.......a lot of comapanies run electric. most of the japanese cars are electric. and they are known for fuel economy. i ithink that its simpler to run a fan clutch thats why they do it. less seized up engines. if you want simplicity than stay with a fan clutch, but i did not build up xj for simplicity.
if electric is good enough for Lamborghini with 585 hp than its good enough for me. jack
Actually the main reason why many cars have only electric fans is because they're front wheel drive and the engine's mounted transversely, so they can't use an engine-driven fan. Most RWD cars e.g. BMW, M-B still use clutch fans as the main fan. Their clutch fans are obviously better designed than the XJ's because their engines stay cool without relying on an auxiliary electric fan to save the day.
Could you replace the clutch fan with a better design(flex-a-lite?) clutch fan and achieve better cooling w/ less power consumption? If so, would the gains be worth the cost?
The type of charging system used in most vehicles including Jeeps works by sensing the system voltage. Current is applied to the windings in the rotor when the voltage falls below threshold. Rotor current can vary depending on load...the result is a variable output charging system.
Some motorcyle and boat charging systems for example use a permanent magnet rotor...on those type the output is truly a function of RPM. Excess voltage is bled to ground through air or water-cooled resistors to cap the max voltage output.
To monitor system operation, the best device is a voltage gauge. It is entirely possible and not at all uncommon for an alternator to supply excellent amperage output but still deliver insufficient voltage due to internal damage such as a bad diode, however the voltage may not be high enough to keep the battery charged.
I will let you guys know how it copes with the 100* plus days while towing my trailer through deep sand when I get back in the new year. We leave in less than 3 weeks time
Ironically, Mopar performance offers a viscous fan package for the 4.0 that is stated to be 10hp/13lb-ft better than the competition but that does not include electric fans. What temp does the viscous fan kick on at and what temp does it turn off?
Hope it works for you.:thumbup: I had a 14" on a 2.5l and it didn't cool well. I put a new water pump, new radiator, and yet it still didn't work well.
I live in Maine(moving south) and with what little heat we get up here, my temp would go up to around 230deg. I went to a flex fan and since then the temp never get above 195deg with a 180deg t-stat. Even when I would wheel back in the summer.
I really hope that it works for you. It didn't for me. Good Luck.
It doesn't just kick on and turn off at certain temps. like an electric fan. The viscous clutch contains a fluid whose viscosity decreases with increasing temperature, allowing the clutch to bind gradually. As the engine gets hotter, the fan spins at a higher percentage of engine speed but it doesn't ever fully lock up and reach 100%. The fan will only spin at a maximum of about 2000rpm even if the engine is spinning at 5000rpm. The fan clutch also doesn't ever fully release, otherwise the fan wouldn't spin at all, therefore it always applies some drag on the engine. The hotter the engine, the more drag there is from the clutch fan and the more HP/TQ is lost.
Actually the main reason why many cars have only electric fans is because they're front wheel drive and the engine's mounted transversely, so they can't use an engine-driven fan. Most RWD cars e.g. BMW, M-B still use clutch fans as the main fan. Their clutch fans are obviously better designed than the XJ's because their engines stay cool without relying on an auxiliary electric fan to save the day.
Most still do, however, some BMWs do have only electric fans behind the radiator. The ones that do have engine driven fans, also have an aux fan in front of the radiator. The BMW for instance has 23 progressively stepped speeds the computer can turn on. On high, it moves some serious CFM and sounds like a plane taking off. Impressive at the least.
I hope this electric turns out great. I know others have tried with poor results, but there has to be a combination that can flow more CFM that stock. Hope this is it.
I also did an electric fan swap but unlike most who look for a large single fan to go in place of the stock belt driven unit I decided to find a double fan setup and eliminate that crappy stock aux fan.
It seems since the rad is about 12" and long one of the most efficient setups would be to have two good 12" electric fans with nice sealing shrouds.
Nice writeup as usual Marcus. I always get a little confused looking at your pics trying to figure out the differences of a right hand drive engine bay
Our local cars here have big sixes in as well and weigh more than our XJ's. They have run electric fans only and no mechanical one for the last 10-12 years. Some run two side by side.
Also
The extra loading on an alternator while the fans are running would still be less than the mechaical one is when in a cool state!
