Diffuser design, per Lotus blog
 

http://www.lotustalk.com/forums/atta...o-005-copy.jpg
and
http://www.lotustalk.com/forums/atta...o-006-copy.jpg

Major improvement by vertically extending outermost diffusers almost to ground level behind rear tires, otherwise apparently the flow past rear tires converges so as to bugger the flow closer to centerline such that it is poor.

Pls. read and consider, then comment.

Interesting. I love the more recent generation of Lotus's with the Toyota engines. They have ditched the luxury items and concentrated on making the cars fast and fun.

Those end fences are probably important to all diffusers to some degree, but I would think they are especially important for extra-steep diffusers such as the Lotus has, all the way to not very important for shallow diffusers like Hucho describes.

The spinning air coming off the rear wheels interferes with the adjacent air fence/ diffuser/strake no matter the angle of incline.

The turbulence coming off those wheel wells can be seen in may CFD images and well as some smoke ones, including the ones on the second page of the article.

It wouldn't be hard to make a Prius-type rear wheel fairing (but larger and extending further aft)--a sort of end plate or flow fence that also acts as wheel fairing.

Perhaps the large Lotus end plate enables use of a much steeper diffuser angle?

BTW, anybody here read or know of Simon McBeath, the source of the latest Lotus mods?

I just did an image search on the name "Simon McBeath", appears to be the author of several handbooks (5).

Simon McBeath - The Tuners Group
http://www.tunersgroup.com/images/large/large2008.jpg

Impressive article.
The next mod on the Jetta is rear diffuser, looks like I med to think about tire find like the prius but larger.

improvement
 

Alberto Morelli used the rear wheel fairings as the capping plates to enhance the performance of the diffuser of the 1978 Pininfarina/CNR research vehicle,killing two birds with one stone.

Read and considered. There's airflow over the 'roof' of the difusser?

Here's my favorite end-plate solution:
http://ecomodder.com/forum/member-fr...bonnevette.jpg
It suggests to me that the outer half of a rear-wheel spat is superfluous.

Had to comment, that Corvette is so beautiful in that configuration. :o I wonder if they had room to remove some more drag by extending the tail from the bottom as well.

Also I think in the Exige if you have the exhaust go out over the diffuser, then you remove the panel that blocks part of the engine bay, and you'd have some airflow due to the side intakes. Though, Lotus side intakes look horribly un-aerodynamic.