SMART TUNER SMT8-L - INJECTOR PWM APPLICATION

Perfect Power Application Notes.

 

Application Note - AN 1

Injector/PWM Interception Method

The SMT8-L has the ability to capture and modify PWM signals. A PWM signal stands for pulse width modulation. Made simple it is a pulsed signal that stays on for a certain amount of time and then goes off for a certain amount of time. The signals on time, changes/modulates. The SMT8-L can increase or decrease the current signals on time.
The most common form of this is an injector signal (I would hope every car has this), but there are other forms such as a boost control solenoid signal, ignition signal or the continuous VANO/VVT signals.

Wiring

The on board driver of the SMT8-L in this method is only capable of driving 120mA of current. If you have a 12V supply the lowest impedance this unit can drive is 100ohms. For 5V its 42ohms. If you need to go less than this, which I would expect is definitely necessary if you are driving injectors, an external driver must be used.
The following diagram is for high impedance applications :
SMT8-L Piggy-Back Unit - Injector/PWM Wiring
The following diagram uses the Perfect Power inverter module's on-board driver to drive low impedance signals :
SMT8-L Piggy-Back Unit - Low Impedance Signal Wiring
The SMT8-L uses the same wiring for PWM and frequency modifications. For PWM modifications the following picture shows which check box to tick in the System Definition (Shift F2) and which is the tuning map (F5)

Possible Applications

 

 

SMT8-L Piggy-Back Unit - F5 - Frequency/PWM Map

 

 

  • Fueling modification in older management systems that only had one injector driver output and an on-board MAP sensor like the Bosch L3 JETRONIC system.
  • Could modify VVT and continuous Vanos oil solenoid signals.
  • Fuel trimming on a single injector or set of injectors in batch sequential fueling applications.

 

BOOST CONTROL SIGNAL MODIFICATION. NOT TO BE MIXED WITH BOOST CONTROL, WHERE THE SIGNAL IS CONTROLLED COMPLETELY BY THE SMT8-L.