Adding to the thread with my plug/coil change notes.

1) can't be overstated, the right tools make the job go a lot quicker

2) total time approx 3.5 hours including 30 mins looking for a coil bolt that fell into some god forsaken crevasse. If it wasn't for an inspection camera and a telescoping magnet that bolt would have been lodged in there until the day the car met a crusher

3) coil pack connectors are a PITA until you figure out the right combo moves like those old video games. PeterUbers used a jewelers screwdriver which tipped me off to an alternate method. Once I got that down it was EZ PZ

4) Goddam everything in that engine compartment has a sharp edge, which your knuckles will find over and over and over. Imagine running naked through an endless briar patch, that's how it felt. Hands are being sent to Hawaii for a well-deserved vacation

5) I tested the assumption that if you properly torque the OEM plugs then they will be automatically indexed. See results below

6) Bosch coils seem cheaper than the Beru

7) I can't imagine you tuned guys doing this every 15k miles. God bless your souls, hands and patience




Bosch vs Beru.




Stock Beru on left vs. new Bosch




Beru is a two-piece as I was able to reconnect the stem when it popped off the coil body




Some put a screwdriver from the plug end, which works OK. Better to wedge the small screwdriver between the grey clip and black tab while pulling with an angled pick



Marker on socket for indexing




Arrow indicates position of open end of strap after 23nM. All but one ended up at between 7 and 8 o'clock

 

Nice work... i started using a dental right angle pick to finagle those connectors off

also - telescopic magnet for the coil bolt? I thought those were aluminum like the cps bolts ... good to know they are ferrous and therefore retrievable with magnets

the beru seem more robust compared to the Bosch but so long as they work the same I'm all good.

 

Yep, it looks like an electro coated steel of some sort. Aluminum, even a hard T6 Al would probably get chewed up quickly with those torx points. Thankfully magnetic, not sure how the hell I was going to retrieve it as it fell behind and lodged in a suspension member. Probably could have dropped the undercarriage shields, put up on a lift and dug around for a while.

 

This is helpful. Thanks

 

I was also able to just shove the flat aspect of a zip tie under the connector interface and this worked well

 

What do people pay for dealers or indy shops to do plugs and coils?

I'm not very experienced working on cars and I read that thread on incorrect spark plugs causing major issues, so I'm probably not going to do it myself on this vehicle.

 

Local mb dealer quoted in the 8xx dollar range for plug replacement. Without coils.

 

You guys just tossing the old coilpacks?

 

Every 10k miles yep

 

Probably no reliable way to test the old ones.

Car feels brand new with a fresh set, wish I had some data to back that up.

 

There's prolly a way to measure voltages at the coils to determine which one has worsening resistance... I'm sure one of these guys on here knows ... my only datapoint/metric was misfires ...

car may pull timing due to bad coil I suppose .. consider the first 20 posts in this thread ... knock and timing retard discussed

https://mbworld.org/forums/w212-amg/...ispreloading=1

 

Here is my new set getting ready to go in.
for those worrying about replacing them every 15k miles, just buy them one time at FCP euro and you get lifetime replacement. Just pay shipping.

 

one tip I saw on a video that I haven’t seen mentioned is to mark the spark plug with a dot with a sharpie so you can easily tell which way the plug is facing after installing.

 

Thanks. Seems bad. Haha

 

Can someone chime in on the way they should be facing?? 12oclock

 

The big hole is for the spark plug. The smaller one is the injector port.
I would think you would want the gap to face upwards in this photo, towards the injector/intake valves.
Clear Video of the M 157 Cylinder Head

 

So the ground strap should face down in the 6 position towards the exhaust valves. Which would imply the torque method of indexing doesn't work, at least in my case.

How is everyone else confirming that simply torquing to 23 ends up with properly indexed plugs?

 

My thing with indexing is we really do not know how these combustion chambers are designed. Gas flow is modeled using computers and is highly researched as it is a source of both power (good) and emissions (bad). We have engines with high volumetric efficiencies, high compression and modern squish designs. It is highly possible the orientation is not where we might normally expect to keep the spark kernel from extinguishing due to high gas velocities. In the case discussed here the orientation is consistent and perhaps the correct design.
It is fun that we can play with these cars and enjoy a well-designed, high-performance automobile. I am not racing mine, so I enjoy the comfort, sophistication and the all too fun kick in the a.. once in a while.

From the NGK site:

GAPPING

Since the gap size has a direct effect on the voltage necessary to jump the gap and ionize (light) the air-fuel mixture, careful attention is required. While plugs are pre-gapped from the factory, the gap may need to be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that higher compression or forced induction will typically require a smaller gap setting (to ensure ignitability under higher pressure).

The voltage requirement is directly proportional to the gap size. The larger the gap, the more voltage is needed to jump the gap. Most experienced tuners know that increasing the gap size increases the spark area exposed to the air-fuel mixture, which maximizes burn efficiency. For this reason, most racers add high-energy ignition systems. The added energy allows them to increase the gap, but still have enough voltage to jump the gap.

Many think the larger the gap, the better. However, if the gap is too large, and the ignition system can’t provide the voltage needed to spark across the gap, or turbulence in the combustion chamber blows out the spark, misfires will occur.

INDEXING

Indexing is done by placing (usually copper) washers of varying thickness on the spark plug shoulder, so that when the spark plug is tightened, the plug will rotate a certain amount, and gap will point in the desired direction. In most engines, performance will improve when the spark plug gap opens toward the intake valve(s). However, without testing different index positions in an engine on a dyno, it is nearly impossible to determine which index increases performance. Indexing spark plugs will typically make only a few more horsepower – usually less than 1% of total engine output. For a 500 hp engine, that’s only 5 hp. It is usually not worth the effort.

There are also drawbacks to indexing spark plugs. When washers are added, the spark plug may loosen if the washers don’t crush properly and hold the torque. Also, if too many washers are added, the firing end of the plug will not be as far into the combustion chamber and performance can decrease.

 

This is the shared MB document in the sticky, so it implies MB has specified the index position:

 

Good rebuttal. I have a new set of plugs waiting for the 50k mark to arrive. When I installed the first set, I did not consider indexing. I will definitely look this time.
I do notice that if swapped the sides of the sketches they would be close to correctly indexed. Anyway, I will have to drive my car more so I reach 50k sooner, then I can experiment.

 

I don't feel any ill effects and no misfires are present so it's probably fine. Maybe I'll buy an MB branded plug (instead of Bosch) even though they're supposedly the same and swap out #5 which is in the complete wrong orientation. No way I'm moving the other 7...

 

@NoVAe63s super helpful info here thank you for sharing...

i'm about to do MB oem plugs/coils on my e63 which is at 48k miles and tuned with new plugs that have 10k miles and starting to get a random misfire.

Quick questions - should the plug ground strap open side face DOWN and pointed away from the injector if properly indexed (or within 45 degrees to either side of injector) ??

Also, did you install the MB OEM plug with stock gap (A0041598103 - made by bosch but with MB star on it) and still had challenges indexing properly at torque 23nm? appreciate any feedback on those before i tackle this

 

The plugs were the 8103 from the FCP ignition service kit. Kept factory gap.

As far as the indexing goes I'm surprised no one had commented on my incorrect position - the straps all faced up or upwards (towards the injector) even though they were torqued to 23nm dry using a digital TW. I'm not tuned so that's probably why I haven't had any issues but it was on the to-do list to get these properly indexed just in case.

But I did want to test the theory that just indexing to 23nm ensured a properly indexed plug, which was not the case. Maybe the pn# and plug are different if purchased from MB direct.... something else on the list to check.

 

Last week i have installed NGK 97506 plugs, i gabbed them to 0.6mm 0.024", i added a 0.8mm washer to all plugs so they were indexed properly and yes the pictures up are false the plugs should face the center of the engine towered the intercooler not front or rear.

 

Sounds about right so the plugs should fall somewhere in the 10-2 oclock range. If you were standing over the fender.