Fried Chicken

Seriously, why?

Someone asked me and I thought I knew, but the more I thought about it, the more the reason escaped me. Anyone have any idea?

AlexMercedes

So Mercedes can milk more money out of you

I recently changed coil packs - costed me $2,500 it's bull****

Fried Chicken

I thought this at first, but even Mercedes can come up with some justification?

ibeforreal

"Supposedly" it makes the engine run more efficient. The idea is that twin flames will more efficiently use all the fuel injected into the cylinders to improve performance and reduce fuel use. Bottom line, it is really designed to cost more to service.

Alex.currie44

Not really. If you have done any reading on the M112, M272 and the 276 engines (and presumably their V8 cousins) the wave propagation of the firing is more efficient in the use of fuel to develop power with two plugs. That is why there are also two intake valves so the fuel volume can be delivered faster. These valves are smaller than the single exhaust valve which makes breathing of the engine more efficient.
I have never had a coil go in any car and do not see it as cynically as some here.

Fried Chicken

So I did a little research on Wikipedia and other websites.
https://en.wikipedia.org/wiki/Dual_ignition

Wikipedia seems to be particularly happy about dual-spark ignition claiming an up to 5% increase in torque and 10% improvement in fuel consumption.

10% is a lot, and it would manifest itself in the life of the car, so I think I'm going to run the numbers.
For fairness let's assume a 5% increase in fuel efficiency and completely ignore the increased performance.
Assuming an average fuel consumption of 25mpg, without dual spark ignition we would get 23.8 mpg on average.

Over 100,000 miles the savings would be over 200 gallons of fuel.

At a fuel price of $3/gallon that's $600.
Based off these calculations it's not worth the added coil packs, wires, and spark plugs. However at 10% efficiency, it would be close to $1200 in savings, and if European fuel prices were considered (generously $6/gallon) that would come out to $2400 in savings which is potentially significant, and that's ignoring the increase in performance.

AlexMercedes

Mercedes just loves to use that stuff as an excuse. If someone has enough money to buy a 12 cylinder car, will they really care about the mpg? The answer is no. Mercedes knows that their cars depreciate like crap, so they have to make everything over-complicated and have their cars constantly in need of repair and service. This will make people like me who bought an S600 for 1/10 of the original price still have to pay a crap ton of money just to keep the car running.

Fried Chicken

I just did the math.

Welwynnick

If it gave 10% better fuel consumption everyone would do it. No question.
However, even Mercedes don't use it any more on their new engines.
Go figure?

Nick

ibeforreal

No doubt these cars are over engineered. The electronics alone can be a complete nightmare.
Don't even think about the cost of purchasing parts and service from the dealer.

kraut56

the design is that the engine controller measures the ionization of the gas in the cylinder AFTER firing, and adjusts accordingly (adaptation).

Also, 2 plugs make sure the cylinder fires even with one plug dead (redundancy).

I agree it is overkill, but, the gas milage is phenomenal.

cybertronicify

Okay, although the person who buys a 12 cylinder car, doesn't care about the MPG. Some of them actually do care about the environment. And Mercedes also gets a tax break if they make them good on gas, hence the cylinder deactivation on the M137. Or the S430 that actually gets really good MPG. It makes Mercedes look better as a company and it sure looks better on paper too. (not the repair bill of course)

Fried Chicken

So it's political reasons?

cybertronicify

Yes. Just like the hybrids that mercedes are making. Makes the company look eco and green.

Fried Chicken

Stupid.
Maybe my next car should be a W140 V12.

AlexMercedes

I have the TTV12, that one didn't came with the cylinder deactivation. So isn't it strange that Mercedes took a step back with not including it in their newer engines? Or is it just because they knew the deactivation thing wasn't gunna work

cybertronicify

The S class's power was falling behind its competitors. i.e BMW PORSCHE. They had no choice but to turbo the engines, and when you turbo the engine you cannot have half the banks not firing. Cylinder deactivation will kill the exhaust output by closing half the exhaust valves, and it won't be able to spin the turbines hard enough to make any useable boost. Even though the new S classes are all turboed, it doesn't affect Mercedes that much because the E classes are their best sellers. With all the new Hybrid and E-Drive cars. GLE, B-E Drive, S400 Hybrid etc. It really makes Mercedes "look" good.

AlexMercedes

Oh it makes sense now. One more thing, I feel like I need to mention this: I was driving the car for a few weeks with only half the engine running since the coil pack went bad for that side. I thought it wouldn't be a problem since I was getting it fixed later that month, but maybe I'm stupid for driving a 12 cylinder car with only half the cylinders working? I still don't know if it did permanent damage to the car.

Fried Chicken

I believe the cylinder deactivation technology switches which side is active at any given time in order to keep the engine uniformly heated.
I don't think you did permanent damage, but it probably wasn't the smartest idea

AlexMercedes

It definitely wasn't the smartest idea but those coil packs are damn expensive and I needed a car to take me places. Also mine is the Twin Turbo which didn't even come with the deactivation, so I believe that just made the damage worse.

wallyp

I still find the split psyche on this forum fascinating...

"These are wonderful cars, the best ever made."
"These cars are over-engineered pieces of over-priced crap."

Often same person, different day...

cybertronicify

Well you have bought a Mercedes S class, an engineering marvel as you can say. (The new ones at least) If they think it's overpriced pieces of crap then just buy a Toyota. A shock costs a couple of Starbucks, and a Airmatic pump costs, what Airmatic?

AlexMercedes

It's funny that you can get a W220 S-Class for less money than a new Toyota.....

cybertronicify

The reason why you can get a w220 for less than a New Toyota is because of the Chrysler era. Everyone knows during the Chrysler era, Mercedes was bad, REALLY BAD. S classes are usually leased, because the owner wants the newest and the best. Most get CPOed and some get auctioned off. The earliest w220 is 16 years old, and it can't really be compared to new Toyotas.

AlexMercedes

In my opinion, the prefacelift W220s were absolute sh*t and shouldn't even be counted as S-Classes. The facelift saw the light at the end of the sh*t tunnel, and I actually like their look and technology innovation for it's time. I have a fully loaded W220, and yes it really is fully loaded. That means I have the extremely rare four-place-seating package with massaging rear seats. It really is amazing, I'm truly lucky for having the best W220 out there. And there is no way any Toyota can even come CLOSE to comparing with my specific W220.