Dear Friends,
I was reading where the radiator fan on my 6V92TA can consume as much as 40 horsepower! The engine is supposedly set up at 330 HP. Many modern vehicles have temperature-controlled clutches on the fans, or electric fans. Is there anything a crazed busnut can do in this department to reduce drag on the engine, and thus liberate some HP and increase fuel economy:
Here is a picture of my setup.
Thanks in advance!
Really don't think 40 hp is bad. Even elect is going to require power generation. Or hydraulic you have to drive pump. Is your bus running cool enough under a hard climb? You wouldn't want to run less if it isn't. Nothing more dependable than belt drive! No pump to fail or electric motor to burn out; always happens at a bad time. Simple is sometimes best and most dependable in long run.
A Horton 2 speed fan clutch, electric fans will do you no good,but you will be wasting your money with 6v92 and a Horton very seldom will you be able to run on low and set down when you get a price for one they are proud of it
I always thought a 6v92 -330 hp used around 50 hp
good luck
A couple more considerations on it.
When you need the horsepower the most is generally the same time that your engine needs the most cooling capacity.
And diesel pushers generally need most of the fan's capability at cruising speed. Unlike vehicles with a front end radiator, the forward motion doesn't help move air through the radiator. In fact it can make it harder to get a good flow into it. Hence the various scoops and air dams that some people use to help with engine cooling while driving.
Dr. Steve Your thinking that's good ! Mechanical is more dependable for your travel plans just listening to your post you plan on desert and mountains. will max out your cooling system. Much easier to find belt on road than elect motor or hydraulic motor or pump. and cheaper. Bob
Quote from: Mex-Busnut on June 08, 2011, 06:19:59 PM
Dear Friends,
I was reading where the radiator fan on my 6V92TA can consume as much as 40 horsepower! The engine is supposedly set up at 330 HP. Many modern vehicles have temperature-controlled clutches on the fans, or electric fans. Is there anything a crazed busnut can do in this department to reduce drag on the engine, and thus liberate some HP and increase fuel economy:
Here is a picture of my setup.
Thanks in advance!
The issue of parasitic fan loss, and available alternative fan solutions, have been things that troubled me since day 1 of owning my bus - because the OEM fan setup was gone, replaced by (gasp) an electric setup.
After a ton of research and fan calculations (I'm a mechanical engineer myself), I have concluded, and MCI seems to agree with me, that a fan only needs its max capacity less than 10% of its time. A fan's power consumption goes up approximately cubic to its rpm. In other words, that 40hp fan would only consume 5hp at half its rpm. At 5hp, the fan would still retain a good portion of its CFM, because as you decrease CFM, you also have less resistance through the rad, which makes flow easier.
OEMs have to cover the worst driving situations: uphill, full throttle, AC full blast, 105 degree and high humidity. As private owners and engineers, we can choose what driving situations to cover.
My bus has never overheated, even climbing through BC rockies in 90 degree weather. How? Because of the relatively little 6V71 and manual transmission. On a 6V92 or 8V92 with an auto, it's a completely difference story. You're now dealing with heat rejection of a much larger engine, more hp, torque converter, and turbo intercooler. Electric fans are pretty much out of the question. But an electro-magnetic fan drive that operates in partial mode, consuming 3 - 5 hp, may perfectly suffice 90% of the time.
My rad is just about shot, and I'm reluctant to pay $1600 to get it rebuilt (because my OEM fan is missing). I've taken on a brave cooling project: an F350 radiator from the 7.3 Powerstroke era, along with two electric fan assemblies (4 fans total, plus one pusher) out of Nissan Altimas. For anyone who's interested, or in serious doubt that it'll work, I'll beposting an update in the next month or so. My preliminary calculations say it will work. Worst case, I'll be using my misters a lot ;D
If I had your setup, I'd install the 2spd air operated fan clutch. I lopes around using about 5hp to gently pull air through at all times (by eddy current-like a slipping motor) then when you need it, it engages to normal fan speed. I have a gear drive on my Vdrive that doesn't allow for the two speed. Good Luck, TomC
The fans used are generally crude, more akin to clubs, not exactly a nice twisted aerofoil prop like an airplane or wind tunnel fan with hig aspect ratio blades. You could get some gain, maybe as much as 20% or more with a decent blade. As suggested, a prop/fan directly driven by an electric motor would be more efficient.
But the only time that fan will ever see 40 HP is in low gear, on the governor, at sea level. Once the Bus is moving, induced airflow will reduce the load, at cruising speed with lower RPM will reduce load, and higher altitude with lower air density will reduce load. Its probably only pulling 15-20 HP or less sailing down the highway once it slows down and has air blowing through it.
I would start with making sure air flow is unrestricted, make sure the fan has good bearings, that its balanced (both in weight as well as loading,that each blade is pitched the same), blade face is clean/polished. Its doubtful you would gain much through engineering changes to ever witness much at the pump.
Dr Steve -
Fan and cooling issues have been beaten to death time and time again on both major bus bulletin boards.
Simple answer?
For the OEM powertrain, it's hard to second-guess the factory.
Fuel economy vs the cooling fan?
It's the weight of the operator's right shoe that has the biggest effect, everything else is minor.
Pushing a vehicle that has the aerodynamics of a brick down the highway is going to take fuel - wind resistance is your second-biggest enemy.
With 10 gears to play with, it's going to be easy to keep the 6V in it's "sweet spot," thus lowering the cooling load on the radiator/fan.
Don't forget the engine's also cooled by the lubricating oil - make sure you're running straight 40 wt - and that the oil cooling system is functioning properly. Additional cooling here, thermostatically controlled, might be a more thoughtful approach to your non-issue.
FWIW & HTH. . .
;)
Buses don't induce air the fan works more at cruising speeds several nice variable pitch thermo control fans on the market for buses I had one on the Eagle not cheap for a 32 in 16 blade but they work
.Boomer has a nice electric fan setup on his Eagle but he done a lot of research and spent some bucks for his Cummins engine and I have doubts his would work on a 8v92. Cat has great info on what hp,size,cfm and type it takes to cool their engines in any application they have a hydraulic system listed by flow,pressure,HP and sizes but no electric fwiw and RJ pretty well hit the nail on the head
good luck
My old Crown Supercoach had two rather very large belts pulling the big fan. A knowledgeable mechanic once said the two could easily handle 50hp. The coolant capacity was 32 gallons and the oil capacity was 44 quarts. (if faulty memory serves) HB of CJ (old coot) :) :) :)
Thanks to all of you for your most enlightening comments. I would like to get 100 miles per gallon on my little bus, and pay 10 cents a gallon for diesel...
;D
Quote from: RJ on June 08, 2011, 09:05:22 PM
Dr Steve -
Don't forget the engine's also cooled by the lubricating oil - make sure you're running straight 40 wt - and that the oil cooling system is functioning properly.
Mr. RJ et al:
The previous owner (a professional tour bus operator) has been running straight Mobil 40-weight diesel oil in this bus. Is this the best oil for it? Also, how often do you guys recommend the oil and filters be changed? I need it to last me trouble-free another 30 years, at which time, good Lord willing and the creek don't rise, I will be 83 years old, and ready to inherit the bus to my most awesome grandsons...
Thanks in advance!
Depending on your kind of driving, I would either just change the oil twice a year or every 10,000 miles.
When I was driving, I found through oil analysis (available at Speedco oil change outlets) that 12,000 miles was the magic number. Amazing to that the 3406B Caterpillar did not need any oil added during that time. As compared now to Detroits DD engines at 50,000 mile oil changes! Good Luck, TomC
Quote from: luvrbus on June 08, 2011, 09:18:06 PM
Buses don't induce air the fan works more at cruising speeds
Then their blowing the air the wrong way.
Quote from: artvonne on June 10, 2011, 07:31:47 AM
Quote from: luvrbus on June 08, 2011, 09:18:06 PM
Buses don't induce air the fan works more at cruising speeds
Then their blowing the air the wrong way.
When in motion (without factoring in ambient wind conditions), the airflow down the side is perpendicular to the radiator grill. That flow actually works against the fan's effort to draw air in. The higher the speed, the more work is required to pull air in.
Why don't buses blow the hot air out through the radiator instead? I'm just guessing here, but perhaps if that much air was being pushed outward while at cruising speed, that same perpendicular air flow that resisted inflow, when confronted with a high volume of air pushing out into it would form back pressure restricting outflow.
I have wondered why they didn't put the radiator on the back of the bus and have the fan(s) push the air through it with the aid of the natural vacuum on the back like they did the AC condenser on my RTS.
I've always thought the roof top scoop on the old Flx's were a great idea, the next best thing to a front mounted radiator. It seems like you could really make a difference combining that with a thermal clutched fan and exhausting the flow out the back. But maybe the extra drag induced by the air scoop consumes more power than it saves. I don't know.
Some buses, even the later 4104, had an engagement system for the fan so that full power was only applied to the fan when the engine needed it. Most new cars that have an engine driven fan (as apposed to electric fans/more common) have a thermo clutch drive in the fan hub so that the fan does not spin below a set temp. It is likely that your bus already has some kind of thing like this so that full hp losses are only realized when you need all the cooling you can get......and you will need full cooling at some point. My old bus has a fixed fan with no variables...it takes forever to get to operating temp, I see shutters in the future....my bus is pretty slow and I could really do with the extra hp but it is a simpler system and not prone to catastrophic failure so I will continue slowly on my way.
Quote from: HighTechRedneck on June 10, 2011, 08:26:09 AM
the next best thing to a front mounted radiator.
Yup, I've often wondered this as well. Older British rear-engine designs, such as the Bristol RE and VR, had their radiators up front, and a good-looking radiator grill makes for an attractive front (in a slightly traditional way). The coolant is already piped up to the front for the heater/defroster, so what's the problem in also running it through a radiator there? Ironically, the more moderate temperatures in Britain are where inherently-better cooling designs have less benefit, compared to the much higher summer temperatures in North America. As has been discussed here before, airflow is the key. A truck with the same radiator and engine as my bus never has cooling issues, so radiator placement seems to be the obvious culprit for our cooling woes. I may try one of those fancy new multi-blade fans in an effort to persuede more air to flow through my radiator, but otherwise it's mister time, or an expensive re-core.
My bus is mid-engineed and has the radiator underneath the bus behind the front axle.
How is the cooling on modern rear-engined buses arranged? It wouldn't surprise me if they also relied on big, power-consuming fans, but I can't help think that a more intelligent solution exists by exploiting the pressure differences around or underneath a bus to naturally draw air through a radiator. Think of the way air is drawn through the radiator of a mid-engined, low-front supercar such as a Ford GT-40 - no big fans or ugly ducting required, just clever design
Jeremy
At the rear of the bus there is relative high pressure along the sides, and low pressure behind and under. But it's not a big pressure differential that promotes strong cooling flow in the same way as the front mount rad on a car or pickup truck does. You still need to pump air at speed, while on a front rad the fan becomes relatively unimportant above around 40 mph.
It is the design of the radiator that determines the amount of air required (& at what pressure drop) to remove heat from the coolant. The design of the fan determines how much pressure it can develop & how much air it can move. I find it interesting that building pressure takes very little power when compared to moving it.
If you deny the radiator the air it needs, the engine will overheat.
For normal driving conditions, you may not need much cooling. It is during those times when you are in a situation that requires max power for a sustained period that you will realize the limits of your system & the benefits of having more cooling capacity. ;D
Quote from: HighTechRedneck on June 10, 2011, 08:26:09 AM
Why don't buses blow the hot air out through the radiator instead? I'm just guessing here, but perhaps if that much air was being pushed outward while at cruising speed, that same perpendicular air flow that resisted inflow, when confronted with a high volume of air pushing out into it would form back pressure restricting outflow.
I have wondered why they didn't put the radiator on the back of the bus and have the fan(s) push the air through it with the aid of the natural vacuum on the back like they did the AC condenser on my RTS.
Well, the outside of the bus, especially towards the rear where flow is highly turbulent, generally has a higher pressure than the engine compartment (which is usually negative, especially if full width mud flap is retained). To blow air out, you'll have even greater pumping losses. If you open a window towards the rear of the bus, you'd see just how much wind naturally flows in.
However, on a mid engine coach like Crown, the radiator may indeed be in a region of low pressure / vacuum, depending on speed. But then again, the air underneath the chassis may have even lower pressure, so it may still be better to suck air in.
Finally, I believe rear radiators aren't used for two reasons: engine accessability and grease buildup. Accessability is pretty self explanatory. As to grease build up, all you have to do is look at some rear engine Class A motorhomes. Engine oil mixed with dirt gets caked onto the radiator over time, and really messes up cooling efficiency. Imagine that on a Detroit!
Quote from: Jeremy on June 10, 2011, 01:21:01 PM
Think of the way air is drawn through the radiator of a mid-engined, low-front supercar such as a Ford GT-40 - no big fans or ugly ducting required, just clever design
If you look closer, almost every mid or rear engine sportscar has a FRONT radiator, with long coolant hoses running to the back. The side or roof scoops are for air intake, or turbo intercooler.
But, if necessary, a rear radiator can bedesigned on a sportscar, due to the following:
The much shorter length, and better drag coefficient, of sports cars meanings flow is often laminar (attached to the body). If you look at wind tunnel tests of Vettes and Porsches, flow normally seperates AFTER the body. Given this, it is easier to design a side intake, with gentle curvature, so that airflow stays attached to the skin, and guided into a radiator mounted at the mouth of the scoop.
Again, the same concept won't work well on a 45' bus, because the flow is already seperated. It'll certainly be better that a sideways radiator, but is the tradeoff in cargo and seating capacity worth it? Not to mention a Prevost with a giant Viper/Porsche style side will be very expensive to design or fix after an accident.
So I guess to conclude, we're pretty much stuck as far as radiator location goes. I even thought about a front radiator with long coolant hoses, but even that may reduce the front interior space too much. Remeber, the air would also require a path to escape. And then the question becomes: how to you drive the fans? And we all know how much electric fans are frowned upon ;)
Quote from: RoyJ on June 10, 2011, 06:06:29 PM
Quote from: Jeremy on June 10, 2011, 01:21:01 PM
Think of the way air is drawn through the radiator of a mid-engined, low-front supercar such as a Ford GT-40 - no big fans or ugly ducting required, just clever design
If you look closer, almost every mid or rear engine sportscar has a FRONT radiator, with long coolant hoses running to the back. The side or roof scoops are for air intake, or turbo intercooler.
Yes I know, but the point is that it's not a traditional front radiator that sits vertically right at the front. The radiator on a GT40 sits at a shallow angle a little way behind the front of the car, with airflow through it being generated by the venturi effect created by air passing over a large slot in the top surface of the bodywork:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwapedia.mobi%2Fthumb%2F4d8e504%2Fen%2Ffixed%2F470%2F360%2FFord_GT40_%252528front%252529.jpg%3Fformat%3Djpg&hash=2ebf03adf9eaa376682d36a6cd49491c56319ace)
Jeremy
The GT-40, Ferrari's, Porsche's, Lambos, etc., they all use and have used NACA ducts, as do all modern aircraft. NACA ducts were deveoped to induce higher airflow with minimal drag by generating a vortex. Those cool door vents on the Ferrari 308 were modified NACA ducts, and do actually promote high airflow.
Perhaps if the air scoops used on MCI's had a large NACA duct placed ahead of them they would flow more air? Could make one out of cardboard and duct tape it on as a test.
Quote from: Jeremy on June 10, 2011, 07:10:32 PMYes I know, but the point is that it's not a traditional front radiator that sits vertically right at the front. The radiator on a GT40 sits at a shallow angle a little way behind the front of the car, with airflow through it being generated by the venturi effect created by air passing over a large slot in the top surface of the bodywork:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwapedia.mobi%2Fthumb%2F4d8e504%2Fen%2Ffixed%2F470%2F360%2FFord_GT40_%252528front%252529.jpg%3Fformat%3Djpg&hash=2ebf03adf9eaa376682d36a6cd49491c56319ace)
Jeremy
Ok, now I see what you were trying to say.
I agree it's a cool aero design, but again, I think it's just about impossible to implement similar designs on a bus body.
The closest I can think of is the Nova transit buses, if you look at the roof radiator's angle, it almost matches that of a GT40:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fimg12.imageshack.us%2Fimg12%2F5624%2Fdscn3330.jpg&hash=aceb9fa765ac5f3164cbc5494e6639c86009df8e) (http://imageshack.us/photo/my-images/12/dscn3330.jpg/)
Uploaded with ImageShack.us (http://imageshack.us)
But sometimes I wonder if the added benefit of ram-air is offset by the lower efficiency of hydraulic drives. Riding on these buses feel slightly slower than side fan models, but that could also be the CVT ???
Didn't MCI starting with the D model mount the radiator and air charger in the rear on the back above the engine ? I was looking at a MCI that the Amerex Fire System had went off and the radiator was above the engine at the rear huge fan 16 or 18 blades
good luck
Yes, the D model MCI has the rad and charge air cooler mounted flat against the back. The fans are belt driven and clutch controlled, the air intakes are from the grated sides, with a cavity ahead of the rad/cooler.
Best of all worlds? belt drive, clutched separate fans for rad and cooler fans, minimal intrusion into the coach interior, engine accessible from both sides.
And then the E and J went to a driver's side low mounted combined rad/cooler single fan with a mitre box set-up.
Who knows?
happy coaching!
buswarrior
Thanks BW I thought it was a D model but this old mind plays tricks on me from time to time LOL
good luck
On the E and J models, do the fans blow air out the side or suck it into the compartment? Is the compartment ducted separate from the engine area?
Brian
Quote from: bevans6 on June 11, 2011, 07:48:38 AM
On the E and J models, do the fans blow air out the side or suck it into the compartment? Is the compartment ducted separate from the engine area?
Brian
Though I've never driven one myself, I can almost gurrantee it sucks air in, due to the following:
1) It's easier that way aerodynamically, due to the reason I mentioned in a previous post
2) The intercooler is on the outside. If air was blown out, hot engine bay air would first pass through the rad, making it even hotter, before hitting the intercooler. By then it would all be but useless. You always want ambient air to hit the charge air cooler, so air needs to be sucked in.
I maintained a MCI D for a hockey team for a few years. What I found is the rear mounted rad and intercooler and fans and associated hardware gets corroded from all the road grime blowing back into that compartment. Following a run in winter conditions, the rear of the bus is covered with dirty slush and gunk. I wonder if that is why they went back to side mounted rads with solid rear cap?
JC
This may be of some use relating to most aspects of engine cooling systems.
http://www.arrowheadradiator.com/14_rules_for_improving_engine_cooling_system_capability_in_high-performance_automobiles.htm (http://www.arrowheadradiator.com/14_rules_for_improving_engine_cooling_system_capability_in_high-performance_automobiles.htm)
Kenny
I have a Dina that has a side radiator. Based on my trip to Florida this past winter I don't know that a side radiator gets any less salt exposure. My intercooler is all white after that trip and I assume it is a layer of salt.
MCI's side radiator design is probably different than Dina so salt exposure may be less.
I would guess that the overhead radiators are easier to work on than my radiator that is jammed between the engine and the sidewall. It was a bitch to replace in 2007. I have to pull the intercooler today to replace the water pump, but it is easy to get out.
Quote from: bevans6 on June 11, 2011, 07:48:38 AM
On the E and J models, do the fans blow air out the side or suck it into the compartment? Is the compartment ducted separate from the engine area?
Brian -To answer your question, the fan draws air thru the radiator and dumps it into the engine compartment - just like 90% of the rest of the industry with side-mounted radiators.
Very few bus manufactures side mount the radiator, then use sheet metal ducting to a fan running in parallel to the engine's crank pulley. Early Gillig skoolie pushers and some Flxible hi-way models come to mind, there are others.
GMC's V-drive allowed the fan to be directly driven w/o any belts/pulleys/miter boxes, etc. Some late production 4104s, and all V-block engines (transit or highway models) incorporated a torus drive to "lock up" the fan when increased engine cooling was called for.
GMC was also the first coach manufacturer to utilize the full-width air dam ("mud flap") behind the rear axle to create a low pressure area under the engine compartment to help draw the heated air out from under the coach. Crown & Gillig used a similar air dam behind the front axle on their mid-engine models.
I remember reading somewhere that MCI originally mounted the radiators up high like they did to prevent the frequent slushy conditions found in Canada from plugging up the cooling system. Don't know how true, but it's possible.
FWIW & HTH. . .
;)
Dina has the radiator parallel to the crankshaft pulley between the engine block and the side of the bus. This is t-drive. The fan is run off the crankshaft pulley. There is a rather large kind of a tunnel on the side of the bus at the rear to supply cooling air.
I have attached pictures of the tunnel and the radiator.
Ahoy, Bus Conversion Folks,
My -01 Eagle has a Cummins M-11 and Roadranger 10 spd. My radiator is ~~25% bigger than the already big Eagle unit, and my fan is a 12 bladed 34" aerodynamic unit, properly shrouded. My first engine was a 6V-92T, but this Cummins engine is very cold blooded.
I had installed a fan drive 'overdrive' unit on my -01 Eagle. It is a Laycock Overdrive J Type S/N 27 115895 038537. It is derived from a '1980's Volvo Laycock transmission overdrive unit. Has a 26% speed-up in overdrive, to run the fan 26% faster. There are a number of mods to permit installation in a bus as a fan drive. It was NOT easy to build. An electric solenoid valve on the case puts it into overdrive, with a temp switch on the engine to do it (plus a manual driver's switch).
This thing started life behind a sort of anemic Volvo engine, but it looks just like the ones behind the Dodge Cummins diesels, so it is likely to last a long time just running a fan. The mods are ordinary machining which are not likely to fail, and are easily re-done if needed. The rest of it consists of replaceable Volvo parts.
YEARS later, and the overdrive had NEVER turned on by itself. The large radiator and the very efficient fan resulted in a cooling package which was 'off-the-bottom' of the cooling horsepower map. I only run that fan at 61% of crankshaft speed, and I was doing some re-arranging so I removed the unit. I do get such good fuel mileage on my Eagle that I'm careful not to mention it around guys with DD-8-V92/old Allison's for fear of a 2x4 upside the head!
Here are some 'gee-whizz' equations having to do with fans/propellers.
As you can see, Power is a cube function of RPM, and Diameter, while flow-Q is only a direct function. So—speeding-up the fan is a lousy way to get more cooling. It costs you a lot of power, which does NOT help the wheels to go around.
A bigger radiator, (or a supplemental) plus a large and efficient fan is much better. I understand that 'misting' is very effective, but is you don't use distilled water, you will 'lime' the radiator. Sort of like peeing in bed to get warm.
I have listed this fan overdrive unit for sale from time to time, but no takers.
If you wish, I can forward high res pix -- big files. Please ask at: rhbelter@comcast.net or ph 831 625 0670
Enjoy /s/ Bob
Ahoy, Bus Conversion Folks,
Sorry to do a 'double' post, but the equations did not come through.
They are there now.
My -01 Eagle has a Cummins M-11 and Roadranger 10 spd. My radiator is ~~25% bigger than the already big Eagle unit, and my fan is a 12 bladed 34" aerodynamic unit, properly shrouded. My first engine was a 6V-92T, but this Cummins engine is very cold blooded.
I had installed a fan drive 'overdrive' unit on my -01 Eagle. It is a Laycock Overdrive J Type S/N 27 115895 038537. It is derived from a '1980's Volvo Laycock transmission overdrive unit. Has a 26% speed-up in overdrive, to run the fan 26% faster. There are a number of mods to permit installation in a bus as a fan drive. It was NOT easy to build. An electric solenoid valve on the case puts it into overdrive, with a temp switch on the engine to do it (plus a manual driver's switch).
This thing started life behind a sort of anemic Volvo engine, but it looks just like the ones behind the Dodge Cummins diesels, so it is likely to last a long time just running a fan. The mods are ordinary machining which are not likely to fail, and are easily re-done if needed. The rest of it consists of replaceable Volvo parts.
YEARS later, and the overdrive had NEVER turned on by itself. The large radiator and the very efficient fan resulted in a cooling package which was 'off-the-bottom' of the cooling horsepower map. I only run that fan at 61% of crankshaft speed, and I was doing some re-arranging so I removed the unit. I do get such good fuel mileage on my Eagle that I'm careful not to mention it around guys with DD-8-V92/old Allison's for fear of a 2x4 upside the head!
Here are some 'gee-whizz' equations having to do with fans/propellers.
As you can see, Power is a cube function of RPM, and Diameter, while flow-Q is only a direct function. So—speeding-up the fan is a lousy way to get more cooling. It costs you a lot of power, which does NOT help the wheels to go around.
P1/P2 = (N1/N2) cubed
P1/P2 = (D1/D2) cubed
Q1/Q2 = (N1/N2)
A bigger radiator, (or a supplemental) plus a large and efficient fan is much better. I understand that 'misting' is very effective, but is you don't use distilled water, you will 'lime' the radiator. Sort of like peeing in bed to get warm.
I have listed this fan overdrive unit for sale from time to time, but no takers.
If you wish, I can forward high res pix -- big files. Please ask at: rhbelter@comcast.net or ph 831 625 0670
Enjoy /s/ Bob
Thanks, Bob.
We had learned some of the same things that you are talking about, and being interested in fuel economy, we looked for something similar in our boat.
It is a 40 ton, 62 foot ex drum seiner, and it has a propeller of nearly four feet in diameter. When the hull is clean, she runs right at 6 knots and burns about 2 gallons per hour. If we had a propeller of only two feet, we would have played hell getting the fuel consumption down to 4 gallons per hour.
FWIW
Tom Caffrey
Guys,
I have read almost all of these suggestions in various threads all over this forum. I think every blessed one of these current suggestions is a must for the DD 2 stroke. One thing I think is missing from all this is a recommended solutions/implementation train of thought. If I miss anything or you think I am out of sequence please holler for everyone's sake. I am tough skinned.
Priority of implementation is driven by our wallets to a large degree and "ease" of install is a significant driver. The easy stuff is also the cheapest.
1. Install that "mud flap" across the rear axle. Mill supply outlets throw away gobs of this stuff all the time. It is remnants of conveyor belt and nothing that bends easily is tougher. I install the thing too long and let it "wear" itself on to the "purfeK" size. This cost nothing to operate and is free if you know which dumpster to peruse. Life span? Ha!
2. This wasn't mentioned. Install a 1 inch lip that is perpendicular to the bus on the leading edge/corner of the rad opening. This edge disrupts the flow of the air across the opening and creates a slight vac directly behind it that turns the air into the opening. I would use a piece of 1/4 inch aluminum flat stock and pop rivet it to the inside edge of the rad opening. A strip of PVc or just about anything will work. This won't do much but it is free to operate and will never wear out. And invisible to the untrained eye.
3. Air scoops are a fraud in my opinion but I have never talked to anyone that had them. Measure the total sq inches of opening with out them and then measure the opening that isn't shrouded by them and add the sq inches of the lead opening. I know there is some ram air but I think the thing is too small to pencil out. Easy install though.
4. Ditch that mud flap across the back. It hurts the cooling so less is better with that gone. Might be of sufficient dimension to use after the axle.
Expensive stuff:
1. If you don't do anything else....shroud that fan. The efficiency of the fan is really improved by a shroud. This one up grade may solve your overheating problem. It will help any generation fan.
2. Install a modern high efficiency molded fan blade assembly. That antique thing with bent sheet metal blades is a power robbing sucker. DC should pass a law and make everybody install these....not really but I thought I would raise some hackles.
3. Install a therm fan drive/clutch if you can afford it. It will really only come into play after you have "over-designed" the rest of the system.
4. Install that expensive ceramic cloth insulation on the exhaust manifolds, piping to the turbo, the turbo drive impeller, exhaust piping running between the muffler and the turbo. This will increase your max HP and efficiency. Not to mention dropping you engine bay temp dramatically. And an engine running in a lower ambient will also need less cooling. Engine oil should run cooler for that reason alone.
5. Install an over-sized radiator. That may be a challenge for a worn 2 stroke but it will last forever.
6. Rad misters do work but I think they are a band-aid that should last till you get the rest of the system fixed.
7. If you could possibly take advantage of ram air from a roof scoop or front mounted rad you will save serious money if you couple that with a clutched fan.
8. I have water injection on my 440 but it's there to allow more spark advance running on regular. It does also lower engine temp and sheds heat better out the exhaust. There is some small increase in power and efficiency. Mine only activates under heavy load. I think these systems are sold for D engines.
anything else? Guys?
John
Makes sense to me 6 knots that is about Bob's highway speeds lol 2 gals a hour I could use my boat more often with that fuel usage beats the hell out of + 50 gals per hour
good luck
Quote from: pvcces on June 12, 2011, 02:38:58 PM
It is a 40 ton, 62 foot ex drum seiner, and it has a propeller of nearly four feet in diameter. When the hull is clean, she runs right at 6 knots and burns about 2 gallons per hour. If we had a propeller of only two feet, we would have played hell getting the fuel consumption down to 4 gallons per hour.
FWIW Tom Caffrey
Proves the old theory that its more efficient to move a large volume of fluid slowly, rather that a small volume of fluid rapidly. That kind of fuel burn in that large of boat is pretty amazing.
Its interesting that most of the electric radiator fans have plastic molded fan blades that are actually pretty decent looking fan blades. I keep looking at the squirell cages and gear box on the MCI and while I know everyones opinion, it just all looks terribly, incredibly power robbing ineficient. It may very well pull 50 HP off the engine at full speed, but I am not convinced it provides 50 HP of cooling.
John, if a 1 inch lip on the leading edge of the radiator opening did anything, then I believe a NACA duct ahead of the opening, with the opening boxed, so all intake air fed to the radiator comes from the NACA duct, would do a LOT more.
With the opening boxed, getting the grill out of there could also help air flow. I had a satelite dish with 1/4 inch mesh. The manufacture (Paraclipse) claimed that above 30 mph the wind saw the dish as a solid disc. Another impediment to flow are the air louvers. Or, replace the grill with aerodynamic vanes.
Perhaps with enough work done to increase natural air flow, a couple of BIG electric fans could work? Or perhaps, a different fan arrangement. Anyone ever think of removing the squirell cages, extending the shafts of the miter box (after remounting it up higher) and driving shrouded prop fans directely behind the radiators?
Quote from: artvonne on June 12, 2011, 06:36:42 PM
Anyone ever think of removing the squirrel cages, extending the shafts of the miter box (after remounting it up higher) and driving shrouded prop fans directly behind the radiators?
Paul -Don't remember where I read it, but IIRC, squirrel cage fans move more air for their size than a prop fan. I think the factor was 3x or 4x more. They're very efficient, comparatively.
FWIW & HTH. . .
;)
Paul saw a MCI 5 few years ago at the rally in the caverns the guy removed the mitre box and used one of the air conditioner blower motor with shafts going to each side with belt driven fans on each radiator he said it worked who knows the bus was for sale and some owners are like some truck drivers when it comes to things that work.
If you go to the BNO board check out Boomers electric fan in a Eagle his system works
good luck
If the AC fan motor could run two belt driven fans, then the AC motor could likely drive the current centrifugal fans more efficiently. Maybe the stock setup isnt pulling as much power as thought, its just got way oversized components.
Quote from: artvonne on June 12, 2011, 06:36:42 PM
John, if a 1 inch lip on the leading edge of the radiator opening did anything, then I believe a NACA duct ahead of the opening, with the opening boxed, so all intake air fed to the radiator comes from the NACA duct, would do a LOT more.
Do you have a pic or a drawing of what you are talking about? NACA isn't in my vocabulary. A link would do it as well. Thanks
Perhaps with enough work done to increase natural air flow, a couple of BIG electric fans could work? Or perhaps, a different fan arrangement. Anyone ever think of removing the squirrel cages, extending the shafts of the miter box (after remounting it up higher) and driving shrouded prop fans directly behind the radiators?
You can't get away from the 50HP worst case max load requirement. Imagine the size of a 50HP electric motor. Even a 25 or a 15. I am amazed that this topic names people that are supposed to have done it. And I am NOT calling anybody a liar. How many HP is the fan that drives the stock air conditioning?
A bladed fan drops all of its air moving ability with just a little back pressure. A shrouded blade is more efficient than a SC only if there is no back pressure. BUT, let there be a little back pressure and the SC passes the bladed fan right up in performance. A little more back pressure and only a SC can move any air at all. The MCI has tiny rad openings and the rads are thick with cores that resist air flow and that's why they used the SC. Pushing air through all that AC ducting also requires a SC.
John
John, you see those big scoops on some of the MCI's. Some say they dont work as well as they appear, the theory is much of the air simply spills around them rather than going in. Air is wierd stuff, and doesnt well follow the way our minds think it would. Cylinder head porting is a good example, you see people open up intake ports and smooth the walls, but testing often shows they flow "less" air.
One of the problems with Buses and rear radiators, and the MCI's particularly, may be the opening is too close to the rear corner; there is likely a great amount of turbulance there, and probably is not the best place, from an aerodynamic standpoint, to put an air intake. If air is trying to suck around the corner, its going to increase with speed and would follow Cliffords contention that they take more power with speed.
You asked about the AC fan. The condensor fan on the 9's are 24 volt DC, 2 HP, the HVAC fan is 1.5 HP. If someone was able to use one of those back there and got adequate cooling, even after adding belt drives further robbing power, then the stock system is either not pulling the power some claim, or its woefully inefficient. In either case, just because it uses a 50 HP rated belt doesnt mean its drawing 50 HP. Its just as likely its overbuilt for endurance.
So the best place to take in air is in an area with higher pressure and more laminar flow, which is likely going to be somewhat forward of the present air intake. The next obstacle is how to get the air to enter as freely as possible without slowing it down or disrupting air flow. If it slows down to where air starts spilling over the vent, either the intake is too large, or the exhaust end isnt venting fast enough (not enough negative pressure), in either case its defeating the purpose.
Here is a primer on NACA ducts:
http://en.wikipedia.org/wiki/NACA_duct (http://en.wikipedia.org/wiki/NACA_duct)
Here is a schematic:
http://images.rcuniverse.com/forum/upfiles/463007/xv63751.jpg (http://images.rcuniverse.com/forum/upfiles/463007/xv63751.jpg)
Like I say, I think one could be fabbed out of cardboard, and with some manometers a guy could figure out the best placement, size, etc.. If it wont work, squish it and toss it, no harm done. If it works, a pair could easily be fabbed out of aluminum and riveted/glued, etc., to the Bus.
Some dont like rivets, want the clean side skin so it looks RVish. Im sure others would see a big NACA duct plastered to the side of a Bus as pretty ugly. But some see the Ferrari F-40 as ugly, and others see it as beautiful. Aerodynamics is often only seen as pretty by gearheads and airplane fanatics.
With enough airflow, electric fans could augment when needed, and not run at all at highway speed.
One of the reasons that Eagles have fewer cooling problems as well as better fuel economy, is that they have a slight taper at the rear 10 feet or so of the body. I think it comes in about 3/4" on each side. A friend who was an engineer with Eagle back in the day, told me that they did extensive wind tunnel tests and came up with that design.
Quote from: Len Silva on June 13, 2011, 06:08:01 AM
One of the reasons that Eagles have fewer cooling problems as well as better fuel economy, is that they have a slight taper at the rear 10 feet or so of the body. I think it comes in about 3/4" on each side. A friend who was an engineer with Eagle back in the day, told me that they did extensive wind tunnel tests and came up with that design.
Buses and trucks with curved rooflines are a common sight here now - I've no doubt there are genuine fuel savings to be had
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.plaxtonelite.co.uk%2Fgraphics%2Fmodels%2Felite12.jpg&hash=49b7c0182f9fb26e6d9e9f309f233c0596d2a562)
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.dp-dhl.com%2Fcontent%2Fdam%2Fmlm.nf%2Fdpwnew%2Fpresse%2Fnews_ab_01_2009%2Fteardrop_180.jpg&hash=0efc4ab32595bb47382bf27acff957e353f42085)
Jeremy
It wasn't the roofline but rather the sides that were tapered. The Eagle bus is about 1-1/2" narrower at the back than at the front.
Both ideas create more laminar air flow, which is less draggy than turbulent air flow.
Brian
Bus design has gone backwards ever since Alfa Romeo perfected it in the 1930s:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.wheelsofitaly.com%2Fwiki%2Fimages%2F9%2F9c%2FAlfa_Romeo_Castagna.jpg&hash=7632ca85d01f66f827a169343ed7e84e3fd09f41)
And you've got to wonder whether GM hadn't solved both aerodynamics and cooling in the 1940(?)s:
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.classicbusdepot.com%2Fimages%2Fuploads%2Fgaryrakes-bus-rear-2.jpg&hash=1fb827f3ca3adb36de079e92561b3a361cc316d9)
Jeremy
That is not a GM that bus is a Flx with the top scoop and they ran hot with their straight 8 Buick engine
good luck
I like the Alfa. ;D It looks like the steering wheel is back at the second window? Now if the whole thing was 35' long it would be a very unique conversion..... or as is, a really kool toad!
Quote from: Ed Hackenbruch on June 13, 2011, 08:24:46 AM
..... or as is, a really kool toad!
Actually, if it was correctly designed, towing a teardrop-shaped trailer behind your bus would probably be a very good way of reducing your fuel consumption. Especially if the rear of the bus was fitted with those 'bargeboard' things that trucks use nowadays to streamline the truck and trailer together
Jeremy
Quote from: luvrbus on June 13, 2011, 08:09:50 AM
That is not a GM that bus is a Flx with the top scoop and they ran hot with their straight 8 Buick engine
I wonder how Jay Leno's mechanic keeps his 400-plus horsepower 6V92 cool in his Flxible? http://www.jaylenosgarage.com/video/hot_rod_bus/766081 (http://www.jaylenosgarage.com/video/hot_rod_bus/766081) It sounds like cost wasn't a major concern with that project, so maybe he also put in a huge radiator and fan.
It's also interesting that the Detroit reps interviewed say that a 6V92 shouldn't run on more than 5% biodiesel, but that's a whole other subject . . .
John
Art,
Yours is an excellent post. Well said, relevant, fact laden, brief as possible, and no showoff'y math to derail minds. My hat is off to you, Sir.
In the write up it sites the "limitations" of the design. The pics of the Ferrari show it integrated into the up sloping hood. I think the air over the hood is trying to go straight and the duct is the easiest way to go. My point is that the design works in a flush arrangement but the flow is enhanced in the example. I have no doubt that if the thing was integrated into the design of the rad. opening there would be significant benefit....logically and with no aero knowledge. That may warrant further investigation for "free" air flow.
The real hangup for me was creating the "neutral pressure" air pickup to put on the ends of the Manometer. All I can come up with is a huge fuzzy ball like the microphones wear in windy interviews. Armed with that info I think that "lip" feature could be evaluated and have numbers attached to the idea. I think it is important to note that all these ideas are free to operate and have an indefinite lifespan. The other thing is that all the meticulous attention to detail can be completely offset by adding a 1/4 inch to the fan diameter or some such thing. We are trying to regain the original capacity without the investment in new rads.
I have heard repeatedly that high pressure car wash water directed thru the rad recovers a lot of cooling by cleaning crud out of there. That squirrel cage must be limping along if it is carrying the crud build up on the cage that I have seen in pics. The outlet of the SC fan was a simple cut out in the sheet metal of the chamber floor. That is a really poor way to design an exhaust and is really restrictive. The later designs have a sort of a short duct that does flo well. The SC inlet shrouds that close up the SC really do add to the efficiency of the fan when not needed. That is controlled by a thermo that could operate when the need for all the cooling isn't there. I think it is pretty much an on/off affair, however....unfortunately. Shutting down the parasitic load of that fan when you are cruising would certainly boost MPG. No doubt some could say we are picking fly shxt from pepper
Thanks for the info Art,
John
Quote from: luvrbus on June 13, 2011, 08:09:50 AM
That is not a GM, that bus is a Flx with the top scoop
Clifford -Surprise! That's a PGA-3301, one of 840 built in 1951>1952 for the Army. Here's a pic (from the same site Jeremy culled his) of the front of the coach - notice the trailer next to it has the same paint scheme as the rear photo.
And, for your enjoyment, I've also included a pic in military dress.
Enjoy! ;D
Never saw a 3301 with a scoop on the top I saw 2 before with the 4-71 engine the radiator sets in the back and the air is sucked in just above the radiator door it has a weird belt driven fan but you never know how the Army ordered a bus
The MCI-D models still have the two rads and two fans mounted high in the rear with side intakes. The new ones have a HUGE fan because the new motors run hot for pollution control and the rads need to keep things tame. Stop by MCI and have a look at one. My experience, though I don't do northern winter driving, is that the top mount rads stay much cleaner than the side mounts. Of course the engine bay is much more accessible.
The J and E models use side rads with one fan doing all the work driven by a belt to T drive.
NACA vents look cool! At least they could be used as engine air intakes. They could also be used to supply air to the passengers in the bays!
In this thread, http://www.busconversions.com/bbs/index.php?topic=9582.0 (http://www.busconversions.com/bbs/index.php?topic=9582.0)
I typed some stuff about Fred Hobe's experiments with large radiator scoops.
The small ones are of questionable value, and may inadvertently swirl the air OUT of the rad opening.
happy coaching!
buswarrior
some of the GM's (the 37 series for sure) had that set up. Here is a 3703 like ours at the Hershey Pa museum showing the intake and radiator mounted above the engine.
In preparation for our summer trip, I have installed an air dam/mudflap behind the drive wheels, did some extra sealing around the blower compartment, and am having scoops made per Fred Hobie's design. My hope is to avoid any hot running going up the Eastern Sierras. If it works well, I may not be able to say for sure which fix gets most of the credit. If I run hot, then maybe none really work. I will let you know come August.
Anyway, I was wondering if replacing the wire mesh on the intake grill with forward facing louvers slightly extended beyond the skin. That would seem to be a way to breakup the laminar air effect.
If I remember correctly, it has been 10 years now since I've had my 4104; I took a piece of 1-1/2" x 1-1/2' stiff cardboard with legs ( __/\__ ) and placed it with both "legs" on the bus skin. Taped it on to see if it would help in getting more air into the radiator.
It seemed to help, so I formed a piece from .060" alum with extra legs ( __/\__ ) and riveted it to the bus skin. You have to experiment with the distance in front of the radiator opening.
Tape some yarn in front of, on the "vee" and on the radiator opening; take her for a drive and see what happens with the yarn. A poor mans wind tunnel.
My 5C came with those ear rad scoops. I removed them. The only difference that I can see is that the bus looks better without them ;D
It doesn't run any hotter without them going up hill on a hot summer day.
I am going to try a lip just ahead of the rad grills.
JC
I suggest not making the lip a "ramp". The lip should be vert to the side of the bus and be at the edge of the opening. I would do this even with a scoop.
Quote from: dougyes on June 13, 2011, 04:57:21 PM
The MCI-D models still have the two rads and two fans mounted high in the rear with side intakes. The new ones have a HUGE fan because the new motors run hot for pollution control and the rads need to keep things tame. Stop by MCI and have a look at one. My experience, though I don't do northern winter driving, is that the top mount rads stay much cleaner than the side mounts. Of course the engine bay is much more accessible.
If the operating temp of the engine goes up, it's actually easier to cool. Heat transfer rate is linear to delta-T (of coolant vs ambient). When I worked in fuel cell design, one of the greatest challenges is cooling, because you're dealing with a cell operating at 150F or so, but putting out the heat of a 2 stroke Detroit. Not only that, all fans have to be electric!
On the other hand, the extra heat rejection of the EGR might have something to do with it.
I'm gonna guess the primary reason is higher effiency of a larger fan and radiator, as previously mentioned in this thread.
I'm not sure of the logic of putting a lip ahead of the radiator. That will create a low pressure zone behind the lip, making it harder for air to get into the radiator. A lip behind the rad might do something. similarly, why would you want to create chaotic air at the rad intake? Smoothly flowing air will create the highest pressure zone, hence the greatest flow into the radiator.
Brian
I have kept quiet for afraid of spoiling a good thing I enjoy. I have a variable speed clutch set up stock from prevost on my 89 with a 8-v92. My main concern in late 90 degree heat towing a load is keeping the temp high enough for good performance. I fought overheating with the MCI 8-new rad,scoops and misters. No good reason as to why: I don't know the science but enjoy the results. Yes I have verified gauges with IF and mechanical Gauge check. Probably should have NOT mentioned it; Knocked on wood! Bob
Your right Bob. You shouldn't have mentioned it. >:(
Just kidding now. I am sure there is a lot of disbelief around here at this moment.
John
Quote from: bevans6 on June 14, 2011, 12:52:04 PM
I'm not sure of the logic of putting a lip ahead of the radiator. That will create a low pressure zone behind the lip, making it harder for air to get into the radiator. A lip behind the rad might do something. similarly, why would you want to create chaotic air at the rad intake? Smoothly flowing air will create the highest pressure zone, hence the greatest flow into the radiator opening. Can't be much.
Brian
Brian,
You hit the nail on the head. The trailing low pressure is supposed to bend the air flow into the opening. It isn't my lie but it sure made sense to me. If you bend the lip towards the origin of the flow it will make the air current cutoff very sharp and reduce turbulence. The air was virtually still on my patio above the Pacific but if you raised your arm the wind was passing overhead at 10-20 MPH.
Many years ago I replaced my exhaust manifolds on the 440. In their place I installed Doug Thorley Tri Y headers. While I had it down I wanted to port and polish the heads a little. What I discovered was that the heads had a HUGE ridge cast into the top of the exhaust port. That "bump" across the entire width of the port was choking up the port by at least 20% in my estimation. No wouldn't you think those Chrysler engineers would have been smarter than that. Drawing on my education porting my dirt bikes I had learned that removing material from the inside of a turn was a no-no as that radius turned the air flow. My porting manual for the 440 didn't mention that so I had to ponder it and figure it ouit for myself. The exhaust manifold on those stock 440's turned up and the manifold ran parallel to the valve covers. The headers swept DOWN so those bumps would have killed the performance of the headers. I ground them off. Some of the common sense would lead to the conclusion that the bump would deflect the gas flow and that isn't the case. I will stake my ME degree that I don't have ;) on this. ;D There are guys on here that build and race cars, sooo ???????
John
Brian, John, so now I am confused. Nothing new though... So for lack of any logical evidence, I will do nothing else to may radiators air intake. The easiest way to keep the temp down is to go easy with the right foot and down shift to keep the revs up and not lug it.
JC
Quote from: lostagain on June 14, 2011, 04:46:10 PM
The easiest way to keep the temp down is to go easy with the right foot and down shift to keep the revs up and not lug it.
Truer words were never spoken!
;D
Quote from: RJ on June 14, 2011, 04:57:08 PM
Quote from: lostagain on June 14, 2011, 04:46:10 PM
The easiest way to keep the temp down is to go easy with the right foot and down shift to keep the revs up and not lug it.
Truer words were never spoken!
;D
But where's the fun in that!
So much better to mash the pedal to the floor, watch the smoke build up, pass a couple old yellow motorhomes, and then get to the top of the hill overheated and buzzer beeping, pull over, and start comlaining about the need for a new fan, rad, or engine swap ;D
You MCI guys were screwed from the factory with their setup not enough radiator,air movement and trying to pump water up hill same water pump will circulate enough to keep a 12v71 cool with the right radiator and fan.
Going to Kingman today I saw 4 MCI 9's and one 102A half way up the grade off to the side of the road cooling off the A looked like it lost engine is was blowing smoke and it is not hot here yet 103 today
good luck
Clifford,
I think that the MCI engineers did a wonderful job and really put their theoretical education to use. The only problem is that it seems they missed the class that taught Murphy's Law.
Pumping water up hill isnt a problem if your pumping it to a tank that feeds the pump, then its just circulating. And as hot water wants to rise, and cool water wants to fall, I think the MCI is simply using that natural tendency.
The thread seems to be drifting to heat and radiation, where the original topic centers on the power consumed by the cooling system, specifically the fan.
It's been suggested in other threads that the MCI's (5's through 9's etc..) are pulling as much as 50 HP off the engine for cooling. Some of the arguments centered around the belt size and its HP rating. But simply looking at the fans, they sure dont look like a pair of 25 HP blowers. No, they look about the size of a residential furnace fan blower, maybe a bit bigger. I should go measure before I stick my foot in my mouth, but they look no larger than the fans in the condensor bay. The pulleys are about simular in size from engine to gearbox, and assuming 1:1 through the box (I dont know) one could guess the blowers are running around engine speed. So Cliffords observation of an MCI fan drive being replaced with a condensor fan motor should be given some weight. IOW, it propbably needs more than 2HP worth of fans on a hot day, but nothing approaching 50 HP. The belt used is likely more for endurance.
While the idea of a lip ahead of the intake might sound good on paper, without some kind of testing your shooting in the dark. Its just as likely to screw up the airflow and blow over the intake rather than let it fall in.
In any case, and on ANY Bus, GM, MCI, Dina, the first order of business should be to keep everything clean and clear. Fans can lose as much as 50% air flow with visible dirt on the blades. Radiators need to be clean and clear as well. Anything that air has to flow through, screens, vanes, all create obstacles that impede air flow. Turns create big obstacles. A 90 degree turn in a 4 inch pipe is equal to 4 feet of pipe in reduced air flow.
And as Bob pointed out above, lifting your right foot has the biggest effect of all. Slow down the engine you slow down the fan, reduce the wind resistance load, use less power, make less heat, burn less fuel. And its not linear, its square. a 10% reduction in speed makes roughly a 40% reduction in required power. With fuel prices what they are and so many expenses coming at us simutaneously, weddings, buying a Bus etc., I decided to drive the Bounder without my foot planted hard on the floor as I have. I drove to Minnesota and back last month, and instead of 6'ish mpg at 70 plus, as ive been used to getting, I pulled off almost 10 mpg at a more sedate 55-60. And while the slowness drags out the trip, the reduced speed reduced the wind noise, the ride was better, the engine was quieter, and I wasnt fighting the wheel as much as I was used to.
MCI on the setup they have it cuts the rate down from a pump that will circulate up to 95 gals a minute down to 70 @1800 rpm I watch that test with my own eyes at Stewart and Stevenson when Cole was figuring how much radiator and fan hp was needed for the series 50 they were installing for Greyhound and believe it or not those fans are high hp draw saw that on the dyno they drop about 15 hp when the bottom doors on that system are working properly and I don't know how they are supposed to work
good luck
The doors work from the shutterstat, same system as the radiator shutters. When it's cold out, and the coolant temp is low and there is air pressure, the shutters close and the doors below the fans close. This blocks air into the rads and effectively stalls the fans so that take less HP to turn. Once the coolant warms up, the shutters open and the doors open, and the fans work again. One door on mine sticks, and the system started to leak air, so i blocked it off. I'm not going to re install it.
Brian