XMS4 - INJECTOR SETUP APPLICATION
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Perfect Power Application Notes. |
Application Note : AN 1 |
Introduction
Terminology
Resistance : As measured with an OHM-METER (multimeter)
Flow Rate : A very obscure number. The manufacturer gives it. It means the flow when the injector is continuously open. In cubic centimeters per second or cubic inch per minute.
1 Cubic centimeter / sec = 3.66 Cubic Inch / minute
If you have a powerful engine, you need to get some fuel into it. At full power, the injectors should be open 50 to 80% of the time.
Opening Time
Activation Time
Injector Utilization
Injector Repeat Time
- A fully sequential injection repeats every 2 cranks.
- A batch sequential injection repeats every 1 crank.
- The XMS4 can do all of the above injection modes.
- The repeat time decreases as the RPM increases.
- The three modes relate to fuel delivery as follows :
4 cyl | 6 cyl | 8 cyl | |
Sequential | 1 | 1 | 1 |
Batch | 2 | 2 | 2 |
Low Resistance Injectors 2-4 Ohm
They normally have a high flow rate and open at 0.4 to 0.6 milliseconds. They require a "stepped" current to reduce the power dissipation when used in parallel, or as a singe injector. The XMS4 cannot provide a "stepped" current, but can activate a 2-OHM injector with the use of an external driver. If this is required, then check the injector temperature after prolonged use.
High Resistance Injectors 12-16 Ohm
These are the most common injectors. They have low to normal flow-rate and open in approximately 1.5 milliseconds. The XMS4 can drive these injectors directly.
Injector Staging
The XMS4 units do not have this ability but it is a method where a second set of injectors is activated once a defined operating point is reached.
Fuel Pressure
A standard fuel pressure is normally between 2-3 bars. Below 2 bars, the injector "SPRAY PATTERN" deteriorates to a "SPLUTTERING", and above 3 bars, the injector may not open under a low voltage condition, as experienced with a cold start. The upper limit can be stretched, if enough fuel is injected BEFORE cranking (because injectors don't open during cranking), to fire the engine, and, once fired, the battery voltage rises and the injectors start to operate.
Progressive Fuel Regulator
This is a device, which has 3 pipe connections, and a double membrane to give it progressive performance. The third connection is the manifold pressure. If set-up correctly, it provides a fuel pressure of, let's say 2 bar at idle, and 0.3 bar AMP, and a 3.4 bar fuel pressure at 1.0 bar AMP. Notice that the AMP changes by 0.7 bars, and the fuel by 1.4 bars.