Spark plugs?

[Angelus359]

I've seen a lot of claims go both ways, where some people say platinum is totally fine, while other people say coppers are the best, while other people say go iridium.

I was wondering if anyone has any hard test data between fresh sets of sparkplugs to see if they actually make any real difference.

I have an aveo, and everyone on the aveo forum says absolutely positively do not run platinum plugs in that car, since it doesn't have enough current for cold weather startup and will have misfires with their specific engine design.
It comes copper from the factory (ngk)

They all recommended either ngk iridium IX, or denso iridium (ultrafine), or to just stick with coppers.

People were saying the ultra fine iridiums were better for cold weather startup due to lower voltage requirement, and the coppers were better once the thing was warmed up due to higher conductivity... I'm no electrician, so I don't really know.

Nobody seems to have actual test results and its all theoretical.

I'll admit the car did startup and run better with the new plugs (new plug syndrome of course), but seeing stats would be nice.

[Daox]

The spark plug type won't effect mileage a noticeable amount. Coppers just last a shorter time than iridiums.

[saand]

i dont know the finer details about spark plugs but if you look at it from a physics point of view it would suggest the spark plugs make little or no difference.

The spark plugs only need to make a spark to ignite the fuel vapor.
The copper plugs that came stock with the car were chosen by the designers and they hopefully tested that they reliably ignited the fuel in the cylinders. If your car is misfiring then you may want to look at spark plugs (which may just mean modifying the gap) otherwise you are likely to get little fuel efficiency benefit or performance benefit.

Having said that a way i can see different spark plugs having advantages over others is from the different geometries of spark plug. The standard plugs that have a single electrode and return has the return covering the spark from where the majority of vapors are. The standard plugs may be very slightly less efficient than the multiple electrode type as the spark goes to the side therefore allowing the ignited fuel at the spark plug tip to propagate more easily to ignite the remaining fuel.
The claim by the manufacturers is that with different materials you will get a more concentrated spark (therefore maybe a hotter spark) and less eroding of materials so a more reliable spark and longer service life. considering a spark temperature is above 1000 degrees i am not sure how a hotter spark will help.

as i said before i don't know all that much about spark plugs so take this with a grain of salt.

[Ryland]

The SAE (those wacky automotive scientists) published a paper on spark plugs, boils down to copper core are great but you need to change them every 15,000 miles or so, the fancy plugs last longer but have resistance closer to a copper plug after 15,000 miles, the platnum tipped plugs also hold up better under high heat, so if you have a turbo you might want to use them, the ultra fine tipped plugs hold up better if you have an engine that fouls easily like a 2 stroke engine.
The only plugs that are much better then the copper core are the silver core plugs... but they also cost alot more.

[gone-ot]

...and, then, there are the Iridium-tipped plugs, which are a VERY hard & brittle metal, and tend to break & snap off easily if even slightly mis-handled...so do NOT try to 'tweek' their preset gap distance!

...however, they DO have very long operational lifes, upwards to 100-150K miles.

[stovie]

From what i understand the hotter the spark the quicker the flame front in the combustion chamber and therefore more power and fe because the ecu has to reduce fuel to compensate for the increased burn speed(the engine can't handle an instant explosion to much force on the piston/rod and it can only move so fast) And the fine tip'd iridium spark plugs are better i think because they allow more vapor around them to increase the burn rate also. You might get better results with a higher voltage coil.

[stovie]

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[NHRABill]

Originally Posted by stovie

From what i understand the hotter the spark the quicker the flame front in the combustion chamber and therefore more power and fe because the ecu has to reduce fuel to compensate for the increased burn speed(the engine can't handle an instant explosion to much force on the piston/rod and it can only move so fast) And the fine tip'd iridium spark plugs are better i think because they allow more vapor around them to increase the burn rate also. You might get better results with a higher voltage coil.

Stick with mfr. reccomendations would be my opinion. the length of the spark and burn of the fuel by the spark is what makes all of the difference putting in a colder plug vs. a hot plug will only cause damage if you don't know what you are doing. I played around ALOT with plugs and changed them hundreds of times when racing supercharged cars. If you had a turbo or supercharger changing the timing curve along with a specific plug type and gap will give you a good amount of difference.

when dealing with a stock vehicle that is designed for economy rather than performance such as yours I would stick with manufacturer recomendations. indexing the plug will be as far as I would go.