MicroSquit Conversion, Giving this a try Options

[Mblizzard]

I am pretty happy with my stock FI. But after seeing some of the setups at Okteenerfest, I thought this might be worth trying.

The stock system is not easy to modify and get things running correctly. I spent a lot of time making minor adjustments by trial and error. While I am not looking for huge HP gains or anything, it is pretty clear that the mods I have could potentially benefit from a bit more precise control.

Going to start with fuel only at this point to get things going and see where it leads me. Any help or suggestions for set up would be appreciated.

[jcd914]

From a MegaSquirt manual:
"Injectors are either high impedance or low impedance. High impedance injectors (usually about 12-16 ohms) can take a 12 supply directly, without a form of current control. Low impedance injectors (generally below 3 ohms) require some form of current limiting."

From the MicroSquirt manual:
"The fuel injector drives will max out at 5 amps each, enough to drive one low-impedance (or 4 high-impedance) injector per bank. To get everything to fit without lots of heat sinking, MicroSquirt® uses the ST VND5N07 from STMicroelectronics to drive the injectors. This is not a 'peak and hold' driver, but it does clamp the current at 5 amps, so it can be used with one low-impedance injector per bank, however the close time may be a tad higher (or you can use resistors). For up to 4 high-impedance injectors per bank, it should work fine."

So you need to keep the injector amperage below 5 amps per driver.
You can add resistors to the circuits for your original low impedance injectors. The resistors can be added either before of after the injectors it does not matter electrically, they just have to be between the power source and the MicroSquirt control unit.
The 1.8 L-jet 914s used a resistor pack with a single power supply wire connected to all 4 resistors which then supplied a reduced voltage to the injectors. There are other EFI cars (older cars) that also used resistor packs for 4 injectors but whether you could find a resistor pack with the correct resistance, who knows.

MicroSquirt has 2 injector drivers so you can wire and run the injectors in 2 batches just like the OE injectors were paired.

There are calculators online to figure out how much resistance you need to add based on injector resistance and the amperage limit you are after.

Jim