Additional Cooling, Running a 3"- 4" Hose directly onto the fan Options

[GBallantine]

Any race guys ever run a 3 or 4 inch hose mounted off the front air dam or attached near the outside mirror thru the rear fire wall and directed onto the fan? Does it add any cooling effect? Any pics of setups?

GB

[Demick]

Some quick calculations:
Fan is rated for 1700cfm if I recall correctly. Maybe you want to shoot for 1/2 of this number as it won't be realistic or necessary to supply the entire volume of air at max fan rating.

So you want to supply ~900cfm. This means that the air would have to travel at over 200mph through a 3" duct to supply this kind of air. Not going to even get remotely close to that.

4" duct would be about 120mph of air. No dice.

But use a 6" duct, and that number drops to about 55mph. Seems fairly realistic. Might get this kind of volume if the car travels at ~80mph (depending on lots of factors).

So you can see that it makes sense that a number of racers use a 6" dia 'sewer pipe' to supply the engine cooling air to the fan. Get too much smaller than that and it won't be real effective.

[Randal]

Some quick calculations:
Fan is rated for 1700cfm if I recall correctly. Maybe you want to shoot for 1/2 of this number as it won't be realistic or necessary to supply the entire volume of air at max fan rating.

So you want to supply ~900cfm. This means that the air would have to travel at over 200mph through a 3" duct to supply this kind of air. Not going to even get remotely close to that.

4" duct would be about 120mph of air. No dice.

But use a 6" duct, and that number drops to about 55mph. Seems fairly realistic. Might get this kind of volume if the car travels at ~80mph (depending on lots of factors).

So you can see that it makes sense that a number of racers use a 6" dia 'sewer pipe' to supply the engine cooling air to the fan. Get too much smaller than that and it won't be real effective.

So Demick, for a race car situation, why not just bolt on one of these powerful electric fans and get rid of the mechanical fan altogether?

http://store.summitracing.com/egnsearch.as...k=KeywordSearch

[davep]

So Demick, for a race car situation, why not just bolt on one of these powerful electric fans and get rid of the mechanical fan altogether?
http://store.summitracing.com/egnsearch.as...k=KeywordSearch

Simply put, the mechanical fan takes less crank horsepower. If you figure 80% conversion factors, then the alternator & electric fan arrangement is only 64% as effective as a mechanical fan on the end of the crankshaft.