thunder550

iTrader: (70)

Let me preface this by saying that I realize the linked article is not for our trucks, and that there are a lot of differences between an RX-7 and a fullsize truck. However, I believe that a lot of the fundamental ideas discussed here are applicable. Like the title says, just some food for thought.

http://www.aaroncake.net/rx-7/efanmyth.htm

l_kusler

I think there is a few problems in the article

I read over it quickly, but this is what i think

My first point, most e-fans we run, whether it be from new trucks, f-bodies, or bought aftermarket, like flex-a-lite have more than enough cooling capacity in my experience, and If they didn't we wouldn't be using them. These fans draw in the ball park of 15-30amps

Say e-fans draw 40 amps running, likely a quite high draw figure, but for numbers sake thats only about .9 of a HP draw off the motor to spin the alternator, contrary to belief on their efficiency. The comparison of effeciency that is made is somewhat irrelevant to mechanical vs electric. Say it takes 1 hp to drive the alternator to create that additional 40 amps. I don't care the efficiency of the alternator or fan motor, so much as the fact that it takes 1hp from the engines rotating motion to make the fans turn on high and cool the motor sufficiently at peak load operation. How many hp do you think it takes when that aggressive stock fan goes into near lockup mode at 6000rpm to cool that bowtie climbing over the hill, or from a wot to stop to wot again? Approximately 10 times.

My whole point is when you are using the fans, they will draw a hp, just one. WHEN you are USING them, in colder months or on highway there is little to no additional power drawn from the engine to cool other than the water pump. There is no true disconnect on a viscus clutch, and you will always be drawing. When the clutch engages, i guarantee far more than 1 hp is used, just listen to a viscus fan howl in summer time heat from a red light. I believe there are gains to be made, both in mileage and power, however they will occur inconsistently through various driving conditions.

AND.. if you want to talk efficiency, electric is efficient

A regular production engine is not. Some general figures on oem are 38% loss on thermal energy out of the exhaust, 36% thermal energy dissapated out of water cooling, and 6 percent loss through internal friction. That means your average combustion engine is only about 20 pecent efficient.

Where do you make your gain, turning a 1-10 hp direct fan with a 20% efficient motor, or turning a 0-1hp alternator load to do the same job?

I dunno, maybe i'm biased, cause i spent money on e-fans, haha,, bla bla bla, but if its not more power efficient, or at least more economical why are all the new vehicles converting?

Let alone the argument that gm magically gave some 15 odd more ponies, to the trucks with no other modification other than beefier alternator and e-fans.

What do you guys think?

AdioSS

iTrader: (2)

for the most part, I agree with l_kusler

thunder550

iTrader: (70)

I think e-fans work well for most people who do them. I have not had good experience with them though, but I abuse my truck more by towing with it during the hot summers here in Phoenix. I used e-fans for awhile, then went back to the clutch fan.

Coban

iTrader: (14)

Here's the issue I have trouble with... Efans require 2 (two) conversions of energy to pull air over the radiator.

The clutch fan uses a belt which does have inefficiencies and the clutch itself allows slip.

Which is these used more energy? They both do roughly the same amount of work, although I'm pretty sure the clutch fan does more because it pulls more air.


I think the real advantage to efans is the fact that they can be shut off at precise temps with very little parasitic drag on the engine. The clutch fan cannot match this although it does slip.

I'm still gonna stay with efans because, like the previous post says, the General does. They are smarter than us.

Wilde Racing

iTrader: (26)

I bet if you wold have had two alternators on your truck it would have worked

I have e-fans.... mostly because I like the time it takes the engine to get up to temp with them...

silveradol33

iTrader: (30)

I race my truck at the sand drags with efans and never have problems on 90 degree days, and its hott as **** in the dunes.