I know the S can use the jcw 380 injectors without a tune but with a 17% pulley and jcw tune could I get away with 440s? A couple months at most until a proper tune.

 

NO..i don't think so....
The computer will toss you tons of codes....
remember, your computer will use the 02 sensor during LIGHT acceleration cruising to adjust the mixture...so you will get a fuel trims error message...no big deal there...
But when WOT, the computer CANNOT adjust the mixture..the o2 sensor is not fast enough...so when you push down the pedal to go...the UNSCALED injectors will flow at FULL FLOW (cause that is what the computer is asking)..and the car will be dangerously rich...
You MIGHT be able to get one trip to the tuner out of it..I would not want to try much more...much more...you will melt you cats, and run so bad the car will lack serious power....short term...longer term...like weeks/months..you are pumping unburnt fuel into your oil...washing down the cylinder walls....

 

Basic rule of thumb is nothing more than 380's w/o an immediate tune, don't know for certain about the 440's but I can tell you with the 550's the car won't run at all on a stock ECU map.

 

Additionally, much like when you're running at wide-open-throttle (open loop), cold starts are also in "open loop" operation, and unscaled injectors will flow far too much until certain sensors meet a criteria(O2 heater & coolant temp), which then tells the ECU that the car is now warm, and it can transition to closed loop. If you run colder plugs and unscaled larger injectors, you will likely begin fouling spark plugs due to overly rich cold starts & cold plugs.

 

That's sorta what I thought. At what point in the mod latter will you max out 380's. With/without a tune?

 

IMO, BVH, up until then you can get by with the 380's as long as you keep your stock rev limit.

Exception to this would be if you did "everything" else and were tracking the car, a long duration of high rpm driving will of course be a bigger factor than your typical "short burst" street usage.