I actually find it harder to come accross a set of low imp. 550cc inj.
I have a set of 550cc 90 TII (oval plug) hi imp. inj, but by shear luck I happend to come accross a set of 87 TII rectangular plug inj for a good for a good deal. To fit the oval plug inj, I was just going to finish breaking off my old cracking stock inj. plug outer section, because the two pin center part plugs right in. here is some good RX7 inj. info I got from DSMTalk.com:
Mazda RX-7(Gen 1 and 2) Fuel injector identification guide
Note that some injectors carry the same part number as others but plug styles and resistances can vary. Low impedance refers to 2-3 ohms, high impedance refers to 12-13 ohms.
Year type impedance plug style plug notch position flow rating color part number
84-85 13B NT low square center 680cc orange 195500-0900
86-87 13B NT low square center 460cc red 195500-1350
86-87 13B T low square center 550cc tan 195500-1370
88 13B NT high square offset 460cc purple 195500-1350
88 13b T high square offset 550cc purple 195500-1370
89-91 13B NT high oval center 460cc red 195500-2010
89-91 13B T high oval center 550cc purple 195500-2020
As a side note, replacement fuel injector clips(for wiring harness) can be obtained from auto parts stores to replace broken stock clips. I got the parts from autozone:
GP Sorenson part 800-9416 Fuel Injector Connector
More about injector impedances on 2nd generations:
86 and 87 model cars used low impedance(2-3 ohm) injectors. Low impedance injectors have a center notch on the plug. The wiring harness used with LI injectors integrates an injector resistor pack, wired inline between the ECU and injectors(under stock air box) to bump overall load seen at the ECU to 12-13 ohms.
88 and after models used high impedance injectors. 88 HI injectors have an offset notch on the plug, and all post 88 injectors are HI with an oval plug(until 3rd generation side feed injectors which are totally different). The wiring harness on these models deleted the injector resistor pacl, carrying the 12-13 ohm load from the injectors directly to the computer.
When performing engine/wiring/injector swaps, the type of setup must be noted and kept together. This is easy as LI injectors will only plug into a harness meant for them(due to the position of the plug notch) and vice versa for HI injectors and harnesses. 88 and post 89 HI injectors and harnesses are not interchangeable.
A car that previously ran one type of setup can be changed to the otherÃ¢â‚¬Â¦keep the injectors and wiring harness together. The ECU will not know the difference.
It is also possible, but not necessarily recommended, to use HI injectors on a LI harness and vice versa:
--TO do so you must modify the injectors to fit the opposing wiring harness by taking off the notch on the plug.
--IF using LI injectors on a HI harness, you must splice into the harness, at each injector lead (for a total of 4) 10 ohm/10watt resistors available at radio shack for a couple of bucks. DoesnÃ¢â‚¬â„¢t matter which wire of the 2 per injector you splice to, polarity isnÃ¢â‚¬â„¢t an issue here. This bumps the LI resistance up to acceptable load for the ECU to see.
--IF using HI injectors on a LI harness, you must unplug the resistor pack. Next, locate the supply wire in the center of 5 terminals. Bridge jumper wires from this terminal to each of the 4 outlying terminals, which basically completes the circuit without resistors, carrying the HI injectorsÃ¢â‚¬â„¢ 12-13 ohm load directly to the ECU just as a HI harness would.
I don't trust RC Engineering anymore since I had a bad experince with them one time I don't wish to get into it. plus they charge $24 per injector! Many on DSMTalk have used Cruzin Performance in Mi http://www.cruzinperformance.com/
they clean/rebuilt/blueprint & balance for $11 each. my 550s are there now.