Here ya go, from a PVO source:
I called RC and it sounds like they use 760 -770 kg/m^3 as the density of their test fluid. We use n-heptane which has a density of 685 kg/m^3. An injector's mass flow is dependent on the density of the fuel. If two different fuels are flowed through the same injector, the volumetric flow rate of each fuel should be the same. This said, both sets of numbers for the injectors that you have are wrong. The correct numbers are as follows:
For n-Heptane @ 58 psi,
2003 Injectors - 359.4 g/min = 47.4 lb/hr = 524.7 cc/min
2004 Injectors - 395.3 g/min = 52.2 lb/hr = 577.1 cc/min
RC Engineering and most aftermarket injector companies flow their injectors at 43 psi. Using Bernoulli's equation, the mass flow can be corrected to:
For n-Heptane @ 43 psi,
2003 Injectors - 309.5 g/min = 40.8 lb/hr = 451.8 cc/min
2004 Injectors - 340.4 g/min = 44.9 lb/hr = 496.9 cc/min
If RC Engineering flowed our injectors with their test fluid @ 43 psi, they would rate the injectors as follows:
2003 Injectors - 343.3 g/min = 45.3 lb/hr = 498.3 cc/min
2004 Injectors - 377.6 g/min = 49.8 lb/hr = 547.8 cc/min
Basically injectors are volumetric flow devices, so a more dense fuel will flow more mass flow than a less dense fuel at the same volumetric flow rate. This is a very confusing subject. As you can see, it is very easy for a company to skew their flow ratings in their favor. There will always be some error in ratings until all injectors in question are flowed on the same test bench with the same test fluid at the same test pressure.
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