Low Impedance Harness ??
- Thread starter dank GN
- Start date
Not really... You still have the stock (saturated) drivers in the ECM. If each injector is 2 ohms, then each injector will draw ~6.5amps. All 6 injectors on simultaneously will draw ~39 amps combined. Improved wiring may even makes things a little worse for the ECM as there is less voltage dropped across the injector wiring.
- Joined
- May 26, 2001
Lance is the "god father" of the FAST system and has been dealing with turbo Buick electronics for over 25 years and is one of the most knowledgable electronic sources in the community along with Bob Bailey and John Spina, so when he makes a tech statement, everyone should shut up and just listen and learn! 
The Caspers harness supplies an improved positive feed source, vs. the factory positive feed to the injectors. Aging wiring in the car, high resistance, worn out connectors and ignition switch resistance can deplete the positive feed voltage to your injectors, and cause them to become sluggish in operation.
The relay uses raw system voltage to feed the injectors with a common positive voltage, and the rest of the engine wiring will provide a ground to each injector, thru the ECM. So, increasing wire gage (14 ga.) on the injector harness only fixes half the problem; the other issue is the wiring from the ECM to each of the injectors via the gray connector.
Ideal upgrade would involve 14 gage wiring from the ECM to the gray connector, along with an ECM that can handle the low impedance injectors (peak-and-hold). As Lance points out, the total current draw for low impedance injectors would be too much for 25+year-old factory 16 gage wiring to handle.
The relay uses raw system voltage to feed the injectors with a common positive voltage, and the rest of the engine wiring will provide a ground to each injector, thru the ECM. So, increasing wire gage (14 ga.) on the injector harness only fixes half the problem; the other issue is the wiring from the ECM to each of the injectors via the gray connector.
Ideal upgrade would involve 14 gage wiring from the ECM to the gray connector, along with an ECM that can handle the low impedance injectors (peak-and-hold). As Lance points out, the total current draw for low impedance injectors would be too much for 25+year-old factory 16 gage wiring to handle.
The relay and improved wiring "sources" the current for the injectors and is a great idea for anyone running low impedance injectors. However, the problem is that the ECM's injector drivers have to "sink" the current and the stock drivers are marginal at best for low-z injectors. They will just switch all the voltage to the injector. A high-z injector will draw less than an amp while a low-z injector may draw over 6 amps. An upgraded ECM will have 4 amp/1 amp, peak/hold drivers which will limit the current to 4 amp opening and 1 amp holding. I'm not saying the stock drivers won't work... enough of us did it back in the day without too many issues...but it is marginal.
