Spark plugs for suprcharger application

[mladjan]

Hi,

Soon I will start fitting my supercharger, and was wondering, do I need colder spark plugs? Supercharger will be fitter on stock untouched 40k km engine, so there is no change in compression ratio.

[Spunkster]

It probably would be a good idea. You should talk to your tuner about this.

[mladjan]

That's the trick, nobody in my country don't have experience with k20 and superchargers. So its everything on my own :(
For turbo setups, I know that is smart to do a colder spark plugs, but not sure this is because of low compression or pressure.

[Hondata]

For low boost stock plugs (7s) will work. Otherwise 8 heat range are a good choice. Don't use non resistor plugs.

[mladjan]

It will be around 1bar of boost. Is that "low" still? :D

[Spunkster]

colder plugs would be a good idea.

[R-12914]

For low boost stock plugs (7s) will work. Otherwise 8 heat range are a good choice. Don't use non resistor plugs.

Define low boost and define high boost!?

[typer86]

The stock plugs are good for daily driving. (my SC setup makes max. 0.8 bar@best conditions/near rev limit otherwise approx ~0.76 bar)
I had the NGK8bk mounted for a couple of months and I had some cold start issues. Swapping back to the OEM NGK-IFR (NGK-7746) issue resolved...
With the IFR7's I have also no knocks or missfires, stable idle etc...

At first time I checked the plugs after 20k KM if the electrode is burned and/or massively fouled (a little black taint is normal! Because in engine must be running richer in WOT (target lambda 0.80/0.81) if swapping from NA to turbo/SC...

An good indicator to go a step warmer!
If the spark plug have a fully black carbon fouled head...
Reason:
It is not hot enough for the plug to start self cleaning process. Or the car running extreme rich in all conditions... (never reach lambda 1)
Further information is documented also on the NGK homepage - check this out ;)

Also interesting:
OE Iridium
OEM Style (for K20Z4: NGK-7746)

With the smallest tip diameter available, OE Iridium spark plugs provide superior ignitability and long service life. The iridium/platinum surfaces ensure a slow wear rate, providing stable idle and superior anti-fouling.

• Laser-welded iridium center electrode tip
• Platinum disc welded to backside of ground electrode provides long life
• Trivalent metal plating for superior anti-corrosion and anti-seizing
• Faster starts and quicker acceleration
• Better fuel economy and lower emissions
• Best OEM Iridium spark plug available
• OEM-approved design

Iridium IX
Ultimate Performance

Designed specifically for the performance enthusiast, Iridium IX offers extreme ignitability, improved throttle response and superior anti-fouling.

• Fine iridium tip ensures high durability and a consistently stable spark
• Iridium alloy has extremely high melting point, perfect for today’s high-tech, high-performance engines
• Trivalent metal plating provides superior anti-corrosion and anti-seizing properties
• Outstanding acceleration, high fuel efficiency and durability
• Ultimate design, technology and performance

I recommend to test the OEM plugs first before go a step colder... Find a good ignition timing and lambda values and the OEM plugs are great enough...

[typer86]

For low boost stock plugs (7s) will work. Otherwise 8 heat range are a good choice. Don't use non resistor plugs.

Define low boost and define high boost!?

If you have in the middle range of the rev (4/5k rpm)@ 1 bar (or more) I recommend to go a step colder... If you reach 1bar @ 8k rpm it is not necessary...
Good turbocharger setups will do this but s/c normally not... (maybe if the biggest rotrex blower is mounted :D :D :D )

[mladjan]

I will have C38-81 charger, and 100mm pulley, so not sure how much boost it will produce.
It will be limited with boost when it reach around 400bhp, to keep it safe.

Will try with stock spark plugs. What are good indications that I need colder ones? Misfire? Knock?

[typer86]

Check the section: Overheating:
https://www.ngksparkplugs.com/about-ngk ... lug-basics

[R-12914]

The stock plugs are good for daily driving. (my SC setup makes max. 0.8 bar@best conditions/near rev limit otherwise approx ~0.76 bar)
I had the NGK8bk mounted for a couple of months and I had some cold start issues. Swapping back to the OEM NGK-IFR (NGK-7746) issue resolved...
With the IFR7's I have also no knocks or missfires, stable idle etc...

At first time I checked the plugs after 20k KM if the electrode is burned and/or massively fouled (a little black taint is normal! Because in engine must be running richer in WOT (target lambda 0.80/0.81) if swapping from NA to turbo/SC...

An good indicator to go a step warmer!
If the spark plug have a fully black carbon fouled head...
Reason:
It is not hot enough for the plug to start self cleaning process. Or the car running extreme rich in all conditions... (never reach lambda 1)

I can absolutely confirm that and the same experience I have also done!