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View Full Version : High vs Low Impedance Injectors



HMatt
12-30-2010, 12:58 AM
After extensive googleing I'm finding mixed results for which is better... What it's looking like is that it comes down to the car, so I figured I'd see if anyone out here has any experience with some of the new High Impedance options for our cars.

Personally I just want something over 1000cc that keeps a nice idle and just works better with the stock ECU.

**Just to be clear, you need to remove your resistor box to run high impedance injectors!**

NativeSS
12-30-2010, 12:59 AM
bump for some info i would like to see.

HMatt
12-30-2010, 01:09 AM
Just did some searching on Injector Dynamic's website... They use High Impedance injectors and seem to be well praised for outstanding Idle and response... I don't know whether to attribute that to their balancing and atomization or to the high-z though...

hpd_wally
04-29-2012, 05:31 PM
This is more of a question as to what drive stage you have connected to the injectors, and with the stock ecu, you need to keep the base impedance close.

The topology for the EVOs' ecu is a basic low-side drive, on=hold, which should be around a 1.4 Amp draw based on ~10.3 ohms, 14mH. The opening time is related to the rate of change of magnetic saturation or seen on a probe as Di/Dt. This ramping rate increases with higher voltage levels.

If you where to happen to place a 1.3 ohm injectors on a circuit that is designed for 10ohms, you may
1-never open the injector to begin with
2-heat the drive stage due to excess current draw
3-fail tracks on the pcb of the ecu due to excess current.

High Impedance Injectors tend to open quicker ( less ambiguity of the Ton time) because they are matched with a drive stage the will place a 40 volt differential across the injector during pull-in, and have a hold phase where the drive is pulsed(PWM'd) to achieve a target current. Better magnetic materials allow the core to magnetize quicker and more efficiently. Its about opening force (N) that can be generated to pull against the fuel that is pressured in rear.

Low Impedance injectors can have this same affect by having a more sophisticated drive stage that has a larger voltage differential to decrease the time of magnetic saturation, and move the pintle quicker and more consistently. It has been the automotive /oems' desire to be penny foolish on this and save cost on the base electronics. This gives me a good idea, to make a drive stage for people who whish to increase the accuracy of the injecto opening times....

If they need 10 amps to open, and 6 amps to hold, and are 1.3 ohms, you will not be able to achieve this with battery volts.

KT Motoring
04-29-2012, 05:47 PM
Since this is on a Evo X topic sub forum, the point of high impedence vs low impedence is basically moot.