Impediance converter (like AEM)
Thread Starter
Launching!
Joined: Sep 2007
Posts: 230
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From: Surrey, BC
Impediance converter (like AEM) A friend of mine is an electronics engeneer at Simon Fraser University up here in Canada. I was talking to him about the AEM converter box and wanted to know how difficult it would be for him to make one. Needless to say he had some questions, which I'm no where near capeable of answering. So hopefully someone here might have some insight for me. Here's our conversation
ME: I remember you saying something about being able to build and ECU for a vehicle (I'm guessing it would take some work/time/money)
But what about building an impediance converter box that would allow a factory ECU that is set up to control high imp. injectors run low imp. injectors? I think AEM makes one. The box would basically have to convert one signal type to another.
HIM:That sounds like it would probably take quite some time to develop especially if detailed schematics weren't provided for both the ECU output channels and the injector inputs. We'd also have to hook up an oscilloscope to monitor the signals coming through, but the only oscilloscopes I have access to are the ones in the electronics labs at SFU which are chained down, which would mean taking the ECU out of the vehicle.
Producing a single printed circuit board costs about a hundred bucks as well, iirc. Without at least some sort of volume, it's kinda expensive per unit. Prototyping could be done on a bread board though, which would be practically free, for what it's worth. Just not nearly reliable enough to use in an engine bay lol.
HIM the next day: You know what? After sleeping on it, I've come to the conclusion that this should actually be a lot more straightforward than I thought initially.
Are the injectors externally powered? As in, are there separate leads to carry the signal pulse and the power to the injector?
Do you have any specs on the actual impedance on the ouputs of the ECU and the impedance on the inputs to the injectors, and the expected range of current that runs through? I probably don't need the schematics, just some specs.
If there's a source of more information on this stuff, link me also
Any info you have would be greatly appresciated.
ME: I remember you saying something about being able to build and ECU for a vehicle (I'm guessing it would take some work/time/money)
But what about building an impediance converter box that would allow a factory ECU that is set up to control high imp. injectors run low imp. injectors? I think AEM makes one. The box would basically have to convert one signal type to another.
HIM:That sounds like it would probably take quite some time to develop especially if detailed schematics weren't provided for both the ECU output channels and the injector inputs. We'd also have to hook up an oscilloscope to monitor the signals coming through, but the only oscilloscopes I have access to are the ones in the electronics labs at SFU which are chained down, which would mean taking the ECU out of the vehicle.
Producing a single printed circuit board costs about a hundred bucks as well, iirc. Without at least some sort of volume, it's kinda expensive per unit. Prototyping could be done on a bread board though, which would be practically free, for what it's worth. Just not nearly reliable enough to use in an engine bay lol.
HIM the next day: You know what? After sleeping on it, I've come to the conclusion that this should actually be a lot more straightforward than I thought initially.
Are the injectors externally powered? As in, are there separate leads to carry the signal pulse and the power to the injector?
Do you have any specs on the actual impedance on the ouputs of the ECU and the impedance on the inputs to the injectors, and the expected range of current that runs through? I probably don't need the schematics, just some specs.
If there's a source of more information on this stuff, link me also
Any info you have would be greatly appresciated.
Staging Lane
Joined: Aug 2005
Posts: 95
Likes: 0
From: USA
Soul:
High Impedance Injectors = 12-16 Ohms
Low Impedance = 2-5 Ohms
Injector coils are wired like so:
+12 from B+ (battery), PCM ground. For whatever duration is required (anywhere from 1.8ms at idle to 18ms at 6500rpm) the PCM pulses he ground, completing the circuit, firing the injector.
Accurate timing and accurate component specs are essential not to disrupt the operation and calibration of the engine. You'll be working in the millisecond/microsecond range.
Good Luck
High Impedance Injectors = 12-16 Ohms
Low Impedance = 2-5 Ohms
Injector coils are wired like so:
+12 from B+ (battery), PCM ground. For whatever duration is required (anywhere from 1.8ms at idle to 18ms at 6500rpm) the PCM pulses he ground, completing the circuit, firing the injector.
Accurate timing and accurate component specs are essential not to disrupt the operation and calibration of the engine. You'll be working in the millisecond/microsecond range.
Good Luck
Low impedance injectors open with a different wave form, peak and then drop to a hold voltage compared to a high impedance that just works on a standard square wave. People in the past used to just put a resistor inline to change the driver impedance but ran into issues with them being sluggish on opening. I've been thinking about this thread but have been reluctant to post anything because I don't really know specifics. Obviously you'll need to know the voltage spike and how long the spike lasts as well as the holding voltage. You can use the 12v square wave as the signal going into your box. The only problem (annoyance) is that there's an "infinitely" small delay between recieving the signal and switching the transistor. You can make up for that though by adjusting when the ecu gives the signal to open, you're going to be tuning anyways.
Yes, this is true that the low-impedance injectors require a varying wave-form to operate. Low-impedance injectors are also called "peak-hold" injectors, and the high-impedance injectors are aka "saturated" injectors. Though it is possible to flow a constant (opening) current through low-imp. injectors like the high-imp. injectors require, but this will likely cause the coils to overheat and damage the injector. The low-imp. injectors need a high, "opening" current to spring them open, followed by a "clamping" action that cuts the current significantly to a level just sufficient to hold them open for the duration of the duty cycle. This is the challenge in building a converter box.
Teching In
Joined: Dec 2003
Posts: 32
Likes: 0
From: Pleasanton, CA
I can answer any of your questions. I hold the US Patent on injector "impedance converter" boxes that AEM is infringing. Unfortunately for me, they can simply thumb their big corporate nose at me because patent litigation is so expensive. PM might be better since I don't visit here often.
http://www.patentstorm.us/patents/6836721-claims.html
http://www.patentstorm.us/patents/6836721-claims.html
