well..both, electrical and mechanical, drain energy from same source and it is crankshaft (during motion)...if that is true, then we also need to assume that certain air mass flow need to produce to cool down engine..force necessary to produce such flow is final force.. so, in case of electrical fan equation will be something like this FF=frictionBelt_Dynamo_crankShaft+(Electrical Energy Produced By Dynamo For Fan)+(electrical resistance for all wiring related to fan including all bearings on fan and support electronics)+(Air Flow force)+(inertial momentum of fan every time it starts) In case of mechanical fan, because its attached directly to crankshaft there is no energy transfer in between but this: FF=Air Flow Force + inertial momentum of fan at startup(once) ..point is that energy transfer is never 1:1. in which case electrical will use less energy..its alwys less that 1:1, so mechanical is closer to that ratio as less energy transfer happening in between..
Al, I pretty sure my engine is M54b25 and not M52 TU. Check VIN and Scanner tool as well to confirm. Also my petrol pedal is "drive by wire" and of course double vanos. If not mistaken, M52 TU is only for b28 engine. I think M52 is discontinue in year 2000 whereas my built is end 2004 Dec.
Ecco, the point is simple. The electric fan is decoupled from the crank shaft and hence no parasitic losses. Whatever drag that is on the electric fan will not impede engine performance, for instance under acceleration, as the energy is supplied by the battery and charged by the alternator when it is low. On the E92 M3, even the AC compressor automatically decouples itself under acceleration! On the mechanical fan clutch, the energy to drive the fan is derived directly from the engine via the crank shaft that drives the crank pulley which in return drives the water pump, air cond compressor, power steering pump and alternator, which are all termed as parasitic losses. That's why in the latest cars, we have electric powered steering and electric water pump. In essence you get higher nett power transferred to the rear wheels
..so what you saying is that fan is not powered by dynamo (during motion) but battery ?? If so, is it battery charged during motion?? Total amount of energy necessary to push whole thing is ALWAYS bigger than desired energy output, regardless how you redirect it..otherwise we will have perpetuum mobiles, and i think they doesnt exist laaa
Don't forget with electric fan, it can be selectively cut off, hence zero load to dynamo, maximum engine output channeled to the wheels and improve fuel efficiency. This happens during the engine warm up time, or when vehicle are traveling high speed, or when engine temperature cooled down after running the electric fan. With the modern engine, during pickup, the fan will cut too, until accelerator pedal is eased. [subject to safety limit of engine temperature not breached] With clutch fan, little can be done and still, an electric fan is needed for aircond. Where as with electric radiator fan, it has different stages and also served as aircond fan. So it's one for all. Effective use of engine space and one less component for maintenance. When it comes to cooling efficiency, clutch fan is always limited to the rpm of the car, imagine stuck in stand still traffic with idling engine speed, even with 1:1 spinning ratio, the clutch fan is only spinning at 800rpm compare to electric fan of over 10k rpm. And yes.. battery powers the electric fan, and only will be charged [load to dynamo] when it fell below certain voltage, otherwise, no load to dynamo despite electric fan spinning.
I think it depend rather on the efficiency as well. Both electrical fan and mechanical fan required the same amount energy to produce the same amount of air flow to cool down the heat in the radiator. Electrical Cooling = Efficiency of Motor (85% to 95% efficiency) + Efficiency of the Alternator (90% to 96% efficiency) + Loss in cable resistance. Mechanical Cooling = Efficiency of the Fluid Coupling (70 to 80%) + Loss in friction drag of clutch fan. However Load on the engine from the Alternator is variable. if the battery is weak, the slip ring will "moved" and produce more charge for the battery, this will put more load on the engine. If the battery is "fully charge", the slip ring will reduced the charge to the battery and lessen the load on the engine. Similarly, the clutch fan also does the same thing. when the engine is hot, the clutch will draw the turning force from the engine. when it is cold, it start to slip and draw less power from the engine.
OKie just checked again, earlier M54s have fan clutch and electric fan but the last batch only has ONE electric fan mounted behind the radiator. http://forum.e46fanatics.com/showthread.php?t=744994&page=14 I remembered seeing BM World Ah Wai doing plenty of such conversions then, and was tempted to do with my M3.
btw, we dont use dynamo anymore. It is alternator lah. Dynamo is constant load on engine and less efficient. Alternator is variable loaded and more efficient.
I wrote many times "dynamo" because brader Ecc0 start using it in the earlier postings, and I dowan to complicate things any further.. I got hang over from last night and having headache now.. :coffee: Dynamo..
seriously, what is the funtion of FF you are trying to derive? if you are actually calculating the energy required to feed the system then, your equation is flawed. One simple one is, the alternator drag still exist even if u have only the mechanical fan...the friction on the alternator does not change according to electrical load significantly as it is a electromagnetic drive system...as the electrical fan is decoupled from the crank, you did not factored in the drag on the mechanical fan created during its operation which is not negligible as it is directly driven by the crank... by the way? the function of the fan is to push the air in order for massive amount of air to pass thru the heat exchanger or what we know as the radiator...not to primarily 'blow' the engine cool as it is not an efficient method to cool engine, the water to air via heat exchanger is more efficient...
..dynamo.. http://www.thefreedictionary.com/dynamo ..by all means my expression was correct as it is exact term used for electrical generator of DC current, so i dont understand whats so wrong with it ?? 1. (Physics / General Physics) a device for converting mechanical energy into electrical energy, esp one that produces direct current Compare generator [1] ..car electrical 'generator' source produces DC, no? ..
Thanks for asking, I just learn that they are not the same thus different name. Alternator - produces alternating current so the current are rectified before supplied to the car. Dynamo is DC but doesn work as good at producing current as alternator at low RPM. http://en.wikipedia.org/wiki/Alternator But we all understand your point in earlier post
thank for the head up of the difference between dynamo and alternator. Sometime we need to be clear to avoid any confusion. Like for example, Petrol Engine and Diesel Engine. One engine got spark plugs and the later dont have spark plugs but both can be use to drive the car.
Brader Ecco, would you like to swap your electric fan with mine? My fan clutch was replaced last year and still in almost new condition. Cheers P/S I am running S54 engine as well
FF = Air flow force + water force + fan start-up drag + the fan brand + temperature - 799rpm this is true for mechanical fan and its correct because its physics that i understand...
