autronic - low or high impedance injectors

[TurboRA28]

Hello, im about to get some new injectors for the 3t-gte. i have an autronic smc ecu. wanted to find out if the autronic can control both low and high impedance injectors ?

Thanks
Joel

[TRD-KINGSWOOD]

AFAIC, Autronic come stock with low impedance drivers. You need to option your ECU with the high Impedance drivers.

[Supercrown]

The Autronic is capable of running both high and low impedence injectors as supplied. My autronic is running the stock 1FZFE injectors which are low impedence and my mate is running high impedence ford injectors. Its only a matter of selecting the right or similar injector from the dropdown menu.

So go ahead and buy any ones you like. My suggestion is to get the low impedence (high current) ones as they snap open faster than the high impedence (low current ones).

The injectors from a turbo or supercharged MR2 with a bosch pump and 60 lb rail pressure will do the job nicely for a fraction the cost of some rochesters or new bosch ones.

Take it easy
Sean

PS if you want to know which one to select from the menu when you're trying to fire it up drop me an email at LOGANNRACEPARTS@hotmail.com.

[elfturbomax]

If you look at the serial number on the ecu the last 2 characters will be either A2 or A4. A2 means it has 2 amp peak-and-hold drivers while A4 means 4 amp peak-and-hold.

A2 will drive high impedance injectors and also low current - low impedance injectors, which are Japanese low impedance injectors and Bosch D-Jetronic (2.5 ohm) injectors.

A4 will drive high current - low impedance injectors (2.2 ohm Rochesters, 0.6 ohm Bosch 351/363) as well as high impedance injectors. Either driver is suitable for Bosch 803's.

The combination that is not recommended is an A4 driver with a low impedance - low current injector.

[TurboRA28]

Thanks all for this info. I have just brought a set of series 5 13b injectors. Supposedly they are 13ohms or so. So hopefully wont be a problem for the ECU.

[Supercrown]

Are the A2 and A4 earlier and later models?

Sean

[KDog]

The combination that is not recommended is an A4 driver with a low impedance - low current injector.
Shouldn't that be A2 with a low impedance -low current injector???

The impedance of the injector is what determines how much current flows. If you had a low impedance low current injector you would have to drive it with a lower voltage.

[elfturbomax]

KDog

The driver rating, 2 amp or 4 amp, determines the maximum current. A 2 amp peak and hold driver lets the current surge to 2 amps to allow the injector to respond (open) quickly and then drops the current to 1 amp to hold the injector open. Similarly, a 4 amp driver goes 4 amps then limits the current to 2 amps.

A high impedance injector (12 ohms or higher) will limit the current itself to about 1 amp regardless of whether the driver is 2 or 4 amp. A low impedance injector (under 3 ohms) will have its current determined by the rating of the injector driver. If the injector is one that needs 4 amps to open (Rochester 988/989 or Bosch 351/363) then everything is fine with a 4 amp driver.

If the low impedance injector is also a low current one (Japanese or D-Jetronic) then the 2 amp driver should really be used. A 4 amp driver will obviously operate the injector, but could overheat the injector winding with continuous high duty cycle operation. OEM ecus will have ballast resistors to limit the current. They don't use a peak and hold driver because it's cheaper to use a conventional transistor and a ballast resistor for each injector.

Supercrown

The ecus come with 2 amp drivers standard. The high current drivers are a no cost option if ordered with the ecu.