So my research on here for colder plugs lead me to NGK 1422.
Went to start the car today after lots of work: timing chain, turbo, lines. It wouldn't start. Put oem back in and it fired right up.
What plugs is everyone using for colder steps?

 

ngk silzkbr8d8s (97506)

 

Colder plugs on their own shouldn’t prevent the car from starting, I suspect something else was going on by coincidence…

 

Did you only try to start it once then changed the plugs back? Fuel pump might of not primed or something else was going on. 90% of the people on here that are tuned run the 1422s without issues.

 

Is it possible to run NGK 1422 plus on stock 2011 JCW? Or does my car have to be tuned?

 

The 1422 is one step colder than the stock JCW plug. You’ll see no benefit from running those plugs, and you might even cause issues. Colder plug can foul easier.