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Red Xtreme and low impedance injectors


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Page 42 of the wire-in G4 manual says that I need ballast resistors to run low impedance (Siemans 3105) injectors on a red Xtreme.  My dealer told me the Xtreme could drive these injectors without ballast resistors.  Is the manual out of date and/or how can I tell for sure whether I need resistors or not.  My G4 is red and looks like the one shown in the brochure on this website and I just updated the firmware to 4.9.3, if any of that helps.

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Current edition of the Extreme(red unit) only has saturated injector drivers.  There for you will need ballast resistors to run your Siemans injectors.  Failure to run the ballast resistors will result in burnt injection drivers as they can not handle the current required to run low impedence injectors.

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Well that's unfortunate.  My harness is all wired up with no ballasts.  I'll have to call my dealer and understand where we went wrong.  He configured the start up map for these injectors so not like that was unclear.  Were there ever red Xtreme's that drove low impedance injectors?

Also, the manual seems to be illogical with regard to the value of the resistor to use.  I copied it below -- it's has the ballast values listed backwards, right?  Why would you use a lower ballast for a lower impedance injector?  I would the goal is to get the total resistance up to 5 or 6 ohms at least, no?

'If the injector impedance is LESS THAN 2 Ohms, use 2R2 (2.2 Ohm) ballast.

If the injector impedance is between 2 and 6 Ohms, use 4R7 (4.7 Ohm) ballast.

If the injector impedance is greater than 6 Ohms, use no ballast.'


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Hi Tom,

No red G4 Xtreme ECUs were or are capable of driving low impedance injectors directly. 

The manual is correct about the injector ballast selection. The aim is not to reach a total of 6 ohms resistance. It is more about controlling the current flow correctly.

The Red Xtreme is not capable of running injectors in peak and hold mode. If the manual does say something different can you point me to where and I will fix it.



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Thanks.  The manual is not wrong, I just did not realize that peak and hold isn't available on my ecu.

One last question on this point:  the harness I received has all the +14v wires tied together inside the haness for the injectors, but has 4 separate wires running from inj1 - inj4 to drive my 4 injectors.  Do the resistors need to be on the +14v side of the injector?  Given how my harness is wired it would be much easier to put the injectors in-line in each of the injector output wires, but the manual shows it on the +14v side...

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