CAN bus and Common rail injection timing
CAN bus and Common rail injection timing
(OP)
Hi
My knowledge so far is that diesel vehicles with electrically controlled common rail use measurements such as: engine load, air temperature, engine temperature, rail pressure etc. to calculate the amount of fuel witch is to be injected to the cylinder (i think with common rail there are about 5 seperate injections in each stroke). I imagine that the injectors are just connected with two wires which open up when an electrical current is applied. The amount of fuel is therefor controlled by a control signal from the ECU. Then, by adjusting the pulse width of that signal would change the opening time of the injectors and amount of fuel injected.
My question is: is there anyway of knowing the opening time of the injectors before the ECU sends the control signal? I know that the ECU calibrates the timing before the injection process starts so maybe by sending a request message on the CAN bus or through OBD i could access that kind of information. I was thinking that there would maybe be some kind of PID code i could send out to get that kind of information from the ECU. Does anyone have a thought on how to do this?
My knowledge so far is that diesel vehicles with electrically controlled common rail use measurements such as: engine load, air temperature, engine temperature, rail pressure etc. to calculate the amount of fuel witch is to be injected to the cylinder (i think with common rail there are about 5 seperate injections in each stroke). I imagine that the injectors are just connected with two wires which open up when an electrical current is applied. The amount of fuel is therefor controlled by a control signal from the ECU. Then, by adjusting the pulse width of that signal would change the opening time of the injectors and amount of fuel injected.
My question is: is there anyway of knowing the opening time of the injectors before the ECU sends the control signal? I know that the ECU calibrates the timing before the injection process starts so maybe by sending a request message on the CAN bus or through OBD i could access that kind of information. I was thinking that there would maybe be some kind of PID code i could send out to get that kind of information from the ECU. Does anyone have a thought on how to do this?





RE: CAN bus and Common rail injection timing
Which brings up a point. You can't 'premeasure' the injection cycle for a given cylinder event, but you can measure the cycle with external instrumentation, and use the collected information to adjust the _next_ cylinder's cycle, if that's what you're contemplating.
Mike Halloran
Pembroke Pines, FL, USA
RE: CAN bus and Common rail injection timing
The plan is to make this an automatic process where the fuel injection is always 50% or 80% of the amount of fuel injected requested by the ECU.
The ideas for a method are maybe by taking a statistical analysis (similar to MikeHalloran's suggestion) of the timing vs. RPM (or something else), bluffing the measurements (with electrical circuits) which the ECU uses to calculate the injection timing or getting the timing information from the ECU before the process takes place (most preferable choice).
You think the amount of fuel injected can be changed so drastically by modifying the measurement signal without the ECU going into some kind of panic mode.
RE: CAN bus and Common rail injection timing
Diesel ECUs are probably not all that far behind. I would not be surprised if the ECU detected your machinations within seconds.
Of course, the same people don't program every ECU, so what you learn on one, may not apply to any others.
I'm not suggesting that you give up. But be aware that your market window may be closing, as ECUs become smarter and more paranoid about their surroundings, and it becomes progressively more difficult (or illegal) to fool them.
Mike Halloran
Pembroke Pines, FL, USA
RE: CAN bus and Common rail injection timing
Most people aren't out to *reduce* the amount of power delivery, though. What is it that you are trying to accomplish at the end of the day?
One thing you should be made aware of, is that current diesel vehicles with particulate filters and de-NOx catalysts have multiple sets of operating maps. At any given speed/load setting, it could be operating in any of the following modes which all have different calibrations: Normal operation, oxidation catalyst warm-up mode, passive DPF regeneration mode, active DPF regeneration mode, de-NOx regeneration mode, de-H2S regeneration mode, and probably more. Some of these may be specific to the VW common-rail for North America, but the DPF handling situation is across the board nowadays.
External tampering with injector delivery signals to any meaningful extent WILL be detected by the diagnostic systems. Re-mapping of the ECU, if not done properly to address every possible operating mode, could give trouble with this, too. If the code that is handling the emission equipment expects stoichiometric operation to regenerate the de-NOx catalyst with a certain fuel delivery and EGR rate, and you arbitrarily reprogram it to deliver less fuel, something isn't going to be happy.
RE: CAN bus and Common rail injection timing
RE: CAN bus and Common rail injection timing
The only exception I'm aware of was the Ficht system used by the defunct OMC company. That injector's fuel delivery varied so much and was so non-linear they programed in the delivery curve for each injector. Service injectors were actually the best of the best and all fell within a narrow band so the technician could reset the ECU to a default curve if an injector was replaced.
There are lots of black boxes in the aftermarket that intercept the ECU pulse injector and send their own with varying effectiveness. I agree it is much better to just reprogram the ECU lookup tables. You can always set them back to stock if you need warranty service.
RE: CAN bus and Common rail injection timing
FWIW Bosch Engineering Group offers aftermarket performance Diesel ECUs if you are interested. These might achieve the disired goal?
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