I am swapping a 1986 N/A 13B back to EFI from carburation and I am going with a MT-4 microtech fuel only and letting the dist. handle the ignition. I can go with either the lo or high impedance injectors as I have a set of both fresh from witchhunter and I will be starting from scratch on connectors. The Q is is there any advantage to one versus the other. The Microtech write up indicates I can use either?

No porting, header, stock NA injectors.

 

Nope. Use either one.

 

i perfer low impedance injectors (having NOTHING TO DO WITH MY NAME) mostly because most of the older cars i come across at the junk yard use low impedance injectors. I guess its a 80's jap car thing.

but in terms of a "performance" viewpoint, Aaron beat me to it.

 

Thanks for the quick reply. I guess the decision could then be based on wether anyone wants to buy a set of four fresh NA S4 or S5 injectors. I'll post them in the FS section and use whatever doesn't sell!

 

Sorry to dig up a old thread.
But, I got the same Question, different car.
1987 Turbo II, w/ MT-4 microtech, resistor pack is deleted from previous owner.

So you can use either low or high impedance injectors?

 

i believe it was already answered above. Use either.

 

Impedance refers to the Resistance of the injector.
Think of it as a valve in a pipe..like restricting flow of current to the ECU.
Now the ECU is set for a certain amount of Flow and resistance and if you use a different Impedance it can alter the performance of the Ecu and may go as far as frying it.
That is why IF the Ecu needs to see HIGH Impedance they Combine a LO impedance injector with a Resistor pack.To even things out and make the LO's "look like High impedance" so the ECU is happy.

 

the microtech can handle either high or low impedence injectors. it can even go as far as running a pair of high impedence and a pair of low impedence injectors and vice versa for each stage.

i have run low impedence injectors on my car for 10 years without a resistor pack.

 

Thanks guys for the info!
Its interesting how these ecu's can use either.

 

It's because the IC used to drive the injectors is a peak and hold driver with current sensing. I forget the part number but it is able to compensate. This isn't done in an OEM application because those driver ICs are 100x the cost of a MOSFET and OEMs don't care if someone wants to swap around injector impedances.

Fact is, the increased resolution of new modern high impedance injectors is wasted on a crude non-interpolating ECU such as the Microtech anyway. So run whatever injectors are good, available and inexpensive. Me, a set of OEM FC injectors drilled for 720 as primaries and the good old Ford 1680 CC secondaries.

 

the high impedance vs low impedance use a different amount of current flow. the Mazda ecu is sized to run high impedance injectors, and thus needs the resistor pack. the aftermarket ecu's seem to use a higher current driver.

ohms law, 12v/12ohms = 1 amp

vs 12v/4ohms = 3 amps