Writer seeking examples of tested DIY aero mods for book

[freebeard]

A thread from 2015 documented Morelli's FIAT research car. EcoModder Forum > EcoModding > Aerodynamics > Morelli's 'Fluid Tail'



This had every trick in the book.

Oval terminus
Active aero evacuated wheel wake
Box cavity/separation edge
Perforated [not even sure what this is]

Here's another picture from the same thread:

https://ecomodder.com/forum/showthre...tml#post503632

It's got speed holes. Maybe those would help with the local authorities.

[JulianEdgar]

Originally Posted by freebeard

A thread from 2015 documented Morelli's FIAT research car. EcoModder Forum > EcoModding > Aerodynamics > Morelli's 'Fluid Tail'



This had every trick in the book.

Oval terminus
Active aero evacuated wheel wake
Box cavity/separation edge
Perforated [not even sure what this is]

Here's another picture from the same thread:

https://ecomodder.com/forum/showthre...tml#post503632

It's got speed holes. Maybe those would help with the local authorities.

The SAE paper is interesting. I have seen quite a few like it over the years where a researcher claims a major breakthrough, and yet car companies do not pick it up and run with it. I'd guess in this case it's because the fans built into the rear wheels (and their associated ducts) are a large part in achieving good results from the 'fluid tail'.

Note also that the suggested shape has (apart from the last tiny bit) no descending roofline - the reason it has little lift. But the corollary of that is a big wake, so then the need for the 'fluid tail' to work really well.

I just skimmed the EM thread but all I could see was a huge amount of extrapolation from the paper, ignoring the bit about the fans! I didn't see any on-road testing of what people were doing or suggesting?

[California98Civic]

Originally Posted by JulianEdgar

The percentage change can be worked out from the bar graph. Cd = 0.215 with mods up to box cavity, Cd = 0.210 after box cavity. A 2.3 per cent reduction.

It's a very small change in drag. What I measured was also a very small change in drag, so I can't see how you can say that I "got quite different results than Ali". Given the different size wakes, I'd say they're in the same ballpark.

Without further evidence, I'd say that box cavities - especially on cars without large wakes - probably aren't worth pursuing... certainly not as first steps in drag reduction, anyway.

Whether 2.3% is worth it depends on what you find attractive, or interesting, or are able to build. When I road tested a box cavity I got results that were not detectable against the noise, but I did not yet have a difuser. Your 2.3% extrapolation ignores both the argument of the presentation and its findings: Ali argued the box cavity was interdependent with other mods and he specifically says the 2° difuser was a benefit only when coupled with the box cavity. They are interdependent. With the cavity and the 2° difuser the measured drag is 0.204, which is more like a 13% reduction from 0.215. The intedependencies as part of the mod.

EDIT: a quick afterword just to add that Ali tested half a dozen different box cavity designs because his results were affected not only by the other mods but by small changes in the design of the cavity. All these considerations increase the difficulty of the mod, but what's cool about it is how rematively low profile and stealthy it could be. A box cavity of Ali's type can be disguised as part of a mounting structure for a bike rack, possibly.

[California98Civic]

Originally Posted by freebeard

... Here's another picture from the same thread:

https://ecomodder.com/forum/showthre...tml#post503632

It's got speed holes. Maybe those would help with the local authorities.

This one was one of my favorites, though it's a lot more conspicuous than Ali's more subtle build. Kinda like a Prius Batmobile!

[freebeard]

It was designed by Takuya Yura, the founder of Mooncraft. And sold through Prius dealers in Japan in 2010.

Prius G Sports - MOONCRAFT YURA STYLE | PriusChat
https://priuschat.com/threads/prius-...a-style.74773/
Jan 15, TOKYO Toyota announced the Prius G Sports - MOONCRAFT YURA STYLE at Tokyo Auto Salon 2010. It is based on 2010 Prius S Turing Selection (Japanese model). The exterior is designed by Takuya Yura, a famous Japanese car designer, but power trains are not modified. This model will be sold as an official Toyota model via Toyota dealers in Japan.

1/5th scale and a moving belt floor.

Mooncraft is a Japanese racecar manufacturer which was founded by Takuya Yura in 1975. Mr. Yura’s workshop was opened near Fuji International Speedway and that is the origin of the company. It became publicly known after Mr. Yura appeared in an advertisement on TV. Mooncraft joined racecar industry by setting up the race team in 1985. They also brought carbon fiber composite technologies into Japanese racecar industry by introducing autoclaves, to create world-class racecar chassis and aerodynamic components.
....
The company has been working on wind tunnel testing for more than 30 years, producing aerodynamically sophisticated racecars. The company has been always pursuing to create innovative products and has also introduced Computational Fluid Dynamics (CFD) in the early days. Mooncraft is working on analysis of vehicle internal and external flows using SC/Tetra.

[California98Civic]

The holes/windows in the sides for taillight visibility were something I was thinking of imitating. I put one such hole in my box cavity test model last year. Ultimately, I want a more stealth look. I don't want the attention of the California Highway Patrol or my local police. Been there. Still... that Prius is land speed racing cool.

[freebeard]

Anything with wiring for trailer lights is an opportunity to repurpose Cadillac tail-lights


http://images.fineartamerica.com/ima...jill-reger.jpg

http://i.ebayimg.com/images/i/282381...-1/s-l1000.jpg

Similar to the way Volvo uses the D-pillar on their wagons.