95FbFormula

iTrader: (25)

What does high or low impedance mean and what is the benefit of each also what is better for a NA set-up

ratxtreme

High impeadence== higher ohms/inductance, generaly 12+ ohms.

Low impeadence== low ohms/inductance, generaly 2-6ohms i think.

Lower ohms means you have more current(v=ir). And the more current flowing through the coil the greater the force that is aplied to the injector mechanism.

So, you can run stronger springs holding the injectors closed on the low impeadence injectors, leading to less leaks. This also allows you to control the injectors especialy at idle.

High impeadence works with the stock computer. Usualy for low impeadence injectors after they open you can pulse width modulate the signal to limit voltage to reduce heat. For high impeadence injectors you just turn them on or off.

No reason to run low impeadence unless you need some BIG injectors.

dan@masportspeedshop

iTrader: (6)

The most important point to remember regarding high- vs. low-impedence injectors is the injector driver (transistor) in the computer! Low impedence injectors do have a lower measured resistance as they are driven by "peak-and-hold" injector drivers, meaning that they are current driven. The injector driver in the ECM applies maximum electrical current to open the injector, then modulates the current to hold it open. A high-impedence injector is driven by a "saturated" injector driver, meaning it is voltage driven. The two have very different electrical waveforms when viewed on a scope and are generally not interchangable. Some injectors, such as Siemens Deka injectors, are capable of being driven by either kind of injector driver. As a general rule of thumb, most OE MPI and SFI systems use saturated injector drivers (high-impedence) while most throttle-body systems (TBI), such as on mid-1990's and earlier GM/Chevy trucks, use peak-and-hold (or low-impedence) drivers. Also note that most aftermarket EFI systems can handle both types of injectors. Be sure to install what your ECM can handle, as installing low-impedence injectors on a car equipped with an ECM that can only handle saturated will leave you waiting for a tow-truck, and that would kind of suck, wouldn't it?

koolaid_kid

iTrader: (21)

Also, think of impedance as resistance (in the frequency domain, for those engineers listening). So, the higher the impedance, the less power (current, voltage) passes. The lower the impedance, the greater the power passes. So running a low impedance injector on a system designed for a high impedance injector could burn it out with too much current if it is not designed to handle the variance.