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 (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
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
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
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, 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
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.
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
Quote from: Merlin-PV on April 08, 2014, 08:12:32 AM
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
Look at www.parker.com (http://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
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
Quote from: uncle ned on April 08, 2014, 08:10:42 AM
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.
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.
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 8)
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
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 " :)
Last I heard 2 Dogs changed his screen name to Tres Perros he really wasn't dumb when it came to buses IMO
Anytime you change power you lose efficiency i.e. from mechanical to a electric generator/ alternator to a electric fan, or from mechanical to a hydraulic pump to a hydraulic motor to turn fan. Keeping it mechanical (directly hooked to engine) is the most efficient and that's what is desired when needing the upmost from any power source.
Sometimes you have to use different power because the end need for the power consumption isn't at the engine. I am trusting that the coach manufactures knows best due to the large number of units they have built over the years. If it isn't broke why fix it?
Clifford
I also miss Two Dogs. He had a different sencs of humor. also was good at telling a story. Hate that he got mad and left.
Every one needs to know that a lot that goes on here is bull crap and pay people like me no attention.
uncle ned
Yea Ned I miss Boxcarokie,Jim(rv safety),Dallas a lot of old timers that are no longer here
Electric fans and other systems such as A/C and power steering work well in limited duty cycle applications because they allow a relatively small generator to store energy in a battery over time for use in bursts. As TomC pointed out, that is not the case with engine cooling.
If you want to increase engine cooling, look at adding external air scoops. There is a thread here or you can find how it has been done on MCIs at coachconversioncentral.com
e3
Air scoops, in my experience, don't work. I have observed no difference with them on or off. Other than they look ugly when on, like a worn out old church bus.
Sent from my iPhone using Tapatalk
I used a flex-a-lite fan that was rated for 300+ hp on a car. After trying to make it work, including adding a huge radiator & ensuring no air could bypass the radiator. I determined the rating had more to do with selling fans and less to do with actual air moved.
If the CFM rating doesn't have a pressure drop listed - then it means absolutely nothing. What you really need is the fan's performance curve, then you can see what it will really do.
If the factory mechanical driven fan used 40 hp, then that is what it takes to cool the beast in the real world.
Only way to reduce the hp required is to get a more efficient fan &/ or a bigger radiator.
Well what happened to those guys? Yes, that twodogs was a character. Does fast fred still come around?
Quote from: luvrbus on April 09, 2014, 08:21:14 AM
Yea Ned I miss Boxcarokie,Jim(rv safety),Dallas a lot of old timers that are no longer here
http://www.newflyer.com/index/cms-filesystem-action/parts/products/featured%20products/mini-hybrid%20bulletin%20final.pdf (http://www.newflyer.com/index/cms-filesystem-action/parts/products/featured%20products/mini-hybrid%20bulletin%20final.pdf)
Have a look...
A 450 amp 24v alternator to run that setup I don't think so 8)
Yes I miss a lot of the old guys with a different view on things. Made us think if not more.
I still keep in touch with the three devils that I woke up to after they fixed my Heart. Cody Dallas and BK. great friends.
Fast Fred posts a few things on the other bus board.
Would love to hear about the series 50 transplant he did.
uncle ned
For those who, like me, are curious...
http://www.emp-corp.com/products/advanced/FI-11-electric-fan/ (http://www.emp-corp.com/products/advanced/FI-11-electric-fan/)
The literature says variable speed, up to 25 amps, and 1400 cfm. 8 would be 200 amps and 11,200 cfm, but only drawing 0.4 Kw at that rate, which is only 16.6 amps so maybe the 25 amps is for when it runs at 12V nominal (it is rated for 9 to 32 V). There are other versions up to 12 fans, and you would have to see what heat rejection the radiator is spec'd for, but I think the application for a two stroke would be harder than for a four stroke. You would need to optimize the radiator to get the cooling with the low air rate. The alternator spec'd at 450 amps is designed to be running at no more than 50% output for cool running and long life, it's an air cooled alternator (they list an oil port block-off kit presumably for 50DN conversions).
The issue with just putting electric fans on a two stroke usually boils down to radiator efficiency more than fan capacity. The stock radiator is designed to have a very large airflow developed by a high horsepower mechanical fan. It's too small to have the high efficiency that lets it develop the cooling capacity with smaller airflow from electric fans. That means a conversion from mechanical to electric means a replacement for both the fans and the radiator, which oddly is exactly what this retro-fit kit is... Look at this picture and you get a sense of the size of the system to cool what is probably a relatively low power four stroke. I've seen buses with that setup running around Toronto, I think.
Brian
I bet a coke Brian with the demands of the HVAC systems in the bus the 450 amp alternator runs around 85 % that sure looks like a expensive and high maintenance system,most of the transit engines are 4 stroke CNG engines wonder how much heat rejection they require it has to be small compered to a 2 stroke
I don't understand why anyone would change what has worked for many, many years-like the mechanical radiator fan drive. I have an 8 blade 32" direct drive fan on my bus. I realize it uses lots of power, but 2 strokes are hard to cool-especially with the addition of the air to air intercooler.
On our new Freightliner trucks, we still use belt driven fans with on/off thermostatically controlled clutches. Fuel mileage is getting to be such an issue, Detroit Diesel just made two modifications to the DD15 engine. First, they eliminated the turbo compounder. This is a second turbo right after the normal turbocharger. But instead of pushing more air, it is engaged to the engine through gears on the back of the engine. On a hill climb, it can add up to 50hp for free back into the engine. That works great. But what the engineers discovered, is on any other type of driving that involved less then full power, the turbo compounder actually pulled power from the engine to keep spinning. Hence by eliminating it, the overall mileage average went up. And second, the engineers have modified the water pump to be a clutched thermostatically controlled unit. They discovered that the water pump draws about 5hp all the time. When the engine is not working hard, the water pump disengages and just turns over slowly. At least they had the fore site to make the clutch fail in the engaged position.
With all these fuel saving engineering tricks going on, don't you think the first place the engineers would have looked would have been replacing the mechanical clutch fan with electric? Obviously, even on a front engine with ram effect from forward motion, the engineers feel that electric just isn't enough. Good Luck, TomC
On my both of my trucks, I had a 1350sq/in copper/brass radiator. With the 2007 engines using 25% exhaust gas recirculation, the raidators went up to 1650sq/in. Now with the 2010 engines reducing the EGR to 10%, we can get away with 1400sq/in radiators up to 505hp and 1650lb/ft torque. When the DD16 is ordered, the 1750sq/in radiator is used.
What's interesting is that the normal Diesel ISL 8.9 liter Cummins uses a 1200sq/in radiator. Order the ISLG natural gas version, and even though the horsepower drops from 380hp and 1250lb/ft torque on the Diesel to 320hp and 1000lb/ft torque, the natural gas engine has a bigger 1300sq/in radiator. Shows how much more natural gas heat rejection is. I don't like natural gas. There are many exhaust emissions that natural gas isn't even regulated-like fluorine, carbon monoxide (you'll never see an inside fork lift powered by natural gas-you will see propane powered indoors), raw gas emissions from over pressured tanks, etc. Stick with good old Diesel which is just a fraction away from being as clean running as natural gas. Good Luck, TomC
Clifford, I was assuming that the cooling system was a stand-alone system and the alternator was dedicated to it, but of course there is no reason it wouldn't also run the AC. At the same time the AC on these buses is different from anything I have ever seen, a big roof-mount package. I have to think the reasoning and payback is in fuel savings and lower emissions plus being able to specify a lower power engine to obtain the same performance. Modern manufacturers are highly competitive when it comes to long term costs. I think that system could be very low maintenance, to be honest. Just an alternator, a controller - both are highly proven technology - and 8 fans. 8 fans gives great redundancy, they are swappable in minutes and they are new on Ebay for $300 each.
I know that when I spoke to people who put S-50's in MC-9's they were able to cool that engine with one stock MC-9 radiator. My understanding is that CNG engines run hotter than 4 stroke engines, so they might be in the middle between a 4 stroke diesel and a 2 stroke in terms of how much cooling they need.
Edit: I went in and read the powerpoint presentation in the link I posted earlier. Kind of neat to see how they have engineered it. They document 4% to 10% fuel savings depending on the fleet, and $2,000 - $4000 reduced maintenance cost compared to hydraulic fans annually per bus. Fun to learn new things!
Brian
Just want to share my experience of a working electric fan bus.
Can the work? Sure, but only for buses with smaller engines and low heat rejection - 6-71 and 6V71s. Unless you are willing to go for a relatively expensive system like the one shown by Brian.
So what's my setup? A radiator from an F350 (7.3 PSD) and two sets of fans of a Nissan Altima. Most people would be laughing thinking that would never work, but living in BC dealing with one hill climb after another I can tell you it works flawlessly in my 27,000 lbs bus.
Sure, a 250hp F350 has a fan of roughly 20 hp. But, big but, it's designed to work with 3 sets of heat exchangers stacked in series - the intercooler, AC condenser, and finally that rad. The air is already hot by the time it hits the rad, and the fan has to overcome the resistance of 3 layers. Where as my air is nice fresh cool air, and the fans has a single two-row fin worth of resistance.
Some simple fluids math would tell you I need less than a tenth the power of the F350. And I was proven right. Even on sustained 6 - 10% climbs in summer, my fans rarely even hit high speed. In the worst case, I do have a set of misters.
Why did I do it? I had no choice. The factory fan was long gone, and the previous owners already had a set of electric fans on the original copper rad. That didn't work so well because the factory rad was 4" thick, and electric fans are not very good at static pressure. By going with a much thinner F350 aluminum rad, I solves that problem.
Is this setup in a school bus with a front mount radiator?
No, it's a 35' Prevost with a side mount radiator. There are louvers / semi-scoop on the side. At a 50 mph slow cruise in cool weather, natural draft is enough to cool the engine.
At higher speeds / hotter weather the fans kick in roughly once every 3 - 5 minutes for about 15 - 20 seconds. I can tell by watching the ammeter.
After studying the details of the engineered system I became of the opinion that electric cooling fans can indeed work for us, but with caveats. The biggest one is that electric fans are unlikely to work with the stock radiator(s). You need to increase the cooling capacity and lower the airflow resistance of the radiator as one step in the conversion. Then you need good natural airflow - in the nose or at the rear side are both natural high pressure points, and the engine compartment can be a nice low pressure area to dump the hot air into. Very good shrouding will help a lot. Then you need good fans, and enough electricity. I'm no longer as against the idea as I was.
Brian
I am convinced keeping the fan belt system intact is the most reasonable thing to do, but had my OTR heater/AC 24 volt fan motor worked, I would have tried to fit it to the squirrel cage engine cooling fans, or use the fans attached to it, to get maximum cfm, even in city traffic at low rpm, lvmci...
Well I'm new here but I'll take a chance and add to this thread...
I researched the same thing because my rig (not a bus) has a hydraulic motor driven and I hate the thing. It's so loud with hydraulic motor noise, and surely pulling more hp than a direct drive.
What I found can be seen here: http://www.electricfanengineering.com/app_truck_turbine_electric_fans.html (http://www.electricfanengineering.com/app_truck_turbine_electric_fans.html)
They seemed confident in my application (which has a front mounted radiator).
For reference, these things weigh about 60lbs vs some of the other lightweight solutions mentioned in this thread.
They are designed for over the road trucks.
In case you're wondering, the one for my 6-71 is about a grand, which if it saved fuel, might be worth it.
Cheers!
That electric system is only for front ram radiators and for engines that don't overheat. Good Luck, TomC
Quote from: TomC on June 09, 2014, 12:05:43 PM
That electric system is only for front ram radiators and for engines that don't overheat. Good Luck, TomC
True.
Being unfamiliar with buses, are almost all of them pushers with rear or side radiators?
Quote from: Audiomaker on June 09, 2014, 03:42:25 PM
True.
Being unfamiliar with buses, are almost all of them pushers with rear or side radiators?
Yes
TOM