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  #16  
Old 06-09-2017, 09:27 AM
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I've considered using an electric fan on my 300D and I may do so if my clutch quits. The power savings aren't quite as important with the 617A as they are with my 220D though.

The issue is the standby power required to run the fan. On the 220D my electrical demands are met with a mini Denso 40amp alternator. If I add an electric fan I need a much larger alternator to run it. This increases engine load all the time due to the need to constantly accelerate and decelerate the large rotating mass of the rotor. Of late manufacturers have added clutch pulleys to decouple the alternator and they produce meaningful gains but they are only found on serpentine belt systems.

The mini Denso has 5 more amps and much less rotor mass than the stock 220D alternator. In trying to free up power on my 220D I considered the electric option but I decided against it due to the large alternator required. If your application requires a large alternator regardless of the fan then the standby power problem is eliminated. Adding a big alternator just for the fan reduces the potential benefit. My 300D is getting the 115Amp SAAB alternator and an afterglow mod so adding an electric fan won't require an upgrade.

Electric fans are very inefficient when compared to engine driven fans. Alternators are typically between 50% and 70% efficient. But unlike engine driven fans electric fans only run occasionally and that's where they can provide an advantage. They reduce noise since they run infrequently. They also reduce hot soak.

Unfortunately when trying to pin down any potential HP gains all we have are the numbers given for a specific fan with or without shroud at various RPMs and always on a dyno. Fan power losses are impossible to nail down. I've seen numbers ranging from 5 to 40HP.

I considered using an electric motor and ammeter to build a crude dyno to measure stock fan (and water pump) load at various RPMs. However, this experiment would be stationary. I'd get the effect of the shroud/radiator but not road speed airflow. That's the part all these fan HP tests seem to miss. If I'm traveling at 65mph the airflow through the radiator is equal to or greater than the fan. If that's the case the fan may have virtually no load at speed and a fixed fan may actually be driven by the airflow.

An on road test is difficult to make but I've read accounts of water pumps being driven by fixed fans when a belt breaks at highway speeds. Given the load of the water pump this indicates a fair amount of energy is being delivered to the blades.

It seems like at a certain road speed/rpm combination the load of a fixed fan would be minimal. Increasing road speed relative to RPM may deliver a small net positive. Conversely high RPM at low road speed (1st gear) will result in power loss. This is only speculation but it would be interesting to know the answer.

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  #17  
Old 06-09-2017, 11:20 AM
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No need for a larger alternator. I ran electric fan only on my '73 220D for over six years, on on my '71 250C (with transplanted M115) since '06, a '73 280 and on my '74 280C here in the desert Southwest and used the stock 35 amp alternator and battery on all of them.

Use a thermostatically controlled relay.

The 16" fans only pull about 11 amps at initial start-up and drop to about 6 amps during run mode. They CAN be run using 16 ga. wire but I prefer using 12 ga. for peace of mind.

Haven't tried all electric on my M117 and probably won't because that alloy engine gets hot FAST!
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  #18  
Old 06-09-2017, 11:22 AM
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A 70a alternator from a later 300d or 190d is all you need. These are small enough to run with a V-belt. This will give you enough available power to run a 20A fan, which is good for 3000CFM in free air.

The drag created by an alternator is more a function of electrical load than the mass of the rotor. Replace a 40A alternator with a 115A alternator, and your load remains 40A. Allowing for the 80-90% efficiency of the average alternator (where did you get 70%), about 1HP of engine horsepower will be consumed by either alternator. The 115A alternator has a higher moment of inertia, so it will be harder to accelerate. It would require a serp belt and a decoupling pulley to prevent inertial effects from snapping the belt, but in steady state would not require more horsepower.

Electric fans are extremely efficient. Even a sloppy design will be 80% efficient. They consume FAR less power than engine driven fans. The reason has nothing to do with turning the fan on and off, it's due to the fact that the power consumed by a rotating fan increases with the cube of RPM. Electric fans run at constant speed, while engine fans run at some multiple of engine speed. This is little or no advantage in my 190DT, which rarely cruises above 2500RPM due to high gearing. Spinning an electric fan at 2200 RPM is small improvement over spinning a mechanical fan at 2500. But most cars have taller rear axles and cruise at much higher RPM's. Here's a diagram that shows the relationship between power, RPM and airflow:

http://docs.engineeringtoolbox.com/documents/196/fan-affinity-laws.png
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  #19  
Old 06-09-2017, 11:26 AM
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Here's a thread from a forum member.
http://www.peachparts.com/shopforum/vintage-mercedes/352925-does-slimline-electric-fan-make-my-radiator-look-fat.html

He used two fans, one as a replacement for that big heavy honker originally used for the condensor air flow.
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  #20  
Old 06-09-2017, 01:37 PM
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The one thing I can say is dont let a plastic bag fly into them off the freeway. Once happened to me on a GM car,I was unable to travel with a hot radiator and an electric fan motor burned up from one sucked into the fan.Another problem is if it has any issue with its electrical supply your in their fixing it yourself ,if not diy the cost for a mechanic will be $$$$$.Mechanical belt driven in this case is the most efficient built system .
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  #21  
Old 06-09-2017, 01:39 PM
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Quote:
Originally Posted by Mxfrank View Post
A Allowing for the 80-90% efficiency of the average alternator (where did you get 70%), about 1HP of engine horsepower will be consumed by either alternator.
The 55% average alternator efficiency number comes from Delco-Remy. The 70% number is from Denso for their proprietary high efficiency hairpin design.

I agree on the efficiency of electric motors and fans in general. I think they make sense if the alternator can handle it. However, they can't approach the efficiency a direct driven fan - too many conversion losses. They work well only because they don't work often.

Decoupling pulleys help with serpentine belt tuning and efficiency. The crankshaft of an engine only spins at an average RPM. Each piston stroke accelerates and decelerates the crank momentarily. The decoupling pulley prevents the mass of the alternator from being decelerated and consequently re-accelerated. This prevents belt flutter and improves efficiency. Even fixed RPM operation is not steady state. Modern alternators are massive and accelerating that mass takes power.

Mike-D: I'm glad your setup works for you and it's encouraging should I ever go that route. On my 220D with all accessories running (no AC) I'm hitting 35 amps - think traffic jam at night in the rain. I'd feel more comfortable with a 55 amp alternator if you add the fan. Easy to do with stock parts.

I looked at the Volvo 850 fan which is a popular choice for conversions. Current on high is 35 amps, low is 28 amps and the starting current peaks at 80 amps. The Lincoln MKVIII fan (another favorite) is even worse. A fan with a running current of only 6 amps can't move much air as compared with these OEM solutions. If you say it keeps your car cool I might give it a try though. Where did you get your fan?

I look at this problem for my 220D from the standpoint of maximum efficiency and simplicity. Adding a serpentine belt drive and an alternator decoupling pulley with an electric fan might yield an efficiency improvement. Serpentine belts have reduced loss because they are thinner and have less power loss with each bend. On a car with a full set of accessories it's possible to replace 4 V belts with a single serpentine yielding definite gains. My 220D has only one belt so the gains are minimal. Especially considering the fabrication costs. Without the serpentine I can't use the decoupling pulley so my only route to improving efficiency is an alternator with the smallest rotating mass.

On a 300D - I'd go electric. The fan clutch is expensive and the engine produces plenty of power. The 300D is efficient for what it is but it's the wrong platform to start with if max efficiency is your goal. A 115 amp alternator, V belts and a Volvo 850 fan make great sense here. AC performance improves too.

The best solution and the one I'd implement if fabricating is the belt driven electric clutch fan from the 190D. Small electrical load and high mechanical efficiency.
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  #22  
Old 06-09-2017, 04:30 PM
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Originally Posted by 97 SL320 View Post
Prechamber diesels can be difficult to start without glow plugs and run poorly when the tips are burned off. The mechanical portion of the glow plug is a hot spot even when the electric is shut off.

I repair light towers and such for a local scrap yard, they don't run so well cold when the tips are burned off. ( RE the cylinders with burned tips miss fire for a while until the engine has enough heat in the combustion chamber. )
That is true, they do help them run a bit better when they are cold, but it's not quite the same thing as a gasoline engine which requires exactly timed high-powered spark to each individual cylinder to run at all, as tjts1 said in his snarky reply.

I've found there are some posters that seem to be more interested in trolling than helpful responses. Differing viewpoints are fine, but there is a difference between that and being condescending and adversarial.
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  #23  
Old 06-09-2017, 05:03 PM
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An engine-driven clutch-fan system is more efficient than electric. That is because of energy losses in the alternator and electric motor. That is why longitudinal engine vehicles still use mechanical fans today (or at least thru early 2000's). If they have stopped is just for assembly, packaging, or cost issues. Some vehicles like the Chevy Corvair went thru extremes to provide a belt-driven fan, though electric fans were probably less developed in the 1960's.

If you do replace your mechanical fan, keep in mind that the M-B electric fan is just an assist, and mainly to cool the AC condenser when idling. People that go all-electric on classic V-8 cars find they must use a powerful fan. The Ford 2-speed fan on the Taurus and T-bird is common among hot rodders. Even then, most realize less cooling than with a clutch-fan.

Some drag racers use electric fans and electric water pumps. That is sort of cheating, because then they can charge the battery pre-race and drive those without loading the engine.
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  #24  
Old 06-09-2017, 05:48 PM
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Originally Posted by BillGrissom View Post
An engine-driven clutch-fan system is more efficient than electric. That is because of energy losses in the alternator and electric motor. That is why longitudinal engine vehicles still use mechanical fans today (or at least thru early 2000's).
The efficiency of of fan is the the ability of that fan to pull air through the radiator. Mechanically driven fans are attached to the engine which moves around on its mounts. To allow for this movement the shroud for a mechanical fan is much larger than the fan itself. That gap between the fan blade tips and the shroud creates lots of noise and turbulence but it doesn't help the fan pull air through the radiator. Electric fans are attached to the radiator so the distance between the fan and shroud is only a couple of mm. An electric fan might move less air but it can still provide better cooling than a mechanical fan because all of that air is moving through the radiator.

Another issue is the speed of the fan. An electric fan can run at its max speed while the engine is at idle. A mechanical fan will always max out at at the speed of the belt pulley its attached to. Not only is the fan's max speed limited by the engine speed, that fan is also spinning the other 99% of the time when its not needed, even a viscous clutch fan. Again wasted energy. A properly sized electric fan will always provide better cooling while consuming less energy than any mechanical fan, clutched or other wise. The only applications where mechanical fans are still used are in heavy trucks and earth moving equipment that need the fan cooling almost 100% of the time and sizing alternators and electric fans and alternators for the application is cost prohibitive. Many of these applications now use an electric clutch which can decouple of fan from the engine in order to save some power.
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  #25  
Old 06-09-2017, 06:10 PM
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Originally Posted by VT220D View Post
AC performance improves too.


This is a huge point everyone missed but you. You have huge airflow at idle with a quality e-fan setup, a clutched fan cannot do this.

Newer Ford half ton trucks have efans. I think they started with the 11th generation, but 12th and 13th have them for sure. GM started in 2005, I converted my 2001 GM truck to the factory '05 setup even. My 1998 Volvo wagon (RWD still) has a dual speed fan from the factory. These are all set from the factory to run a low speeds and high speeds, not all or nothing. Only time the Volvo ever ran full blast is when I had a CTS issue.

I can also assure everyone, that an e-fan on high speed will be less parasitic than a locked fan clutch. A locked clutch absolutely kills off the line performance and fuel economy. About 10 years back a pal dyno tested his truck with an unlocked clutch versus no clutch, difference was about 7rwhp I recall. Minimal. Locked was significantly more, in the 23rwhp area before it finally uncoupled.

FWIW, the 960/V90 style dual speed fan fits the W126 300SD. Barely. As soon as I can figure up a good way to mount it, it will be on my car. It will not fit the 560, but Ford Contour V6 SVT ones should.

Engine warm ups are faster as are cool downs.
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  #26  
Old 06-09-2017, 07:16 PM
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FWIW, the 960/V90 style dual speed fan fits the W126 300SD. Barely. As soon as I can figure up a good way to mount it, it will be on my car. It will not fit the 560, but Ford Contour V6 SVT ones should.

Engine warm ups are faster as are cool downs.
I've had a 960 fan running in my 190e for 8 years now. Its far more powerful than the stock setup and just barely fits the 4cyl. The AC is always ice cold.
https://i.imgur.com/fz3t3Ya.jpg

https://i.imgur.com/lHoua5M.jpg
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  #27  
Old 06-09-2017, 08:03 PM
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Originally Posted by VT220D View Post
I agree on the efficiency of electric motors and fans in general. I think they make sense if the alternator can handle it. However, they can't approach the efficiency a direct driven fan - too many conversion losses. They work well only because they don't work often.

Decoupling pulleys help with serpentine belt tuning and efficiency. The crankshaft of an engine only spins at an average RPM. Each piston stroke accelerates and decelerates the crank momentarily. The decoupling pulley prevents the mass of the alternator from being decelerated and consequently re-accelerated. This prevents belt flutter and improves efficiency. Even fixed RPM operation is not steady state. Modern alternators are massive and accelerating that mass takes power.
Let's take an example. Say we have a fan (don't worry about how it's powered) that moves 1500CFM and requires 1 HP at 2000 RPM. If the speed is doubled, how much more air does it move, and how much more power does it consume? (Ans below)







At 4000 RPM, the fan would produce 3000CFM, but it would draw 8 HP. The output increases linearly, but power consumption grows with the cube of speed.

That's why a mechanical fan is grossly inefficient at high RPM's. An electric fan runs at constant speed, so if it draws 1HP in traffic, it will still draw 1HP at highway speed. The electric fan pulls hard at low road speeds, where you need it. By contrast, the mechanical fan soaks up power at road speeds, even though natural airflow is often enough to satisfy cooling demand. And yes, there's a small incremental benefit to and electric turning on and off. But that's not the principal benefit.

An electric clutch driven fan is the worst of all possible worlds...it's going to add lots of parasitic drag, and the power required to engage the clutch will be comparable to what would be needed to drive an electric fan.

Transverse engine cars benefited from the invention of the electric fan, but electric fans were originally designed to reduce parasitic drag on high performance, heavily loaded, longitudinal engines. The first production electric fan was designed by Lucas for Jaguar's E-Type, very much a longitudinal car. Since they were still using generators in 1961, only 7 amps was available for the fan! They solved the problem with a little windshield wiper motor and a two bladed fan bent up from sheet steel. This was fitted into a well-shaped shroud and the pitch was adjusted to balance airflow vs current draw. The resulting fan drew only 400 CFM, yet this was just enough to keep a 265HP engine cool. The design was revised in 1968, to a two motor setup with aerodynamic plastic fans. This was good enough for 1000 CFM at about 18 amps draw, which allowed a/c. The fans were arranged to concentrate flow along the hot side of the radiator, with the cooler 1/3 of the radiator completely exposed to natural flow. It was a minimalist design, but completely satisfactory. After that, electric fans generally became oversized, generic, off the shelf items rather than bespoke designs. You'll find them in Jags, Ferrari's, Lamborghini's, MGC's, DeLoreans, Pantera's, and Maserati's of the era. And on any number of US and Japanese cars today.

A lot of concepts seem to be getting confused here: power, efficiency, airflow...what problem are you trying to solve?
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  #28  
Old 06-09-2017, 10:33 PM
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Originally Posted by VT220D View Post
Mike-D: I'm glad your setup works for you and it's encouraging should I ever go that route. On my 220D with all accessories running (no AC) I'm hitting 35 amps - think traffic jam at night in the rain. I'd feel more comfortable with a 55 amp alternator if you add the fan. Easy to do with stock parts.
Just as an example. Lots of other suppliers.
UNIVERSAL 16" HEAVY DUTY RADIATOR ELECTRIC FAN 3000 CFM REVERSIBLE SBC BBC 350 | eBay

I use Mill Supply because I am familiar with them but all the companies are pretty much the same, more's the pity.
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  #29  
Old 06-09-2017, 11:56 PM
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This thread is interesting. I'm almost convinced to go with an electric fan myself. The only thing stopping me is the fact that I like the reliability of mechanical things so much. I do like that there would be less horsepower robbed by the mechanical fan and better cooling (only when it is needed and never when it is not).

I ended up replacing the little 12" auxiliary fan in my W116 300SD and replacing it with a 16" fan from a second generation W126 (plus a parallel-flow condenser) for maximum cooling power (though I still don't have the air conditioning operational).



I got two of those 16" W126 fans and cleaned them up and installed new sealed bearings in both. I could probably put the second one to use and install it on the other side of the radiator in place of the mechanical fan so I have one that pulls air out of the radiator, too. I think it will pull if I reverse the power wires (unless the blades aren't designed to pull). It's something worth considering if I can figure out how to mount it.
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  #30  
Old 11-15-2017, 04:37 PM
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Interesting topic. I just started investigating e fans. My research quickly took me to the 18" Lincoln Mark Vlll fan and dccontroller variable speed controller designed to control the very large current demand. Apparently the Lincoln fan is a favorite of custom/OHV/rodders. I happened to be at the Pick n Pull yesterday and found one in a 98 Lincoln for cheap so I picked it up to check it out. The size is almost a perfect match to the original shroud in my 280SE. With the original shroud the fan is 1-2" smaller than the shroud to accommodate engine movement, some of the fan is in an area of low airflow above the radiator and the shroud has holes to allow air to flow through the oil cooler. I think this is because a turning fan actually impedes air flow at highway speeds where an electric fan is not running at speed. The mechanical fan is always turning-even when disengaged.

constant temperature controllers
Electric Radiator Fans - Hot Rod Network

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