ACR Diffuser

[Voice of Reason]

I keep cluttering up other threads with my questions on this so I thought I'd start a new thread.

The diffuser appears to come in multiple pieces:
- 3 pieces (left, center, right) that attach to the underside.
- 6 blades that attach to the above pieces

The full setup isn't going to be street friendly with how low to the ground they are. But my thought is a person could use the 3 main attachment pieces and then get 6 blades made that will allow for a little more clearance. I think that would work for the road, "do its thing" well enough on the track, and give it a nearly identical visual look.

Does anyone have a cost for the 3 attachment pieces? I think that's where the issue may be after seeing all these other ACR only pieces. The blades themselves would be cheap to design so I'm not worried about those.

[SSGNRDZ_28]

Do you have any good photos of the attachment brackets? I've seen a few but they were more from the top.

[Voice of Reason]

Do you have any good photos of the attachment brackets? I've seen a few but they were more from the top.

It sounds like we've seen the same pics, always from a top angle. A good shot of them from the underside would be nice if anyone has one.

[Rapidrezults]

Wait, hold up. Am I reading this right? Street friendly? Looks? This is a track car not a show car. Maybe the ACR isn't for you. Is this like a cars n coffee mod? Lol.

On a serious note, since i will be one of the few driving it on the street and track, I would be interested in something like this.

Regards,
Your Hood Liner Specialist

[timberwolf]

Is this like a cars n coffee mod? Lol.

Regards,
Your Hood Liner Specialist

Good one(s)! Funny man, and sort of sums it up. I was thinking about adding diffuser blades then I realized it was probably more for bling purposes as you stated, rather than functionally moving stagnant air from under the car lol...

[Voice of Reason]

Wait, hold up. Am I reading this right? Street friendly? Looks? This is a track car not a show car. Maybe the ACR isn't for you. Is this like a cars n coffee mod? Lol.

On a serious note, since i will be one of the few driving it on the street and track, I would be interested in something like this.

Regards,
Your Hood Liner Specialist

I needed a laugh this morning

I like the idea of aero improvements without the big wing. The diffuser looks nice so that's a bonus. I'm actually wondering if the diffuser combined with the TA 2.0 canards up front added to my TA 1.0 would balance things out. I'm not an airflow expert though so I'm unsure if those would work well together.

[Courtney @ViperExchange]

I keep cluttering up other threads with my questions on this so I thought I'd start a new thread.

The diffuser appears to come in multiple pieces:
- 3 pieces (left, center, right) that attach to the underside.
- 6 blades that attach to the above pieces

The full setup isn't going to be street friendly with how low to the ground they are. But my thought is a person could use the 3 main attachment pieces and then get 6 blades made that will allow for a little more clearance. I think that would work for the road, "do its thing" well enough on the track, and give it a nearly identical visual look.

Does anyone have a cost for the 3 attachment pieces? I think that's where the issue may be after seeing all these other ACR only pieces. The blades themselves would be cheap to design so I'm not worried about those.

Just out of curiosity, what have you seen which leads you to believe the diffuser comes in three pieces? From what we saw on a *pre-production* Extreme Aero'd ACR there wasn't anything about that diffuser that led me to believe it was separated into Left, Right, and Center. Again, since there have not been ANY production ACRs with that aero, it'd be hard to make any factual statements as we have seen discrepancies between actual production and media cars. There will absolutely be attachment pieces, but specifically to the diffuser I have not seen anything that leads me to believe it is in more than 1 piece. I will find the answer and let you know. The Hood liner thing was easy to find part numbers and associated costs as it is something already on many Vipers. This is much more difficult as it is speculation, and a hunt for parts that are not in any system yet.

[Voice of Reason]

The pics I've seen appear to have three sections. Each section has 2 blades attached to it. From the rear it doesn't look like one piece, but that doesn't mean as it flows towards the front of the car they don't join back up into a single piece.

Did you have the pre prod car up on a lift?

[Courtney @ViperExchange]

The pics I've seen appear to have three sections. Each section has 2 blades attached to it. From the rear it doesn't look like one piece, but that doesn't mean as it flows towards the front of the car they don't join back up into a single piece.

Did you have the pre prod car up on a lift?

From what I saw it was all one piece, U shaped, and obviously came with extensions. No ACRs are shipping with extensions applied, which is why you see them being put on at the track. Our ACRs are not coming with Splitter Extensions applied, I anticipate this will be the case for the Extreme Aero cars as well.

We had no reason to put it on a lift, but as it was on jack stands at the track I absolutely crawled under it. Again, not seeing that the actual diffuser was in more than one piece. I am speaking to an experience with a pre-production car though, and that always has the possibility of not being the case when they roll off the line. Email sent to the gurus at FCA, awaiting response.

[Rapidrezults]

I was under the impression there was a base diffuser with smaller blades and a set of 6 strake extensions that get put on for track duty. Andy posted a picture of one of the Chrysler guys installing the extensions on the extreme that was at COTA.

I thought it was a 2 piece design.

https://instagram.com/p/7OzP6yiUKo/?taken-by=1flatout1

If you look at other pictures closely you can see the extensions have a slightly different color and go on one side of the base strakes.

[Voice of Reason]

I can't zoom in on that pic on my phone.

I thought there was a lighter blue ACR posted in the past couple days with a good rear shot. I can't find the pic now.

[sadil]

These photos might give some light to the left, center, and right pieces. Seems like the diffuser's 6 strakes are created by 3 "[" channel shaped carbon pieces installed on the underside of the chassis. Further 6 extensions are then added, one to each strake, to create the full diffuser. I am still not sure about the center piece, it might be a "[" channel shaped or 2 "L" channel shaped carbon pieces.

[Rapidrezults]

These photos might give some light to the left, center, and right pieces. Seems like the diffuser's 6 strakes are created by 3 "[" channel shaped carbon pieces installed on the underside of the chassis. Further 6 extensions are then added, one to each strake, to create the full diffuser. I am still not sure about the center piece, it might be a "[" channel shaped or 2 "L" channel shaped carbon pieces.

Great pics Sadil...Always finding the best pics out there. This is exactly what I thought it was.

[sadil]

These were taken by yours truly! =D I was getting my hands dirty at the Dodge event during the Woodward Cruise. It was the first ACR I had seen in the flesh, and I wanted to get to the bottom of this extreme aero business. I am assuming they wanted to keep it a multi piece design for manufacturing, customer maintenance/storage and cost of replacement purposes. I think it is a win win design. Given Dodge's aerospace grade pricing for carbon fiber (im not hating on dodge, every premium manufacturer is charging an arm and a leg for quality carbon parts) hopefully they don't cost $1000 each to replace.

[Jack B]

There is another thread that is now active. That thread shows the underside fascia removed. The OP added five fins. I just bought five fins from his link, they were $25 each.

[ACR Steve]

doesn't look that low from those pics

[SSGNRDZ_28]

The pictures don't include the extensions.

[ACR Steve]

Doug then I was right they aren't that low in the pic

[Jack B]

For those that have had a car with diffusers, do you notice a difference and if so, what is the diff.

[VENOM V]

For those that have had a car with diffusers, do you notice a difference and if so, what is the diff.

Jack, I haven't yet had a car with one (I will in a couple of weeks), but I think I understand how they work. The diffuser extensions are very low to the ground, which traps the air under the car in between the extensions. As air goes under the car and reaches the diffuser, it goes into a small gap. The gap widens increasing the cross-sectional area as the air approaches the rear of the car, expanding the volume of the air and thinning it, reducing pressure under the car and thereby creating downforce. Not sure if I explained that very well, but that's what it does.

[Jack B]

What is a bit confusing is that the fins are parallel sometimes and in a fan pattern other times.

Jack, I haven't yet had a car with one (I will in a couple of weeks), but I think I understand how they work. The diffuser extensions are very low to the ground, which traps the air under the car in between the extensions. As air goes under the car and reaches the diffuser, it goes into a small gap. The gap widens increasing the cross-sectional area as the air approaches the rear of the car, expanding the volume of the air and thinning it, reducing pressure under the car and thereby creating downforce. Not sure if I explained that very well, but that's what it does.

[SSGNRDZ_28]

https://m.youtube.com/watch?v=PPsoxXvMtCE

Some info at ~3:25

[steve911]

16 ACR rear Diffuser 2.jpgIMG_0010-407x610[1].jpg

Here are a couple of closeup pics from the extreme ACR rear diffuser. There are a total of 10 pieces that make up the diffuser NOT counting the fasteners to hold it all together.

Each outer segment (left and right) is a curved carbon "U" channel that bolts to the bottom of the car, and has the composite extensions that attach to the "U".

The inner extensions are a carbon "L" angle (contoured left and right) that also have a composite extension fastened to them.

[steve911]

I'd say you did a good job of explaining it...

[SSGNRDZ_28]

A diffuser provides very efficient downforce (less drag for the same amount of downforce than other features such as a wing). It controls the exit of low pressure air travelling under the car and maximizes the use of that air to gain downforce and reduce drag and turbulence.

The low pressure (higher speed) air under the car needs to exit, back to ambient pressure (and lower speed) and the diffuser controls this transition. Without it there would be a lot of turbulence or just a lessened benefit.

Part of what controls the exit of the air is the angle (side profile of increasing bodywork height) of the diffuser. If this is wrong (too steep or shallow) the diffuser won’t work well. As the rear of the car gets higher, dirty air can enter from the sides. This is what the vertical strakes or extensions do, they keep the air where it needs to be instead of being disturbed. Parallel or expanding strakes are just part of the design to make this more efficient.

All of these underbody aerodynamics become more effective as the car sits lower to the ground or has bodywork on the side that keeps the air in place under the car. So if your car is several inches from the ground and the diffuser strakes are higher up they aren't as effective. This is why the ACR has them as low to the ground as possible while attempting to maintain clearance for the street. Typically (generally speaking) the lowest ride height that can be achieved on a specific track surface for a specific car setup is ideal for aerodynamics.

The ACR is a good design, it has plastic strakes that can go lower to the ground instead of carbon. So these will be cheaper to replace. Also a track only car might utilize custom extensions that go even lower than OEM to increase the benefit.