Electric cooling fans for bus engine

[Merlin]

Hello guys.  Long time, no see!  I used to post here while doing my conversion, but have since finished and taken to the road to enjoy the fruits of nearly ten years of labor, frustration, confusion, dirt, and grease.  Sweet ... it is done, but now I have a hankering to do a modification to the engine cooling fan system.  Long story how this came up, since the OEM fan, gearbox, and Rube Goldgerg rigging was doing a good job of cooling.

Anyway, the bus is in my favorite Diesel engine/transmission repair shop as we speak.  Transmission first and reverse gear dirt napped when we were in southern Alabama.  After much agony, the decision was made to have the bus towed all the way back to central Ohio.  The engine (8V92T) and Allison (HT-754CR) are now out of the bus ... hanging from a forklift.  My mechanic phoned me yesterday with an idea: "How about doing away with that cooling fan rigging and replacing it with a set of electric fans?"

Here is some background on what had been done to the OEM fan system by a former owner of my bus:  he had welded a heavy brace to solidly hold the fan gear box in such a way that the fan belt was permanently tight.  I think this was done to avoid replacing the air cylinder that kept the belt tight (when air system was holding air), and allow the belt to be easily changed if the air was dumped manually by a valve (above the engine access door latch).  I've lived with this "after market" rigging for over 12,000 miles with absolutely no problem except for the obvious exception ... replacing the big triple groove fan belt was a beast of a job.  Did it twice.  First time my wife helped, but she threatened divorce if I asked for help again.  It was a learning experience for her, as she now knows all the magic words to scream out when fingers get pinched.

Now back to my mechanic's solution.  We have located 24v high efficiency engine cooling fans and shrouds ( http://www.flex-a-lite.com )  The combined output of two pairs of dual fans would be around 11,000 CFM, and they are thermostatically controlled to cycle on and off as needed as well as there being an adjustment for fan speed from 60 to 100 percent.  I think I'm clever enough to manufacture a new shroud from heavy aluminum that would hold the fans.

Reason I'm posting here is to get feedback opinions on the advisability of going to electric fans, as well as asking if the CFM of 11,000 maximum is enough to live up to the needs of the DD 8V92.  The radiator is HUGE, and I've never questioned its ability to keep the big hunk of iron cooled. It was a new radiator in 2002, but I'm having it replaced with another new one while the engine, etc. is out.  Hey ... it is only money, eh?  Spend it now or give it to the IRS eventually.

Mechanic and I have searched with no results concerning the current CFM of the Prevost fan rigging.  I'd feel better if I knew my electric fan idea would not be a step backward in cooling ability.  Sort of like ... I'm hesitant to reinvent something without knowing the specs of the original.  Of course the electric fan supplier's hype is all rosy about reducing the horsepower drain on the engine, especially when cooling demand is low at cruising speeds.  This point may be moot because a side-rear radiator does not by design take advantage of fresh ram air like it would if mounted in the nose of the vehicle.  Another "advantage" of an electric fan system is the elimination of belts, gear box, and spinning shafts.

I'm in the dark with respect to the reliability track record of electric radiator fans.  Hopefully my shroud design will allow for easy swap of a fan should it malfunction.  Since the idea is for four fans, I don't feel too queasy about having one go bad.  Now a bad wiring harness or blown fuse could create a total failure.  Things to ponder.

Sorry about the gassy post.  Around the campfire, I don't talk much, but at a keyboard, I'm uncontrollable.

Merlin
85 Prevost, 8V92T, Allison 5sp

[Iceni John]

There have been a lot of posts here during the last few years about this exact subject.   The general concensus is that electric fans are not going to pull enough air through a large radiator an an OTR bus, especially to cool a 8V92 (the hardest engine to keep cool, especially in a bus with a side radiator).

Instead of electric, how about getting a two-speed hydraulic fan, such as from a scrapped RE skoolie?   It will pull a lot of air when needed, but the thermostatic valve will reduce its speed and engine load when not needed.   You'll just need to make sure your hydraulic pump has enough capacity to run it.   Just an idea.

John

[luvrbus]

The Prevost had a good system what is the problem,most just had a small 90 angle box at the fan driven from a belt drive drive shaft off the engine I can tell you 4 electric 11,000 cfm fans are not going to cool a 8v92 the 8v92 requires more heat rejection than the 4 fans will allow. It is hard to replace the 45 hp needed to drive the mechanical  fan with electric fans IMO  

good luck

[uncle ned]

Where is Two Dogs and his electric fan donor for his 8v92.

We have never heard the results of the test.

he just disappeared


uncle ned

[Merlin-PV]

             Merlin, go with the hydraulic fans with a diverter to run your power steering, I did that a view years ago never looked back. easy to install mounted pump just to the left of crank pulley with triple belt foolproof!  Merlin

[Merlin]

Thanks guys for the input advice.  That's what I feared ... the electric fans would be lame compared to the torrent of air from the present fan system.

I will study the hydraulic fan idea a bit though.  Might have to run a separate pump system. The only hydraulic on the bus is the power steering and that pump is likely sized for just that purpose. Have not been to a junk yard for parts since I was in high school, but as I recall those were fun times ... hunting and picking.

[usbusin]

Hi Merlin,

I can't help with your fan idea, but glad to see you're still on the board!  

Thanks again for the time we spent at your house many years ago.  We'd love to see your finished conversion.  What we did see at the time was a "work of art"  in progress.

If you're every out on the "left" coast, give us a call.  We have 30 amps,a sewer dump and way out in the country!

Your friends in California,

GaryD

 

[Merlin]

            Merlin, go with the hydraulic fans with a diverter to run your power steering, I did that a view years ago never looked back. easy to install mounted pump just to the left of crank pulley with triple belt foolproof!  Merlin

We need to talk again ... Brother Merlin !!  For those who do not know either of us; Merlin-PV and I chatted years ago about Prevost bus converting.  Ironically our personal lives are as similar as our first names.  Uncanny !!

Now I may even deepen the similarity with installation of a hydraulic fan system.

Merlin
Dublin, Ohio

[luvrbus]

Look at www.parker.com under hydraulic fans a ton of info there on how to size a hydraulic drive. You can change the hydraulic power steering pump to a double pump that gives you really 2 different pumps one for the steering and 1 for fan. The diverter system I don't know about that one but it seems to work for the other Merlin, me I would want the steering to work full time at normal pressure and oil flow JMW 

[busguy01]

Changed to a hydrilic fan when installing a 60 series in my Eagle 01. Worked well EXCEPT- went thru several different pumps before figuring out that the pump MUST as big of capacity as the fan moter. Sounds simple but not when you are trying differen things. Ended up with a 31", 28 GPM fan and pump as well as a 10 gal resevoiur and a air to oil cooloer. Drove the pump with a 3 belt setup off the crank pulley. The faster the engine turned the faster the pump and fan ran. Do not remember what ratio the pulleys were but think it was slightly faster than the engine rpm.
Good luck!
JimH

[bobofthenorth]

Where is Two Dogs and his electric fan donor for his 8v92.
We have never heard the results of the test.
he just disappeared
uncle ned

I was wondering exactly the same thing.  I think we can all pretty well imagine how that test worked out.  Assuming it ever even happened.

[Jim Eh.]

We were doing some suspension and alignment work for New Flyer Industries a couple of years ago and we were requested to swap out some of the electric cooling fans (I believe 6 in all) mounted directly on the side mount radiator of one bus. The system was driven by a controller that sensed engine temperature and controlled the number of fans operating according to conditions. The systems works fantastic in high temperature city driving so it should work well on a highway driven coach. I have an engineer buddy who still works there and could get the brans name if you wish to seek further info.

[luvrbus]

2 dogs was alive and well the last I heard next time I go through Amarillo I'll see if I can find him for you guys.  Electric fans will work Boomer has proven that with a well design system but his didn't come from AutoZone

[TomC]

Electric fans work well with transit, stop and go service. But get out on the road with a long 5 mile pull (like the Grapevine) and you'll over heat. Stick with the direct drive rather then hydraulic. You loose power through hydraulic. If you want better fuel mileage, there are 2 speed fan clutches that are made that you can adapt to the direct drive system. Good Luck, TomC

[Paso One]

I have a set of flex a lites  mounted in a 77 Corvette with a 350 ( they typically run hot )
They move a lot of air but I doubt they would keep my 6V71 cool.

Amazing I too was thinking about "two dogs " the other day  " must be spring "