Rear diffuser?

[freebeard]

Five fences is about right.

[aerohead]

Originally Posted by airbiteses

Hello, do these rear bumper extensions improve aerodynamics?
The factory bottom of the bumper looks like this:


and there are such replacements, i.e. additions to the bottom of the bumper:



Because there are tests on the Internet that reduce air resistance

1) You'd need to be extremely specific about what you actually mean by the use of the word.
2) We'd need a technical drawing with an accurate side elevation view, of a specific car, depicting the exact geometry, before and after, without and with.
3) The presence of a separation-caused, vortex-induced 'upwash' on a steeply-angled diffuser would be indicating for increased air resistance.
4 The diffuser on a Lucid Air would be a better 'benchmark' for a low drag diffuser.

[airbiteses]

hmm, the question is whether it does anything to reduce fuel consumption. I understand that it doesn't do anything?

Is it possible to improve the rear of the chassis, e.g. the tank, spare wheel?

[j-c-c]

Originally Posted by aerohead

1) You'd need to be extremely specific about what you actually mean by the use of the word.
2) We'd need a technical drawing with an accurate side elevation view, of a specific car, depicting the exact geometry, before and after, without and with.
3) The presence of a separation-caused, vortex-induced 'upwash' on a steeply-angled diffuser would be indicating for increased air resistance.
4 The diffuser on a Lucid Air would be a better 'benchmark' for a low drag diffuser.

IMO the pictured solutions are for mostly cosmetics and marketing.
Use of "diffuser" in their description would be very disingenuous.
They also seem to completely ignore any proven Kamm beneficial simplistic KISS solutions.

[freebeard]

Is it possible to improve the rear of the chassis, e.g. the tank, spare wheel?

It's always possible. The question is would you like living with the result.

For instance, one might remove the spare tire well, put a 90 degree elbow ahead of the muffler and run it laterally behind that crossmember between the struts to exit on the other side.



Then you could ramp the diffuser from [ahead of] the crossmember itself.

[j-c-c]

And weigh any aero advantage against the offset of adding another 180 degrees of exhaust bending plus the added weight of both at the with at the most of just highway speeds?
That is a tough stretch.

[freebeard]

What would you suggest?

A diffuser-shaped muffler?

[j-c-c]

Don't waste time chasing one's tail, set your tire pressure to max, drive like there is a tennis ball on the dash, look ahead of the car in front of you, never carry a spare tire, sort of things, or not.

[j-c-c]

Originally Posted by freebeard

What would you suggest?

A diffuser-shaped muffler?

It you are fixated on the muffler, modify/relocate it to be a narrow slit but very wide diffuser enhancer?

[freebeard]

I've suggested VW Beetle engine cooling air into a Coanda nozzle, as it's less corrosive than exhaust.