Using a Resistor pack for a non-Resistor MAP injector setup?
08-10-2007, 08:46 AM
Post: #1
Using a Resistor pack for a non-Resistor MAP injector setup?
Guys, as we all know, the MAP sensored 4ag came without resistor pack. The ECU limits the amount of current flowing through the injector using a injector driving transistor. On US cars (AFM equipped), current is regulated by using an external solenoid resistor to limit current through the injectors. So what if I used a resistor pack for my map sensor setup? What would this cause?

Some logic reasoning:

Resistor pack (2.5 ohms) + Injector (2.5 ohms) = total 5 ohms.
Using Ohms Law, the (V=IR), the current flow is about 2.5 amps using a nominal voltage of about 12.5 Volts.

If I omit the resistor, total current flow through the injectors is about 5 amps.

If the current is controlled by the ECU, with me adding a resistor pack will this cause an always lean condition because of the added resistance? Or will the ECU know and compensate? Reason I'm asking is that I just converted to MAP using a US Harness. I kept the provision for the resistor pack (really the person that did the conversion). I'm using ~ 2.5-3 ohm 182 cc injectors to try to match the original map setup rate. I have no clue if the car is running rich or lean just that my check engine light flashes.
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08-10-2007, 09:33 AM
Post: #2
Using a Resistor pack for a non-Resistor MAP injector setup?
If you use low-Z injectors without resistors with hi-Z intended ECU - there is serious chance to burn injector driverd (transistors) into ECU.
Some ECUs are capable of PWM in order to handle that (like Megasquirt).
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08-12-2007, 06:02 AM
Post: #3
Using a Resistor pack for a non-Resistor MAP injector setup?
I bypassed the resistor box and it seems to be working fine and dandy.
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