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2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by streborx
The Wikipedia page on Gasoline Direct Injection (https://en.wikipedia.org/wiki/Gasoline_direct_injection) deserves a read (actually 2 or 3 reads to comprehend it all), and while spark plug indexing is not addressed, the methods of direct injection described therein provide some insight into the benefit/necessity of indexing.
Direct injection can implement either a homogenous charge mode or a stratified charge mode. The homogenous mode injects fuel just prior to the intake stroke. Fuel and air are mixed during intake and compression. Ignition then occurs with a homogenized air/fuel mixture, and the location of the ignition spark within this mix is irrelevant (how would the spark plug know where the fuel/air mix originated?). In contrast, stratified injection occurs just prior to ignition (at the end of compression), and because the air/fuel mix is not homogenized, the location of the spark becomes critical (this seems to be the implication of the 2014 MB "technical" paper). I would agree spark plug indexing in an engine designed for stratified fuel injection charge would be critical and imperative.
Indexing spark plugs on an engine that uses homogenous charge mode doesn't hurt anything, but does it help?
And I believe our engines use stratified fuel injection.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
So, that's about $118 or $14.75 each BEFOREVAT. The plug price is good. The VAT sucks! That would bump them to about $17.70 each. Still not too bad for Genuine plugs. They are $17.79 at FCP Euro.
So, that's about $118 or $14.75 each BEFOREVAT. The plug price is good. The VAT sucks! That would bump them to about $17.70 each. Still not too bad for Genuine plugs. They are $17.79 at FCP Euro.
The exchange rate currently in the UK is 1.31, so the total price including vat is around $120, or $15 per plug?
I emailed FCPEuro and asked which spark plugs is OEM and WILL index if torqued properly. Below is the response I received: Comments?
Jason M1 (FCP Euro)
Oct 7, 2024, 3:11 PM EDT Hello Randall,
Thanks for contacting FCP Euro!
The spark plugs do not need to be indexed for this model, so we do not have any that will index when torqued. These are the spark plugs that we offer for that vehicle:
The attached document describes the M276 as having two variants -- a homogenous injection mode direct injection version for the US and a stratified injection version for Europe (see pages 8 & 9). Also described is a hybrid version that uses both modes. Can this get any more confusing?
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by rmorin49
I emailed FCPEuro and asked which spark plugs is OEM and WILL index if torqued properly. Below is the response I received: Comments?
Jason M1 (FCP Euro)
Oct 7, 2024, 3:11 PM EDT Hello Randall,
Thanks for contacting FCP Euro!
The spark plugs do not need to be indexed for this model, so we do not have any that will index when torqued. These are the spark plugs that we offer for that vehicle:
I'm here to help with any further questions or concerns!
Best regards,
Jason
Jason M
Customer Service Senior Technical Specialist
Quality & Service, Guaranteed for Life
I had gotten a similar response from them, as well. Honestly, that is the only time I had my doubts about their recommendations. I should have asked for a reference document that confirms what they said. Instead, I got the NGK plugs from Rock Auto and they indexed perfectly.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by streborx
The attached document describes the M276 as having two variants -- a homogenous injection mode direct injection version for the US and a stratified injection version for Europe (see pages 8 & 9). Also described is a hybrid version that uses both modes. Can this get any more confusing?
The problem with that document is that it precedes the M276.8xx bi-turbocharged version of the M276. The turbocharged version of the M276 (DE30 LA) was introduced in 2013 and the document was published in 2010. So, we don't know if the turbocharged version uses homogenous or stratified combustion. Further, the document concerning Spark Plug Indexing for Direct Injection Engines (attached) was published in 2014 and calls out specifically the M276 engine.
The M276 in the SL400 is designated DE30 LA where the original NA 3.5-liter engine was DE35. So, while FCP may be right about the DE35 version, we still don't know about the turbocharged version. Personally, I'm not taking chances. I've been running the NGK plugs for thousands of miles with absolutely no problems. I also index my plugs in my 2014 C350 with the M276 (DE35) engine.
I have to agree with JettaRed. A little extra effort to index the plugs is worth it IMHO. When it comes time I will do so but still a bit confused as to which plug to purchase. I'm going to talk with a MB Tech at my local dealer and see what he has to say.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
The part number for the spark plug from the EPC is 0041596903. The NGK-96427 is the ONLY plug with the same cross-reference part number. The other four plugs listed by FCP do NOT have that cross-reference part number.
The part number for the spark plug from the EPC is 0041596903. The NGK-96427 is the ONLY plug with the same cross-reference part number. The other four plugs listed by FCP do NOT have that cross-reference part number.
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