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what would be the best a/f/w ratio?
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Sort of difficult to give a hard and fast number, so will throw out these guide lines. The really serious racers ie folks like the unlimited air plane racers running boost pressures near 30- 50 psi and all the WWII combat aircraft generally used 50/50 mixes of water methanol at a .5 lb ADI fluid to 1 lb fuel rate. That is pretty much an upper limiting case situation so you can safely assume you won't have to go above (or probably near that ).
Most recommendations are to start in the 10% to 25 % fuel to injection fluid range.
Lets say your running a 40 lb/min turbo (about 400 hp) at a 12.0:1 AFR that means your flowing about 3.3 lb/min fuel. Your 10% low limit would be 0.33 lb/min of WI fluid and your 25% upper limit would be 0.83 lb/min.
Depending on how you spec you nozzles you are probably interested in either cc/min or gal / hr flow rates.
0.33 lb/min = 150 cc/min or about 2.4 gal / hr
0.83 lb/min = 380 cc/min or about 5.9 gal/hr
My total flow in all my nozzles for the stock turbo has generally been 3 or 4 gal per hour and was probably a bit high. ( I did not have the tools to tune it, on the edge, so went on the safe side)
I've seen a few higher but I don't recall anyone using less than 2 gal/hr rates.
My best guess not knowing your setup, would be to start with about 4 gal/hr ( 250 cc/min) rates and work from there either up or down as your tuning indications suggest.
I generally figure rates based on air flow rather than fuel flow, and like numbers in the 2% (by weight) of max power air flow as a typical safe starting point.
Thinking in those terms the .5 lb ADI to 1 lb fuel used by the unlimited guys figures out to be 4% of air flow on a 12.5:1 fuel air ratio.
25% fuel/WI rate comes out to 2% of airflow on a 12.5:1 fuel air ratio.
10% fuel/WI rate comes out to .8 % of air flow on a 12.5:1 fuel air ratio.
If you figure based on air flow you don't have to refigure each time you lean out the mixture. Air flow is also handy because you can guesstimate your air flow based on hp or guess your hp based on air flow. It takes about .105 lb of air to make 1 hp, so to make 400 hp (at the crankshaft) you need about 42 lbs/min air flow.
So for a quick and dirty calculation take your estimated crankshaft hp and mulitply by either of the following factors to get a starting point injection rate of 50/50 WI .
for gal/hr rates ----- hp x 0.0144 = WI gal/hr
for cc/min rates ----- hp x 0.9080 = WI cc/min
Hope that helps?
Larry