I have an 06 s model. I have a 17%, upgraded intake, and no other mods. I know you can swap in a set of 380cc injectors without a tune. But, is the combo of 380cc with the 17% pulley safe without a tune?

I understand it's better to tune, but is it any worse than just the pulley alone? It seems like the slight increase in fuel would only be beneficial.

 

Your AFR is already out of whack. Adding the injectors without a tune will only add to the whack but given your mods you need additional fuel. A tune, considering your mods, is worth another 15hp, maybe more. Touch base with "adriancl" on this forum for a remote tune. You won't regret it.

 

Yes, the increase in fuel will be beneficial.
And yes, a tune is highly recommend to make sure the ECU compensation is adjusted and correct.

You have to keep in mind how the ECU and injectors work with each other.
The ECU can only pulse the injectors 100%, there the extra fuel demand of the additional air from the smaller pulley, may (and usually will) not be able to meet that demand with the 330cc injector, but the change is normally not so great that the 380cc injector won't be able to keep up. And in most cases the factory ECU settings can compensate for that amount of change in extra air from that pulley.
But
This is where the tune comes in, it not only helps with any additional adjustments needed for the extra fuel and air (that the factory adaptations may not be able to cover), it verifies these adjustments are are working properly for your individual engine parameters.

And yes.... Before anyone makes the statement that "people have had no problems running pulleys with the factory 330's for years" and this is true. You have to decide if you want to risk those 330cc injectors running at 100% duty cycle far more often than normal, (Depending on your driving habits) and not knowing for sure if they are actually keeping up to the demand.

 

I have had 380cc injectors with a 17% pulley without a tune for about 18 months, including a couple of track days. My car has been running fine but I know a tune will really dial everything in. The only reason I haven't tuned yet is I want my A/F ratio gauge installed and I'm waiting to install that until I get a header. My other cars have needed some work so a lot of my time and money have been tending to those issues while my R53 patiently waits for its turn again.

I am now running a stock JCW sized pulley (a very long story why) on a Stiegemeier ported supercharger and basically fully ported intake system and my car is doing fine (as far as I can tell) on this setup as well. My big hang up is I won't feel comfortable running my car hard without that wideband installed so I can be certain bad things aren't going on in my combustion chambers when I am pushing it.