New Diffuser For S550

[CrazedAntelope]

Hi I will do the best I can to answer the question. I feel I have relevant information to pass along here. My experience is in multi-physics CFD modeling of turbine diffusers and aerodynamics of turbine blades and vanes. The stuff Velox does is amazing. I am really excited to see them coming out with true engineered components.

That being said, you cannot increase the angle of the diffuser lest you risk flow separation. Flow separation creates a huge pressure drop, unwanted drag and tons of turbulence. The optimal angle for a diffuser is around 7-8 degrees. Any more than that and you blow the boundary layer right off the surface of the diffuser and it will be pointless drag. They are using real aerodynamic approach number 1. by simulating their design using CFD analyses and 2. implementing industry standard practices that have been used for nearly a century in the design of aerospace components.

There are hundreds of research papers written on the topic of flow diffusion. You can google the following term, static pressure recovery ratio. This number is the amount of pressure you can recover from a moving stream by slowing it down into a static stream, the most effective way to do this is with a proper divergence angle, 7 degrees or so. The angle also varies, a very rough surface can actually handle a higher angle 8-9 degrees or more. This is due to the boundary layer thickness, of course you will need to analyze the Reynolds number, verify your Y+ and ensure you are capturing the correct flow at the boundary layer using the correct turbulence model.

I cant speak for velox, but I can assume they are doing it right from what I have seen on their Instagram. I follow them and I really like their approach, true flow simulated engineering and the rigors of aerodynamics are NOT just crunching numbers, it takes experience and R&D, and that is not easy. Props to them.

Dang, thanks for the detailed response. I knew I was forgetting some of the stuff I learned in school. I guess that's what happens when a M.E. goes off and works in software/networking...

I suppose that's why DTM race cars have their diffusers stick out so far. The angle has to be shallow or else you get flow separation.

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[stoli]

I'm ready to bolt it on.

 

[bluestang50]

I'm ready to bolt it on.

+1

I love the fact that they are putting function over form.

 

[tsunami]

The OEM splitters were developed to help bring up air from the vehicle belly into the rear low pressure area that almost all cars develop. Adding another flat splitter below will probably kill the upflow causing additional drag. Too bad no one has a wind tunnel to test these types of add-ons.

 

[l'Ingegnere]

The OEM splitters were developed to help bring up air from the vehicle belly into the rear low pressure area that almost all cars develop. Adding another flat splitter below will probably kill the upflow causing additional drag. Too bad no one has a wind tunnel to test these types of add-ons.

Uh, highly unlikely. Just look at the angle of the OEM "diffuser", definitely greater than 7-8 degrees. I'm pretty sure it's the OEM bumper that only creates drag.

Did you even bother to read the post made by Velossa?

 

[Lost Cosmonaut]

Hey guys, figured I'd chime in on here!

We have revised the design slightly from the prototype to better become "part" of the car instead of an addition. Ford didn't make it easy for us but we're doing the best we can . The revision tucks the diffuser further into the bumper. We are also working on rear spats that will help complete the rear end, as well as other aero devices.

Most of the "diffusers" on the market are not functional pieces, and that was our goal with our unit. We hope you like the looks at the end of the day as well, but this is more geared towards reducing drag and lift. That aspect is more important to us than having something look pretty. There are plenty of nice faux diffusers out there, we're not interested in competing with those.

As far as it being weak, it is not weak; and is in fact quite strong. I dropped by Full-Race to show this, (this is still the prototype):

And finally, regarding a "fly by the night" company, we are not that either. We have been in business for a few years now. While we are coming from humble beginnings, we have a very strong foundation in engineering, and we believe that brings a lot to offer to the end user.



Thanks,
Eric

Wow wow wow, I will be watching, this is exactly what I need :love:

 

[Veloxeric]

The loads on those parts are different. A splitter just reduces the air under the car. A diffuser causes a partial vacuum under them to suck the diffuser (and the car its attached to) down. So a functional diffuser has strong forces trying to pull it off the car while a functional splitter has much less force trying to dislodge it.

On road cars, splitter forces are generally quite a bit higher than functional rear diffusers. Note, I said road cars. Race cars with properly designed diffuser tunnels can generate high amounts of load. So typically, on street/road cars, I'd say the exact opposite, splitters see higher loads than rear diffusers. Doesn't mean it shouldn't be built to handle a reasonable amount of load though.

I think it would look WAY better on a base car without the factory "diffuser" fins in there. Send me one, and I'll post a bunch of pics to prove it! ;)

We think so as well, the factory fins kind of mess things up a bit. Combine the fins and that the faux diffuser on Full-Race's car was white instead of black, which makes the OEM diffuser stand out even more.

Looks a lot better now than your first prototype pics. I'd rock it but doubt it'll clear my ROUSH ABs.

The entire unit can translate vertically an inch to fit different exhausts, tip sizes, etc.

Maybe I'm not understanding something here. I thought the end point of the diffuser should be as high as possible so that the expansion chamber at the back of the car is as large as possible. Increasing the size of the exapnsion chamber forces the air under the car to move even faster, with a lower pressure. Lower pressure under the car equals more downforce.

I'm not really seeing the point of decreasing the height of the rear diffuser. Looks like a smaller expansion chamber and less downforce.

The OEM splitters were developed to help bring up air from the vehicle belly into the rear low pressure area that almost all cars develop. Adding another flat splitter below will probably kill the upflow causing additional drag. Too bad no one has a wind tunnel to test these types of add-ons.

The OEM "diffuser" is not a diffuser. It is a bumper, that has a "diffuser" molded into it for aesthetic appearance. All you have to do is look under the car and see that the diffuser is merely part of the bumper and is for looks, which looks awesome! But as far as function, it does very little for aiding flow exiting the underbody.

As far as diffuser angle of attack (AOA) or expansion chamber angle, VelossaTech hit most of the important points. Aerodynamics are quite complex and no single rule applies to every vehicle body from our experience.

Thanks,
Eric

 

[Joe 5.0]

I would also love to see this functional diffuser on a base rear bumper!

I have a base, black 5.0! Send me one and I'll take high quality pictures!

 

[Brostang]

[MENTION=26218]Veloxeric[/MENTION]

Any pictures of the second iteration? I'm very interested in this product. It's great to see "cosmetic" upgrades being run through flow sim. Also, I think it would be more visually appealing if it deleted the factory "diffuser" section and worked like a replacement, similar to the rtr except functional. On premiums the trim could be removed and the diffuser cut, allowing for 2 higher divergence angle tunnels. The multi-geometry, while not optimized for a single speed or ride height, would increase the domain where -L is generated. The "factory replacement" design would also allow for a smaller pressure relief gap, so it wouldn't have to hang below premium bumper fins. Are the forward and aft heights independently adjustable?

 

[Digital_Synapse]

Looks great

 

[johnson.ba]

And how does it transfer that downforce to the wheels ? Through crappy looking plastic and tiny bolts ?

it transfers downforce by reducing lift, you know, physics.

 

[Digital_Synapse]

it transfers downforce by reducing lift, you know, physics.

LMAO

 

[z06psi]

That looks terrible.

Not political correct.

Not a huge fan of the look...

Politically correct.




Looks like ass in my opinion.

 

[Veloxeric]

Production pieces are in, below are some pictures. These show the changes in the profile to better "fit" the rear bumper and look a bit less like an add-on. There is not much more we can do to the looks department and retain functionality, which was our ultimate goal.

















Product photo off car:





Thanks,
Eric

 

[rvlyssup]

Production pieces are in, below are some pictures. These show the changes in the profile to better "fit" the rear bumper and look a bit less like an add-on. There is not much more we can do to the looks department and retain functionality, which was our ultimate goal.

*snip*

Thanks,
Eric

I'd rock it....price point?

Again, my only concern is diffuser clearing the lower portion of my ROUSH ABs. I like how it is flush, doubt it'll be that flush with my set up though.

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