Vems Map + Injector Sizing

[repo]

It has nothing to do with 3 bar.

Fuel flow with the present fuel pressure counts, so Your injectors with 4 bar fpr are good for roughly 730hp.

General thumbrule is HP = (injector flow capacity x number of cylinders) / 5 at lambda 0.85

This makes it interesting: HP = (duty cycle x injector flow capacity x number of cylinders) / 5

So You can get rough estimate of Your horsepower by multiplying injector rate with duty cycle, but only if Your lambda is 0.85 or close.

[Jamo]

Is 0.85 the target lambda you aim for in tuning or 12.5 AFR ? I've seen a lot stating 0.80 is the aim ( 11.8 ) and Garretts tuned on here at 12.2 or 0.83

[quattro84]

0.85 of course. 12.5 AFR is based on the stoichiometric air/fuel mixture for RON95 (14.7 air/fuel ratio) fuel. So it doesn't mean nothing really.
For E85 the ratio it's something like 10. But the 'lambda=0.85' point still be the same to aim for.
Over λ=0.85 the enrichment is starting to cool down the exhaust gasses and lowering contained energy thus turbine energy and doesn't give extra turbine efficiency.

My way of calculating injector size:
stoich. air/fuel RON95: 14,7:1
lambda=0,85
=12,5kg air per 1 kilogram of fuel, so actual ratio is 12,5:1

specific mass RON95: 0,7kg/dm^3
total injector flow capacity: 5x 730cc/min
=3,65l/min
=219l/h
=153,3kg/h

153,3kg/h*12,5=1916kg/h of air

Rule of thumb: 300kg/h of air equals 100hp (with normal engine efficiency and NA VE =0,8).

1916/300= 6,4
6,4*100=640hp