Spark plugs 400i

Champion plugs are not available anymore. The recommended ngk alternative are BP8ES. I do prefer the Beru Z42 (equally cold) as they do not foul as easily.

Some do prefer hoter plugs such as the BP6ES (beru equivalent is Z22) . If you do not rev the engine a lot these are more suitable.

The gaps for the plugs have to be reduced as per the manual, otherwise the coil will not be able to cope at high rpm.

I am trying the more expensive UPT8 from beru. Regapping these thin tips plugs is much more difficult. Will probably get back to the cheaper Z42.

 

I'm still a believer in small-diameter-electrode, Iridium spark plugs. I'd suggest trying a set of NGK BPR7EIX or BPR8EIX in your model ("8" NGK plugs, regardless of the electrode material/design, are a little on the cold side for rational street driving unless you are driving on Autobahn or Autostrade roads regularly at triple-digit MPH-speeds).

Your OM spark plug gap spec of .024" - .028" seems perfectly reasonable to me.

(PS If in the US, www.clubplug.net usually has the lowest price for spark plugs IME.)

 

Thin plugs are the best of both worlds: these are cold which is better for high load, while providing a stronger spark at idle. Their only drawback is that they do not last long when fouled.

As said I am giving the UPT8 a try. Theses are thin tips plugs, but are cheaper than iridium (less expensive coating). I am about to break the engine in, and it will operate at moderate rpm, so thin tips plugs do make sense. Will report back once completed, but I will probably get back to the regular Z42 plug: more reliable, cheaper and a V12 is smooth even if one or two cylinders are misfiring.

Z42 are ~€2 (BP7ES are equally cheap), UPT8 are ~€3.80, Iridium are close do ~€10. I prefer to pay less for the plugs and replace them more often. On my other car (4 cylinder) I used to change the plugs twice per year: cold NGK plugs (BP7ES) for summer, hot plugs (BP6ES) during winter. Now I am using Z42 all year long and change the whole set as soon as idle is rough.

 

I tried iridium plugs in my 308 and had lots of fouling issues. I think it was a combo of the fuel I used, as well as the old school coils not punching out enough grunt to really use the plugs to their full potential, as opposed to modern cars with high energy coil packs. My daily Ford ran iridium plugs with coil packs, and same fuel as I used in the 308, and never missed a beat. I swapped back to the NGK BP7EY plugs and barely had issue after that. I chose the Y spec over the S spec cause they reckon it give a more even spark pattern for efficiency and fouling. I intend to use similar for my 400 should I ever get it going

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Another aspect to be taken into account, is that these iridium plugs do not like "rich" mixture (as said they do not like fouling). The issue here is that k-jet is rich>lean>rich at low/mid/high rpm. If you tune for lean mixture at idle, this could be too lean at part throttle and if you tune properly at mid rpm the iridium spark plug will not last long. That's the reason I prefer regular (copper) plugs. There used to be some copper spark plugs with multiple straps (side electrode). These are more foul proof. Unfortunately, I just cannot find such plugs any-more.

In order to answer the OP's original question, your mileage may vary, so start with NGK BP7ES, and then "read" your spark plug strap in order to determine if you need a hotter/colder spark. There is a nice paper on the subject: https://sites.google.com/site/kensautomachineshop/technical-information/articles-and-tips/tips---reading-spark-plugs .

 

And my experience was the opposite -- standard electrode NGK plugs fouled quickly in my ex-308 carb while Palladium/Platinum/Iridium NGK plugs fouled much less quickly.

 

I have seen advertisments for Purespark Twin Iridium Upgrade Spark Plugs 5607-14 - ULTRA FINE ELECTRODE - what do members think? I have copied their statement below:

Iridium is an extremely hard metallic element with a very high melting point (almost 2,500 °C) which makes Iridium attractive as an electrode material for spark plugs. All PureSpark™ Iridium spark plugs are manufactured with a 0.5mm diameter center electrode, which is extremely fine when compared to a traditional copper spark plug tip. The narrow diameter concentrates the electrical charge and therefore a much lower voltage is required to jump the gap. PureSpark™ spark plugs offer a number of benefits when compared to OEM copper spark plugs.

• Less strain on the vehicle ignition system.
• Larger gap than a copper electrode for more efficient combustion.
• Improved throttle response, engine power and MPG.
• Cleaner emissions and long service life.

PureSpark™ are also suitable for vehicles with factory fitted Platinum or Iridium spark plugs.

PureSpark™ offer 3 different ranges of spark plugs.

Single Iridium: With its iridium center electrode this spark plug will match most other Iridium spark plugs available while still at an affordable price.

Iridium/Platinum:With its iridium center electrode and a platinum ground electrode. Ideal for long service intervals or an upgrade from standard copper spark plugs. Suitable for classic vehicles or modern vehicles.

Twin Iridium: The ultimate spark plug with its iridium center electrode and an Iridium ground electrode. Ideal for long service intervals or an upgrade from standard copper platinum or Iridium spark plugs. Suitable for all vehicles from classic vehicles to high performance modern vehicles.

 

That is small. My notes have the center electrode diameters of the NGK plugs as they changed over the years/materials as:

NGK standard (ES)= 2mm
NGK Palladium = 1mm
NGK Platinum = 0.8mm
NGK Iridium (EIX) = 0.7mm

 

These two are somehow incompatible: the larger the gap the higher the strain on the coil. Big gap means big spark which in turn means more energy. On the plus side the thin tip means the spark is more focused, so maybe these plugs can achieve a longer more focused spark that does not suck so much energy from the coil (or not).

Let's not forget that we've got a single coil that is supposed to deliver 12 sparks, which is 50% more than a V8. To crown it all, most our coils are old (these are impossible to source). At high rpm, the coil may run out of juice with big gaps.

I do not gap iridium plugs as the tip is really delicate, anyone did it successfully?

 

I do, but you do need to be super-careful to only put loads on the side electrode, and be very gentle when gauging (I use the wire type of spark plug gap gauge).

 

@fez1238 most of us are loyal to NGK because these are cheap, reliable and well documented (it is for instance super easy to understand the the heat range of the plug).

This being said some alternative manufacturers do offer excellent products and should not be overlooked. As said I do appreciate Beru (and Eyquem as I am biased toward "made-in France"). I would be cautious about these PureSpark plugs as these are not well known, no website, no technical documentation.

Whenever I am hunting for new spark plugs, I first identify the NGK plug recommended for my car then I search for cross-references (https://www.sparkplug-crossreference.com/) . I do not take the suggestions for granted though: I always check on the manufacturer website that the proposed alternatives do deliver the appropriate heat-range. From then on I "test" the plug: drive the car for one or two days then "read" the strap and decide whether I should test a hotter/colder set from the same manufacturer. If the idle is rough but the strap (= correct heat-range) and base-ring (= proper CO) are correct I adjust the gap.

 

Typical Ferrari, a different experience for everyone....

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I'm using Denso iridium plugs and have been happy with them.