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3.14 Fuel Pressure Regulator (FPR)
For NIRA i7x to correctly calculate fuel injector on- times, a linear fuel
pressure regulator needs to be installed in the fuel system. In a linear FPR,
the fuel pressure rises linearly as a function of the intake pressure.
When so called progressive or rising-rate regulators are used, FlexiPorts™
should be adjusted in a way that compensates the fuel injection according to
the difference between a linear fuel pressure regulator and a progressive fuel
pressure regulator.
3.15 Fuel Injectors
The fuel injectors are extremely important when tuning a high
performance engine. Thus, choosing injectors with diligence is
necessary. Below are instructions that aim to facilitate the process
of choosing the right injectors for your engine.
For high impedance injectors, connect the wire marked “Fuel Injector X
supply” and “Fuel Injector X” to each injector.
3.15.1 Choosing the Injector Capacity
Do not choose injectors with overly large capacity if there is a need to
calibrate lambda with precision at low-load conditions, e.g. for emissions
tests.
No injectors are manufactured with high enough precision to avoid
fluctuations in the injected amount of fuel due to temperature and other
running conditions, especially when the fuel injector on-time is less than
1.5ms.
A good rule of thumb when sizing injectors is 500 cc/ 100 hp. I.e. 400 cc
injectors on a 5-cylinder engine is enough for approximately 400 hp unless
lots of additional fuel is needed to cool the combustion.
NIRA rk will automatically alert you if the injector ”bottoms out” and can’t
supply enough fuel. The alarm is called ”DG Max Total Fuel Time”.
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