4Hp is what I was expecting to spend to get a 10% increase in pressure. That would give me between 15 and 20Hp. Does anyone here work on Volkswagens? They have a fan to cool the engine that looks like the shape I need, but I'm clueless as to the dimensions. Here is what I'm talking about: http://www.chircoestore.com/catalog/product_info.php?cPath=109_115_124&products_id=3295&osCsid=hclq20d2slrq1qh3eec132ii90