Iridium Spark Plugs and Cold Start - User Beware

[supperduc]

Changed her oil last weekend and decided to replace/upgrade her spark plugs to Iridium IX (NGK DCPR8EIX). I took her out for a test run afterward and she did just fine (ambient temperature was around 60 °F). I took her out again this morning but to my surprise it took her about 10 cranks to start and maintain idling (the ambient temperature was around 30 °F, and yes, I did follow the owner manual cold start procedure). I tried to start her up again just an hour ago and the same thing happened (ambient temperature was also around 30 °F). Good thing I still kept her old OEM plugs so waited about an hour and put them back on, and she started on the first crank and maintained idling without any hesitation. What a waste of time, effort and $14.98!

2010 Monster 696 ABS

[Twizted]

Ahhhh...the pleasures of having an Italian mistress. They're as temperamental as a pretty girlfriend but they will keep you on your toes. 

[supperduc]

Note to self: Unless you plan to put 100,000 miles on your duc, you may as well stick with your OEM plugs.

Copied and pasted from the ducati.org site - Regarding the use of platinum and iridium spark plugs in a Ducati:

Platinum or iridium plugs will give you worse performance than a conventional plug unless you use a larger gap than is recommended for the steel electrode plug equivalent. One by-product (and benefit) to having platinum or iridium as an electrode material is that the harder material erodes more slowly and consequently allows you to reduce the size of the center electrode and still have a long-lifetime plug. Re-gapping is infrequent or eliminated. In fact, the initial reason this type of plug was developed was an attempt to meet the 100,000-mile durability/maintenance requirement mandated by the US EPA for exhaust emissions, not because they offered any improved performance over conventional electrodes.

A smaller electrode, however, will arc at a lower voltage. This is good because the lower arc-over voltage is not as demanding on your less-than-new ignition coils and wires so the firing is more reliable. But this is also bad because a lower arc-over voltage presents a weaker spark kernel (lower arc current and duration) that is less likely to light off the air/fuel mixture.

Consequently, dyno testing shows a performance gain with specialty plugs only when their intrinsically lower arc-over voltage has allowed users to increase the plug gap above that possible with conventional steel electrode plugs. A larger plug gap needs a higher arc-over voltage to fire, and a larger gap, combined with good plug wires and coils, will span more fuel molecules resulting in a more reliable burn with fewer misfires. So you get better throttle response. Not more power mind you, better throttle response.

The transition between throttle positions involves a wide range of fuel/air mixtures and the ability to fire these less-than-ideal mixtures with a minumum of misfires is what throttle response is all about.

When it comes to spark plug gaps, bigger IS better. The larger the spark kernel that is generated by a spark jumping the electrode gap, the more likely and complete the fuel burn will be, and the smoother the engine will run. That is, the larger the spark gap that's exposed to the air/fuel mixture, the easier it is to initiate combustion. This translates directly into improved throttle response.

Conversely, I have seen several examples of Ducati throttle response problems cured by replacing platinum/iridium plugs that were gapped too small (i.e. the 0.024 in. Ducati recommends for conventional plugs.) Both NGK and Denso pre-gap their Ducati application specialty plugs to 0.035 in. This should be considered a minimum gap for this kind of plug.

If you have a older bike, you may arc-over the plug wires before you can fire an optimized larger plug gap. If the spark plug wires have inadequate insulation, the wire cannot maintain a high enough voltage across the insulation and will arc to ground before firing the plug gap. The factory spark plug leads are stranded wire covered with an EPDM jacket and although the wire itself will last a long time, the insulating jacket will start to break down after a couple of years which is why most good aftermarket wire is insulated with silicone.

If this becomes a problem, replace the stock spark plug wires with a set of Magnecor or similar quality wires. This will allow running a larger plug gap without a concern for insulating the higher voltage needed to jump the gap. Ducati Superbike Magnecor #2549 wires, for example, run $67.

For street bikes, you should use carbon core wires, preferably carbon wires with a spiral wrap center conductor. Straight, multi-stranded, unshielded wire conductors offer theoretical gains resistance-wise, but produce lots of electromagnetic interference (EMI). One major concern is with the computer found used on fuel injected bikes since the radiated EMI can interfere with the computer and corrupt sensor and internal signals which can affect engine performance and reliability. This concern also extends to the use of non-resistor type spark plugs.

For older Super Sport bikes, Dynacoil replacement coils are also available and a recommended upgrade.

[booger]

Iridium plugs are a gimmick and a total waste of money IMO. I even broke down once because of them. They were NGKs.

Ignore the marketing, use copper plugs, and enjoy not having ignition problems.

[alibaba]

Great article supperduc!  I have been running Iridiums in my BSA Gold Stars which are notoriously hard starting.  I am going to rethink that now.

[Heath]

I put Iridium Spark plugs in several months ago have been very happy with the results.  The article you quoted says the plugs are good just make sure your gap is correct.

[supperduc]

Health, I think the issue with iridium plugs is cold start when ambient temperature is around freezing. IMO, the iridium electrodes are just too narrow to produce large enough sparks to start a fire when the combustion chamber is still cold. Good point about re-gaping the plugs to 0.035 in. Did you re-gap yours?

[Howie]

Iridium plugs are neither a gimmick or a waste of money.  Simply a  matter of the correct plug for the correct application.  Platinum and iridium plugs became popular with auto manufacturers in the late '70s to cut both emissions and extend maintenance intervals.  This was used alongside more potent ignition systems like GM's High Energy Ignition, capable of producing as high as 40K volts, compared to the  18-20K available from conventional ignition.   Gaps were also sometimes as wide as .060'', as compared to the more usual .035" gap.  This change also required using larger distributor caps to prevent cross arcing and fatter ignition wires.  Larger gaps will give you better starting and idle in any engine.  This is true for any engine.  The problem is the wide gap may fail to fire correctly at higher RPM, particularly at high load.  

Credit to the person who wrote the article on the other board would be a nice thing to do.  The article is accurate and well written, though I do think Ducati, as well as most European manufacturers use the optimum secondary ignition wire, solid core with resistors.

[Heath]

Health, I think the issue with iridium plugs is cold start when ambient temperature is around freezing. IMO, the iridium electrodes are just too narrow to produce large enough sparks to start a fire when the combustion chamber is still cold. Good point about re-gaping the plugs to 0.035 in. Did you re-gap yours?

I started my bike up in 30ºF temp the other day and it started right up.  I hadn't rode my bike in a couple weeks and had no problem.  According to NGK the DCPR8EIX gap is 0.031.  So that is pretty close to the 0.035 the article suggests. I did not gap mine or even check them before putting them in.  I just threw them in and have been happy since. I never even read about having a bigger gap until this tread. I'm not sure why your bike didn't like them.

[supperduc]

Adjusted the gap to 0.035 and she started and maintained idle on the first crank. Ambient temp was around 34 F. Simply amazing! Here she is, my sexy Italian mistress...

[Heath]

   I might need to check my gap out see if I can get it even smoother.

[ducatiz]

  I might need to check my gap out see if I can get it even smoother.

that's what she said

seriously, this is a very useful thread, i am going to regap my plugs on my s2r and see if it helps.. 0.35 seems huge though

[Bill in OKC]

I've put NGK IRs in all my bikes but I read somewhere not to gap them so I didn't.  I'll be checking them the next time I have them out.  Interesting info/results. 

[koko64]

I've found the best plugs irrespective of whether they are standard or iridium, to be fresh ones.

IMO Iridium plugs resist a certain gooey '98 Octane fuel down here a little better and bounce back a little better from carb flooding. But they are too expensive if something does take them out. With standard plugs I'm not cursing if I have to bin 'em, I just consider it a service item. I use iridium plugs in bikes that require a lot of effort to replace them (a small mercy to the customer).

Whether standard or iridium, plugs never quite seem the same after a good carb flooding.

LT Snyder also advises to increase the gap on iridium plugs.

[Nero-92]

I've had cold start problems with my s4 sometimes it starts fine with the choke other time you have to churn it over and sometime turn of the choke in case it floods could this be plug and or gaps they are the iridium ngk once started and warm the bike pulls clean any help info would be appreciated.

P.S the plugs were only just fitted at the last service and were new out of the box but I don't know how old they are as I got them with the bike.