulic fan switch to the thermal valve kit (see earlier posts), I experienced something new. As we were leaving Simi Valley onto State 118 I immediately encountered some uphill grades before my engine reached normal operating temps. I was checking my coolant temp, but failed to notice that my intake manifold temperature had risen to 227 and my engine "de-powered". It occurred to me that since my conversion, the hydraulic fan motors were "waiting" for the thermostat to open before they kicked in. Without the airflow through the radiator and thus the CAC, the hot air (from increased rpm) from the turbo was not being cooled. I'm not sure at what point the fans begin to turn, but I know that they are stationary at idle on a cold engine. If there are other theories, I would be glad to hear them.

Other than that, the results from the conversion have been impressive. My temperatures on long grades are down 15-20 degrees and my fuel consumption has improved by about 10% (roughly). On fairly level ground, with rolling hills, I get 9-10 mpg, which I have only observed once in eastern Oregon with a tailwind.
Source Engineering Inc | Custom RV Chassis | Eugene, OR

Re: CAC lesson learned

Reply #1 – July 22, 2018, 12:22:39 pm

Not supposed to be stationary ever as far as i know.

Re: CAC lesson learned

Reply #2 – July 22, 2018, 12:23:31 pm

Sven,
I have not had intake manifold temperatures anywhere near those highs, when the engine is cold or hot. Based on that info it sounds like removing the orifice at the thermal valve was not the way to go.

Bob

Re: CAC lesson learned

Reply #3 – July 22, 2018, 12:32:05 pm

Quote from: Wattalife54 – July 22, 2018, 12:23:31 pm

Sven,
I have not had intake manifold temperatures anywhere near those highs, when the engine is cold or hot. Based on that info it sounds like removing the orifice at the thermal valve was not the way to go.

Bob

Good point Bob. The mechanic that told me about the smaller oriface adapter, said that its purpose was to allow the fan to operated for the purpose of cooling the dash air conditioner condenser. Since ours isn't attached to the radiator and has its own fan, I removed it. The high temp was a one time occurance - it is usually less than the coolant and trans. temps. I will keep an eye on it and re-install if this continues to be an issue.

Re: CAC lesson learned

Reply #4 – July 22, 2018, 12:34:55 pm

Had the same problem on a SOB. Found intake manifold temps way too high with fans completely off.
Had to set up hyd valve to allow some oil to bypass to hyd cooling fan,.. to keep it running slow even if engine temps did not require it

Re: CAC lesson learned

Reply #5 – July 22, 2018, 01:18:02 pm

Yup, on any turbo, CAC engine you have to have air flow over the CAC all the time.

So fans can only be LOW- HIGH, never OFF-ON.

And just having the thermostat open should not trigger high fan speed, that would be a waste of fuel and HP. Said another way, if the thermostat is able to control temperature even on low fan speed, why waste HP to turn the fan faster?

Some SOB's place the dash A/C condenser in the "cooling package" so that the engine fan cools it. Doesn't work! With insufficient air flow, the A/C head pressure quickly triggers the high PSI trianary (sp) switch and compressor shuts off.

Re: CAC lesson learned

Reply #6 – July 22, 2018, 01:31:14 pm

Along the same lines,I have rebuilt hundreds of large turbos,99% of them were heat related problems,oil baking in the bearing
area,the other 1% were engine valve pieces hitting the impeller.

Re: CAC lesson learned

Reply #7 – July 22, 2018, 02:02:43 pm

I wonder how high the intake air temperature on the non cac 250 hp cats goes?

Re: CAC lesson learned

Reply #8 – July 22, 2018, 02:26:24 pm

When we did our cold idle fan speed comparisons in Pendleton, one of the U320s fans were still and the owner had no heat issues whatsoever, causing me to think this was how it should be. I will install the smaller orifice adapter to be on the safe side - this will be my lesson learned.

Re: CAC lesson learned

Reply #9 – July 22, 2018, 02:41:34 pm

Quote from: Old phart phred – July 22, 2018, 02:02:43 pm

I wonder how high the intake air temperature on the non cac 250 hp cats goes?

Believe the 250 hp 3208 non-cooler engines only ran about 14 psi max. Lot less heat from compression than on a 27-30 psi boost engine.

Re: CAC lesson learned

Reply #10 – July 22, 2018, 02:55:23 pm

Quote from: Old phart phred – July 22, 2018, 02:02:43 pm

I wonder how high the intake air temperature on the non cac 250 hp cats goes?

With a 10.6 liter engine putting out only 250 HP, doubt it is too much of an issue. That doesn't mean it would not benefit from one. Kind of hard to get too much cool, dense air.

Some of those old-timers who had Izusu powered Safari Treks know there was a difference between the non CAC and CAC models on the same chassis and engine.

Re: CAC lesson learned

Reply #11 – July 22, 2018, 06:41:00 pm

Quote from: wolfe10 – July 22, 2018, 01:18:02 pm

Some SOB's place the dash A/C condenser in the "cooling package" so that the engine fan cools it. Doesn't work! With insufficient air flow, the A/C head pressure quickly triggers the high PSI trianary (sp) switch and compressor shuts off.

Brett, it actually works fine if it is done right. The two Country Coaches I have owned have the A/C condenser in the cooling package located furthest outside to get the cooling air first. It works great because the compressor head pressure is used as one of the control inputs to the Sauer Danfoss Fan Drive Controller. On these coaches, including my 2003 Magna, the high side pressure is measured by the trinary switch on the receiver/drier. High pressure results in fan speed ramp up. Other inputs to the controller are coolant temperature and charge air temperature. My chassis A/C includes a 19,000 BTU dash evaporator and a 13,500 BTU bedroom evaporator. The system blows cold all day.

Re: CAC lesson learned

Reply #12 – July 22, 2018, 09:41:55 pm

Quote from: gsander1 – July 22, 2018, 06:41:00 pm

It works great because the compressor head pressure is used as one of the control inputs to the Sauer Danfoss Fan Drive Controller.

These controllers are not expensive, the software for the programmable inputs is free, frankly the wax capsule seems like a downgrade. Is there some inherent weakness in these things? Seem like they would be pretty easy to troubleshoot.

Re: CAC lesson learned

Reply #13 – July 22, 2018, 10:41:29 pm

Wax capsule is the most reliable. The variable speed is the benefit plus a straight mechanical design.

Re: CAC lesson learned

Reply #14 – July 23, 2018, 04:11:25 pm

Quote from: Caflashbob – July 22, 2018, 10:41:29 pm

Wax capsule is the most reliable. The variable speed is the benefit plus a straight mechanical design.

No doubt about it, really nothing to fail with the wax capsule.

My point with the Danfoss controller is that it is configurable for multiple inputs (like a CAC), and different fan curves rather than a straight proportional unit. Of course this would require an owner willing to program and set up, small chance of finding a shop to do this. I believe failure mode is full force fan, and any input could cause this. That's when they get pulled out and replaced in lieu of trouble shooting.

Re: CAC lesson learned

Reply #15 – July 23, 2018, 04:27:59 pm

My Cummins shop commented that the electric failure locking the fan on high is a fairly regular occurrence. Versus the wax capsule hardly ever.

The additional programming options available for the condenser being mounted in front of all the other coolers on the country coaches dual dash a/c system seems to be a good idea for their builds.

On first thought Foretravel being from HOT Texas not cooler Oregon may have had them separating the a/c condenser from the engine and trans and CAC cooler and maxing the hydraulic fan controller to lock the warmed up engine on high speed at 180 degrees.

Less panicked "my engines overheating" calls from owners? Wanna bet.

They are/were extremely conservative in temp extremes and backup systems and long lived components.

Take that to the end and that's what I think we are seeing?

Re: CAC lesson learned

Reply #16 – July 23, 2018, 05:16:50 pm

The Sauer Danfoss fan drive controller is not a high speed/low speed device. It is infinitely variable between low and high speed. The device is about 4 inches square by 2 inches thick and is generally mounted at the aft end of the fan and radiator housing. It is easily replaced on most coaches and costs about $450. It does have a failure rate in excess of the wax controller. I have replaced 4 in 14 years of Country Coach ownership. Two years ago they replaced the original part numbers with an "improved" version. So far, no one I know, including myself, has had the new part number fail.

the programming of these devices is handled by Sauer Danfoss at time of manufacture. The part number and the specific electrical connectors is defined by the part number.

Re: CAC lesson learned

Reply #17 – July 23, 2018, 09:20:40 pm

Looks like firmware is loaded at the factory, I'm getting from the current info that it is field programmable per Danfoss:

The PLUS+1®
Service Tool is a free program that must be installed on a personal computer and is used to
communicate with the FDC to change parameters, load new software or troubleshoot a system. Below is
a link to download the free version of the PLUS+1®
Service Tool.
Danfoss Power Solutions | Danfoss

I have no experience with these devices, just interest in this kind of stuff.

Re: CAC lesson learned

Reply #18 – July 23, 2018, 09:33:18 pm

I always liked country coaches engineering. That being said having the dash air radiators head pressure control the fan speed on the hydraulic fans on the motor would seem to be a large power consumer of the engine IF the other controls wired in are not calling for that much fan speed.

Like the idea. The 30k btu capacity of the dual engine driven ac circuits may have necessitated this versus the separate dash air radiator Foretravel installed on the opposite side with a seemingly long lived electric cooling fan on it.

But the 99 and up Unicoaches have nearly the same btu capacity.

But the cold air dash output might be more with the cc system?

Fan on high when any of the up to six sender fails would require significant monitoring to avoid excess power losses imo.

Your main unit failed 4 times? Engine got hot the symptom?

Re: CAC lesson learned

Reply #19 – July 24, 2018, 05:57:03 pm

The symptoms of a failed fan drive controller were always the same.

Continuous high speed fan.

The coldest air conditioner output you can imagine as the condenser is constantly under intense cooling.

Reduced coolant and transmission oil temperatures

Reduced fuel economy because of the heavy hydraulic load.

Reduced performance because of power robbing load.

Noise. The high speed fan is load.

If I had my way I would remove the condenser from the stack and relocate it cooled by an electric fan. But it's really not worth it I don't think. The existing system is much better than the wax valve as the additioal control from A/C and CAC improves comfort and performance.........when it all works.

The controller is field programmable as mentioned above but, in my experience, there is not much value to that.

Re: CAC lesson learned

Reply #20 – July 24, 2018, 09:19:45 pm

Quote from: gsander1 – July 23, 2018, 05:16:50 pm

The Sauer Danfoss fan drive controller is not a high speed/low speed device. It is infinitely variable between low and high speed. The device is about 4 inches square by 2 inches thick and is generally mounted at the aft end of the fan and radiator housing. It is easily replaced on most coaches and costs about $450. It does have a failure rate in excess of the wax controller. I have replaced 4 in 14 years of Country Coach ownership. Two years ago they replaced the original part numbers with an "improved" version. So far, no one I know, including myself, has had the new part number fail.

the programming of these devices is handled by Sauer Danfoss at time of manufacture. The part number and the specific electrical connectors is defined by the part number.

Having to replace the controller every three years or so isn't much of an endorsement; I'm glad I made the conversion. When I priced the Danfoss unit, I was quoted $925 - looks like they doubled in price.

Re: CAC lesson learned

Reply #21 – July 24, 2018, 09:23:04 pm

"The symptoms of a failed fan drive controller were always the same.

Continuous high speed fan.

The coldest air conditioner output you can imagine as the condenser is constantly under intense cooling.

Reduced coolant and transmission oil temperatures

Reduced fuel economy because of the heavy hydraulic load.

Reduced performance because of power robbing load.

Noise. The high speed fan is load."

I have to disagree. Mine was stuck on low speed, resulting in higher coolant, charged air and transmission temps. The A/C isn't affected on our coach, since the condenser has its own fan on the opposite side of the radiator.

Re: CAC lesson learned

Reply #22 – July 24, 2018, 10:34:25 pm

Sven I wonder how many coaches had electric controllers?

Re: CAC lesson learned

Reply #23 – July 25, 2018, 01:28:17 am

My old coach defaults to high speed on any power failure. Safe mode. Anything else has to be powered up.

Re: CAC lesson learned

Reply #24 – July 25, 2018, 08:49:29 am

Quote from: Caflashbob – July 24, 2018, 10:34:25 pm

I wonder how many coaches had electric controllers?

Our coach, the best I can tell, has NO fan speed controller of any kind. When I first start the engine, the fans are immediately turning. I think the cooling fan speed is totally dependent on the dedicated hydraulic pump RPM, which of course is dependent on engine RPM. So, the faster the engine turns, the faster the pump turns, and the faster the fans turn. Must work, because we have never had any overheating problems.

Seems like a simple, but effective, system to me.

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