General Spark plugs for Seicento sporting

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General Spark plugs for Seicento sporting


New member
Oct 14, 2007
Can anyone suggest a foolproof way to confirm correct plug for a given car?It's a 99 Abarth,do I need an engine number?I have seen the Denso Irridiums reccomended here,anyboby have some thoughts on this?
It depends on whether you're changing plugs just because they need replacing and just want a standard set, or want to upgrade to more performance type of plug.

I've tried every kind of 'performance' plug over the years and on many different modified cars, not just centos and if I'm being honest I have always been disappointed and then wished I'd just bought a cheaper alternative. I'm talking Champions, NGKs, Splitfires, the lot. Don't get me wrong, they aren't bad plugs, on the contrary, they all performed okay (apart from 1 set of Splitfires, years ago) but no better than their respective cheaper 'basic' versions.
I've recently fitted some Denso Iridium and they are brilliant. Whether or not they are 'needed' on a stock engine is debatable (my engine isn't standard but I'm sure they would give the similar benifits on a standard one).

Before I bought these I did a lot of research on various make car forums to get a more rounded opinion and didn't find any negative views (if you just go on a single make forum's opinion you can get a bit of a 'what I'm using is great and everything else sucks' )
All the benifits that were mentioned in all the forums are exactly what I've found - much better throttle response, smoother power delivery, more stable idling, and a slight improvement in mpg. Have a look at

It's up you, of course, what you want from a new set of spark plugs and how much you want to spend. Any new set will give you a bit of a 'pep up' especially if your old are knackered, but I can 100% recommend the Denso Iridium.
Like I said, I'm not saying the Denso plugs are definitely the best and everything else is rubbish - Champion and NGK are great plugs and they didn't become the 2 biggest names in this field for nothing. I'm just offerering you my opinion on Denso Iridium which are the best plug I've ever fitted.
Sorry folks, the Denso link in my last post ain't working :( , so anyone wanting all the technical info, test graphs, etc.. on the Iridium plugs will have to just get to the Denso site through Google.
Took the link straight out my 'favorites' and it worked before so :confused: .
It depends on whether you're changing plugs just because they need replacing and just want a standard set, or want to upgrade to more performance type of plug.

I've tried every kind of 'performance' plug over the years and on many different modified cars, not just centos and if I'm being honest I have always been disappointed and then wished I'd just bought a cheaper


Were the Iridiums on standard leads or Magnacores etc?
Well, cc1, the thing is they are working now on the crappy original leads that have been on the car since new. So, with them making such a difference already, when eventually I do get my Magnecors (or another type of upgraded lead), I imagine then I'll see the full performance out of them as they can't be giving 100% of what they're capable of at the moment, but even at 80-90% they are still the best plugs I've used. (y)
whats the damage for a set of denso iridiums?
i had a new set of champions a while back, with new splitfire leads i think it was, and it was crackingfor a short while, untill my foot got a bit too throttle jolly... probs time for some new ones...
I use Denso Iridiums in my Sei, paired up with KV85's. It all got fitted at the same time as a whole host of other things so can't tell you about what it felt like. Bear in mind though that essentially, a spark is a spark, good leads and plugs will give you a reliable spark, but not any extra power.

I got mine from some online outlet, with the magnecors too, forgotten the exact price, think it was around £36.
I got my Denso Iridiums from and they were about £36 inc. VAT & delivery.
A spark isn't just a spark - there is a lot more to it than that - flame kernal duration/expansion, minimising misfires etc. Denso's lab and track tests have shown consistant improvemants in power and acceleration over normal plugs that use conventional metals, gaps and electrode diameters.
So you've stated the benefits of having a reliable spark from good leads and plugs (no misfiring), but what does a 'better' spark do? As far as I'm aware, a strong spark can be obtained from a 99p spark plug, just as much as an all singing all dancing Iridium one could.

I chose Iridium because of the supposed longevity that, I am lead to believe, is the difference between the 'premium' and the 'value' plug (although Peter @ GSR tells me that may need replacing soon, having been in for 10 months). I am also aware that modern engines are built around Iridium plugs, why or how I don't know. I would imagine the longer service intervals modern cars have now are a factor.

Just out of interest (and with due respect), do you know what a flame kernel is? From my limited web trawling of the past on the matter, spark plugs have nothing to do with their duration or size (I'm guessing that would be more down to mixture and timing), I understand them to be the start of the combustion process in the cylinder.

The spark plug initiates this kernel and, of course, a nice strong spark will no doubt reduce the chance of the kernel 'dying' and causing a misfire, but this brings me back to my original point. Mr 99p plug could do this, albeit supposedly not for as long as Mr Energiser plug.

Even the longevity credentials are questionable. I'm only looking at what I hear from the makers themselves, the public and my own logic. And we all know that the makers are trying to sell their product. Only recently, the makers of Innocent Smoothies were in hot water for advertising false health benefits. Don't believe the hype that's sprouted from the horse's mouth; marketing get paid a healthy (ahem) salary for a reason.

There are many sides to a story, however. There are people who have running troubles with a particular type of spark plug, so maybe there is a difference somewhere. I know that the Bosch "super 4" plug is supposed to be bad due to the four terminals hindering the flame kernel's development. After all, the spark will only occur where there is least resistance, meaning only one terminal will be used at any one time anyway. I used these in my old, stock, Punto 60S; could I feel any difference (for better or for worse) after these were installed, plus an oil change? No. Would there have been any difference on the rolling road, if I had put it on one? I very much doubt it.

If you, or anyone here, know more on how these processes work, it would be great to hear further explanation/correction. I'm open minded on the matter. Also, if you got this far then wow, you must be as bored as me :D
The next generation of plugs will probably be 18 carat gold to increase life due to better heat insulating properties...???? erm??? right.
Okay, briefly because I am getting a bit bored with this thread now :D Ha!

The research I did on different spark plug types was mainly using science based websites or university technology sites as you are right, just going on what a manufacturer's site says is a bit risky (fell into that trap years ago when the Splitfire plugs came out (n) ).

All the tests I read had been done on what most termed as 'finewire' electrode plugs (of usually 0.6mm, so Denso's should be an improvement on this at 0.4mm), showed consistant power gains and vast reduction in misfires due to the spark's flame kernel being allowed to expand and grow more than it did with conventional plugs. I'm assuming that iridium is the metal used because normal spark plug metals would simply disintigrate in a short space of time if they were made to such a small diameter. With the conventional plugs, some of the tests tried increasing the plug gap to give more space for the flame kernel to grow and become stronger, but that then increased the rate of misfire as the sparks would sometimes not jump the gap.

So, after seeing these independant tests, I then figured that the test results shown on Denso's own site could be believed and that was enough reason for me to buy some - in addition to all the positive reviews on different car forums.

At the end of the day, to coin a phrase, I have found them to produce a real noticable difference, which is all I was saying in my first post when I recommended them. Incidentally, the Bosch Super 4 plugs get a lot of negative comments on here, and maybe they aren't suited to the cento engines, but I've had a set in my modified XR2 for years and they have been fine, so anyone with other non Fiats, don't discount them - they aren't a bad product.