Writer seeking examples of tested DIY aero mods for book

[Ecky]

Originally Posted by JulianEdgar

It's been a long wait but the book is now finally available on Amazon.

How much do they keep?

[JulianEdgar]

Originally Posted by Ecky

How much do they keep?

No idea. The book is published by a commercial publisher - Veloce. It's a complicated formula but I don't get much of that cover price.

However, in this case I think the book is well worth it - I honestly doubt any purchaser will be disappointed.

(But maybe that's not true - I think some people modifying their cars have developed some rules of thumb that are widely accepted, but are not supported by evidence. So those people may be disappointed!)

[JulianEdgar]

Note sure if I have posted these here:

Author introduction -

https://www.youtube.com/watch?v=_sQlaR4qylI

Book leaf-through -

https://www.youtube.com/watch?v=vJtHsfwXUu0

[aerohead]

Mine came in yesterday,here at Copy-Pro and I just got it right now.
Thanks Julian!

[California98Civic]

Originally Posted by aerohead

Mine came in yesterday,here at Copy-Pro and I just got it right now.
Thanks Julian!

@ 0:34

Book looks good, too!

[kach22i]

Originally Posted by JulianEdgar

Book leaf-through

Cool.

[aerohead]

I thought the book was a nice dive into aerodynamic waters.
Julian covered a lot of ground and comprehensively,without overwhelming the reader with extra-technical material which would only retard the experience.
I especially like the pressure profiles and crosswind (yawed) drag tables,which gives an appreciation between the 'ideal' and likely 'real' world.
Great data,graphics,layout,format,and easy organization.
Really slick!
A nice addition to the library,plus a nice reminder of all the cool modding owners are doing, worldwide.

[JulianEdgar]

Originally Posted by aerohead

I thought the book was a nice dive into aerodynamic waters.
Julian covered a lot of ground and comprehensively,without overwhelming the reader with extra-technical material which would only retard the experience.
I especially like the pressure profiles and crosswind (yawed) drag tables,which gives an appreciation between the 'ideal' and likely 'real' world.
Great data,graphics,layout,format,and easy organization.
Really slick!
A nice addition to the library,plus a nice reminder of all the cool modding owners are doing, worldwide.

What Philip didn't say (he's too nice a guy!) is that in the book I also cast some doubt on techniques that many people here use. I did that only after looking at the SAE papers (and other aero references - every published book I could find on car aero back to the 1930s) that covered the topic, asking people to support their statements with evidence, and then trialing it for myself.

Coast-down testing is a good example:

https://www.youtube.com/watch?v=ebyHpKBBR-M

The SAE papers referred to in the video (and book) are 950626 - ABCD –An Improved Coast Down Test and Analysis Method and 940420 and A Detailed Drag Study Using the Coastdown Method.

[JulianEdgar]

And another misconception is that assuming that completely covering the wheels always drops drag:

https://www.youtube.com/watch?v=pTunD32hO44

The relevant peer-reviewed engineering papers I refer to in the book include:


- Chalmers University of Technology, Gothenburg, Sweden (Investigation of Aerodynamic Resistance of Rotating Wheels on Passenger Cars)

- SAE paper 2007-01-1047 (The Influence of Rotating Wheels on Total Road Load)

- SAE paper 2011-01-0165 (Influences of Different Front and Rear Wheel Designs on Aerodynamic Drag of a Sedan Type Passenger Car)

- SAE 2012-01-0178 (The Aerodynamic Development of the Tesla Model S - Part 2: Wheel Design Optimization)

- SAE 2004-01-1307 (Numerical Simulations of a Car Underbody: Effect of Front-Wheel Deflectors)

[JulianEdgar]

Why measure aero pressures:

https://www.youtube.com/watch?v=hSqVmTyYJHU

Using a Magnehelic gauge to measure aero pressures (no more guessing or just using rules of thumb!):

https://www.youtube.com/watch?v=CQZ4hciT6h8

Measuring surface body pressures:

https://www.youtube.com/watch?v=gVQ9ttHRq8U

..allowing you to do things like this:



Note the relatively high base (wake) pressure on the Jaguar, and how you can measure underside pressures as well. My measured on-road data (shown here) matched Jaguar's official data very well. Add the force vector for the panel angle and you can see which panels are causing drag and which are causing thrust.