Why are there 12 spark plugs in a 6 cyl ?

TechSuperstar · 04-18-2012, 03:56 PM

So I'm about to replace my spark plugs and saw the helpful threads regarding the DIY. I didn't see any threads addressing the topic of why MB is using two spark plugs per cylinder. Are there any MB tech's that can explain, from an engineering point of view, why MB designed it this way? Seems to me it only takes one spark to create combustion.

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Kevwood · 04-18-2012, 04:09 PM

Simply, to achieve a more 'complete' burn.

Glyn M Ruck · 04-18-2012, 04:14 PM

Benz used dual plugs on all M112/113 etc engines mainly to achieve LEV (low emission vehicle) status for cars so equipped in Europe. It is intended to burn every last ounce of fuel that gets into the combustion chamber even with detrimental AF ratio when running open loop.

As injection & ignition systems have improved & 3 Way Cats are fitted so they have become irrelevant.

The M112/113 engines blow squeaky clean tail pipes for the time.

Rudeney · 04-18-2012, 10:34 PM

Quote:

Originally Posted by TechSuperstar

So I'm about to replace my spark plugs and saw the helpful threads regarding the DIY. I didn't see any threads addressing the topic of why MB is using two spark plugs per cylinder. Are there any MB tech's that can explain, from an engineering point of view, why MB designed it this way? Seems to me it only takes one spark to create combustion.

Your MY2007 CLK350 with an M272 engine only has 6 spark plugs - one per cylinder. It was the M112/113 engines that used two plugs per cylinder. As other have pointed out, using multiple plugs allowed for a more complete combustion in those engines and they were cutting edge for their time. Note that on some of the latest MBZ engines (not those in our CLKs) use only one plug per cylinder, but the igniter actually fires multiple times per combustion. Again, this is to improve performance, efficiency and reduce emissions.

TechSuperstar · 04-19-2012, 09:09 PM

Thanks a ton Rudeney! I should have done a bit more investigating. Good thing I didn't order 12 of them already. You the man!

Thank you Glyn for the very helpful info. May come in handy another day.

04-18-2012, 04:09 PM	#2
Kevwood MBWorld Fanatic! Garage is empty, add now Join Date: Jul 2010 Location: A Canadian in Dubai, United Arab Emirates Posts: 4,761 Drives: '05 C200K SS, '05 Kleemann CLK500K, '08 Hummer H3 & '92 Z34 5sp (track car in Canada)	Simply, to achieve a more 'complete' burn. __________________ KLEEMANN< Kleemann supercharger, cams, headers & tune \| H&R springs & sways \| Koni suspension Brembo GT BBK, 6/4 pot, floating composite rotors \| GPT pulley \| Magnecor KV85 wires Carbon fiber; vented hood, Vorsteiner spoiler, diffuser, front lip and custom side vents Quaife LSD \| Magnaflow quad exhaust w/ 100 cell cats \| E55K airbox w/ kevlar tubes AMG Black Series strut bars \| 360 Forged wheels, carbon fiber \| eXce1on AV system Mods/build thread

04-18-2012, 04:14 PM	#3
Glyn M Ruck Super Moderator 1965 Jaguar 3.8 S Type Join Date: Jun 2008 Location: Llandudno, Cape Town, South Africa Posts: 15,968 Drives: late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires	Benz used dual plugs on all M112/113 etc engines mainly to achieve LEV (low emission vehicle) status for cars so equipped in Europe. It is intended to burn every last ounce of fuel that gets into the combustion chamber even with detrimental AF ratio when running open loop. As injection & ignition systems have improved & 3 Way Cats are fitted so they have become irrelevant. The M112/113 engines blow squeaky clean tail pipes for the time. __________________ Llandudno, Cape Town, South Africa Last edited by Glyn M Ruck; 04-20-2012 at 10:17 AM.

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04-19-2012, 09:09 PM	#5
TechSuperstar Member 2007 Mercedes-Benz CLK-Class Join Date: Sep 2002 Location: Worcester, MA Posts: 157 Drives: 07' CLK350 Cab	Thanks a ton Rudeney! I should have done a bit more investigating. Good thing I didn't order 12 of them already. You the man! Thank you Glyn for the very helpful info. May come in handy another day.

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