different plugs front to back

[edds11]

Having read Tony.mom comments on Iridium plugs I thought I would check mine out and found the following. Front was indeed a DPR9EVX-9, quite pleased really, and then took out the rear and it is a DPR8EIX-9 , can anyone throw any light on the reasons for this, or was it just a previous owner/mechanic who could be arsed to reach a little higher for the correct one.
I know the 8 refers to heat (operating temperature) of the plug, but cannot see why it should be any different, have I stumbled across a secret tuning mod' without knowing or is it like stated earlier.
If you think about it everything else is different between the 2 cylinders so why shouldn't it have a hotter/cooler plug ( can't remember which way around it is).
All comments/observations/experiences welcome

[seb421]

possibly different jets used front and back to help cooling on the rear head, possibly why its got a different temp rated plug so it fires / sparks burns cooler than the front does?

[edds11]

yes thats my whole point, its a non standard fitment, is it worth anything

[oldbikeman]

It is liquid cooled just like a car engine so there should not be any temp differences.Both should be 9s of what ever type plug.

[seb421]

It is liquid cooled just like a car engine so there should not be any temp differences.Both should be 9s of what ever type plug.

I would argue this, rear is going to run hotter liquid cooled or other simply because it has got hot air flowing over it from the front head / engine and the front has cool / ambient air aiding cooling

[tony.mon]

It is liquid cooled just like a car engine so there should not be any temp differences.Both should be 9s of what ever type plug.

I would argue this, rear is going to run hotter liquid cooled or other simply because it has got hot air flowing over it from the front head / engine and the front has cool / ambient air aiding cooling

Not inside the combustion chamber it's not, Seb!
How's the breeze going to get in there, except via the airbox, where it's all mixed together anyway?

Air flowing over the engine doesn't really aid cooling at all on liquid cooled engines- no fins or anything sticking out into the breeze to radiate heat away.
The radiator does all the work, and the oil cooler, if fitted.
Otherwise cars wouldn't have bonnets over the engine...

Plugs should be the same on liquid cooled engines, but may be different on air cooled ones.

Centre pot on a triple often runs hotter, so needs a different plug to the outside ones, as well as front/rear differences.
But only on air cooled engines.

Someone's had a (wrong) idea.... Fit two 9 grade Iridiums.
It won't have done any damage.

Here's what NGK USA say about heat ranges:
Heat Range Selection

Let's make this really simple: when you need your engine to run a little cooler, run a colder plug. When you need your engine to run a little hotter, run a hotter spark plug. However, NGK strongly cautions people that going
to a hotter spark plug can sometimes mask a serious symptom of another problem that can lead to engine damage. Be very careful with heat ranges. Seek professional guidance if you are unsure.

With modified engines (those engines that have increased their compression) more heat is a by-product of the added power that normally comes with increased compression. In short, select one heat range colder for every 75-100 hp you add, or when you significantly raise compression. Also remember to retard the timing a little and to increase fuel enrichment and octane. These tips are critical when adding forced induction (turbos, superchargers or nitrous kits), and failure to address ALL of these areas
will virtually guarantee engine damage.

So even when I have higher compression and 20 more bhp, I still use standard heat range plugs.

[Stephan]

I would argue this, rear is going to run hotter liquid cooled or other simply because it has got hot air flowing over it from the front head / engine and the front has cool / ambient air aiding cooling

+ heat coming from rear header pipe where is not incoming cool air, thats the reason why storm has different jetting, richer air/fuel mixture helps to cool down the rear cylinder.

[Vtrkidda]

The owner before you probs couldn't be arsed changing the rear plug simples

[tony.mon]

The owner before you probs couldn't be arsed changing the rear plug simples

Maybe.
Or went into shop, bloke behind the counter only had one correct one, but said "this'll do" for the other one.
Or Parts bloke needed new glasses, owner didn't check, that's theory three.

It doesn't really matter how it came to be there, though, you can fit whatever plugs you want, but if you change anything from standard you would do well to understand what effects the change will make.
Some changes are for the better, but some aren't.

[edds11]

Hence my first post....is it a stumbled across tuning tip that no one knows about, or some lazy B'stard

[tony.mon]

Hence my first post....is it a stumbled across tuning tip that no one knows about, or some lazy B'stard

Lazy/ignorant B'stard, I would imagine.
It's harder to read Iridium plugs, but you could, if you felt inclined, try the bike on one or both grade 8 ordinary type (fat electrode) plugs, and read them after a while using the colour chart in any Haynes manual.

You should be able to tell if there's any performance loss (more likely) or gain.
And back to back testing would show on the temp gauge, if there's any effect.

But my humble opinion is that there would be no advantage to changing heat ranges for normal bikes in normal use, even with normal jet kits, cans, filters, etc.
If you were running constant below-freezing conditions, using it very high up all the time (mountains) or planning a run across Death Valley you might see a benefit, but not for general use in the UK.

[edds11]

I'll go buy another 9 then

[lumpyv]

question is, how long have you been running it like this? and was it running ok?. if its been going ok for some while i guess its not all that critical?

[edds11]

it seems ok, but then I don't know any different, its the only storm I have owned or ridden, it will travel a long way without any heat issues, it CAN fly when it fits, its good on fuel, it starts every time, rain don't bother it, never miss fires, only coughs and farts at 2800rpm a few times. Sounds like its normal to me.