Nanook

My first plug(s) seems to be going south so I ordered a new set today...I think I have about 30k kms..got a cel cylinder 5 misfire but seems to be running fine for the most part..for now anyways..I might pull that plug or just wait for the new set to arrive and change the works

KLR CLS

The big thing for high boost motors is closing up the gap, or you get spark blow out. Figure on gaping between .022-.026. Anything equivalent to a NGK 7 or 8 heat range should be good. So what I can gather is we need a 12mm x 26ish mm reach resistor spark plug. should be able to find options near that without breaking the bank.

kponti

Everything you stated is on point for the stock plugs except the heat range (unknown mystery). Now if only we can find an NGK plug in the right heat range that is also the right reach.....

zulumerc

what is the gap for the stock plugs?

anyone have the part number for the stock plugs are they the same for the m278 as they are for the m157? Do i have to buy oem ones or does bosch make them for mb?

Davidkuo0330

I may be wrong, but all the misfires seems to come from tune AMGs. I had mine Renntech/NGK plugs installed when I first had my Renntech ECU tune.

Now with AMS Alpha 9 or the prior tune, never had a misfire.

KLR CLS

Misfires are 100% due to spark blow out. Closing up gap on even stock plugs will help prevent that. Oem gap is typically on the wider side to ensure more complete burn and prevent fouling. As the electode errodes, the gap becomes wider and begins to blow out during high cylinder pressure transitions
As for heat range, 7 to 8 should have sufficient cooling properties to reduce plug tip heat and prevent detonation for anything under 1000whp.

From a performance perspective you want electrode material that delivers the most spark energy. Typically coppers or silver are best, but errode quickly and cold heat range copper plugs tend fout more on cold start conditions. Iridium are used due to low erosion properties but because of the thin electrode doesn't carry same spark energy.

Last thing is projected tip or not. Typically FI motors are better with non projected tips as they run cooler, but idle quality may suffer.

All this to say nobody should be spending 350 on ****ing spark plugs. Do homework and find what works

Nanook

I just received this back from my contact at Renntech...interesting and unfortunate as I just purchased a new set from Ebay

"We no longer sell the plugs we strongly recommend a fresh set of OEM
(they improved on them) and if you drive hard most likely best is 20-25 k miles
(we change them on ours with OEM’s every 15 k ! DI and fuel enemy nr 1"

sdg1871

That is the same information I received directly for rent around Labor Day of 2014. As a result I did not get aftermarket spark plugs. I prophylactically changed my OEM spark plugs at 15,000 miles to new OEM once a but the dealer did tell me that my original one showed no signs of wear. But I changed them anyway.

AHI

Ok.... So we've concluded not to change the plugs? LoL

Davidkuo0330

The question I want to ask members here is, anyone with tune E63 and upgraded plugs throw a code/misfire?

KLR CLS

It's not about the plugs of any one kind or manufacturer, its about the right gap and spark energy to keep them from blowing out under high cylinder pressure load. All plug types erode the electrodes after time, and that gap erosion combined with reduced conductivity of the plug as carbon builds leads to blowout.

A colder heat range helps prevent pre-ignition at high engine speeds, but that is not material to the cause of these misfires. Basically colder heat ranges are cheap insurance to add another layer of protection against detonation, but colder plugs tend to foul easier and need more frequent changing. The only way to ensure the engine runs at its peak is to change plugs frequently, and ensure a tighter gap. Stockers are fine ( not sure of the cost vs say a brisk QR12LS @15 bucks a plug, but thats what I would recommend since I can't seem to find any NGK or Denso 12mm x 26 mm reach plugs cheaper than that any how.)

Davidkuo0330

The RENNtech performance spark plug upgrade utilizes high quality NGK spark plugs in a cooler heat range than the OEM Bosch plugs. With the increased performance and boost pressure generated from performance tuning comes increased combustion temperatures. With OEM plugs, this additional cylinder pressure can cause pre-ignition and premature spark plug fouling. RENNtech performance spark plug package uses a "colder" heat range plug which allows spark plugs to fully ignite the mixture and allow the engine to maintain higher boost levels across an extended RPM range. This plug upgrade also improves idle quality and is the perfect replacement for vehicles experiencing spark plug or rough idle issues.

kponti

They no longer recommend their plugs, they say change your plugs every 10-15k miles.

Also their plugs are shorter than stock which makes me wonder....

KLR CLS

FWIW I found and NGK iridium option in a 7 heat range that should work:

https://www.ngk.com/product.aspx?zpid=10231

Interestingly seems to be the same plug for ford GT's and mod motor mustangs so should be other options there too

joseyu

Recently had a set of the Weistec branded Bosch silver core plugs installed in my AMS tuned car. I was also getting the Weistec valve body and TCU upgrade, so I figured I should order the spark plugs and air filter as well. My car has about 8K miles on the tune, and if the 10-15K plug change recommendation is true, I was getting pretty close to it. Cost of the plugs, air filter, labor and taxes was $750. The car idles smoothly like before.

TonyC

that's the SECOND time on the board today where "proactively" was changed to "prophylactically". Is this some kinda weird android/iOS autocorrect issue? Cuz it's hilarious.

Sorry, no real comment on the plugs cept to say $350 on plugs is gdamn insanity.

Traffic53

what's so funny?

gaspam

i got one about 1,000 miles after my renntech tune (was on original plugs at 33K miles)

i pulled the plug and electrode had come loose, so i bought a new plug and changed it and misfire/stumble went away and cleared code... all is good

renntech also told me to use OEM plugs and that they dont do cooler plugs anymore as they said the new oem plugs are improved over the original ones from the 12-13 build m157's

Toadster

down to $17.56/ea

NGK SIZKBR8A8HS Laser Iridium Spark Plug

cheap insurance to keep up with the tune

KLR CLS

I wouldn't recommended those. Yes they are an 8 heat range, but 3mm shorter than required and other options for cheaper that do work. Brisk QR12LS for example.

kponti

Wow man, this is perfect. The heat range is low, reach is accurate, Hex size is correct, as long as thread pitch and diameter etc etc are correct we have a winner here.

And being on a MB forum, you nailed it on the head by comparing it to parts in a $150+k car. You know how we love to pay the luxury tax on here

kponti

Here is that plug side by side with a stock plug. The seat shape bothers me

vdubpower

they dont even look like they should fit in the same hole

kponti

That's what she said

kponti

But on a more serious note, they are the same thread pitch, size, shape etc etc. It is pretty much a colder version of the stock plug except for the seat