You need to estimate your flywheel HP. Then, assuming you continue to run at the stock 43.5psi fuel pressure, without the FMU or a boost referenced fuel pressure regulator, multiply the flywheel HP times 0.09
Example 450 flywheel HP x 0.09 = 40.5 #/HR
That is the minimum injector size. Keeps you under 85% duty cycle, while assuming that you have a "average" tune that produced a brake specific fuel consumption (BSFC) of 0.60 #/HR/HP. That's a fairly conservative basis.
You can also increase your fuel pressure with an adjustable fuel pressure regulator, to allow a smaller injector. If you run at 4bar (58psi) instead of 3 bar (43.5psi) you can change the mulitiplier to 0.078
Example 450 flywheel HP x 0.078 = 35.1 #/HR
These calculations assume that the injector has been flow rated at 43.5psi. If they are flow rated at any other pressure, you have to make additional corrections.
I run 64 #/HR Bosch injectors at 58psi. That makes them equivalent to a 78 #/HR injector, and they will supply 800 flywheel HP at no more than 70% duty cycle. But the tune is the result of a huge amount of dyno time, both engine dyno and chassis dyno.
Example 450 flywheel HP x 0.09 = 40.5 #/HR
That is the minimum injector size. Keeps you under 85% duty cycle, while assuming that you have a "average" tune that produced a brake specific fuel consumption (BSFC) of 0.60 #/HR/HP. That's a fairly conservative basis.
You can also increase your fuel pressure with an adjustable fuel pressure regulator, to allow a smaller injector. If you run at 4bar (58psi) instead of 3 bar (43.5psi) you can change the mulitiplier to 0.078
Example 450 flywheel HP x 0.078 = 35.1 #/HR
These calculations assume that the injector has been flow rated at 43.5psi. If they are flow rated at any other pressure, you have to make additional corrections.
I run 64 #/HR Bosch injectors at 58psi. That makes them equivalent to a 78 #/HR injector, and they will supply 800 flywheel HP at no more than 70% duty cycle. But the tune is the result of a huge amount of dyno time, both engine dyno and chassis dyno.
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