Originally posted by T3man
Why would a close ratio gearbox cause the problem? I can't understand how the gearbox can be causing you to use "consistently higher revs". Sure, when you change up the revs don't drop as much but the fact is the engine max revs is the same and you must be in top gear most of the time. Or have you changed the diff ratio? This would have the effect you describe I s'pose but many ppl do it and have no probs such as you've described so I'd be looking elsewhere. BTW, what leads you to believe the power steering fluid is overheating?
I don't really think you'll have any power gains by changing the pulley size? Think you might need a microsope to notice any change.
Remember also, slowing down the rate of fluid flow means lower pressure to your box - this will mean more load back on your pump from the steering box - more load on pump is more load on motor - guess you can't have your cake and eat it too!
I wrote a lengthy and articulate explanation why you are not correct in my particular situation, but the forums logged me out automatically I took so long and it was all lost.
You explain yourself why a close ratio box would make the PS hotter - consistently higher revs. This is a rally car so we use all the gears and slow down periodically for corners, which can be either left or right-hand corners. More revs equates to more heat. You bring up diff ratios, but that really does not have any effect.
The PS fluid overheats and loses its viscosity, same as engine oil. When this happens it no longer works properly, just like engine oil, and the result is heavier steering (and blowing the seal on the lid of the reservior) through reduced fluid pressure. As soon as the fluid has a chance to cool, the steering comes back, without adding any fluid to the system.
There are quantifiable gains from changing pulley sizes on many engines - this info is freely available elswhere. As far as I am concerned this is a by-product - you will notice I did not refer to horsepower as such, only a few small ponies.
We actually have a steering rack ('97 model Falcon). PS pumps (like water pumps) are designed to operate properly at idle. At speeds above this they produce far more assistance than is required and the fluid flow is regulated, which wastes energy and turns it into heat. Changing the regulator will alter the characteristics of the steering, which we do not want. Nor do I care if the car is a pig to drive at slow speeds, which will probably happen with larger pulleys as there will be insufficient assistance at idle. This same principal can be applied to water pumps and Davies Craig have a good explanation on their website, excplaining why an electric waterpump releases power from the engine.