Finally got the airbag unit, went with black stitchings to match the steering wheel better.


Big chunks of steel bolted to the back of the unit

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Looking nice,

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Will try to fit them later on today.

 

Looking nice.. Seriously, what are those chunks of steel behind the unit?? Is it to help prevent the airbag from going off somehow?

Mind if I ask how much?

 

Airbags have been packaged pretty odd over the years, My guess is, just as you said that it is made to reduce damage if it went off.
The last airbag I ordered was delivered in a sturdy steel cage.


The unit cost around 8500 SEK, around 1200 USD

 

How to:


Disconnect ground wire from battery.
Use a Torx T20 screwdriver and insert in dimples behind the wheel, pull it in towards just above the center of the star, the airbag unit should pop out slightly, repeat on left side, disconnect the yellow connector.

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Use the T20 and unscrew the two screws holding the "metal" trim

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Starting at the outer edges (at the button units) pull the metal trim outwards very carefully not to brake it, it is just clamped into place.

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Unplug the center connector and pull out the trim, use a T15 to unscrew the Three screws holding the button units at each side

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Before and after

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Install in reverse order, when you have connected the yellow airbag connector make sure the cables are placed correctly and not pinched, Place the airbag on the wheel and push evenly and firmly with both hands to snap it into place.


Done, shouldnt take more than 15-20 minutes.

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Hope you like it!

 

That's a lotta cash for such a subtle difference, nice write up, glad you are enjoying it

 

Couldnt stand that big piece of cheap looking plastic, after all you spnd a lot of time looking at it


I love the feel of the new leather airbag, made of same smooth leather as the steering wheel.


Also, prices I mentioned above are retail

 

Looks good!. Yes I'm sure you got the bits at the right price.

You do some interesting mods.

 

Wait....you put an S Class air bag on a W205? How did you confirm the crash pulse of the two different platforms resulted in the same bag calibration, size, and fill rate? I would wager they are quite different!

 

Nice! and the metal buttons looks great too!

Does this airbag with leather come in espresso brown or just black?

 

the bag itself does not have any sensors. Whatever sensors there are in the car are probably telling the airbag to go off through the yellow cable

 

The issues are more complex than the signal from the sensor to fire. The firing time is synched based on the crash pulse of the platform to coordinate with when the dummy (in testing) engaged the bag. With such different size vehicles, the specs are likely quite different for the inflation timing. Further, the rate of fill may be different and the total volume of the bag may vary. A smaller mass vehicle probably has a more aggressive deployment. Substituting a bag from a much larger vehicle could result in under-performance in a frontal impact. Without MB signoff after impact testing, this is risky at best.

 

Totally agreed.

 

in before the next thread, my stupid dealer voided my warranty

 

Looks great!

 

Calm down, I have confirmed that the two stage charge are the very same in the S Coupe as the C Class,
Also comparing the rear of the units they are exactly the same, same numbers and specs.

 

I AM that stupid dealer, do you really think I am worried about warranty issues if I published an how to on MB World?

 

 

vic viper, u da man

 

Quite calm here, I can assure you. I'm not the one driving!

In any event, glad to know you investigated that. Not everyone would have had that on their radar.

One thing does still seem odd to me, though. If the appearance is different, the part number should also be different. So, if that assumption is correct, how does one confirm that all the performance characteristics are the same for different part numbers? It continues to seem unexpected that vehicles of such different mass and spindle-to-H-point measurements would have air bag deployment timing, volume, and fill rates that are the same.

Anyway, hope I am wrong and you are right.....
And, I'm still very calm about it!

 

Airbag unit part numbers arnt the same, but on the back of the units both of the charges are visible with their individual part and manufacturing numbers, they look exactly the same, it is just the plastic/leather fronts that differs.


I really dont think the units are that precisely matched for each individual vehicle, I checked EPC and it turns out that a lot of cars share airbag units, for instance the B-Class and the W218 CLS uses the same units.

 

I would doubt that the airbag system is as advanced as indicated. How can the system know in advance, the mass of what you will hit, and at which speed you will be travelling at the time of impact.

From my understanding, airbags are set to deploy when an impact of a pre-determined magintude is dected by sensors at the front. This is why you can cheat airbags to deploy, f.ex by hitting the front of a car with a bat.

The exact time at when decellration begins to affect your body, in relation to time of impact, is going to be very different depending on what you hit.

Take two examples, in both you are doing the same speed when the accident occours.

First example you drive head on into a huge Tree trunk at 150 mhp.

Second example: A car traveling in front of you doing 120 mph, and you drive into it doing 150 mph.

In both cases the airbag will have to deploy to protect you, but the decellation in the first example if going to occour much earlier then in the second example.

Anyone who has done racing, knows that certain corners on some tracks can be lethal in the event of sudden and total brake failure. So you bulid in a safety margin on your entry speed. You scrub off just enough speed to avoid serious trauma if worst comes to worst.

This example is taking into account, - in advance, what you are going to hit and at what speed. I do not see how it would be possible for a system to detect in real time, the mass of the object you will impact.

 

No I dont think anyone has said that the car could detect impact mass, I think Sportstick was refering to the size of the airbag charge wich in certain cases need to be adapted to the vehicles size.


However there are in most modern cars today two charges in an airbag, if the impact is lighter only one charge will ignite, if the crash is more severe both charges will ignite at the same time deploying the canvas faster and harder.

 

he mentioned vehicle size in relation to timing of the deplyment. I interpret that as earlier stated in my examples.

Imagine sitting in a train with 10 carriages, all carriages equipped with airbags. You would not want the airbag in carriage 10 to deply at the time carriage 1 makes impact.

You would want the airbag to deploy at the time carriage 10 begins to decellerate. so a delay has to be set.

Interesting point with the two charges, i was not aware of that.

 

But it works that way, if using your example with driving into someone driving 120 while you are driving 150 it would be the same as hitting a non moving car at 30mph, that would probably deploy the lighter charge.


But driving into a tree at 150 will set off all front airbags at full effect.

 

My point is different from your reply. Airbags for vehicles sold in the US are designed to meet or exceed the requirements of FMVSS 208, the frontal 30mph barrier impact test (this is not the elective 35mph NCAP). From my experience at the car company where I worked prior to retirement, I learned about the "tuning" of the air bag to the vehicle platform based on its crash pulse. In order to comply with the standardized head and chest acceleration parameters required, the air bag in a smaller vehicle had a more challenging task than did one in a larger one. They are all usually set to deploy with a delta V of 9-14 mph in a few milliseconds (don't remember the number of milliseconds sorry). As I recall, all vehicles had to reliably generate below 20gs of force on the chest sensors in the dummy and the HIC (Head Impact Criterion) had to be below 1000. In a smaller car, there is less impact absorption in the frontal structure (depending on how the engine is packaged) and there is less mass. In the test, all vehicles hit the same unyielding barrier, so the real-world variability issue is true, but doesn't apply here. To successfully pass this test, a more aggressive bag which would need to fill faster and potentially have a larger volume is set to be fully deployed before the dummy can engage the bag's frontal surface. One does not want to engage a bag while it is still deploying. OTOH, if a less aggressive bag (possibly tuned to a larger vehicle platform) is used in a smaller mass car, it may not deploy sufficiently before the body meets the moving air bag surface (bad news), and may allow the body to push through the bag to impact the steering wheel/column.

That is the concern. If MB has figured out how to reduce complexity, develop a common crash pulse across platforms, and re-use the same spec bag, more power to them. Since this issue can have unfortunate consequences, I thought it was worth mentioning.