custom ud pulley

[sam c.]

Thanks for the reply, Jake. The smaller the diameter, the more the components are under-driven and the less parasitic losses. That was really my question... has any research been done to see how small the pulleys can be made without having an adverse affect on cooling and charging? (This would be for a strictly street driven car interested in the performance gains that would not be held to any rule mandated pulley size).

Thanks!

[Homeboy981]

Well @sam c., looks like YOU are OUR research and development department.

Let us know IF you decide to do it and how it 'turns' out.

Way to think outside the Box.

Good Luck!

[sam c.]

Well alright then... off we go. I'll be sure to post what I discover.

[Topless]

It's a simple math problem really. Calculate the change in wp rpm at different pulley sizes and make your best guess. A flow rate gauge on a coolant line would be useful also. Ideal flow rates for rads is pretty well understood.

I have never seen a smaller one than 4" so I assume someone did the math already.

[sam c.]

Originally Posted by Topless

I have never seen a smaller one than 4" so I assume someone did the math already.

Maybe I'm just cynical about human nature, but my couple of decades in mechanical and nuclear engineering suggest to me quite the opposite. It may not be once a week, but it's prob not too far fetched to say once a month, I hear the general equivalent to this sentiment: "if that was a good idea and/or worked better than what we're doing, someone would have already done it."

The shorter, more common version is: "...this is how it's done and it's always been done this way."

While I have tons of respect for any experimentation/trials/prototyping, even if the results were simply to prove what doesn't work, I honestly have zero respect for any reason for why something isn't done that sounds even remotely like "this is the way we've always done it and there's nothing better."

Just my $0.02

[sam c.]

The other thing I'd be interested in is how much cavitation is occurring in the stock pulley driven WP.

Right now, it's known conclusively that a stock 6" pulley can be swapped with a 4" pulley with no negative effect on cooling despite the WP turning a third or so slower. There's a number of variables in the cooling system including (but not limited to) the radiators heat xfer coefficient, the fluid friction through the system and engine coolant channels, the heat xfer of the block, the thermostat, ambient cooling, oil cooling, etc. All together though, the one thing we know for certain is that the WP is currently being turned a lot faster than necessary.

[sam c.]

I'm with you RK... I'd guess the alt. is really the bigger question here.

[Topless]

Originally Posted by sam c.

The other thing I'd be interested in is how much cavitation is occurring in the stock pulley driven WP.

Right now, it's known conclusively that a stock 6" pulley can be swapped with a 4" pulley with no negative effect on cooling despite the WP turning a third or so slower. There's a number of variables in the cooling system including (but not limited to) the radiators heat xfer coefficient, the fluid friction through the system and engine coolant channels, the heat xfer of the block, the thermostat, ambient cooling, oil cooling, etc. All together though, the one thing we know for certain is that the WP is currently being turned a lot faster than necessary.

Math and experimentation time then! Let us know what you find.

I grew up around scientists and engineers so I understand your burning curiosity very well. One of my friends used to be a model rocket hobbyist and always wanted to build bigger and better. He was building liquid fueled rockets in his garage until a man with money and vision offered him a partnership. The company is now called Space-X Technologies.