Hey guys,

Since i am not mechanically exceptional, beyond the point of changing my own oil and the basics, i often
make the mistake of trusting mechanics for diagnosis of problems with my 250,000km old machine.

Its dual fuel, and the number of times i have had problems with spark plugs is effing outrageous,
whether cylinders just drop or i get no power off the line because they are misfiring.

A friend of mine who is into bikes mentioned that bikes spark plugs operate on different temperatures depending on what they are running on. He went into "self cleaning temperature ranges" and the like, whereby they get clogged up if they do not reach this temperature.

Since gas and petrol burn at different temperatures, are these 8 dollar spark plugs the morally upstanding mechanics
at southern mitsubishi right for the job?

*or do i require special sparkplugs for a dual fuel setup?*

I know very little about gas so anyone with a better understanding than I feel free to step in and correct me.

My understanding is that generally one needs a spark plug with a lower heat range, with a smaller gap because

* LPG burns hotter
* LPG increases the voltage requirement at the electrode gap, this is because the mixture for LPG to combust is denser than that of a petrol\air mixture.

Also keep in mind that you're more likely to notice a misfire on LPG than on petrol, because LPG (the mixer system mainly) requires your ignition system to be spot on (being vacuum loss free is helpful too), so something as simple as a dodgy set of leads can affect it.

I know very little about gas so anyone with a better understanding than I feel free to step in and correct me.

My understanding is that generally one needs a spark plug with a lower heat range, with a smaller gap because

* LPG burns hotter
* LPG increases the voltage requirement at the electrode gap, this is because the mixture for LPG to combust is denser than that of a petrol\air mixture.

Also keep in mind that you're more likely to notice a misfire on LPG than on petrol, because LPG (the mixer system mainly) requires your ignition system to be spot on (being vacuum loss free is helpful too), so something as simple as a dodgy set of leads can affect it.

hes right i got lpg had to get the lower range spark plugs as using lpg it goes through spark plugs more often and leads ive been told puts more strain on them i just put platinium in mine says it will do 100.000k thats on petrol so i reckon will do about 50.00km on gas

Iridium plugs are usually recommended for mixer type LPG, with that a smaller gap is usually set to avoid pre ignition, blowing up your MAF. And strangely, as it is a cleaner burning fuel, plugs last longer if you buy the right heat range to begin with.
Vapour injection LPG won't suffer from pre-ignition as the gas is Sequentially injected 2/3 to 3/4 of the way in the intake manifold, not pre throttle body.

Thanks for confirming that guys, so look, if i put in some standard platinum spark plugs all around, in theory i should be in the clear right?

Bosch have a specific LPG plug available listed on this link:

http://www.bosch.com.au/content/language1/html/6578.htm

ive used iridium on both my dual fuel cars - no probs
both were around 250,000 ks old

if you are not getting a strong enough spark, using the same plug in planitnum or iridium will just make the issue worse. A set of copper plugs at 3bucks each, suited to the application (heat range and gap) will be fine for the life of a service (10oookm) just change them when you change the oil and filter. For the same plug gap and heatrange and used in the same testbench, coppers will produce the most powerful/ largest spark.

we only use ngk plugs and leads. always get a heat range colder than factory spec and then gap them down. eg if the gap is 1.5 the gap it to 1.2. if its 1.1 gap it to 1.0

we only use ngk plugs and leads. always get a heat range colder than factory spec and then gap them down. eg if the gap is 1.5 the gap it to 1.2. if its 1.1 gap it to 1.0

Why? I know 2/5 of stuff all about this kind of stuff.

Cheers, Greg.

basically gapping them down is because generally the colder plugs come with bigger then suitable gaps. Well gaps good for petrol. With lpg, cylinder pressure on the compression stroke is usually greater then when on petrol, and getting a spark to jump the gap is harder the most pressure is inside the combustion chamber. Its always best to run as big a gap as you can, but there comes a point where you will get a misfire because the plug cannot produce a spark jump.

platinum/ iridum plugs do last longer, but only under ideal conditions, which usually means they dont last there rated 100oookm anyways in a car. Ive run coppers for 30oookm and still had no misfire/poor running on my verada when it was still in good nick. Once the engine got old i was lucky to get 10ooo out of a set of coppers and the last set of platniums i got only went for 40oookm before i had a bad miss.