CedarZ4

So after being a fickle pickle for the past 3 months... deciding between an E, then SLK, then S, and back to SLK, I finally decided to get myself a 2012 E350.

Just special-ordered it today. Says it won't be in until after New years

Hopefully they can get me this baby before Christmas and it can be my Christmas "surprise" gift!

Steel Grey, Black/Black, and pretty loaded. P1/2, Driver's Assist Package, ParkTRONIC, Heated wheels, Multi-Contour seats, Panoramic roof. I know I'm missing something, but MSRP was $67,000! Luxury model. Anyway, not the point. Just thought I'd share my soon to-be vehicle with everyone!

Point of this thread is to ask about the Distronic Plus and Pre-Safe Brakes.

I've found different sources telling me different thinks, and I'm not exactly sure if I trust my consultant (because most of us here know more than our salesman about our car, but that's not the point!)

So correct me if I'm wrong....This is what I've gathered but just wanted to make sure from anyone who actually has this option.

Distronic Plus is Adaptive Cruise Control. That is, cruise control where you set a certain speed, and if the car in front of you slows down, your car will automatically brake. If the speeds up again, so will. Also during a turn, the car will slow down. This also works in Stop-and-Go traffic because if the car in front of you comes to a complete stop, your car will to. When traffic moves again, your car will resume to its previous speed.

Pre-Safe Brakes : Using the Distronic Plus radars, they will detect possible collisions. If within 2.5s of impact, you will have an audible warning. At about 1.6 seconds, brakes are applied at 40% and primed to be put into full strength ONLY IF the driver steps on the brakes. The seat belts also tighten along with closing of the window/sunroof and (if you have multicontour) adjusting of the seats for more support. Now my question is this....

If you are NOT using the cruise control, will the car still come to a complete stop? Some sources says that if .06s of calculated impact, 100% of the brakes will be activated and you will come to a complete stop so no accident will occur. Other websites says that it only primes the brakes at 40% to reduce impact but if the driver does not actually step on the brakes, collision will still occur. All too confusing, and couldn't find an accurate answer. Can someone clarify this for me please!

Anyway, thanks a lot in advance! Will post pics when my car comes

Arrie

Your explanation of Distronic seems correct other than the slow down in turns. I don't know what you mean with that. I know the car will slow down on sharply winding roads with metal rails close to the driving lane as the radar reads the rail and obviously thinks it is an obstacle. This I concider being a "malfunction" of the system.

Distronic will make the car to a full stop in stop-and-go traffic but will not automatically start follow the car in front of it when traffic moves again. You will need to either give it a small press on the gas pedal or the resume pull on the cruise control stalk.

Pre-safe brakes will only give 40% braking if you don't hit the brake pedal. I have actually seen an instructional video about this and I think it was in Utube by MB. Audible alarm comes as you explained and when you then step on the brake it will really work as the brakes are "primed". I have had a situation with this a couple of times.

I don't have distronic in my car (and regret not getting one) but have been lucky to have the opportunity to drive several rental cars in Germany with it and really liked the system.

mnje350

With distronic cruise on, the car will slow when cornering in a sharp turn. It does not apply the breaks, unless you are approaching an obstacle in the curve. I have not had it interperate a guard rail as an obstacle. That would be annoying if it did. I was under the impression that it would apply the breaks at full if the driver did not react to a ubruptly stopping vehicle in front to help prevent a rear end collision with that vehicle. Then, you have to hope the guy behind you has a similar system. Not much can be done to make sure you don't get rear ended.

It's a remarkable system.

WEBSRFR

It will brake fully only .6 seconds before an accident if you DO NOT react to the beeps. The point being that if you want the car to stop and not have an accident, you need to brake as soon as you hear the beeps as it is an indication of an impending accident. My understanding is that MB wanted the driver to have the ability to use speed and steering to avoid the accident if the driver chooses to so that OR apply brakes and the car will modulate the correct amount of braking power.

If you wait until .6 before an accident when the car brakes fully, you are pretty much using pre safe braking as an electronic crumple zone, as you WILL hit the car if it stops very quickly and 40% is not enough

What I find really nice about the system is that if you slam on the brakes when you hear the beeps, the car controls the braking power and might not brake as hard as you apply the brakes but will will apply enough braking power to avoid an accident. This is done to give the idiot following you too closely behind you more time to react. I thought that was particularly smart and thoughtful for your safety and the safety of the person behind you.

Arrie

I tought the slow down in a curve came from the guard rail so close in front of the car. If you have the system (or someone else) you could verify it in a big empty parking lot, i.e. set it to low speed and turn sharp in an open area with no obstacles in sight and see if it indeed slows down.

In general, there usually is an obstacle right in front of the car while driving thru sharp curves. Often this is the guard rail but can be a building wall or a hill side etc too.

mnje350

I have the distronic plus and the car slows in sharp curves without guard rails. In fact, if you have the cruise set in a very slow speed and turn the steering wheel sharply it will actually cancel the cruise control. I have done this in a parking lot. On a highway, with the cruise set at 60 mph and cornering at a relatively sharp corner, the car slows to about 55 and then resumes normal speed. If I apex the corner more accurately, the car does not slow. There is no guardrail on this corner. If the distronic sensed an obstacle, like a guardrail, an audible warning would sound and a red triangle would flash on the instrument panel. The breaks would also apply if the driver continues toward the obstacle. This does not happen in the corner I have described.

It makes sense, the distronic adjusts speed based on the speed differential of the vehicle in front of you. If the difference is slight, as when you approach a car on an interstate hwy, the distronic slows the car without warning alarms etc. I have had the pre-safe break apply in a curve in an area where there is a sharp curve with say something like a stone column as the entrance to a facility. If you are at a speed over 20 mph and corner in front of such a pillar, the pre-safe break warnings go off. Since the pillar is passed quickly, the breaks do not apply. If I headed straight into the structure without turning, the breaks would apply in an attempt to save me and the car. This is for sure, not what happens in the curve I described at the beginning of the post..

ttoE550

Turning the wheels adds rolling resistance and can be the cause of the slowing down in a sharp curve. Hitting the apex generally means the wheels are not turned as sharply, so there is less resistance.

I think whether the car sees a guardrail as an obstacle depends on the road. If the car can see the edge of the lane - a white line or the edge of the pavement - then in my experience I would be very surprised if the car beeped or slowed. But if there are no markings and the pavement extends under the guardrail, then the car has no way to distinguish the guardrail from some other object you might hit in the road.

It's not quite the same, but every day the car thinks I am going to run into my neighbor's car. It sits on a curve but for some reason the car can't see the curve.

I've also has distronic turn off at slow speeds in a sharp curve. I've only had it happen when following another car. IIRC this happens when the car is braking because of the car in front and that car disappears (from the car's perspective), which happens in slow sharp turns.

mnje350

Other less sophisticated cars I have had with cruise control did not slow in a sharp corner, the same corner, that I have driven the Benz on. I believe that this is a function of the distronic and other features that the E-350 has on it.

mnje350

This corner and several others, are not that sharp. It will bite you if you are not on your toes but it is not an OMG corner.

ttoE550

I know exactly what you are talking about. I use cc on a road all the time that's got some snug corners at about 40 mph. It does slow down, but just think it's just front tire resistance. Whatever. It does slow down.

Here's something I think is true: have you noticed the car follows the car in front closer when going uphill and farther downhill? This might make a little sense because you get better braking uphill and worse downhill, but I'd be astounded if this was put in the engineering.

mnje350

I have not noticed this but perhaps it is because I have no hills where I live. A pity.

CedarZ4

To my understanding, what you are saying is.... It will not full-brake .6 seconds prior to accident to void the accident as a whole. That is, if it takes 2 seconds to complete stop, the system will full brake at 2.6seconds. Rather it will full brake .6 seconds before the collision, but at that point the collision WILL occur because it takes more than .6 seconds to complete stop but it just creates an extra .6 second electronic "crumple zone". And this is on 100% of the time if you have PreSafe Brakes package (Driver's Assist) even if you have Distronic PLUS off is that correct? And if you do have Distronic PLUS (cruise control) on, it WILL complete stop.

Also, in regards to slowing down on turns. I saw a MB video on the Distronic PLUS and it says if you are doing a "sharp" turn where your current speed will result in significant roll, it will drop the speed. Now as others have pointed out, wether or not they do this by detecting the guard rails or what I'm not sure.

ttoE550

Well there you go - perhaps it is more than rolling resistance. For me, it seems to happen concurrently with turning the wheels, rather than by anticipation. But geez, how much less body roll is there at 55 than 60, to use the example above? And why isn't this cr*p optional?

CedarZ4

Distronic PLUS with PreSafe brakes is an option

ttoE550

Touché

Arrie

The car has inclinometer and I would bet distance to the car ahead of you comparing uphill and down hill driving is engineered in it.

69armando

Can Distronic Plus be disabled same way that Pre-Brake can?

KEY08

You can turn it off in the instrument cluster. Yes

69armando

Can you give me instruction on how to disable Distronic Plus. I was able to disable Pre-Brake assist, but not Distronic Plus.