I have two high impedance RC 750cc that my friend gave me for free. I have a 87 TII which uses low impedance injectors. I was wondering is there any way to eliminate the resistor packs for the two secondary injectors.

 

just sell them and get low impedance and just drop them in, somebody mite grab them up quick if there going to run a standalone or something.

 

You should be able to cut just the wires for the secondaries at the resistor pack, and then connect them (taking the resistors out of the circuit). That way the primaries would still have their resistors inline.

 

does anyone have a diagram showing which wires are the ones for the secondary injectors

 

A multimeter would be the quickest way to tell.

 

don't hack up the resistor pack. you are eventually going to want to go bigger, and you can't really go bigger without going low impedence.

 

so just cut out the resistor pack completely and put it off to the side. Then wire in the resistor packs to injectors that are still low impedance

 

the diagram should be in ur FSM

 

checked FSM says nothing as to which wires are secondary and which are primary.

 

I would have posted it earlier, but I found nothing in the FSM about the resistor pack either. The S4 FSM is technically for '88s, so it doesn't surprise me. I do know that Hailers has posted a how-to for bypassing the resistor pack in a bunch of threads, so search for that. It may give you an idea of which are for the secondaries, but if not, it will show you how to bypass the resistor pack. You could then wire in 2 resistors at the ECU for your low imp. primaries, as you mentioned.

 

I'm not sure I follow you. If he ever upgrades his primary injectors to something low impedence, or gets secondary injectors that are low impedence (anything bigger than 720 usually), he'll either have to reinstall the resistor pack or wire in resistors at the ECU. If you reinstall the resistor pack you may have match a bunch of degraded wire colors. If you install resistors at the ECU, those big bulky things take up a lot of space and make wiring in that area a cluster ****. Either option requires a bunch of solder joints/crimps that could fail or just creating a wiring mess that looks ugly and is harder to troubleshoot.

Why don't you just install injectors that were meant for your car? When I decided to replace my 88 turbo engine harness I bought an 87 harness just so I wouldn't have to deal with the bullshit of wiring in resistors. Plus the factory resistor pack is 6 ohm which is more responsive than the big bulky 10 ohm radio shack resistors that most people use.

 

Bypassing the resistor pack doesn't require any cutting / soldering of the original wiring or pack itself IIRC. It just means making a few short jumper wires to connect the proper contacts in the harness-side plug.

EDIT: found one of Hailers' posts on it (no pic though). He cut the pack's plug off and spliced all 5 wires together, but it doesn't have to be done that way. Simply unplugging the pack, then splicing 5 short wires with together with female spade connectors on the other ends would do the same thing. The 5 wires would plug into the harness-side plug.

The only soldering would come in at the ECU, and 6 ohm resistors purchased from an electronics distributor like Mouser Electronics can be used. They're more compact than the 10 ohm radioshack ones people love, and as you pointed out allow better response.

But I do have to agree, for any future injector upgrades, 90% of bigger injectors are low impedance anyway. The OP did get these ones for free, but they could be sold off, and some brand new low imp. Densos could be picked up for a little more money.

 

using 6 ohm resistors? I thought they required the 10ohm/10 volt resistors in order for the ecu to receive the proper signal?

 

No. The stock resistor pack uses four 6 ohm resistors. The only reason anyone ever uses 10 ohm resistors is because they think they can only buy them at radioshack, and that's all they sell. Also, there is no "signal", it's just 12V power in a pulsed cycle. On, off, on, off... The resistance is necessary to protect the ECU from excess current. Resistors are rated in ohms & watts, not volts.