Rear diffuser?

[aerohead]

Originally Posted by Phase

I’m not saying I have a 2mpg boost from one mirror removed. It’s probably like 1 to 1 and a half mpg. I’m saying it seems like 2 mpg is gained when cd is dropped 0.01

When my passenger mirror is removed, I can definitely feel less air resistance and use less throttle when driving. When both are removed, I can feel an even bigger difference. With the wheel skirts, I can also feel a difference in how the car move thru air.

I when I said I did the rest diffuser test and it made the car feel more grippy and like it’s being tugged, I guess I was right with how it felt since the next week when I tried to do the testing at higher speed, the diffuser ripped in half because air was getting underneath it

So hopefully with a smoother underbody or wheel flarings and behind the wheel boat tailing, I can actually feel a physical difference and improvement when driving like the mirror and wheel skirt mods

I don’t know if my mind is playing tricks on me or not though, but it seems like these mods so far only help at the lower highway speeds at like 65 mpg. I see an improvement there. But when I’m going 80-90, my mpg is practically the same. Not even 1 mpg higher…

The mathematics I provided for your car will allow you to 'calculate' the difference within a high probability. You don't have to speculate.

[freebeard]

I don’t know if my mind is playing tricks on me or not though...

There is no doubt. Everyone's and all the time.

The grab-bag of tricks includes confirmation bias.

[Phase]

Originally Posted by aerohead

The mathematics I provided for your car will allow you to 'calculate' the difference within a high probability. You don't have to speculate.

The ones that said I’d only get 61 mpg at 55 mph steady state? Which was way off? Or another one

[aerohead]

Originally Posted by Phase

The ones that said I’d only get 61 mpg at 55 mph steady state? Which was way off? Or another one

It would be original calcs for 80-mph, since that was your original target velocity.

[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

[freebeard]

I think not. Can you provide a link to these tests?

[airbiteses]

https://www.slideshare.net/slideshow...-cfd/239129607
https://aia.springeropen.com/article...74-020-00054-7
https://www.verus-engineering.com/bl...to-function-76
USM Digital Commons
Sedan Performance/Economy Rear Diffuser

https://occamsracers.com/2023/12/10/...-flat-bottoms/

[freebeard]

I looked at the first one.


http://www.slideshare.net/slideshow/...-cfd/239129607

"The diffuser acts as an expansion chamber to manage as it exits the car from underneath..."

This is the only example from #95 that has any bellmouth to it.

[freebeard]

Here's a proper diffuser:


https://cdn.motor1.com/images/mgl/0q...ction-body.jpg

Here's my own design applied to aerohead's Template:

[j-c-c]

My diffuser application is primarily seeking downforce. It is usually thought a proper diffuser design/installation usually compliments a proper rear wing. In this pic car has mini spoiler, with rear trunk mounted oil/trans fan cooled exhaust vents, the two still foamed diffuser slots are with high temp epoxy material that will have shaped exhaust outlets. The center upper open area is for tag mounting and the exhaust of the rear end fan cooler. Length is nearly to rear axle housing and taper much lower than 7%. Its all CF/Kelvar construction, 1972 Dart.

edit: Something included in my above DF solution, and seldom mentioned with diffusers, there is allowed and intended an amount of "waste/bleed" airflow to had above the diffuser, since it is extremely difficult to efficiently seal all air intrusion above the diffuser, and to gain the additional benefit to be found by extra heat extraction here from the very nearby exhaust plumbing that might degrade the composite diffuser with long exposure.