ACR Top Speed?

[johnk]

What's the scoop with this vid? Only 173MPH in the salt? Is the slow speed just a function of the soft salt, huge tires and big downforce, or is that a representative top speed for an ACR?


YouTube - 2008 Dodge Viper ACR: From L.A. to Bonneville

 

[Fast Viper]

I heard the word slippery, I would be afraid of taking it on a slippery surface, maybe the driver backed off the pedal?

 

[rcl4668]

Various magazines have tested the top speed of the ACR at about 177-180 mph. The reason for the lower top speed compared to the coupe and roadster (202 mph) is the aero components on the ACR which create fantastic downforce; the downside is increased drag.

/Rich

 

[Camfab]

The car is not designed for high speed runs. It's a track car, and all that downforce plays against top speed runs. Seems to me, this is probably why you have'nt heard any official "Ring" numbers either. That track has monster long straights that would seem to play against the ACR's limited top end capabilities.

 

[mjorgensen Woodhouse]

They could always make adjustments to wing angles and rake in the chassis to increase the top and sacrifice the down force. Bet you would see high 190's with that alone.

 

[Brad04Mamba]

Top speed per SRT engineers is 181 compared to 202 for the Coupe

 

[Andrew/USPWR]

The ACR has 1000 lbs of down force at 150mph.
The z06 has negative -256lbs at 150mph to get a higher top end. Smart or Dumb?

 

[Grant]

At first, I was confused by the ACR's stated top speed of 177 to 180. According to the data given by SRT, I'd guesstimated it would be around 188.

However, when you look at '08 dyno runs and the gearing in 5th, you see that the car isn't putting down a lot of power at 180 mph due to the low RPM. I think with a bit more power to push into the higher RPM ranges, the ACR could see a significantly higher top speed.

I'd really like to see some wind tunnel data from SRT, though. I wonder what removing the front splitter, reducing the angle of attack of the wing and maybe adjusting rake would do? I'm sure they've played with all that stuff. I don't have my car yet, but it would be nice to have a variety of aero-balanced setups to choose from ranging from low to high downforce.

 

[Paul Hawker]

Believe the salt flats are about 4,000 ft. elevation. That may be most of the reason for the lower top speed.

 

[Viper X]

Pull the wing, take the center section out of the splitter and it would do much, much better in a straight line, similar to the coupe. These are very simple things to do for a top speed run.

This is a track car, set up for going very fast around corners / turns. It's not a top speed car. Without huge power, you can't have both good top speed and speed in corners / turns.

 

[doctorbob]

Here is my philosophy on this topic. This fastest I have gone on a "closed course double lane highway" is somewhere around 180. Maybe you could go 202 at the Silver State Run. I want a car that sticks on the road and on the turns. The ACR is faster to 60 so why not have the ACR? The odds of going over 180 on a frequent basis is quite low. I have decided I am looking for something different so an ACR is definitely in my future.

 

[mjorgensen Woodhouse]

AMEN!

Here is my philosophy on this topic. This fastest I have gone on a "closed course double lane highway" is somewhere around 180. Maybe you could go 202 at the Silver State Run. I want a car that sticks on the road and on the turns. The ACR is faster to 60 so why not have the ACR? The odds of going over 180 on a frequent basis is quite low. I have decided I am looking for something different so an ACR is definitely in my future.

 

[bluestreak]

The question is how fast can it get to 180. There are several track in this country that allow speeds over 170 for many of todays cars. As long as it gets there fast, non issue, but if it takes as long as the other cars getting from say 130-200 then it's a problem.

I knew there would be some sacrifice, you cant have DF like that and no drag added.

 

[Newport Viper]

Believe the salt flats are about 4,000 ft. elevation. That may be most of the reason for the lower top speed.

Maybe they can use a do hickey like this to figure it out?

The SAE J1349 relative horsepower calculation shows how air density alters the power output of a properly tuned engine. For example, at 85 deg F, 30.14 in-Hg barometer reading, 58 deg F dewpoint and 5000 ft altitude, the engine only produces about 81.1% of the rated horsepower.

Engine Tuning Calculator - dew point

Equations: Dyno Correction Factor and Relative Horsepower

 

[SoCal Rebell]

To put it into perspective, one of the best Viper road racers Terry Rossi took an alignment prepped stock '08 coupe to Willow Springs, he hit 151 mph at the end of the front straight. A hack like me took a stock un-aligned '08 ACR to 148 mph at the same point. The downforce out of turn #9 made up for the "parachute" effect.

 

[rocman]

To put it into perspective, one of the best Viper road racers Terry Rossi took an alignment prepped stock '08 coupe to Willow Springs, he hit 151 mph at the end of the front straight. A hack like me took a stock un-aligned '08 ACR to 148 mph at the same point. The downforce out of turn #9 made up for the "parachute" effect.

Hey, I told you to keep under 65.

 

[black mamba1]

The ACR is kicking ass on the tracks in all the rags. All of them. The rear wing is what kills you at top speeds, but the wing is removable. So, for highway roll ons in Mexico (where its legal ) remove the wing and get your top speed back up to around 200 mph. On road races, put it back on and kick ass.

You have the best of both worlds.

 

[Fiorano]

How is the wing on the ACR mounted? Does it mount into the chassis?

 

[mjorgensen Woodhouse]

It is mounted to the deck lid but reinforced very well

How is the wing on the ACR mounted? Does it mount into the chassis?

 

[slaughterj]

Hey, I told you to keep under 65.

Ron heard you say "165"