ACR E Without Rear Wing

[One Viper Bite]

I like to play around with the idea of, if I manage to get back into a Gen V, that it would be awesome to install an ACR-E rear diffuser and maybe the front dive planes.

Came across this gorgeous shot of a Stryker Purple ACR-E with the rear wing removed. Apparently it has the heads and cam package from VE.

Don't know any more details but I think it looks awesome without the wing! Just needs the TA 1.0 rear spoiler and I think it would look wicked!

http://i580.photobucket.com/albums/ss249/brianjames624/12697281_10156553042160574_1845497799857609504_o.j pg (http://s580.photobucket.com/user/brianjames624/media/12697281_10156553042160574_1845497799857609504_o.j pg.html)

[BRACR]

Sorry Rexius....not a fan of this idea......ACR-E is the ticket for this stuff....looks add on with a stock car. Hope you get the car we discussed.

[NT-ACR]

I like it. Looks great!

[Special Ed]

I think itls a great idea. Buy a 150,000.00 ACR/E and turn it into a 100,000.00 SRT with a front splitter. Lets do this!

[Murpowa]

I think itls a great idea. Buy a 150,000.00 ACR/E and turn it into a 100,000.00 SRT with a front splitter. Lets do this!

Plus the hood, brakes, wheels, suspension and other tidbits but we get what you're saying...

[Bruce H.]

I think owners should do whatever they want to their cars if that's what they need to make them feel special, and they shouldn't worry about what anyone else thinks.

But having said that...it just feels wrong on many levels.

[Dman]

I completely get it. The wing is such a functional thing, the irony is, people will say that the wing is THE defining characteristic of the ACR, and yet 95% will never use its true function - and it is a singularly functional piece, not an aesthetic. I could see having an ACR and removing the wing for street driving or acceleration events, and installing it for track events. I'd make sure to not have the splitter extension on the front without the rear wing, I'd also adjust the rake and rebound/dampening for the lack of the few hundred pounds of downforce you'd have with it in street driving. Kind of a config for less than 100mph and one for the track. The ACR is the some of its parts, the air craft carrier wing is but just one single part.

Of course, if you weren't after the ACR in particular, you could do a TA group car and add the full set of canards, you'd get the look, but of course not all the other ACR bits or the wing when you want it. Modifying to your liking, is IMO what the car enthusiast hobby is all about.

[One Viper Bite]

I completely get it. The wing is such a functional thing, the irony is, people will say that the wing is THE defining characteristic of the ACR, and yet 95% will never use its true function - and it is a singularly functional piece, not an aesthetic. I could see having an ACR and removing the wing for street driving or acceleration events, and installing it for track events. I'd make sure to not have the splitter extension on the front without the rear wing, I'd also adjust the rake and rebound/dampening for the lack of the few hundred pounds of downforce you'd have with it in street driving. Kind of a config for less than 100mph and one for the track. The ACR is the some of its parts, the air craft carrier wing is but just one single part.

Of course, if you weren't after the ACR in particular, you could do a TA group car and add the full set of canards, you'd get the look, but of course not all the other ACR bits or the wing when you want it. Modifying to your liking, is IMO what the car enthusiast hobby is all about.

I don't think my original intention of this post was clear.

After much debate, I decided the ACR was too much track car for my needs. I want a car that I can cruise around LA in on a nice night and a car I can occasionally track, so, this leads me to a GTS spec car with TA 1.0 aero.

However, we all know the GTS can be a bit twitchy on track. I like the idea of adding the ACR rear diffuser to see if it helps stabilize it a bit more without having to resort to a giant rear wing on it. Plus, it looks cool. Many super cars like the 458 have integrated rear diffusers without giant rear wings on them. Doesn't sound out of this world to me if a non ACR had one too. I love the lines of the Viper without the giant front and rear wings, hood cutouts, etc.

Again, my intent is not to cut corners and buy a non ACR to then build one. My intent is to have a nice street car with slightly higher capabilities for the occasional track visit. The ACR diffuser and canards could be the middle ground. Would require testing, obviously. I hear Doug is currently working on a non-ACR rear diffuser application as we speak.

[BJG32]

This is the same basic look I have on my GTS, but I feel dive plans look unbalanced without a wing.

21663

[mjorgensen]

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[Bleed viper]

Rexius, this is currently what I am slowly doing. I have a GTS, and I never bought it with intentions of being a track king or being even with the ACR. I know that the "CAR" I have is faster than almost everything out there on the track and I just need to continue to work on the driver. That said, I'm doing a few upgrades that I wanted ever since I was shopping for my car. I passed on a car that was identical to mine that had the TA 1.0 aero on it but they wanted an additional 30K for it. So I bought mine with the intention of adding it myself or going aftermarket with Wayne. I've already added the TA sway bars and will upgrade to the Corsa Pirellis, add the rear TA 1.0 spoiler and the front splitters and call it a day. I'm on the fence too about the dive planes, I may just do the lower set or none at all. But at the end of the day I feel like I have the best of both worlds, because I know it's not a track God and I didn't buy it with the intent to be. Like others have said, just do what makes you happy!

[Dman]

I don't think my original intention of this post was clear.

After much debate, I decided the ACR was too much track car for my needs. I want a car that I can cruise around LA in on a nice night and a car I can occasionally track, so, this leads me to a GTS spec car with TA 1.0 aero.

However, we all know the GTS can be a bit twitchy on track. I like the idea of adding the ACR rear diffuser to see if it helps stabilize it a bit more without having to resort to a giant rear wing on it. Plus, it looks cool. Many super cars like the 458 have integrated rear diffusers without giant rear wings on them. Doesn't sound out of this world to me if a non ACR had one too. I love the lines of the Viper without the giant front and rear wings, hood cutouts, etc.

Again, my intent is not to cut corners and buy a non ACR to then build one. My intent is to have a nice street car with slightly higher capabilities for the occasional track visit. The ACR diffuser and canards could be the middle ground. Would require testing, obviously. I hear Doug is currently working on a non-ACR rear diffuser application as we speak.

Ahh, for track tuning, the most impact IMO would be to a move to VE suspension, &/or brake bias module, for better handling and dial out the threshold braking wiggle ... just my opinion on tracking a GTS a few time, it seemed to need these things to be solidly awesome. I don't thing the read diffuser is going to make much handling dynamic impact on a GTS. As for looks, it's too subjective, I'd think they would look cool, but maybe a smaller version on a GTS so as to not overwhelm the rear. If I had an ACR, I'd not even run the rear diffuser myself on the street, so it's really about what you like, pics also may not do it justice, for ex BJG's post on that pic, I think the pic looks good, but he says it's unbalanced in person, so may be not a good look, dunno.

[BJG32]

Ahh, for track tuning, the most impact IMO would be to a move to VE suspension, &/or brake bias module, for better handling and dial out the threshold braking wiggle ... just my opinion on tracking a GTS a few time, it seemed to need these things to be solidly awesome. I don't thing the read diffuser is going to make much handling dynamic impact on a GTS. As for looks, it's too subjective, I'd think they would look cool, but maybe a smaller version on a GTS so as to not overwhelm the rear. If I had an ACR, I'd not even run the rear diffuser myself on the street, so it's really about what you like, pics also may not do it justice, for ex BJG's post on that pic, I think the pic looks good, but he says it's unbalanced in person, so may be not a good look, dunno.

To clarify. The diffuser looks great with the fins on them in the rear with a TA 1.0 spoiler. I think dive planes on the front bumper look unbalanced without the an actual wing. Just my person preference.

[One Viper Bite]

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Cool, but not a fan of the squared fins. Any reason those are the way they are?

I'm more interested in the factory ACR look.

[One Viper Bite]

This is the same basic look I have on my GTS, but I feel dive plans look unbalanced without a wing.

21663

Yeah, I exactly what I am envisioning but I want the OEM diffuser for function and I like how the factory outer fins curve outward.

[One Viper Bite]

Ahh, for track tuning, the most impact IMO would be to a move to VE suspension, &/or brake bias module, for better handling and dial out the threshold braking wiggle ... just my opinion on tracking a GTS a few time, it seemed to need these things to be solidly awesome. I don't thing the read diffuser is going to make much handling dynamic impact on a GTS. As for looks, it's too subjective, I'd think they would look cool, but maybe a smaller version on a GTS so as to not overwhelm the rear. If I had an ACR, I'd not even run the rear diffuser myself on the street, so it's really about what you like, pics also may not do it justice, for ex BJG's post on that pic, I think the pic looks good, but he says it's unbalanced in person, so may be not a good look, dunno.

Agreed that the front dive planes might be a bit overkill. But I don't think the diffuser is.

And yeah not saying the diffuser would make a big difference but I'm still curious to see the effects of it on the cars behavior alone. I imagine it must add some kind of stability to the rear end. TA sways, reactive suspension and maybe the rear bias brake kit and in my head that would be one solid car on the track.

[mjorgensen]

Cool, but not a fan of the squared fins. Any reason those are the way they are?

I'm more interested in the factory ACR look.

Could possibly be done, but these are a more race oriented design, that's why he's doing it that way, longer channels.

[commandomatt]

I seems apparent that some people dont appreciate the work that was put into the aero on these cars to make it all come together. The different levels of aero, especially on the ACR, I am sure went through some serious testing to determine what would ultimately perform as intended and what would not. There was probably plenty of hours spent with wind tunnel work and actual on the road/track testing to make it all balance out

While this certainly wont matter much at normal and lower speeds, it's funny to me how people want to change, add, remove, enlarge and subsequently change the aero the way it was designed to work.

Take these 'home engineered' cars up to 100 mph ++ and you may quickly find out what was thought to look 'cool' at 50, may really screw up the way the car was intended to work. Much of it may not even be noticed but could adversely affect the tires, suspension and related parts.

While I definitely appreciate the custom aspect of modifying and personalizing cars, some of this may be better left alone.

[speedtactics]

What he said!

I completely get it. The wing is such a functional thing, the irony is, people will say that the wing is THE defining characteristic of the ACR, and yet 95% will never use its true function - and it is a singularly functional piece, not an aesthetic. I could see having an ACR and removing the wing for street driving or acceleration events, and installing it for track events. I'd make sure to not have the splitter extension on the front without the rear wing, I'd also adjust the rake and rebound/dampening for the lack of the few hundred pounds of downforce you'd have with it in street driving. Kind of a config for less than 100mph and one for the track. The ACR is the some of its parts, the air craft carrier wing is but just one single part.

Of course, if you weren't after the ACR in particular, you could do a TA group car and add the full set of canards, you'd get the look, but of course not all the other ACR bits or the wing when you want it. Modifying to your liking, is IMO what the car enthusiast hobby is all about.

[Dman]

Agreed that the front dive planes might be a bit overkill. But I don't think the diffuser is.

And yeah not saying the diffuser would make a big difference but I'm still curious to see the effects of it on the cars behavior alone. I imagine it must add some kind of stability to the rear end. TA sways, reactive suspension and maybe the rear bias brake kit and in my head that would be one solid car on the track.

Yeah, would indeed be a street cruiser and track crusher. Then power could be added if ever desired. It's an interesting plan. I struggle on this myself.

Right now, I'm waffling between a TA2.0 and an ACRE. I KNOW the TA is mentally a better choice, it'll ride better for all my street miles. Most of my track time is done racing, and not in a viper, so the Viper would see only 3-5 trackdays a year, and just for fun. The ACRE is kind of a sledgehammer on a tack for my use, vs the TA being the perfect fit, and then I have budget for customizing a bit. Too many options with the gen5, haha.

[One Viper Bite]

I seems apparent that some people dont appreciate the work that was put into the aero on these cars to make it all come together. The different levels of aero, especially on the ACR, I am sure went through some serious testing to determine what would ultimately perform as intended and what would not. There was probably plenty of hours spent with wind tunnel work and actual on the road/track testing to make it all balance out

While this certainly wont matter much at normal and lower speeds, it's funny to me how people want to change, add, remove, enlarge and subsequently change the aero the way it was designed to work.

Take these 'home engineered' cars up to 100 mph ++ and you may quickly find out what was thought to look 'cool' at 50, may really screw up the way the car was intended to work. Much of it may not even be noticed but could adversely affect the tires, suspension and related parts.

While I definitely appreciate the custom aspect of modifying and personalizing cars, some of this may be better left alone.

I get what you're saying, but again, I'm not talking about taking an ACR and removing the rear wing as the photo in this post suggests. Perhaps my title is misleading.

I'm talking about putting an ACR diffuser on a non ACR Viper. I don't really see any risks in doing so without the remaining ACR aero. The Viper already has significant rake from front to rear, meaning there is already a venturi effect happening at the rear of the vehicle. The issue is that the further the rear of the vehicle is from the ground or the larger the gap is between the car and the ground, the easier it is for the air to become disturbed as it exits and expands behind the car, unsettling it.

The ACR diffuser was likely put in place because the SRT engineers realized how much rake the rear of the Viper has and the exiting air was becoming disturbed. Adding the diffuses channels helps guide the airflow and prevent it from becoming disturbed. Even without the ACR's rear wing, the diffuser, in principal would still serve it's purpose as there is still higher pressure air flow above the car than there is underneath the car. The Viper's body was engineered to have natural downforce and high pressure airflow above the body. The ACR's front and rear wings simply add to that downforce significantly.

[ViperGeorge]

I seems apparent that some people dont appreciate the work that was put into the aero on these cars to make it all come together. The different levels of aero, especially on the ACR, I am sure went through some serious testing to determine what would ultimately perform as intended and what would not. There was probably plenty of hours spent with wind tunnel work and actual on the road/track testing to make it all balance out

While this certainly wont matter much at normal and lower speeds, it's funny to me how people want to change, add, remove, enlarge and subsequently change the aero the way it was designed to work.

Take these 'home engineered' cars up to 100 mph ++ and you may quickly find out what was thought to look 'cool' at 50, may really screw up the way the car was intended to work. Much of it may not even be noticed but could adversely affect the tires, suspension and related parts.

While I definitely appreciate the custom aspect of modifying and personalizing cars, some of this may be better left alone.

Agree, in fact development of the aero was one reason the ACR did not launch earlier. They launched the TA and TA 2 because their aero is not as sophisticated. An engineer friend who worked on the ACR say they did countless hours in the wind tunnel to tune the car. Any changes you make will have adverse effects. You probably would not notice them at lower speeds but on a very high speed track, be careful.

[Bill Pemberton]

George and Matt are correct. Just think for a minute about the massive amount of front downforce produced by the splitter and all the dive plains , with virtually nothing in the rear -----gotta be a riot with the nose planted into the pavement and the rear end starting to lift at 150mph. George hit it on the head --- SRT Engineers spent a ton of time in the windtunnel and a change could have very dramatic and drastically scary results!!

[bluesrt]

why don't you guys just buy the challenger drag pack car? be done with it, a ready to go drag car done right,

[One Viper Bite]

George and Matt are correct. Just think for a minute about the massive amount of front downforce produced by the splitter and all the dive plains , with virtually nothing in the rear -----gotta be a riot with the nose planted into the pavement and the rear end starting to lift at 150mph. George hit it on the head --- SRT Engineers spent a ton of time in the windtunnel and a change could have very dramatic and drastically scary results!!

Again, I can see the argument for the front dive planes and front splitter, but not the rear diffuser.

I think the rear diffuser would only improve overall downforce on the car without the front or rear wings of the ACR. The Gen V already has massive rake in the rear of the body, adding the channels for keep the airflow undisturbed will help decrease the pressure underneath the car, increasing downforce via the high pressure airflow over the top of the body.

[One Viper Bite]

why don't you guys just buy the challenger drag pack car? be done with it, a ready to go drag car done right,

I'm not interested in drag racing. Interested in road course racing.

I need a moderator to change the title of this thread. It is mis-leading.

I want to apply the ACR rear diffuser (and maybe the front dive planes) to a non ACR Viper. Not remove the rear wing from an ACR.

[Bill Pemberton]

Can only tell you that over the years talking to the main Engineers , two who are National Champion Racers , changing what came from hours and hours and hours of wind tunnel testing , thinking other items will work , will likely end up with a car that has surprisingly dangerous attitudes at speed. George put in his two cents and he knows the same guys, but as he noted , the process was delayed because it is very precise. Heck, the Woodhouse inspired ACR Convertible has it's own distinct rear wing , as the Aero Group one, and the larger ACR one , did not function properly in their wind tunnels. If that small change in a wing makes a difference , just think what taking it off could cause.

[Terminator02]

I don't think my original intention of this post was clear.

After much debate, I decided the ACR was too much track car for my needs. I want a car that I can cruise around LA in on a nice night and a car I can occasionally track, so, this leads me to a GTS spec car with TA 1.0 aero.

However, we all know the GTS can be a bit twitchy on track. I like the idea of adding the ACR rear diffuser to see if it helps stabilize it a bit more without having to resort to a giant rear wing on it. Plus, it looks cool. Many super cars like the 458 have integrated rear diffusers without giant rear wings on them. Doesn't sound out of this world to me if a non ACR had one too. I love the lines of the Viper without the giant front and rear wings, hood cutouts, etc.

Again, my intent is not to cut corners and buy a non ACR to then build one. My intent is to have a nice street car with slightly higher capabilities for the occasional track visit. The ACR diffuser and canards could be the middle ground. Would require testing, obviously. I hear Doug is currently working on a non-ACR rear diffuser application as we speak.

The middle ground wouldn't be the canards and diffuser. The middle ground without the wing is the tires. When they tested the TA around Laguna seca and got the 133.62 they immediately switched tires and ran a 130.xx. That makes up for a TON of time. The wing does a TON too. Adding the TA 1.0 wing would be for more aesthetic reasons but it still has some functionality with some downforce at speed. However I like the idea because it has heads and cam. But if you think an ACR with the heads and cam is a cruiser, I would probably disagree with you there. I have one and do cruise in it but it's more of an event. It's so different than stock...both have pros and cons for cruising but not nearly the experience you have had previously.

[Dman]

I'm not interested in drag racing. Interested in road course racing.

I need a moderator to change the title of this thread. It is mis-leading.

I want to apply the ACR rear diffuser (and maybe the front dive planes) to a non ACR Viper. Not remove the rear wing from an ACR.

LoLz

Yea. What you're really talking about, I think most would support and have some tips. I think it's throwing people off and getting focused on how SRT knows best and detracting from the ACR etc. You're looking to make a GTS or like model better at the track while keeping aesthetics in mind, very normal and reasonable goal and several good ways to get there, and it doesn't undo the design of the viper program, lol.

[donk_316]

What you want is a TA with an ACR rear diffuser. Easily done as soon as Doug releases his "retrofit kit"

Agree the wing is gaudy

[One Viper Bite]

LoLz

Yea. What you're really talking about, I think most would support and have some tips. I think it's throwing people off and getting focused on how SRT knows best and detracting from the ACR etc. You're looking to make a GTS or like model better at the track while keeping aesthetics in mind, very normal and reasonable goal and several good ways to get there, and it doesn't undo the design of the viper program, lol.

LOL thank you!


What you want is a TA with an ACR rear diffuser. Easily done as soon as Doug releases his "retrofit kit"

Agree the wing is gaudy

Bingo, Donk.

Again, I really don't think adding the rear diffuser to a TA or GTS poses ANY danger at all without the ACR rear wing or the front splitter. Again, just basing that assumption off of physics.

Why would stabilizing the air exiting the rear of the already dramatically raked rear end of the Viper pose any threat at all?

I agree that removing the rear wing of an ACR while keeping the front splitter and diver planes on is dangerous.

[Mopar'er no car]

I'm not interested in drag racing. Interested in road course racing.

I need a moderator to change the title of this thread. It is mis-leading.

I want to apply the ACR rear diffuser (and maybe the front dive planes) to a non ACR Viper. Not remove the rear wing from an ACR.

I'd be watching your back and make sure there isn't a contract out on your head. One of the posters in this thread will be at you house tonight to make sure the tags are on your mattresses.

[VenomSnake]

This is the same basic look I have on my GTS, but I feel dive plans look unbalanced without a wing.

21663

I love the look of the rear of your car. What diffuser is that? Looks great!

[BRACR]

I agree with Pemberton...........bad things are going to happen at speed with that setup.....looks like a half baked ACR. Lots of downforce on the front and not enough on the back....

[LABrit]

I do agree with Bill on this.

Body kits on cars that haven't been extensively wind tested...puts you in the same category as a ricer.

[SilveRT8]

This thread got me thinking, how much downforce would an ACR E have with added TA 1.0 rear spoiler ?
Would look killer !

[BlueAdder]

LOL thank you!

I agree that removing the rear wing of an ACR while keeping the front splitter and diver planes on is dangerous.

If you install the ACR diffuser and dive planes, at least you should install the TA spoiler, not the TA 2.0 wing (that would defeat your purpose).
My concern is that the dive planes (AKA canards) plus the splitter up front will generate quite a bit of down force at speed, while the diffuser may not counteract that. So, in fast turns, you may end up like the first Audi TT did and spin out because of lack of down force on the rear.

I like the idea of the adding the diffuser/dive planes and ACR-E splitter since they are really awesome looking. As I said, I think the small TA spoiler in the back would help with stability but I'm not an aero engineer so your guess is as good as mine :D

[The_Ruski_Driver]

Thread is so derailed.. wow...
All I gotta say is I am waiting for them (whoever them is) to come out with a ACR rear diffuser because those ebay fins people buy just don't look right to me. Hopefully they have something to bolt to the front to match. I like my 9 year warranty but I love modding. I'm left with aesthetics so be it lol

[One Viper Bite]

If you install the ACR diffuser and dive planes, at least you should install the TA spoiler, not the TA 2.0 wing (that would defeat your purpose).
My concern is that the dive planes (AKA canards) plus the splitter up front will generate quite a bit of down force at speed, while the diffuser may not counteract that. So, in fast turns, you may end up like the first Audi TT did and spin out because of lack of down force on the rear.

I like the idea of the adding the diffuser/dive planes and ACR-E splitter since they are really awesome looking. As I said, I think the small TA spoiler in the back would help with stability but I'm not an aero engineer so your guess is as good as mine :D

The car I have spec'd out has the TA 1.0 aero. You're right, TA 2.0 would defeat the purpose of not wanting a wing on the back. I've also reverted my decision to do the front dive planes. I only want the ACR diffuser.


Thread is so derailed.. wow...
All I gotta say is I am waiting for them (whoever them is) to come out with a ACR rear diffuser because those ebay fins people buy just don't look right to me. Hopefully they have something to bolt to the front to match. I like my 9 year warranty but I love modding. I'm left with aesthetics so be it lol


LOL seriously. Probably my fault with the mis-leading title, but I've clarified my intentions at least 3 times now.

I'm with you, I don't want the bolt on plastic fins sold on eBay. I want the OEM, functional ACR diffuser as I truly believe it poses no danger to the cars stability without the remaining ACR aero bits. I think it will actually improve stability in the rear slightly.

[Bruce H.]

I think the rear diffuser would only improve overall downforce on the car without the front or rear wings of the ACR. The Gen V already has massive rake in the rear of the body, adding the channels for keep the airflow undisturbed will help decrease the pressure underneath the car, increasing downforce via the high pressure airflow over the top of the body.

Just a question for anyone regarding the actual function of the rear diffuser...

Is it not more to reduce drag by helping air under the car detach more smoothly, and to provide high speed stability with the strakes acting to help prevent the rear from stepping out?

I would have thought the flat bottom on the car, including the rear, was to reduce drag in an effort to reduce lift, but does the diffuser also actually provide significant downforce at the rear?

[One Viper Bite]

Just a question for anyone regarding the actual function of the rear diffuser...

Is it not more to reduce drag by helping air under the car detach more smoothly, and to provide high speed stability with the strakes acting to help prevent the rear from stepping out?

I would have thought the flat bottom on the car, including the rear, was to reduce drag in an effort to reduce lift, but does the diffuser also actually provide significant downforce at the rear?

Just going off of what I know about aero (I'm a private pilot and currently study aerospace engineering)...You're right, a flat bottom that is low to the ground causes the air flow underneath the car to increase. Bernoullie's Principle states that as the velocity of air increases, the pressure decreases. This creates a pressure differential as the air flowing above the car is moving slower and is higher pressure. So, the car is essentially sucked into the ground. This is how airplanes fly, but the other way around. The wings on an airplane create low pressure above the wing and high pressure below the wing, causing the wing to get sucked upwards.

The problem is, the Gen V has a significant "rake" or slant angle at the rear end. The further away the bottom of the car becomes from the ground, the more tendency for the low pressure, fast moving air to become turbulent as it expands into a larger area and other forces such as wind from the wheels / sides of the car collide with the exiting air which actually CREATES drag at the rear of the car. This is likely why SRT Engineers decided to add it to the ACR, because it would only increase the benefits of the downforce from the rear wing. Remember, it's an upside-down wing, so it creates low pressure underneath it and high pressure above it. Couple that with an even lower pressure underneath the car and you have even more downforce with less of a chance of getting disturbed thanks the the channels in the diffuser.

The purpose of a diffuser is to guide and shield this low pressure, fast moving air along the ground and out the back of the vehicle without becoming turbulent or changing direction dramatically. This is why many supercars have them integrated without having massive rear wings or front spoilers. It can only help.

Hope that makes sense and curious to hear anyone else's understanding. Again, this is just my understanding based off of my studies in both getting a fixed wind license and current studies in engineering.

[Arizona Vipers]

Just going off of what I know about aero (I'm a private pilot and currently study aerospace engineering)...You're right, a flat bottom that is low to the ground causes the air flow underneath the car to increase. Bernoullie's Principle states that as the velocity of air increases, the pressure decreases. This creates a pressure differential as the air flowing above the car is moving slower and is higher pressure. So, the car is essentially sucked into the ground. This is how airplanes fly, but the other way around. The wings on an airplane create low pressure above the wing and high pressure below the wing, causing the wing to get sucked upwards.

The problem is, the Gen V has a significant "rake" or slant angle at the rear end. The further away the bottom of the car becomes from the ground, the more tendency for the low pressure, fast moving air to become turbulent as it expands into a larger area and other forces such as wind from the wheels / sides of the car collide with the exiting air which actually CREATES drag at the rear of the car. This is likely why SRT Engineers decided to add it to the ACR, because it would only increase the benefits of the downforce from the rear wing. Remember, it's an upside-down wing, so it creates low pressure underneath it and high pressure above it. Couple that with an even lower pressure underneath the car and you have even more downforce with less of a chance of getting disturbed thanks the the channels in the diffuser.

The purpose of a diffuser is to guide and shield this low pressure, fast moving air along the ground and out the back of the vehicle without becoming turbulent or changing direction dramatically. This is why many supercars have them integrated without having massive rear wings or front spoilers. It can only help.

Hope that makes sense and curious to hear anyone else's understanding. Again, this is just my understanding based off of my studies in both getting a fixed wind license and current studies in engineering.

Wow, great post!

[Bruce H.]

Great explanation and background to stimulate your interest and help guide your decisions! I did some research into aero mods years ago for a car I tracked, and perhaps you'd be interested in continuing the discussion about aero a bit more.

I could be wrong, and quite likely am, but for some reason I was under the impression that a diffuser's purpose was generally what you said, but even more related to the expansion of air required with increasingly more effective airdam/splitter, as with the ACR's extended splitter, and with venturi and tunnel effects on cars so designed.

Is a diffuser also somehow needed to work in conjunction with a high mount rear wing's effect of detaching the airflow from following a fastback design's rear hatch where it causes significant lift? Mid-engine supercars are generally of the "3 box" aero design that avoids the lift of a fastback design, and where a high mount wing is perhaps slightly less important for that reason.

It seems to make sense that a rear diffuser would benefit any and every car at high speed if it helps to reduce drag under the rear of the car, and reduce drag behind the car if it aids blending that air with the air coming over the top of the car. That just sounds like it would reduce the coefficient of drag more than reduce rear lift enough to necessitate any or much added downforce at the front from canards or larger splitter.

How would you test the impact on high speed handling of adding a rear diffuser? I knew I needed to reduce front end lift on that other track car when the steering got light at high speeds, and knew I had addressed it with a front airdam and splitter when it no longer got light. In my case I also added rear aero at the same time and never experienced the effect of the front aero by itself, or to see if it had any negative impacts on other aspects of handling.

I like the idea of reducing drag...and as the newer competition gets better there's a few of us that just might look for that improvement as well!




The purpose of a diffuser is to guide and shield this low pressure, fast moving air along the ground and out the back of the vehicle without becoming turbulent or changing direction dramatically. This is why many supercars have them integrated without having massive rear wings or front spoilers. It can only help.

[SharpMan]

Need computer controlled active rear wing. Flattens in the straights and pitches under braking and for the corners.

[Boosted Motorsports]

But if you remove it you can't go camping anymore!!! :D

http://st.automobilemag.com/uploads/sites/11/2016/04/Hot-Rod-Dodge-Viper-ACR-stars.jpg

[Arizona Vipers]

21664
21665

Hey Mark, is that diffuser setup for sale now?

[mjorgensen]

Hey Mark, is that diffuser setup for sale now?

These are just the extensions, you have to already have the ACR just to be clear. I have yet to start selling them, still working out pricing, they are currently close to 2X the cost of the factory parts and I'm trying to find a way to close that gap. They are different though and should be pretty effective so maybe worth it.

[Arizona Vipers]

These are just the extensions, you have to already have the ACR just to be clear. I have yet to start selling them, still working out pricing, they are currently close to 2X the cost of the factory parts and I'm trying to find a way to close that gap. They are different though and should be pretty effective so maybe worth it.

ahhh, the pic was cutoff so I couldn't see that it was an ACR lol

[One Viper Bite]

Great explanation and background to stimulate your interest and help guide your decisions! I did some research into aero mods years ago for a car I tracked, and perhaps you'd be interested in continuing the discussion about aero a bit more.

I could be wrong, and quite likely am, but for some reason I was under the impression that a diffuser's purpose was generally what you said, but even more related to the expansion of air required with increasingly more effective airdam/splitter, as with the ACR's extended splitter, and with venturi and tunnel effects on cars so designed.

Is a diffuser also somehow needed to work in conjunction with a high mount rear wing's effect of detaching the airflow from following a fastback design's rear hatch where it causes significant lift? Mid-engine supercars are generally of the "3 box" aero design that avoids the lift of a fastback design, and where a high mount wing is perhaps slightly less important for that reason.

It seems to make sense that a rear diffuser would benefit any and every car at high speed if it helps to reduce drag under the rear of the car, and reduce drag behind the car if it aids blending that air with the air coming over the top of the car. That just sounds like it would reduce the coefficient of drag more than reduce rear lift enough to necessitate any or much added downforce at the front from canards or larger splitter.

How would you test the impact on high speed handling of adding a rear diffuser? I knew I needed to reduce front end lift on that other track car when the steering got light at high speeds, and knew I had addressed it with a front airdam and splitter when it no longer got light. In my case I also added rear aero at the same time and never experienced the effect of the front aero by itself, or to see if it had any negative impacts on other aspects of handling.

I like the idea of reducing drag...and as the newer competition gets better there's a few of us that just might look for that improvement as well!

Glad my explanation helped!

I think you are correct as well, though in respect to the front splitter and the large rear wing. The front splitter certainly increases the airflow and velocity underneath the car, adding to the venturi effect and the large rear wing adds to the disruption of airflow at the rear of the car, creating significantly more drag.

In terms of testing, I'm sure taking the car to a race track with high speed corners (like COTA) and running some tests with and without the diffuser could easily determine if the diffuser adds to cornering speed on it's own. Maybe if I get my 1 of 1 and can retrofit a diffuser to it I could be the one to spear-head a test like this. Could make for an awesome project for school.

Again, I don't see any risk in adding the diffuser on its own. Can't imagine it would upset the balance of the car in any way.

[Bruce H.]

^ Thanks, and good luck with getting another Viper to try out your ideas on!

[CHAP]

the Woodhouse inspired ACR Convertible has it's own distinct rear wing , as the Aero Group one, and the larger ACR one , did not function properly in their wind tunnels. If that small change in a wing makes a difference , just think what taking it off could cause.

Bill, can you tell me more about this ?
I was thinking about putting the front ACR canard on my 2009 convertible with aero groupe .
Do you sell the larger wing ?
If you do , how much for the wing ?

Thanks

[Bill Pemberton]

You can chat with Mark Jorgensen, but the ACR Convertible is likely almost unobtainium and if located , quite pricey. You could pick up an Aero Group easier , along with some other options. Mark's email is Mark.Jorgensen@woodhouse.com and his toll free is the same as mine, but he is on a well deserved vacation this week.

[FLATOUT]

I agree with Pemberton...........bad things are going to happen at speed with that setup.....looks like a half baked ACR. Lots of downforce on the front and not enough on the back....

Also agree 100%. Customer rolled in off the street like that, we had NOTHING to do with it. I literally ran over to him in the staging lanes at the Viper Nats and tried to get him to either put the wing back on or at least remove the front splitters TRACK extension!

Looked at me like I was nuts. Rolled up clicked off a 10.4@136.5 and that was that. Is what it is I guess.

[Stealth78]

Just going off of what I know about aero (I'm a private pilot and currently study aerospace engineering)...You're right, a flat bottom that is low to the ground causes the air flow underneath the car to increase. Bernoullie's Principle states that as the velocity of air increases, the pressure decreases. This creates a pressure differential as the air flowing above the car is moving slower and is higher pressure. So, the car is essentially sucked into the ground. This is how airplanes fly, but the other way around. The wings on an airplane create low pressure above the wing and high pressure below the wing, causing the wing to get sucked upwards.

The problem is, the Gen V has a significant "rake" or slant angle at the rear end. The further away the bottom of the car becomes from the ground, the more tendency for the low pressure, fast moving air to become turbulent as it expands into a larger area and other forces such as wind from the wheels / sides of the car collide with the exiting air which actually CREATES drag at the rear of the car. This is likely why SRT Engineers decided to add it to the ACR, because it would only increase the benefits of the downforce from the rear wing. Remember, it's an upside-down wing, so it creates low pressure underneath it and high pressure above it. Couple that with an even lower pressure underneath the car and you have even more downforce with less of a chance of getting disturbed thanks the the channels in the diffuser.

The purpose of a diffuser is to guide and shield this low pressure, fast moving air along the ground and out the back of the vehicle without becoming turbulent or changing direction dramatically. This is why many supercars have them integrated without having massive rear wings or front spoilers. It can only help.

Hope that makes sense and curious to hear anyone else's understanding. Again, this is just my understanding based off of my studies in both getting a fixed wind license and current studies in engineering.

I realize this is an older thread but your post is awesome. What baffles me a bit is that I believe all Vipers ACR or not have the diffuser's​. Although by your explanation confirms some of my suspicions and adds some knowledge too. I thought the diffusers under my GenIV were more for high speed cornering while directing airflow but after reading this it also aids in downforce. Correct?

[bluesrt]

the viper isn't a drag car anywho, go get a dragpack challenger that is already from dodge to dragrace

[Stealth78]

I realize this is an older thread but your post is awesome. What baffles me a bit is that I believe all Vipers ACR or not have the diffuser's​. Although by your explanation confirms some of my suspicions and adds some knowledge too. I thought the diffusers under my GenIV were more for high speed cornering while directing airflow but after reading this it also aids in downforce. Correct?

To correct my post, I meant to say "all GenIV Vipers"!

[One Viper Bite]

I realize this is an older thread but your post is awesome. What baffles me a bit is that I believe all Vipers ACR or not have the diffuser's​. Although by your explanation confirms some of my suspicions and adds some knowledge too. I thought the diffusers under my GenIV were more for high speed cornering while directing airflow but after reading this it also aids in downforce. Correct?

Glad I was able to offer some insight. And correct!

If I find myself in another Gen V, retrofitting an ACR diffuser is going to be my project. As I stated above, I see no reason why it would hurt...it can only help.