Rear diffuser?

[aerohead]

Originally Posted by Phase

I’m still shocked that Hyundai didn’t add a rear diffuser to the Ioniq hybrid. Even Hyundais Elantra and Sonata hybrids have decent looking rear diffusers for gas engine cars. Toyota Prius even has a rear diffuser. I don’t get the flat bumper reasoning for the Ioniq when they were making a low drag fuel efficient car

As Wolf H. Hucho eluded to, long ago now; whatever Hyundai's committee, who had absolute authority over design, was satisfied with what ended up to be the production specification.
' the design of a vehicle is not dictated wholly by aerodynamics.'
' To what extent basic ( streamline half- ) bodies with high fineness ratios can be used as the starting point for vehicle development depends upon the value placed upon low drag in the future.'
It appears that low drag is NOT a priority at KIA/ Hyundai/ Genesis.

[Phase]

Originally Posted by aerohead

As Wolf H. Hucho eluded to, long ago now; whatever Hyundai's committee, who had absolute authority over design, was satisfied with what ended up to be the production specification.
' the design of a vehicle is not dictated wholly by aerodynamics.'
' To what extent basic ( streamline half- ) bodies with high fineness ratios can be used as the starting point for vehicle development depends upon the value placed upon low drag in the future.'
It appears that low drag is NOT a priority at KIA/ Hyundai/ Genesis.

I mean low drag was obviously a factor with the Ioniq and sonata being 0.24. That’s still lower than most other car companies out there. And now the new Ioniq 6 is 0.21 drag which is literally going to be the lowest mainstream production car that’s mass produced

[Phase]

Anyone know of other studies showing diffusers lowering drag?

[freebeard]

More downforce with less drag.

https://grassrootsmotorsports.com › articles › downforce-sorcery-diffusers-explained
Downforce Sorcery: Diffusers Explained | Articles - Grassroots Motorsports
21 May 2021Since the diffuser is making downforce, there is likely to be an increase in drag. Generally this effect is small at normal speeds, but it can be substantial as a car approaches terminal speed. The key, of course, is designing an effective diffuser and then properly testing and tuning it for maximum efficiency. Like what you're reading?

https://www.carid.com › rear-diffusers.html
Custom Rear Diffusers | Carbon Fiber, Fiberglass, Urethane - CARiD.com
1 Oct 2021Although components like rear wings can also be used to provide downforce, they create much more aerodynamic drag while doing so than a rear diffuser. The diffuser provides the space for the high velocity, low pressure air flow to decelerate and expand at the rear of the vehicle, creating a pressure differential and more downforce.

[Phase]

Originally Posted by freebeard

More downforce with less drag.

yeah both say even a little drag is created...

so why should i bother with a diffuser? im focused on the lowest drag possible and getting extra mpg, not increased handling and performance

im assuming the diffusers on teslas and the porsche taycan are for handling and perfomance, since people expect those cars to hug the road around turns for their price...

yet julian edgar and mercedes were saying diffusers lower drag and increase range and mpg

so many conflicts!

[Phase]

https://www.mdpi.com/2076-3417/12/8/3763

check out the full pdf for this new study. drag is slightly increased. about 1 cd point. that usually translates to about 2 mpg for my car. im not willing to lose 2 mpg for better downforce

[aerohead]

Originally Posted by Phase

Has anyone on here made a rear diffuser for any of their vehicles?

Any tests done?

Since I’m doing a smooth under tray, I’m going to obviously fabricate a rear diffuser. Seems like it’s all benefits and no downsides

So far my inspiration is making one that’s like on the vision eqxx by Mercedes

I'm at eight so far.
All improved mpg.
Three speed records at Bonneville. Up to 247-mph.
Two got full-scale wind tunnel testing.

[aerohead]

Originally Posted by Phase

https://www.mdpi.com/2076-3417/12/8/3763

check out the full pdf for this new study. drag is slightly increased. about 1 cd point. that usually translates to about 2 mpg for my car. im not willing to lose 2 mpg for better downforce

Their diffuser lowered the Cd by up to 2.5% below an 8-degree angle ( page 22 ).

[Phase]

Originally Posted by aerohead

Their diffuser lowered the Cd by up to 2.5% below an 8-degree angle ( page 22 ).

There are only 21 pages on the pdf?

[aerohead]

Originally Posted by Phase

There are only 21 pages on the pdf?

Went back in and found no pages!
Look at bottom of 1st paragraph after Figure 8.
----------------------------------------------------------------------------------------
okay! in the PDF, it's on page 8 / 21 after Figure-8