C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Injector Impendance Question???

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Old Jul 24, 2008 | 01:00 PM
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Default Injector Impendance Question???

Is the impendance in a 1992 corvette LT1 injector low or high??? I do not have testing equipment, and can you use either one on your car or no???
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Old Jul 24, 2008 | 01:35 PM
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Originally Posted by saoco
Is the impendance in a 1992 corvette LT1 injector low or high??? I do not have testing equipment, and can you use either one on your car or no???
Your car uses a high impedance injector.. DO NOT try to use a low z injector or your ECM will be trash.. What are you trying to do anyway?
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Old Jul 24, 2008 | 01:44 PM
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Your ECM will NOT be trashed. The injector drivers are protected. It's standard engineering practice to fuse protect any sort of driver.

Let's say the harness grounds out, should you have to replace your ECM?? Of course not.

But yes, our cars are high impedance injectors.
and the testing equipment is a standand DVM (meter).
you can get a cheap one for < $20.
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Old Jul 24, 2008 | 01:55 PM
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...and with a DVM, you will be measureing the resistance, not impedance, across the 2 terminals going into each injector. You want to ensure that you have close ohm'age readings between the 8 injectors..

Not sure what the spec's are for a 92 injector, but my '95 measures around 15 ohm's on a cold engine.

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Old Jul 24, 2008 | 02:00 PM
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and for our purposes, measuring the resistance is sufficient.
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Old Jul 24, 2008 | 03:04 PM
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Im asking because I bought 8 low impendance Bosh 280-150-403's without knowing that they are low impendance and now I will have to send them back and change them for high impendance ones. Thanks guys for the help, I really appreciated.
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Old Jul 24, 2008 | 09:45 PM
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Originally Posted by larryfs
Your ECM will NOT be trashed. The injector drivers are protected. It's standard engineering practice to fuse protect any sort of driver.

Let's say the harness grounds out, should you have to replace your ECM?? Of course not.

But yes, our cars are high impedance injectors.
and the testing equipment is a standand DVM (meter).
you can get a cheap one for < $20.
The problem has to do with heat, which can be correlated to resistance in this case. For those ECUs not designed for low impedance injectors, their injector drivers can heat up and fail because of the added current. Even the injectors themselves can heat up. With peak and hold drivers(low impedance), the 12V is still delivered to the injector but current rises. Testing has revealed nearly double the temperature when using low impedance injectors on the wrong application. It's important to note that resistance decreases current and that current creates heat. If current can't be reduced then the chances of the drivers heating up and failing is increased. Of course, some of this depends on driving habits as well. High engine speeds and injector duty cycles can also create added heat, like when driving up a hill or at the track.
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Old Jul 24, 2008 | 09:52 PM
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Originally Posted by larryfs
and for our purposes, measuring the resistance is sufficient.
What is the purpose? Measuring d.c. resistance is almost worthless. It will find gross injector coil errors, but the injectors work on pulses, not long periods of direct current. A coil with an adjacent turn to turn short cannot be found with an ohmeter, but it can easily be found with an impedance bridge.
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Old Jul 24, 2008 | 10:05 PM
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Originally Posted by jfb
What is the purpose? Measuring d.c. resistance is almost worthless. It will find gross injector coil errors, but the injectors work on pulses, not long periods of direct current. A coil with an adjacent turn to turn short cannot be found with an ohmeter, but it can easily be found with an impedance bridge.
I agree with you 100% on any injector but a Multec. We are not looking for turn to turn shorts nor does anyone want to. All they want to know is why the car runs like $hit. So to make it easy and very inexpensive to diagnose, we tell anyone with a 89-93 GM product to test the injector resistance. Most of the time you will find the Bad multec causing the stumble, miss, overheating and generally bad performance. These inje ctors are failing at an enormous rate because the coils are getting wet with fuel that has soaked into the coil housing through the fuel orfice. The only seal between the two is a coating of epoxy that is breaking down from the alcohol in the fuels used today. This subject has been beaten for months. If your car is running bad just check your injectors before dumping all the money into replacing parts that are not bad.
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