MB Fanatic

Does anyone know why Mercedes uses 2 spark plugs per cylinder? What are the advantages and what are the disadvantages to this setup? If it is a far superior design then why is it that many companies do not use this 2 spark plug setup per cylinder?


Thanks.

I just wanna blame Houston for getting me thinking on this topic. lol.

Rafal

It's obviously a factory error of over-generosity on the part of M-B! Immediately undo the 8 surplus plugs and send back to your dealer with an apology...LOL
Seriously though, Alfa Romeo has made a lot of noise out of their crappy 156's being Twin Spark! When I showed my friend who owns one, that my E500 and E55 were also twin spark, it shut him up for good.
Twin Spark seems to improve combustion, I guess we get a bigger BANG after each cylinder compression!

MB Fanatic

So the the fuel burns better inside the cylinder then? Which would inturn lead towards better emissions right?

Gregs210

Larger cylinder bores mean larger squish areas for compressed gasses and if you combine that with leaner mixtures (for emissions) and typical hot spots in compression chambers, that can mean a more serious power drop as you increase RPMs, as well as increasing the likelihood of detonation, unburned hydrocarbons, shockwaves, etc. Adding the second spark plug increases the speed of combustion -- particularly important in larger cylinder bores -- by providing two flame fronts. In turn that produces more complete combustion (hence, lower emissions) and reduces the possibility of detonation and shockwaves.

Take care and enjoy the double-sparked ride,
Greg

mbprince

heck that almost sounds scientifical!!

vraa

BECAUSE IT IS!

Wow Gregs210, that was an exercise in reading. And to think, school has been out for a few days now!

Evolution Marine

I would like to add a bit to Gregs210's analysis. The major reason for two sparkplugs is the motor does not need as much advance ignition timing to complete the burn cycle, because the flame front has been started in two different areas of the combustion chamber and therefore the combustion process is completed more quickly. The need for less ignition timing means less chance of detonation. The flame front is not traveling any faster, there is just two flame fronts traveling the same speed but covering the combustion chamber more quickly. Quench areas ( Squish Areas) promote cooling of the combustion chamber and true there is potentially more area for quench area in a larger bore diameter, however in the 55 motor the third valve will take any of that extra room and then some, so I say, MB having put the third valve in the combustion chamber, reduced the quench area to the point that they needed some other way to reduce the probability of detonation, so that is when the second spark plug was added and it most likely also allowed more boost to be used.
A little more clarification on detonation and shockwaves. Detonation occurs when the end gases (the last A/F mixture left to burn, to complete the combustion process) become to hot and ignite before they are supposed to and start another flame front which collides with the original flame front, causing a violent rise in peak cylinder pressure prematurly, which rattles the pistons back and forth in the cylinder bore as they are approaching TDC. This is not good especially on a forced induction motor. Even with the twin spark plugs MB still has to retard the hell out of the ignition timing under boost to maintain safe operation of the 55 motor.
The 55 Motor is very impressive, having to deal with all of the variables that are constantly thrown at it, and still run like a bat out of hell. - Bob

blackbenzz

The E55 and 500 are not the only twin spark plug mercedes cars. Even my 1999 CLK430 has twin spark plugs.

MB Fanatic

Even my 2001 W210 E320 had twin spark plugs. Clearly some amazing technology. I wonder why many auto makers have not adapated this technology. Probably to keep costs down or something. Clearly its a stupid mistake after having learned something on here right now.

GTA23109a

Because that's how Feuling designed those heads before Mercedes stole the technology !!!!! :v :v :v

E55AMG99

It was the 3 valve heads that Jim designed and patented back in the early 90's. His orignial design did not have 2 plugs. Didn't MB win a dissmissal for that case or was it because they settled?

E55 and 993

My 911 has two plugs per cylinder.

That means between my two cars I have 28 plugs!

GTA23109a

Feuling had several head designs (both 2 and 3 valve designs) and I believe one of them even included a twin-plug setup, but I may be mistaken.

As far as the lawsuit, the last I heard was Feuling was out of $$$$$ to pursue it and the company was being sold. This was quite a while ago though.

Vadim @ evosport

In simple terms:

Twin plugs provide better combustion efficiency, thus less emissions. In terms of power, 3-valve, twin plug design is not very good. Twin plugs shroud exhaust valve, limiting power potential.

Jim Fueling setteld with MB for undisclosed $$$$. He passed away several years ago from cancer, may God bless his soul. He was a genuis when it came to cylinder head design.

GTA23109a

That's for sure . . . a lot of Big Block Chevy guys still use his designs. It's stuff that looks like it should never work, but ends up not only making huge power but increasing efficiency too.

E55AMG99

I figured they settled. Kind of a slam dunk case since most of the other auto makers were already paying him royalties for his designs.

Genius does not even begin to describe the man. It's a pity that more people did not know of him while he was alive. He was into EVERYTHING! If it had an internal combustion engine (diesels, airplanes, motorcycles, boats, racing cars, etc.), he made it more powerful and more efficient. Two of his most interesting achivements IMO are his 500MPG engine and the QUAD4 motor he designed and built that made over 1250HP from 120 c.u. (2.0L). He was even into aerodynamics. GM claims his Bonneville streamliner is the lowest drag car ever tested. His speed records are a tribute to that.

MB Fanatic

E55AMG99 Please elaborate if you will, on this 500mpg engine that he designed. Clearly this is an astonisghing feat in itself as no other car company or person has been able to do, to this date.

E55AMG99

I think it was Honda that tapped Jim for his expertise in both engine efficiency and aerodynamics. He had already been running one of the fastest streamliners on the planet with some astonishingly small, low output engines. Many of his records still stand today. Anyway, the vehicle achieved 500 mpg at 55 mph steady state cruise using a VERY aerodynamic vehicle and a VERY small engine. It was purely an experiment in efficiency and nothing else.

MB Fanatic

Only if they could make cars like that now. I am sure they would put oil companies out of business though. Clearly he was an intelligent and remarkable person. Too bad there are not many people like him around these days.

Gregs210

check out the Honda (motorcycle) NR/NS/500/750

It had oval combustion chambers -- sort of like Dodge's Hemi design -- except that these were really oval. And for good reason: the piston and cylinder were oval, too...and eight valves per cylinder.

Matthew Shumway

Well, this is actually a very old technology. Having first been used back in the early 1900s (30s and 40s). There is actually no necessary reason for the second spark plug in each cylinder. As adding a second spark plug is not only a waste, but it also reduces the usable space in the combustion chamber. It really is only there to provide a spark when the other plug in the cylinder fails. (Similar to the E3 plugs that are always shown during NASCAR races or NHRA Drag Races - has 3 ground straps for the spark to jump to, as they engineered it so that if the other 2 prongs become coated with carbon or corrosion, fuel fouled, etc - then it will still have a spot for the spark to ground itself to. However - they did not plan on the fact that technically everywhere in a combustion chamber experiences almost identical conditions, thus resulting in an unnecessary amount of over-engineering (the theme of this post ironically)). Which makes troubleshooting exponentially more difficult (especially with intermittent misfires). Other than ensuring one of the two plugs will fire, there is really no other advantage for this setup. It is more expensive to engineer and more expensive to replace and maintain. In fact it's basically creating a similar scenario to detonation with a second flame front. A combustion chamber is designed in a way so that only one flame front is to be used in order to produce combustion. When the second flame front hits the first, that's when knock is detected, and thus ignition timing is pulled (retarded) to stop the detonation/pre-ignition (by the way, pre-ignition would also be of higher potential with this type of combustion chamber design as the temperatures from the two fronts clashing would ultimately result in higher combustion temps mimicking a very lean air fuel mixture resulting in pre-mature failure of exhaust and emissions control devices (catalytic converter)). So essentially MB produced a planned obsolescence engine that is designed to knock from the factory...that or they switch off which plug ignites (every other stroke cycle) which again would just cause extra wear and tear for the plugs and cause them to foul out quicker.

There truly is no advantage to the system. It can be used as a clever ploy for salesmen to use to attract those that do not understand it. ICE (internal combustion engine's) individual cylinders are designed to have 1 or 2 valves for intake of air or a mixture of air combined with atomized fuel, a method of ignition (spark plug or high-enough compression), if direct injection - an injector to spray the atomized fuel at an insanely high pressure, then 1 or 2 exhaust valves to allow for the air and burned up fuel mixture to exit the combustion chamber (and of course the "overlap" where both int and exh valves are both open shortly after the end of the powerstroke (beginning of the exhaust stroke) to clear the cylinder of any remaining gases), that is all that is needed, any other components can and most likely will, in fact, cause unnecessary, premature wear and can be another variable that potentially results in catastrophic failure.

So when you ask why other manufacturers arent creating engines with two spark plugs per cylinder, you now know why. Because it's unnecessary - it's less cost effective (to engineer, build, and maintain/repair) and less efficient if it can utilize a single spark then why waste all the time engineering it to utilize a second? Again, two flame fronts colliding is the very definition of detonation and can result in bigger headaches that did not need to ultimately happen just because the Germans went and once again overengineered it. Technically speaking though, since they would've had to engineer the cylinders, internals, block, and heads in order to handle and safely operate with the extra pressures and temperatures from what is essentially "engineered-in detonation", then technically if the heads were modified to take just a single spark plug, that may actually be one of the strongest engines by material and design from the factory of any consumer/mass-production manufacturer.

Source: several years working as an automotive master mechanic (worked at independent shops, dealerships, and nationwide franchises shops), attended a trade school that had specialty manufacturer training programs for the graduates at the top of the class. I graduated from both BMW and Mercedes-Benz's manufacturer-specific accelerated training programs. Have also built countless cars (heavily modified project cars - for road courses, drag strips, rally/rallycross, restorations, some of which are well known high profile cars, and a few that were restored classics with a ton of modern modifications). I have spent the better part of my life wrenching, building, maintaining, and repairing some truly amazing cars.

Matthew Shumway

Apologies for the novel.

E55AMG99

Not sure why you signed up to post this in a 15 year old thread other than to show off your textbook knowledge.

W205_Merc

<3

i think its a copy and paste from the wild world wide web

BrokenBarryBenz

So what if one would just disconnect the plug wires to the secondary plugs? Just out of curiosity.