[robbilau]

That sounds reasonable. But I don't think you are running rich enough at 12.8 - 13.3 to restrict yourself to just using the 3-8%. That's right around the correct AF for max power on gasoline. Some of the stock import turbos run very rich under boost - up to 10:1 - to cool combustion. That's really the case where you need to lean up the fuel for power as you add water for knock suppression. You can generally run up to 25% water compared to fuel depending of course on the heat of the air etc.

So I think you could run up to the .5mm or .6mm jet. Let's see, the stock injectors are about 270cc/min. With the .6mm jet you have 250cc/min which is 23% of fuel flow which is about as high as you want to go. So your 0.4mm jet is probably quite well suited at about 15%. You might switch up to progressively bigger jets up to .6 as the summer heat grows if you find they help.

In terms of what can probably be run on water I had a tech from MoTeC help get my car baseline tuned. He typically tunes drag cars and is well known in those circles. While getting boost control sorted we hit over 15psi by mistake (fun mistake, I must say) and he remarked out of the blue that I could probably run 15psi on 91 octane with water injection.