How to choose an injector
The amount of fuel injected is determined by the time the injector is open (controlled by the ECU) and the physical size of the internal passage ways inside the injector.
Injector sizing is commonly identified by stating the flow rate, which is the amount of fuel that flows through the injector when held fully open for one minute. Flow rates are usually quoted at 3 bar fuel pressure. Doubling the pressure increases the flow rate by approximately 30%, injector dependent.
Example: Through a 500 cc/min injector flows 500 cc (½ litre) of fuel per minute at 3 bar. This would increase to 650 cc/min at 6 bar.
What size will you need?
The engine power divided by the number of cylinders, gives you hp/cylinder.
As a rule of thumb you will need 5.5 cc fuel per hp.
For example a 600 hp eight cylinder engine requires an injector flow of at least
600/8 x 5.5 = 412 cc/min per injector.
Low Ohm versus High Ohm Injectors
The impedance (resistance) of different injectors can vary from 0.5 ohm to 16 ohm. This requires different operating currents to open them.
High ohm injectors need low current to open. They do not need current control as the high resistance ensures that the current does not build to dangerous levels.
Low ohm injectors need maximum current to open and then a much smaller current to remain open. MoTeC uses a 'Peak-and-Hold' system of current control where the injector is allowed to build to a high current flow to open and then controlled to a quarter of its peak value. This allows accurate control of the injector while reducing the heat generated in the ECU.
Low ohm injector have a much faster opening time. This is important at idle and low throttle openings where the required opening times are small.
Bosch 007 Djet 50 hp, 260 cc/min
Bosch 036 Djet 63 hp, 320 cc/min
Bosch 036 Djet 75 hp, 380 cc/min
Bosch 215 Ljet 34 hp
Bosch 363 Ljet 90 hp
Bosch 403 Ljet 80 hp
Bosch 706 Ljet 34 hp
Bosch 775 Ljet 44 hp
|Bosch 803 Ljet 56 hp, 290 cc/min||#34803|
Bosch 945 Ljet 48 hp
Indy, Bosch 839 260 hp
Bosch 842 Ljet 300 hp
Rochester 988 128 hp, 640 cc/min
Rochester 989 168hp, 840 cc/min
| || |
|Injector manifold seal, square (ea)||#34002|
|Injector O-ring Ljet Rochester (ea)||#34000|
O-rings for Bosch 363 injectors (ea)
|Pintle cap for Bosch 363 injectors (ea)||#34005|
|Spacer for Bosch 363 injectors (ea)||#35009|
Pintle kit for Bosch 363 injectors
(1 x pintle cap, 1 x O-Ring, 1 x spacer)
Retaining clip for Ljet Injector (ea)
Injector pintle caps alcohol black (ea)