Larger pully on engine?

Yes it would.

If you have a stock or near stock engine that doesn't rev unusually high, then there are no illeffects that I know of. It would rob a little power from the engine because the fan, turning faster, would cause more "drag". But the increased cooling would still make the engine run cooler.

Or so they say, I have no first hand experience. I can't use those, my engines rev much higher and I don't think it would be a good idea to spin a stock fan that fast.

Jan

When I saw this thread the word "cavitation" came to mind because I seemed to recall people throwing that term around before when this topic was brought up, but when I checked with

I found cavitation has to do with vacuums caused in liquids by something like a fast-moving propellor and although I could be swayed towards believing "air" is a liquid of sorts, I still think that cavitation is the wrong term to use in this discussion. Sucking up more HP to drive the fan faster by using a larger crank pulley will be like driving uphill, causing the engine to work harder, producing more heat. I think that much is certain. I also find it hard to believe that the original VW engineers didn't experiment some with various sized-pulleys to get the best balance. Who knows, (not me), maybe in extreme heat circumstances a compromise to the "best balance" is good for your engine. Maybe if VW engineers were designing the pulley size in Arizona, they'd have made it a little bigger. I think it should also depend on the average RPM your engine is turning. Should be a cheap enough experiment as long as you keep a close eye on engine temps to make sure you don't melt something doing this. Seriously. It may help. You'll only know for *sure* by doing one thing. And you know what that one thing is. I'm sorry to break this to you, but "you are the best mechanic that you can afford." heh heh... That line always cracks me up.

Will it help increasing fan speed when you install a larger pully on the engine (not where the clutch is, other side)? I was thinking a larger one would increase alternator (and so fan) rpm. This to compensate a bit for the hot african weather here.

Bart Bervoets

Air is a Fluid, not a liquid...............hence the word cavitation is applicable..................It doesn't look the same as liquid, but it does have a similar overall problem. Basically the lack of resistance to the air around it will eventually occurr when a fan is truned too high an RPM...............turning too fast to "suck in more air" . In some cases this would cause overspeed of a fan, but in this case , overspeed is not an issue for it is controlled by the drive belt. The rest of your cogitation I can't answer, as I am not versed in power/drag equations that could answer the questions raised.

That and the fact that I am very tired and did good to remember the bit about air being a FLUID, not a liquid.............blah blah blah.

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MUADIB®

one small step for man,..... One giant leap for attorneys.

They DID experiment with many different pulley sizes, and they even produced T1 engines with at LEAST 3-4 different size pulleys right from the factory. I have 3 examples at home and I have made a post about it before. Google it up if you like.

Jan

What the heck, i just try it. The center of the pully is quite special, so i brought a spare pully in engineering and told them what i want. They will use the center of the pully to create a new one. I keep everyone posted of the result, and yes, africa is hot, VERY hot.

Call me ignorant, but isn't very *dangerous* to just put a home-made pully on the engine?? As far as i know the bearings will wear very fast if the pully is even a hair off-centre. (wcs: the bearing housing will be fubar)

just an idea...

...Roger...

"Bart Bervoets" schreef in bericht news:coh42m$2q8$ snipped-for-privacy@ctb-nnrp2.saix.net...

I bought an aluminum oversize pulley and belt from a VW parts place, I don't remember which one nor who made the pulley, but they sell it for added cooling. Isn't a new idea or a non-commercialized one. Tim

As long as the edge of the fan does not exceed the speed of sound, cavitation should not be a problem.

Very rough calculations (probably with pathetically obvious errors that will illustrate how little I know about How Things Work):

Engine pulley roughly 6.5'' diameter, gen pulley roughly 4'' diameter, fan roughly 9'' diameter (don't have one out to look at).

If engine is at 1,000rpm, outside edge of engine pulley is going 41,000 inches/minute, outside edge of gen pulley is going 25,000 inches/minute, circumference of fan is going at 57,000 inches/minute. This is 80 feet/second. Speed of sound at sea level is 1,100 feet/second. So if you crank your engine up to around 14,000 rpm the circumference of the fan will be at or near the speed of sound.

Since my bus goes around 65 mph at about 3,800 rpm, it stand to reason that if the engine were brought up to 14,000 rpm there would be lots of hot little metal pieces scattered all over the place.

But, unfortunately, no matter how I do the numbers, time travel is not possible. I would not go back in time. This I find very disappointing and am not sure if it is Mario's fault or John Connelly's fault.

Cavitation isn't an issue but over-reving the fan has one real and one arguable downside. First, some fans are just not made well and can 'frag' or blow up at high speed. The arguable issue concerns 'stuffing' too much air into the system so that it does _not_ improve cooling.

Correct me if I am assuming incorrectly, but would increasing fan speed with a larger pulley increase the amout of warm/hot air into the heating system?

-- the Grokdoc Tom Malmevik all that groks is god

67 Baja "marti"

I don't know. :( I don't have heater boxes in either of my hot engine vehicles.