I have an 87 GN and the original injectors are a mess. I also have a couple of new sets of low impedance (2.5 ohm I believe) 42 lb/hr injectors that are Porsce 944 turbo Bosch replacements. Can I simply add a resistor to the wiring harness, or inside the ECM after the injector drivers to make up the difference in resistance? If so, will I be able to obtain a chip (say from Red Armstrong) for the car using these injectors, or can I simply get a chip calibrated for 42 lb/hr injectors? What size and impedance are the factory injectors? Can I measure the resistance of the injector by probing it's contacts with a meter?
The factory injectors are approximately 28 lb/hr and are about 14 ohms resistance. You can measure the resistance by probing the injector with a multimeter.
Remember that impedance and resistance are different things, though both are expressed in ohms. Don't think sticking resistors in line with the injectors is going to accomplish what you're hoping. The injector drivers in the ECM have to be modified to the 'peak and hold' style to handle low impedance injectors properly.
Injectors with the same flow numbers may not have the same flow at all fuel pressures and pulsewidths. So a chip for the '009' 42/43 lb injectors may or may not work well with the ones you have.
Thanks for the info. I think I'll just get rid of those injectors. 42 lb/hr would way too much for my stocker,I don't ever plan on going 11's with it anyway.
I think in the long run you'd be much better off with a high impedance injector that's commonly used in the TR community so there is good chip support, etc. A 30 lb/hr 'green stripe' or 36 lb/hr 'blue top' or '868' would probably be a good choice.
My thoughts exactly, Scott. I've had these laying around for a couple of years. Curious as to wether they could have been made to work. I'd much rather buy a proven setup. I dont have the finances anymore for seat of the pants R&D. I used to mess around with Turbo T-birds, and they are a drop in in that car. Doesn't really matter, I could have dropped that car off a cliff and it wouldn't go any faster that a mid 13.
Scott and Ken, I wasn't content to let this injector issue of mine die, so I dug out one of the sets. The part number is Bosch 0280150803, and I located it in the high impedance chart but I measure only 4.7-4.8 ohms across the terminals. They're listed in the chart as a high impedance injector. I was happy to see the part number in that area of the chart, but I believe it's wrong.
Although they're 40 lb/hr, I don't think they can be used without modifying the ECM. Correct me if I'm wrong. I'm glad this resource is here to shed light on technical issues such as this. I eat this stuff up.
You can run those on the stock ECM with a custom chip. I got one from Modern Musclecar (now Ramchargers). The only issue I had was that I thought they were rich at idle and a little lean up top. I just cranked the FP when I was at the track and they ran perfect. You are right about the impedance, though, they are not high or low they way people define them here.
If you know anyone looking for a set of these, I'll make them a real, real, good deal on them. I put the stockers back in when I sold the car, and they're just taking up space in the garage.
Geoff Bouma
gdouma@home.com