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Tech Articles
Fuel Flow & Formula's
Fuel flow is controlled by varying the pulse width or duty cycle of the injectors. Pulse width is the time in milliseconds that the injector is open, while duty cycle is the injector’s overall percentage of open time. A 70 percent duty cycle means that the injector is open 70 percent of the injector’s maximum cycling time.
Ultimately, to find the optimum injector size for a given application you have to test it. You can map it out on a dyno, sizing the injector based on observed maximum brake horsepower (BHP), and the brake specific fuel consumption (BSFC) at the peak power. You can also use a wide band oxygen sensor that tells you the air/fuel ratio at the load points you’re tuning for.

The following formulas will get you close to the correct size injector for wide throttle performance:

(BHP x BSFC) = Injector Size (Flow Rate)
# of Injectors x 0.8
The scaler 0.8 adjusts the calculated injector size to produce the fuel necessary for peak power at 80 percent duty cycle. An accurate BHP figure is critical for proper injector sizing, but not all dynamometers have fuel flow hr. for normally aspirated engines.
For example, look at an engine with a known BSFC of 0.49 making 300 horsepower:
Applying the formula we derive:
300 X 0.49 = 45.9 lbs. /hr (required injector flow rate)
4 x 0.8

1) The STD injectors for a 2.2 Cavalier N/A is 17 lbs. So if you want to figure the injector size for whatever HP you want to achieve just plug in your figure.

Let’s take for example, you want 150 HP then the figures would look something like this.
* (150) x .49 = 7.35 = 22.96 Injector Flow rate
4 x 0.8 = 3.2

For motors that want to make high HP like 175-225, just insert that number above where the * () is located.
Some guys try to get more out of their injectors by adding more fuel pressure to the existing injectors. This practice will significantly reduce the injector’s life span by over working.

In cases of turbo's there is a complete new set of rules, we can help you establish an injector size (usually 30lbs or over), and upgrade the fuel pressure. Let us know what your project goals are.

2) For upgraded motors and all turbo's, we do have the ability to adjust your ECU for tuning, rev limiter, and fan switch adjusting and injector size. Again let us know your projects needs.

Call us anytime at (985) 956-7009, and we can help you achieve your project goals!

Delphi Fuel Injectors for Chevy Cavalier 2.2
CLICK HERE for our Cavalier 2.2 Fuel Injectors!
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