Grant
Viper Owner
This thing has got some strange fasteners on it. Can anyone give me some hints on what tools to use to remove them? Or do they need to be drilled out and replaced with something different?
Thanks!
Thanks!
ACR wing adjustment?
- Thread starter Grant
- Start date
mjorgensen Woodhouse
Enthusiast
You need a tamper proof 4mm allen wrench. You should be able to get one at a Harbor Freight or hardware store. Maybe even Sears?
Paul Hawker
Enthusiast
Be very careful with wing adjustments.
SRT has commented that the wing, while adjustable, has been sealed into its factory recommended position. Changing the wing might even affect warranty issues. It is balanced with the front downforce, and changing it will upset the carefully calculated and measured downforce. It has tamper proof fittings for a reason.
SRT has commented that the wing, while adjustable, has been sealed into its factory recommended position. Changing the wing might even affect warranty issues. It is balanced with the front downforce, and changing it will upset the carefully calculated and measured downforce. It has tamper proof fittings for a reason.
WHAT PAUL SAID !!
Before meddling, be certain to read every word of SRT's Matt Bejnarowicz Summer 08 article in Viper Magazine, and SRT's Mike Shindelings "Wings and Things" in Winter 08 Issue.
I have been tracking my Vipers since 1993, and instructing even longer. Matt Bejnarowicz' piece [Summer 08] on Viper suspension and aero setup should be declared a MUST READ for anyone who plans to track their any-year Viper, and certainly anyone who purchases an '08 ACR. Matt provides a lot of track savvy BEYOND his own years into an easy-reading, well illustrated, easy to grasp primer on Viper track-prep. It could simply save your hardware, if not your life.
Lee00blacksilverGTS
Enthusiast
AND, if you strip the threads in the holding mechanism (imagine an internal moly you can't see that the fasteners go into) you will be buying a new wing as it CANNOT be repaired, you really don't want to know what that would cost, OR how long you would wait for it.
j-rho
Enthusiast
C'mon guys, you're adjusting a wing, not opening the Ark of the Covenant. Tilted down = more drag and rear grip at speed, tilted up = the opposite. If you think you can even tell a difference between the two extremes of adjustment at highway-legal speeds, you're fooling yourself. For the track, there is no one optimal position, as every track is different and lots of other variables affect where you might want it. Don't be afraid to make adjustments to this, or anything else, to gain a better understanding of how it all works.
And when you are experimenting with a full-down angle, (assuming you dont bugger the hardware as Lee warns) and you did NOTHING to increase front downforce...and you try to corner a highway sweeper at 70+ mph wet on the interstate or deserted country highway, as your car fails to turn, preferring to go straight...
You will then LIFT (or worse, BRAKE) in panic, hooking up the front tires again, as the rear then gets light due to your deceleraton....and THEN the car will go sideways..... You can then remember the various advice in this thread......
Seriously.............Be sure to read the warrantee warnings..........you have enuf downforce at OE settings for street use and most dry track days. You should probably adjust your SUSPENSION before you start monkeying with the Aero.....
Grant
Viper Owner
Thanks Mark.
Jon, unfortunately I haven't been able to get back-issues of the Viper magazine featuring ACR setup information. I'm a new VCA member and those issues appear to be sold out. I have read many other pieces of literature on more generic race car aerodynamics, such as Katz's and the Millikens' books.
Jon, unfortunately I haven't been able to get back-issues of the Viper magazine featuring ACR setup information. I'm a new VCA member and those issues appear to be sold out. I have read many other pieces of literature on more generic race car aerodynamics, such as Katz's and the Millikens' books.
Y2K10 SRT#39
Enthusiast
Perhaps if we asked Viper Magazine to put those two articles up in the "Illustrated Upgrades" area of this forum, they might actually do it for us!
I'll send a note to Mark Giannota to see if he can!
PBR
I'll send a note to Mark Giannota to see if he can!
PBR
Cop Magnet
Enthusiast
Oh, you are wrong, for what I have seen is that the ACR IS, in fact, the Ark of the Covenant...
+1, yes please
j-rho
Enthusiast
Jon, the magnitude of forces the ACR wing produces at 70-75mph are not capable of producing the effect you describe. You'd be hard pressed to produce that situation were you contrasting a car with a new ACR wing at full tilt vs. no wing at all, much less two different positions of the same wing. Not to mention, the ACR already has those front dive planes and a centerless splitter on all the time anyway.
I think in general people overstate the effect these aero devices have on the car at street speeds. Remember that their effectiveness increases as the square of your speed, so at 70mph, you are getting less than 1/4 the effect you do at 150. Even at the track, you get to feel how they gradually work more and more as your own speed increases. The notion of surprise or "suddenness" doesn't really apply to aero devices, except when they fall off.
If the ACR wing had a significant up-angle in its range of adjustment, that could get a little dodgy if used, I would hope they lock it into an angle of attack range between ~0 and -15.
In any case, certainly, people should read their warranty information, owners' manuals, and any other literature they need to gain some idea of what they're doing, before embarking on any changes.
So THATS why SPELLCHECK is always trying to make ARC out of ACR !!!
T
toofast
Guest
Grant, I have a security 4mm if you need it. Would love to see the car also
-David
-David
Grant
Viper Owner
There are 7 wing positions (1 being the least AoA, 7 being the greatest). Each increment increases the AoA by 1.5 degrees. The wing comes in position 2, so you really only have one adjustment point that can cause more oversteer.
I'd planned on setting the wing to position 7 for a local low-speed miniature road course. I'm uncertain how to adjust the splitter to compensate, or if it will even be possible. I'm guessing the best that can be done is to lower it until the rub strip scrapes under braking.
SoCal Rebell
Enthusiast
Mark I adjusted the rear wing on the ACR and it was not a Allen/Hex wrench head, it was 5 sided. I had to improvise with a "star" driver (which worked).
.
jamie furman
Enthusiast
Heard that !
Lee00blacksilverGTS
Enthusiast
Jon, the magnitude of forces the ACR wing produces at 70-75mph are not capable of producing the effect you describe. You'd be hard pressed to produce that situation were you contrasting a car with a new ACR wing at full tilt vs. no wing at all, much less two different positions of the same wing. Not to mention, the ACR already has those front dive planes and a centerless splitter on all the time anyway.
I think in general people overstate the effect these aero devices have on the car at street speeds. Remember that their effectiveness increases as the square of your speed, so at 70mph, you are getting less than 1/4 the effect you do at 150. Even at the track, you get to feel how they gradually work more and more as your own speed increases. The notion of surprise or "suddenness" doesn't really apply to aero devices, except when they fall off.
If the ACR wing had a significant up-angle in its range of adjustment, that could get a little dodgy if used, I would hope they lock it into an angle of attack range between ~0 and -15.
In any case, certainly, people should read their warranty information, owners' manuals, and any other literature they need to gain some idea of what they're doing, before embarking on any changes.
The warning in the ACR manual says changes can be significantly affected above 50mph. Before you mess with the thing why don't you stop over to the Grail Keeper forum and ask Herb Helbig. Maybe it's possible the SRT guys know more about this than you? I own one too and after talking to them at VOI I would not touch that thing. And I saw the stripped out ones at Prefix, to give you an idea of the price of this stuff, the RUB strip on the front, not the splitter itself, just the one inch wide rub strip is well over $1000, what do you think the wing costs if you strip the inner sleeves where the screws go?
Lee00blacksilverGTS
Enthusiast
For those that wanted a peek at the ACR manual here you go....full sections on adjustment of everything. I'm going to see if I can park it in the illustrated upgrades forum also.
http://www.kansascityvca.com/ACR_Owners_Manual.pdf
http://www.kansascityvca.com/ACR_Owners_Manual.pdf
j-rho
Enthusiast
What would I ask Herb? Anything printed in the manual has gone through the same lawyer filters that gave us warning stickers to put children in the back seat. Nothing magical happens at 50mph.
FWIW, I have studied aerodynamics for years, and built from scratch several of my own wings - from the simple single element pieces, to 2 or 3 element wings, one was movable from inside the cockpit. My wings have had extensive CFD time and been in wind tunnels; I've been playing with this stuff long enough to be speaking from experience.
"Because you might strip the fastener" is a completely different problem than "because if you adjust it a couple degrees you'll careen off the next corner". I don't have anything to say about the former, only the latter.
mcar00
Viper Owner
That would be awesome as I too have contacted Viper Magazine about trying to get those issues with no luck.
No one suggested "because if you adjust it a couple degrees you'll careen off the next corner" as you mis-quoted.
I, for one, DO suggest that 'Don't be afraid to make adjustments to this, or anything else,' is a BAD suggestion, (and an accurate quote). The owners manual references this, and so to SRT engineers. (And its why you may NOT see these parts anytime soon as accessories!)
I stated that a full-tilt adjustment, then driven WET even at hiway speeds would be the extreme issue, and a therefore could be a bad mistake for a novice experimenter taking ill-conceived advice.... I also stated to tackle SUSPENSION first.
WHATEVER IS CHOSEN..........keep a small logbook of changes, before-after, and the results. This so you can easily correct mis-steps.
I, for one, DO suggest that 'Don't be afraid to make adjustments to this, or anything else,' is a BAD suggestion, (and an accurate quote). The owners manual references this, and so to SRT engineers. (And its why you may NOT see these parts anytime soon as accessories!)
I stated that a full-tilt adjustment, then driven WET even at hiway speeds would be the extreme issue, and a therefore could be a bad mistake for a novice experimenter taking ill-conceived advice.... I also stated to tackle SUSPENSION first.
WHATEVER IS CHOSEN..........keep a small logbook of changes, before-after, and the results. This so you can easily correct mis-steps.
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As a precaution I actually asked ViperMag permission back on July 1 ! I am happy to make copies of the 7-page illustrated guide, and give them free to customers who drop me an email.
mcar00
Viper Owner
j-rho
Enthusiast
A wing capable of contributing 70% (you generally want more on the rear so you can feed in more power) of the ACR's stated 1000lbs. @150mph would produce around 150lbs. @ 70mph at the same setting. Since the 1000lb. figure is likely with the front splitter extension in and the wing at max AoA, the wing as delivered 5 clicks flatter (7.5 degrees flatter) would produce about 50lbs. less downforce. Put differently, adjusting the wing from the as-delivered 2/7 clicks to max tilt will produce approximately 50lbs. of additional rear downforce at 70mph.
The rear wing works on the car at a place about 18" behind the rear axle centerline. With a 96" wheelbase, the lever arm lifting the front tires is disadvantaged by 5.3:1. The 50 lbs. additional downforce produces about nine and a half pounds of lift to the front axle.
A 3400+lb. ACR with driver tips the scales around 3600lbs, with a little under 50% on the front, the front tires have 1780lbs static load. The 9.5lb. load reduction from our wing change constitutes a reduction in load of one half of one percent to the front tires.
Disregarding the bad-idea-ness of performing testing of any sort (especially aerodynamic!) on a public road of any type, the inference that a .005% reduction of static front load would make the car "fail to turn" is a fallacy, regardless of surface conditions. If anything, I would wager that in the majority of Viper-wrecking accidents, grip is lost at the rear first through an itchy throttle foot, a situation where any additional rear grip is going to help.
I stand by my statement that people should not be afraid to make adjustments to their car, but I'll add what should have been common sense - that the place to experience these changes is the TRACK or AUTOCROSS where you can gradually work up to, explore, and understand, the different limits of the car in the wake of your change. The street is NOT the place for this, and you should never be anywhere approaching the limits of any car, much less something with as stratospheric limits as the ACR, on the street. And of course, if you don't care to understand all the causes/effects of the different adjustments, or don't feel qualified with your hand on a wrench, you are best off following a generally prescribed setup, and having that setup performed by a qualified professional.
The rear wing works on the car at a place about 18" behind the rear axle centerline. With a 96" wheelbase, the lever arm lifting the front tires is disadvantaged by 5.3:1. The 50 lbs. additional downforce produces about nine and a half pounds of lift to the front axle.
A 3400+lb. ACR with driver tips the scales around 3600lbs, with a little under 50% on the front, the front tires have 1780lbs static load. The 9.5lb. load reduction from our wing change constitutes a reduction in load of one half of one percent to the front tires.
Disregarding the bad-idea-ness of performing testing of any sort (especially aerodynamic!) on a public road of any type, the inference that a .005% reduction of static front load would make the car "fail to turn" is a fallacy, regardless of surface conditions. If anything, I would wager that in the majority of Viper-wrecking accidents, grip is lost at the rear first through an itchy throttle foot, a situation where any additional rear grip is going to help.
I stand by my statement that people should not be afraid to make adjustments to their car, but I'll add what should have been common sense - that the place to experience these changes is the TRACK or AUTOCROSS where you can gradually work up to, explore, and understand, the different limits of the car in the wake of your change. The street is NOT the place for this, and you should never be anywhere approaching the limits of any car, much less something with as stratospheric limits as the ACR, on the street. And of course, if you don't care to understand all the causes/effects of the different adjustments, or don't feel qualified with your hand on a wrench, you are best off following a generally prescribed setup, and having that setup performed by a qualified professional.
Thats the best advice in a nutshell...............
I could also tell you some true stories on Wing-Equipped Vipers that resulted in scares and near-wrecks due to improper aero-balance by 'cheapskates' who would not buy the full package....
Quote:
Originally Posted by JonB - PartsRack
As a precaution I actually asked ViperMag permission back on July 1 ! I am happy to make copies of the 7-page illustrated guide, and give them free to customers who drop me an email.
Mike, the article is re-printed with permission, and in the mail. (Now, you HAVE to become a customer!)
Originally Posted by JonB - PartsRack
As a precaution I actually asked ViperMag permission back on July 1 ! I am happy to make copies of the 7-page illustrated guide, and give them free to customers who drop me an email.
Mike, the article is re-printed with permission, and in the mail. (Now, you HAVE to become a customer!)
Grant
Viper Owner
I'm not going to argue that the OE wing is going to significantly unload the front tires, but you are forgetting the torque arm created by drag (which I'm sure is pretty negligible).
Can anyone recommend some fasteners to replace the OE pieces? I'd prefer something that, if it loosened up, could not fall out of the wing and cause catastrophic failure. I'm guessing some sort of c-clip would work well here; I'm not sure what is generally used in this situation.
Anyone adjusting the wing should also take note of the thread locker, and probably apply some blue loctite each time the fasteners are tightened.
mcar00
Viper Owner
Quote:
Originally Posted by JonB - PartsRack
As a precaution I actually asked ViperMag permission back on July 1 ! I am happy to make copies of the 7-page illustrated guide, and give them free to customers who drop me an email.
Mike, the article is re-printed with permission, and in the mail. (Now, you HAVE to become a customer!)
Thanks Jon. Much appreciated by a future customer.
j-rho
Enthusiast
I didn't forget it, just figured we didn't want to get into stuff in the fourth position right of the decimal point.
There are plenty of second-order factors we could take into account (loss of front DF through rake change for instance) but if the largest factor is insignificant, so shall be the smaller things.
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