[Dick]

My guess is the change to electric fans is not done for efficiency reasons. Automotive alternators and small electric fan motors are at best 80% efficient (e.g. 50DN is 78%). Between the two of them you are only 64% efficient. The right angle belt drive is probably closer to 90% efficient.

The big advantage of electric fans is compact physical packaging freeing up a lot of space. More fine grained fan control is helpful but not a game changer.

Gerald

[Philip]

Recently returned from a trip to Branson, MO. Ran the entire trip at just under 1800 rpm, around 63/65 mph. There were numerous 5, 6 and 7% grades and I didn’t see any water temps above 185. No, it didn’t get to the top at the same speed it was at the bottom but the 8V92TA handled it without a problem.

I hope you get it all figured out Georges, it’s no fun when our girl isn’t running right!!!

Harry

[Archived]

I agree with Gerald. Everytime you change from one type of energy to another there is a loss in efficiency.

Here is a wild *** guess. It could be that electric fans are designed to draw power ONLY from the batteries when the engine is under extreme load (like climbing a hill/mountain or under heavy acceleration) leaving the engine free from the old fan load and any alternator load to run the fans to provide that power directly to moving the coach.

I may not be right, but if Buddy and I were designing a system for this at the East Tennessee Luxury RV Resort on our down time, I think this is likely what we’d come up with.

[AL]

Sounds to me like you’re blowing a lot of hot air there Dick!

Harry

[James]

Dick, you make the assumption that if it is not connected to the engine as in a belt that there is not use of engine power.

The power comes from the alternators which really do require engine power. Energy is energy and if by some means electric fans do not take the equivalent HP as an engine driven fan then it means either the engine driven fan uses more power than it needs to move air, or the electric fans do not have the equivalent air moving power.

[Archived]

I haven’t cleaned the outside of my radiator yet, the turbo cooler has a sticker that says no caustic material to clean because of aluminium, Is simple green ok to use?? just spray on then let sit then hose off, No nozzle just hose??

[Darcy]

Art,

There is a simple green just made for aluminum.

June

[Reagan]

What my mechanic heard was there is a good deal of loss in the mechanical linkages. He said in the newest buses they added a 3rd alternator just for the fan.

BTW, he also told me about the Prevost test track session he did where they demonstrate how you can’t flip the bus in a tight turn. Said he was white knuckles but it was amazing tech.

[Archived]

There is a loss of power in every means of transmitting power, not just in mechanical power delivery.

[Archived]

Talked to Tom about your questions. He said Prevost has a computer management gizmo that shuts-off the alternator when the engine is under load. Pulling from a dead stop or pulling a hill. The fan runs off the battery freeing up engine horsepower.

[Corey]

Liam is correct, but what I cannot wrap my brain around is this quest for what seems to be free energy.

While disabling the alternator(s) does in fact free up engine power (remember how I said it still takes power to drive the fans even if they are electric) all if does is postpone when that power will be used.

If to use the fans and alternators as an example the hill is long and steep and it is hot outside the fans are going to be sucking a lot of power from the batteries. When the coach crests the hill and the alternator(s) resume functioning then the batteries will need the alternator(s) to produce a lot of charging current to restore the batteries to a fully charged state. Guess what, that is going to require horsepower to drive the alternator(s) as additional charging current is required.

BTW, on coaches that do not have OTR, but instead are set up to run A/C units through the inverters the exact same thing is happening in that the alternator that charges the house batteries is working very hard to supply power to run the AC units.

[Archived]

Smart. All true. But…i do think electric fans make more sense than belts gearboxes, clutches etc.. especially when set up by Prevost at the factory with the charging needs and controls taken into account. Retrofit-probably a different story.

[Archived]

Auto makers have long ago proved the benefits of electric fans. There is no doubt in my mind there is a certain simplicity that is realized by eliminating the mechanical drive train of a radiator fan, especially when those fans are attached to clutches with the service life of a gnat.

It not only eliminates the belts, pulleys, the gear box, the troublesome pneumatic bellows and associated fittings, it is likely to reduce weight. The electric fans can have the potential to be regulated to such a fine extent that we shouldn’t see temps cycle as we do with a clutch driven fan that has a spread between the on and off temps. The electric fans could probably have speed control that varies to the extent that a degree of temp change, up or down causes a slight change in fan speed to meet the need for more or less air flow.

But to suggest it doesn’t take power to drive fans big enough to replace the clutch driven fans seems wrong. Unless you have been at the rear of the coach and had the engine driven fan go from low speed to high speed it is impossible to understand just how much air is flowing through the radiator under high power conditions. It moves enough air to blow the face off a dog.

[Archived]

I agree Jon. I had zero doubt about the claim of 50hp savings. If you are running a bus line, not being pokey on hills is a huge advantage even in a “pay me later” scenario.

[Archived]

I don’t think the claim is that electric fans give free energy, but rather that you can have a little flexibility in when they draw power. If you can postpone their power draw on the engine such that they draw from the battery for a period of uphill driving, you free up that 50 horsepower temporarily. The batteries will be at a lower SOC and need to be charged eventually. Ideally, that happens when you are going back down the other side and you get a bit of a regenerative braking effect. I don’t know how it’s set up to work, but theoretically, the capability is there.

If, instead of thinking about power (energy/time) you think about just the energy, the electric fans give you the flexibility to use the reserve energy available in the batteries to help the bus up the hill by relieving the engine of the fans’ energy requirements (temporarily). Then you have to “pay the debt back”, so to speak, hopefully when you don’t need full engine power for propulsion. Even if you have to recharge the batteries while you are still climbing, if it is programmed to just maintain the SOC until you aren’t at WOT, it would be no worse than simply powering the fans directly. Whether that makes a significant difference, I can’t say. I can say that OE’s spend a lot of R&D dollars for very marginal increases in efficiency though.