Injector Drivers

[Wez]

Hey All,

Does the S6 support both hi and lo impedance injectors or is a resistor pack/peak and hold driver required.

Wez

[TLicense]

Hello,

I'm interested in knowing this too, as I'd like to know if I need to keep the peak and hold injector driver I've got to be able to run the low impedance injectors I've got.

Cheers,

Tony

[Ryan.g]

The S6 will only run high impendance injectors directly, so a resistor pack is needed for low impendance injectors.

Ryan

[pat]

Just a little supplemental info :

• The injector driver transistors can cope with a continuous 10A drain current, which exceeds the requirement for most, if not all, Peak&Hold injectors (it is unusual to see more than 4A hold current)
• The timing processor has sufficient spare logic to modulate the injector outputs to keep the RMS current within both the transistors' and the injectors' SOAs (safe operating areas)
• There is adequate space left in the control code Non Volatile Memory to include a Peak&Hold strategy

Despite this, the S6 was designed without Peak&Hold for the following reasons :

• Heat is generated in a switching transistor a) during drain slew and b) under steady state (drain current squared times Rds(on)). If a PWM signal is applied to the injector driver to maintain the hold current in the SOA, the heat generated increases greatly. The design ethos of the S6 was that it should be possible to fit into the standard ECU case for most production road cars, therefore unlike the S4 and S8 whose cases are also heat sinks, there was no way to guarantee effective heat sinking in any arbitrary OEM case. Thermally, then, it is impossible to guarantee that the injector driver transistors will remain within their thermal SOA when used to drive Peak&Hold injectors. The heat dissipation from driving saturation injectors is vastly less; there is less drain current to start with and there are only two slew events per injection pulse.
• The vast majority, if not all, modern production cars are equipped with saturation injectors, and those which are not tend to be fitted with ballast packs, allowing a Peak&Hold injector to be driven from a saturation injector driver. While it is true that the S6GP can / should be used on project / race cars (or those road cars where numbers make a Plug'n'Play solution non-viable), it is equally true that there exist a large number of high quality saturation injectors from reputable suppliers such as Bosch, which will perform as well, if not better, than their Peak&Hold predecessors. Only esoteric builds should "need" modern Peak&Hold injectors, and these builds would probably be better suited to running on an S8, which supports those injectors anyway.

Hope this clarifies the situation a little,

Pat.