Nippon Denso plugs

[Dark Skies]

I'm changing the plugs on my bike whilst I'm tinkering with the ignition.

The owners manual says I can use either W24ES-U or W24ESR-U

The only ones my local bike shop had in stock were the W24ESR-U flavour. Anyone know what the R stands for? I thought it might be some kind of resistor plug but it might be some kind of performance boast.

[london calling]

R is for resistor,I think

[Dark Skies]

Thanks. Shouldn't pose a problem then. I was a bit concerned they might be a hotter grade or something that might cause grief.

[london calling]

I always use W24ES-U in my bikes
The resistor plugs seem to be an American specified plug according to my Denso application book.
Check 'em out with www.sparkplugs.co.uk

[Al]

Seem to remember that you couldnt use r plugs and r caps together as a combination. Worth checking what caps you got!!

Measured the resistors on my NGK's recently. They were from the sublime to the ridiculous. Now changed!!!

[knut]

think the "R" is for radio suppression so it doesn,t interfere with radio/audio etc.

[Dark Skies]

think the "R" is for radio suppression so it doesn,t interfere with radio/audio etc.

Probably be useful to keep the plugs then - so's it won't interfere with my SatNav

I've got regular non resistor plug caps.

[toycollector10]

There are plenty of websites that can specify the correct plug for your model.

Here is one of them.

http://www.densoiridium.com/find_part.php?tab=2

[Dark Skies]

There are plenty of websites that can specify the correct plug for your model.

Here is one of them.

http://www.densoiridium.com/find_part.php?tab=2

At £8 + a pop plus postage I think I'll pass on the Iridium flavour. If the standard carbs and ignition are in good shape the most expensive plugs in the world aren't going to add anything that a standard plug isn't already providing. Fools gold I reckon. Same with all those U and multipoint plugs. The spark is only going to pass from the electrode to one earth at any given pulse.

[Pigford]

Dark Skies, thats not 100% true
The 'u' or 'v' groove does actually help promote faster burn, a smidgeon
The spark & fuel mix needs to meet quickly & fully for best 'control' burn
Proof...... rememebr back to the 80's and those trick plugs really did help the 2-strokes run cleaner
Turbo & nitrous motors run better with 'em too...
And as documented on this very site, better plugs have a major effect on a bikes performance... ie: NGK vs DENSO
The posh plugs may not be worth 5 x the std ones, but ---- pays yer money & makes you choice

[Dark Skies]

Dark Skies, thats not 100% true
...

'Appen as maybe but I've tried them in my Porsches and some big bikes and noticed no perceptable gains in otherwise standard motors. They may last a bit longer between changes but ... I could get maybe four to five changes of quality plugs for the same money - negating any benefits. If I was dragging or racing a really tuned motor they might prove the cherry on the cake. But I'm not.

[Z1_Kerry]

Darkskies, I think Mr Pigford is referring to the 'U' or 'V' negative electrode design rather than to Iridium plugs. I agree that iridium plugs are expensive and any gain would be at the high performance end.
Me I've not noticed any real difference between NGK and NDs. Any new plug that replaces a used plug will always fire better, just cos it's new. So what happens is generally we replace a set of used plugs (maybe a little sooty from trying to start an engine that's sat for a while) with a new set and instant ignition and bike seems to run better. Run a set of NDs for a while or leave the choke on a little too long and then replace with a new set of NGKs and same instant energy.
However, the groove in the negative electrode does provide better spark when the spark runs from the negative electrode to the centre positive electrode. I don't know the science behind this (well not compleatly) but a groove in the negative electrode assists the current to jump the gap. Now correct me if I'm wrong but a Z1, like a lot of bike brands, uses a single coil to fire 2 cylinders. The principle is that the current travels down one wire to the plug, jumps the gap to the negative electrode, travels across to the other plug, jumps from the negative electrode to the centre electrode, on up the coil via wire 2 to complete the circuit. The timing of the bike is such that it collapses the windings of the coil when the other cylinder is at TDC. In effect two spark plugs fire at the same time whilst only 1 cylinder is at TDC on the ignition stroke and vice versa.Now before I get shot down in flames and people tell me I'm pissing in the wind, I am not sure if this is how a Z1 ignition system works but my CBX works on this principle and so do other ignition designs. If this is the case, it has been demonstrated that a groved plug is marginally better for this type of application, if the published data is correct. I hasten to say marginally and like the iridium plug, is at best, for top performance applications. The "R" in the plug type is indeed referring to resistor or radio suppression and these shouldn't really be used with suppressed caps.
Anyway someone will correct me if I'm wrong about the Z1 ignition, nevertheless Mr P is correct, albeit by a bees dick. KP

[RALPHARAMA]

It is my belief that if you run suppressor caps as most of us do, the 'R' grade plugs are unnecessary and having a second resistor in series can only weaken the available welly to give the spark.

As far as the ND / NGK argument goes: it is my belief that NGK plugs are fine in an engine which is fuel injected in perfect tune; the problem we have is that our engines are old and our carburration is never going to be 100% perfect and especially when starting with a manual choke the plugs are going to get wet from time to time. NGKs seem to roll on their backs and die with this treatment, whereas NDs seem to be far more forgiving. Modern engines with their uber accurate fuelling don't need plug changes anything like as often as in the 70's and 80's. Many vehicles need a major strip out to even get near the plugs these days, where as in the 70's plugs were changed very regularly. As I'm riding older bike I'll never buy another NGK again as they are simply not reliable any more.

I also don't thing the fancy pants plugs have any place on old bikes like ours, unless you are tuning for racing.

[Z1_Kerry]

Ralph, You're probably right about engine age and carb tune, and I forget that our environments are totally different. I rarely use the choke to fire an engine as there is little need in the tropics. But when an NGK plug soots up or gets wet it won't fire ever and I concede that's happened to me a few times. NDs are just so damn hard to source here these days. KP

[Pigford]

Always a good debate.......
My opinion is that once you start upgrading the ignition... why stop... keep going and you'll do ALL of it....

No point having a DYNA S and using 'normal' pliugs
I like tech bling... so:
DYNA 2000 + DYNA COILS + DYNA LEADS + BESTEST SPARKPLUGS
Just peace of mind & Pig-headedness