I wanted to throw this out for somebody to check and assure me. Are these injectors the same? The set on LR says they are 2.8ohm, while the racetronix set says they are 2.35ohm. Are they actually different, or is it just a typo?

Racetronix Set
and
LR Set

 

Dave:
From the Ecu Injector driver standpoint, both are the same.

 

Thanks. I tried to look on the Siemens VDO site for information about there injector lineup, but I couldnt find the information on this particular model.

 

So, the racetronix will work fine for a TO4b upgrade on a 951?

 

I'm running the delphi 55# from racetronix with 1.5 ohm resistors, working great.

 

Consider me an idiot on this, but the ballast resistors are necessary to get them down from 2.35 ohms as necessary for our cars? Do the resistors come with the injector purchase from racetronix?

TIA

 

where did you get the resistors and where do you install them? Anyone have pics of the resistor install?

 

Bought the ballast resistors from my local electronics shop, i mounted them in a metal box to act as a heat sink and protect the connections, velcroed the box to the DME box. will add a pic tomorrow.
You need the resistors to match up with what the DME injector drivers are expecting, otherwise you can fry your DME box!

 

There are more factors that determine the load on the DME injector drivers than the injector DC resistance.

Since the injectors act as solenoids they also present a significant inductive load, meaning that the current draw to open them is much higher than what Ohms law would suggest using the simple DC resistance. Also, higher flow injectors will have shorter pulse width (shorter duration holding current) and therefore from that perspective lower the power requirement.

Adding a resistor pack will slow down the injector opening time, which particularly for high flow injectors at idle will lean it out (unless the AFR remains within the authority range of the closed loop correction).

I have not seen a full power and current analysis on the injector circuit comparing original and aftermarket injectors (with or without resistors). Unless someone has done this, it is a bit of a guess whether or not resistors are needed.

To be more concrete though, a number of people have run 72 lb injectors for years without resistors, me included, without problems.

Laust