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Either one is fine copper has best conductivity but iridium has good conductivity with awesome life.
 

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I've run all types with all varying degrees of success or failure. Just stay away from brands like OBX, or the econotypes. For the Impreza NGK, and Denso are both fine.
 

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On the LotusTalk forums i'm on, theres a guy who installed those Pulsar spark plugs with a supposed increase in "kick" from the engine... I don't know if anyone wants to try those out otherwise NGK Iridiums is what i'd get...
 

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On the LotusTalk forums i'm on, theres a guy who installed those Pulsar spark plugs with a supposed increase in "kick" from the engine... I don't know if anyone wants to try those out otherwise NGK Iridiums is what i'd get...
iv heard mixed about the pulstars. anyone have any actual exp with them?
 

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I would use either
IKH20 < std iridium
SK20HR11 < long life iridium = stock
K20HR-U11 = copper

DG-1 Pulstar

I am leery because it is not application specific
 

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Sorry folks...

I should have been more clear. I want use the iridium's and go a step colder but I need part #'s. Anyone already have these? if so... part numbers pleeeaaase...

cheers
Why do you need to go a Step colder?

I would use NGK Iridiums or Denso Iridiums.
 

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Discussion Starter #16
i don't need to go a step colder but from what i have read it helps make a little more torque and hp. it seems to be a popular mod for stg2+. i have read about this many times before and i still don't get the concept totally and i will not try to explain as a result. if anyone is a spark plug boffin please chime in...
 

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A spark plug's heat range has no relationship to the actual voltage transferred through the spark plug. Rather, the heat range is a measure of the spark plug's ability to remove heat from the combustion chamber. The heat range measurement or specification is determined by several factors:

The length of the ceramic insulator nose
The insulator nose's ability to absorb and transfer combustion heat
The Material composition of the insulator
The material composition of the center electrode
Let's first look at the length of the insulator. The longer the insulator nose, the larger the surface area that is exposed to the combustion gasses and heat. With the long insulator nose heat is dissipated slowly. This also means that the firing end of the plug will heat up more quickly. Make sure you understand that we are talking about the actual exposed insulator length, not the extended tip length.

The insulator nose length is the distance from the firing tip of the insulator to the point where the insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling. No matter what engine the plugs are installed in, be it a lawnmower, a boat, your daily driver or your race car, the spark plug tip temperature must remain between 450¬?C to 850¬?C. If the tip temperature is lower than 450¬?C, the insulator area surrounding the center electrode will not be hot enough to deter fouling and carbon deposit build-ups, thus causing misfires. If the tip temperature exceeds 850¬?C, the spark plug will overheat which can cause the ceramic around the the center electrode to blister as well as the electrodes will begin to melt. This may lead to pre-ignition/detonation and expensive engine damage. (see the plug pictures that are part of this article)

In identical spark plugs, the differences from one heat range to the next is the ability to remove approximately 70¬?C to 100¬?C from the combustion chamber. Note, that a projected style spark plug firing temperature is increased by 10¬?C to 20¬?C due to more area exposed to the combustion temperatures.


The firing end appearance also depends on the spark plug tip temperature. There are three basic diagnostic criteria for spark plugs: good, fouled, and overheated. The borderline between the fouling and optimum operating regions (450¬?C) is called the spark plug self-cleaning temperature. This is the temperature point where the accumulated carbon and combustion deposits are burned off automatically.

Bearing in mind that the insulator nose length is a determining factor in the heat range of a spark plug, the longer the insulator nose, the less heat is absorbed, and the further the heat must travel into the cylinder head water jackets. This means that the plug has a higher internal temperature, and is said to be a "Hot" plug. A hot spark plug maintains a higher internal operating temperature to burn off oil and carbon deposits, and has no relationship to spark quality or intensity.

Conversely, a "Cold" spark plug has a shorter insulator nose and absorbs more combustion chamber heat. This heat travels a shorter distance, and allows the plug to operate at a lower internal temperature. A colder heat range can be necessary when an engine is modified for performance, subjected to heavy loads, or it is run at high RPMs for significant periods of time. The higher cylinder pressures developed by high compression, large camshafts, blowers and nitrous oxide, not to mention the RPM ranges we run our engines at while racing, make colder plugs mandatory to eliminate plug overheating and engine damage. The colder type plug removes heat more quickly, and will reduce the chance of pre-ignition/detonation and burn-out of the firing end. (Engine temperatures can affect the spark plug's operating temperature, but not the spark plug's heat range).
 

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I was running Denso Iridium for a while and was satisfied with them. With my new motor, my shop switched me over to NGK (1 step colder).
 

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