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Audi Adaptive Cruise Control (ACC) – In Depth Review

Oct 15

Audi Adaptive Cruise Control is a nice feature that really pays off if you spend any amount of time on the highway or on long distance drives. You would probably never know that you wanted ACC (Adaptive Cruise Control) unless you had the opportunity to experience it, much like the Audi side Assist. However after using Audi’s ACC (Adaptive Cruise Control) you would almost make it a must have when ordering your next new Audi. Now the ACC is not available on every car in the Audi line up such as the A3 and the TT and is harder to find on some models such as the A4 and A6 sedan but they do exist. Our good friend John Woo happens to be one of the lucky few to have it on his 2009 3.2L, Prestige, S-Line, A4 and he did a great in depth review of this system.

Black Dome component pictured is actually the business end of A.C.C.
North Bend oregon
A.C.C. is Audi’s designation for their Active Cruise Control option. What exactly is Active Cruise Control and what capabilities does it offer beyond the standard equipment electronic cruise control systems installed on the vast majority of every Audi model offered in this country? I invite you to read on.
Downtown Seattle
Recently, over about a six week period, I’ve had the opportunity to accumulate an excess of 3,500 miles in a 2009 A4 mostly driving on I-5 in Oregon and Washington. Beginning with a trip down to the small communities of North Bend-Coos Bay on the southern Oregon Coast… and then above to the greater Seattle area.
North Bend oregon
Of course our friendly neighbors to the North, beautiful British Columbia
Vancouver BC
That’s a lot of highway driving in a short period of time roughly exceeding the distance traveled from Portland (that’s Oregon and not Maine) to Key West, Florida plus a little beyond. All the many hours behind the wheel of an A4 on the Interstate has provided me the opportunity to gain some very real world experience using Active Cruise Control.

For some of you like myself, when we first began to drive during the time B.C.C. (Before Cruise Control), we made those long drives while attempting to apply some level of constant pressure against or on the gas pedal in our cars. If you have forgotten the level of pain and suffering possible in one’s right leg from performing this exercise hour after hour, I invite you to bring back those fond memories from yesteryear on your closest Interstate.

The arrival of the first cruise control units in cars around the 1960-70’s greatly alleviated this impediment to comfortable long distance travel in an automobile. Unfortunately, like the concept of “available” unlimited top speeds on the Autobahns of Germany, ever increasing traffic congestion on our roads and highways have greatly reduced our opportunity to engage the cruise control devices in present day vehicles for any extended periods of time.

Typically, once we are far enough out of a metropolitan area, cruise controls are activated and work to perfection “if” traffic is thin or everyone is traveling at exactly the same rate of speed. Of course having all trucks traveling only in the farthest right lane as is SOP in Germany, with everyone else never in the left lane except when passing would help immensely. Unfortunately, as we are all well aware, not the real world we drive in which is where Active Cruise Control comes in and restores most if not all of the benefits of this feature.

You activate A.C.C. in exactly the same manner you would with most other Audi cruise controls. In the case of this A4, once you have reached the speed you wish to maintain, press the small button at the end of the cruise control stalk mounted on the lower left hand side of the steering column. The speed is set and held pretty much constant even when transversing hills or valleys unlike many early units from some manufactures where +/- 10 mph was an acceptable level of operation.

The first difference you will note is the reduced number of possible speed intervals that A.C.C. will accept verses a conventional cruise control unit. The latter can be adjusted in an Audi between ½ to 1 whole M.P.H. faster (lift cruise control lever up briefly) or slower (hold cruise control lever down briefly) while accepted speeds differentials with A.C.C. is in +/- 2.5 M.P.H. increments only though it will hold whatever speed (i.e. 61.0 M.P.H.) when the system is first engaged. Increments though will only be at the +/-0.0/2.5/5.0/7.5 M.P.H. levels. Example: if the A.C.C. was engaged at 61.0 M.P.H., the range of change possible at the touch of the stalk would be down 1 M.P.H. (to 60.0 M.P.H.) or up 1.5 M.P.H. (to 62.5 M.P.H.). Ultimately, this isn’t a limitation one would expect after much use in the real world.

The key advantage of A.C.C. is that the system is “Active” rather than passive meaning instead of just holding your vehicle at a single speed (whatever speed the cruise control was engaged at), it will automatically vary your Audi’s speed to match that of traffic “in your lane” up to the top speed that the system has been set to. Traffic slows down…you slow down. Traffic speeds up…you speed up. You need to do “nothing” except to enjoy the drive without the constant strain of when to disengage or resume the use of the cruise control system traffic permitting.

For most of us, that’s possibly quite a leap of faith in technology. My first experience with this capability was in a new 2005 A8L on a drive up to Seattle (where else?). I first engaged the system where I-5 and I-205 merge together just north of Vancouver, WA. The A.C.C. operation was so smooth, seamless and natural; it wasn’t until I was approaching Olympia, WA that I remembered the system had been functioning for the past 1.5-2 hours!

Active Cruise Control works by emitting a narrow radio frequency beam forward from the emitter mounted next to the right fog light in the lower grille area of the front fascia (bumper) as seen in the picture above. Impress your friends with this little known nugget of information when you next spot an Audi with this telltale feature. There’s more than a few we’ve delivered at Sunset with this feature and from our current inventory when this article is being written, our e-Newsletter’s highlighted feature is immediately available to you on a couple of very special A4 models in stock. Contact one of our Audi Brand Specialist for assistance or further questions should you find this advanced technology as beneficial and useful as I have.
Adaptive Cruise Control
When A.C.C. is engaged, one of the possible displays in the trip computer area of the instrument cluster is shown here by cycling through the different ones via touching the reset button underneath the windshield wiper stalk mounted on the steering column.

The default spacing interval between your Audi with A.C.C. and the vehicle directly in front of you traveling in the same lane is “Distance 3” (see trip computer display above) which varies with the speed you are traveling. The slower the speed, the narrower the gap while conversely the faster the speed, the greater the spacing. Since almost all accidents involving tailgating are caused by following too close to the vehicle in front of you, this default setting can be increased to “Distance 4” which I have found very beneficial (greater margin in reaction times) on most portions of I-5 I’ve driven but counter to conventional wisdom, in heavier traffic congestion (say between Olympia and Everett on I-5), I have found reducing the spacing to “Distance 3” results in a smoother operation of A.C.C. which I will explain later on in this article. The trip computer display above also provides a visual graphic of the gap interval you have selected. Changing to Distance 4 will move the right vehicle indicator to the right where the last horizontal underline is presently shown.
Adaptive Cruise Control
Anytime A.C.C. is engaged, the emitted beam (radar) is seeking the next vehicle in front of you. If there is none within range, your Audi will travel at whatever rate of speed selected. In all three of the pictures of the instrument cluster/trip computer above, note the two small white “triangles” on either side of what appears to be the road in front of your car extending to the vehicle directly in front of you. If no vehicle is in range, “NO” triangles will display. Once you begin approaching a slower vehicle in front of you, the two white triangles appear next to the “grey” portions of the road display while your vehicle maintains it’s set speed. As you approach the vehicle directly in front of you, notice the two different positions of the white triangles in the photographs above. The display on the left indicates the vehicle we are traveling in is at the “maximum” safe (Green bars) distance to the car in front of us. The display on the right indicates we have now reached the “minimum” safe (Green bars) distance and this is when the cruise control begins to go “Active.”

Very gently, the Audi’s throttle is decreased and you begin slowing down to exactly match the speed of the vehicle in front of you. You need to do “Nothing” which is the entire reason for Active Cruise Control. It will maintain this gap/spacing and speed as long as you change nothing and remain in the same lane following the vehicle in front of you traveling slower than what you’re A.C.C. system is set for. If the vehicle in front of you speeds up…you will too, automatically up to the top speed you have set in the A.C.C.

Should the vehicle traveling ahead of you suddenly apply their brakes and rapidly decrease speed or should another vehicle merges into your lane between you and the previous vehicle in front of you allowing the gap/spacing/interval to drops into the “Red” portion of the trip computer graphic, the brakes will automatically be applied with an application level matching the deceleration rate of the vehicle in front of you attempting to restore the gap/interval/spacing to the distance you have selected.

In fact, the system has the ability to brake from whatever speed the A.C.C. was set to (up to a maximum of 95 M.P.H.) all the way down to under 20 M.P.H. before disengaging and yes, I have let it do its thing on I-5 around Tacoma where traffic always comes to a crawl. Needless to say, look in your rear view mirror to determine if or how close someone is following you when the brakes are automatically applied. Surprisingly, I have yet to experience a single situation where this has been an issue since I have begun using this feature very extensively even driving through downtown Seattle on I-5 with their usual level of traffic congestion from the Safeco/Q-West Field/I-90 interchange and north while on A.C.C!

This was the situation I was referring to earlier about in heavier traffic, reduce the gap to Distance 3 from 4 if so selected. I have noticed that if the gap is too wide when driving in metro area traffic, other vehicles will repeatedly merge into the lane directly in front of you causing the A.C.C. to constantly slow down by rapidly reducing throttle application and/or applying the brakes.

My other driving tip concerns passing when A.C.C. is active and you’re following a slower vehicle while another car is also in the left passing lane. Do not pull into the left lane to pass until that vehicle has already completed passing the slower vehicle in front of you. If not, because the interval between the vehicle passing in the left lane is less than the gap/spacing to the slower vehicle directly in front of you, the moment the A.C.C.’s radio frequency beam is redirected as you begin sliding over into the left hand lane, your throttle will be reduced and actually slow down instead of speeding up as desired.
Adaptive Cruise Control
One visual difference between Audis equipped with their standard electronic cruise control systems and one with A.C.C. can be seen in the speedometer shown above. Please note the series of “Red Triangles” that mark the left side of the speedometer from the range between 20 to 95 M.P.H. where A.C.C. will function. Audis with conventional cruise control will not have this series of lights.

Also notice in the photograph above, two of the “Red Triangles” at both the 55 & 60 M.P.H. positions are brighter than the others. This is a quick visual reference to determine if A.C.C. is actually managing the vehicle’s current speed or the system is simply on but not operational at that particular moment (all lights same intensity). Because the A.C.C. system is dynamic and your vehicle’s actual speed is dependent on outside traffic factors, your speed can vary from what was set, this indicator has proven very helpful presenting the vehicle’s current operating status.

It also performs a secondary function of visually indicating what speed you have set the A.C.C. to maintain. If only one “Red Triangle” is lit, the speed set is at the 5 M.P.H. increments (i.e. 55; 60; 65; 70 M.P.H. etc.) while two “Red Triangles” lit will indicate a speed setting at the X2.5 or X7.5 M.P.H. intervals (i.e. 57.5; 62.5; 67.5; 72.5 M.P.H. etc.).

Is there yet another benefit of A.C.C. that I’ve personally experienced? Absolutely! The system will also operate the throttle much smoother with far greater consistency than I ever could without the disadvantage of human fatigue or lack of concentration when driving. All these factors have resulted in operating fuel economy that has exceeded my personal expectations as well as the E.P.A. Fuel Economy ratings. Needless to say, I won’t retype the government’s disclaimer about the potential for accuracy of their numbers in this article but for reference, the A4 in this article has an E.P.A. rating of 17 M.P.G. City and 26 M.P.G. Highway.

Around town driving, I have been pretty consistent never dropping once under 20 M.P.G. when A.C.C. is typically not used. Get this A4 out on the Interstates and A.C.C. is fully utilized, my entire round trips back and forth to the Seattle area have never been under 30 M.P.G. (during the 4-5 hours crawls) with most drives averaging 32-32.5 M.P.G. What had me really excited was achieving 33.4 M.P.G. when there was only 3200 miles on the engine during my first trip to North Bend, OR.

Thought that was pretty impressive until one of my drives from Everett, WA back to Beaverton last month. Below are four shots of the trip computer display upon my arrival home. I provided all 4 screen shots as validation (odometer, temperature, date & time displayed) the results were really achieved.
Adaptive Cruise Control
One August 9th, drove a distance of 199.2 miles which took 3 hours 17 minutes to accomplish at an average speed of 60 M.P.H. for the entire trip which achieved a 34.0 M.P.G. average!
Adaptive Cruise Control
It can be done and A.C.C. is a real contributor to this type of superior vehicle performance and economy. Did I neglect to mention the engine in this A4 article is the 3.2 Liter V-6! Wonder what I could achieve with a 2.0T and A.C.C?

Do you have any idea if we get the latest version of the ACC if we buy an A4 today ?
I mean, the A4 is from 2008, but the ACC has been improved in 2009 (better angle, better sensitivity, …).
It’s hard to know if they fit their new car with the old version or not …

Any info ?

From Jack on March 7th, 2011

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