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dradernh · 05-21-2014, 01:56 AM

1: 6-12 degrees - determine most effective angle using flow visualization fluid (e.g., diluted motor oil sprayed onto the roof of the diffuser); strakes no lower than the car's floor bottom; if possible, exhaust over the diffuser roof if running a rear exhaust; if no flat bottom, gently curve the forward edge of the diffuser up into the suspension/diff area of the underbody so that underbody air cannot flow above the diffuser roof; extend it no further than 100mm/4" behind the rear of the car; first (only?) pair of intermediate strakes placed 100-150mm/4-6" inset from outside strakes

2: Over the diffuser roof offers more flexibility in diffuser design/construction; side exhaust is ideal (i.e., lighter, solves diffuser issue, looks cooler, all good); because they have to (i.e., the packaging is what's called for by a road-going car)

3: Lower the air volume (i.e., if flat-bottomed, place it as low as possible without its hitting the pavement)

3a: Shaping air flow to your advantage is the goal - that means controlling all of it that you are able; use a vented bonnet and, to the extent possible, ensure that air venting behind the radiator is made to flow through the vents; use vents that will release air as gently as possible into the stream already flowing over the bonnet

3b: Good

4: If you can use a 15" wheel, use it; however, please do tell us which 15" wheel will accomodate the AP Sprint Kit's 325mm/12.81" rotor/caliper combo

5: Side skirts, horizontal as well as vertical = good; some of the new materials have excellent wear characteristics, enabling you to mount the vertical skirts' bottom edges extremely low (see: NASCAR Sprint Cup cars)

Given the amount of money you're spending, you might consider the aero consulting service offered by Simon McBeath, author of Competition Car Aerodynamics and aero columnist for Racecar Engineering magazine. I did, and it was well worth it, both in terms of first principles applied to my specific car model, and in terms of time and money not wasted trying one thing or another without the resources to necessarily determine whether or not they were working optimally. In the context of the money I was already throwing at the car, the cost was surprisingly acceptable. More here: http://www.sm-designs.ndo.co.uk/smarthome.html. Full disclosure: I have no affiliation with Mr. McBeath other than as a satisfied customer of his service and reader of his works.

05-21-2014, 01:56 AM	#252
dradernh Senior Member Join Date: Feb 2014 Drives: Used to Drive:Grand-Am GS #54 E36M3 Location: So. OH Posts: 561 Thanks: 77 Thanked 237 Times in 163 Posts Mentioned: 8 Post(s) Tagged: 0 Thread(s)	1: 6-12 degrees - determine most effective angle using flow visualization fluid (e.g., diluted motor oil sprayed onto the roof of the diffuser); strakes no lower than the car's floor bottom; if possible, exhaust over the diffuser roof if running a rear exhaust; if no flat bottom, gently curve the forward edge of the diffuser up into the suspension/diff area of the underbody so that underbody air cannot flow above the diffuser roof; extend it no further than 100mm/4" behind the rear of the car; first (only?) pair of intermediate strakes placed 100-150mm/4-6" inset from outside strakes 2: Over the diffuser roof offers more flexibility in diffuser design/construction; side exhaust is ideal (i.e., lighter, solves diffuser issue, looks cooler, all good); because they have to (i.e., the packaging is what's called for by a road-going car) 3: Lower the air volume (i.e., if flat-bottomed, place it as low as possible without its hitting the pavement) 3a: Shaping air flow to your advantage is the goal - that means controlling all of it that you are able; use a vented bonnet and, to the extent possible, ensure that air venting behind the radiator is made to flow through the vents; use vents that will release air as gently as possible into the stream already flowing over the bonnet 3b: Good 4: If you can use a 15" wheel, use it; however, please do tell us which 15" wheel will accomodate the AP Sprint Kit's 325mm/12.81" rotor/caliper combo 5: Side skirts, horizontal as well as vertical = good; some of the new materials have excellent wear characteristics, enabling you to mount the vertical skirts' bottom edges extremely low (see: NASCAR Sprint Cup cars) Given the amount of money you're spending, you might consider the aero consulting service offered by Simon McBeath, author of Competition Car Aerodynamics and aero columnist for Racecar Engineering magazine. I did, and it was well worth it, both in terms of first principles applied to my specific car model, and in terms of time and money not wasted trying one thing or another without the resources to necessarily determine whether or not they were working optimally. In the context of the money I was already throwing at the car, the cost was surprisingly acceptable. More here: http://www.sm-designs.ndo.co.uk/smarthome.html. Full disclosure: I have no affiliation with Mr. McBeath other than as a satisfied customer of his service and reader of his works.