Fuel injection timing of Common rail engines
Fuel injection timing of Common rail engines
(OP)
I know how to adjust fuel injection timings of MC engines.
But, In CR(Common rail engine) I don't know how to adjust it.
The only thing that I know is it is controlled by solenoid valve.
and, It is possible to control fuel injection timing on engine side? Is there any cam shaft or fuel rack in high pressure pump?
But, In CR(Common rail engine) I don't know how to adjust it.
The only thing that I know is it is controlled by solenoid valve.
and, It is possible to control fuel injection timing on engine side? Is there any cam shaft or fuel rack in high pressure pump?





RE: Fuel injection timing of Common rail engines
Injection timing on a common-rail engine is done purely by controlling the timing of the pulses to the injectors, and therefore, the only way to "adjust" it is to change the mapping in the computer. It is otherwise non-adjustable. Same situation as ignition timing in newer gasoline engines with no distributors.
RE: Fuel injection timing of Common rail engines
Regards
Pat
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RE: Fuel injection timing of Common rail engines
RE: Fuel injection timing of Common rail engines
RE: Fuel injection timing of Common rail engines
RE: Fuel injection timing of Common rail engines
Regards
Pat
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RE: Fuel injection timing of Common rail engines
Common rail exsisted, long before electronics controlling engines. The timing was accomplished on a cummins by varing the relationship of the follower to the cam, as the injectors were actuated by cam action similar to the valves. And yes anything newer and controlled by a computer, with either solenoid or piezo injectors, the timing is constantly adjusted by the computer, as it reads information from the various sensors. Its trying to maintain the most power with the best exhaust emissions.
So your outa the loop, unless you can reprogram it like the one guy says.
RE: Fuel injection timing of Common rail engines
There was a cross-over period (e.g. the Lucas EPIC pump). Does any OEM still use unit injectors?
- Steve
RE: Fuel injection timing of Common rail engines
I don't think there are any production automotive or light truck diesel engines that use anything but some variation of common-rail any more, for any place subject to the more stringent emission standards (Tier 2 or Euro 5). They are generally using multiple injections per stroke to control noise and emissions, and they generally have an alternate operating mode with late injection to initiate a regeneration of the particulate filter. It's too hard (I reckon impossible) to do this with anything other than electronic control.
RE: Fuel injection timing of Common rail engines
Base fuel pulse width = raw (map) value x microsec/bit(mspb)
Fuel sync is the overall injection start point delay measured in internal units. the numbers can be changed for best emissions or power.
RE: Fuel injection timing of Common rail engines
Bill
RE: Fuel injection timing of Common rail engines
- Steve
RE: Fuel injection timing of Common rail engines
RE: Fuel injection timing of Common rail engines
Cariboo GTi
Bill
RE: Fuel injection timing of Common rail engines
Controlling rail pressures and flows in a mass-produced 180 bar fuel injection system is actually quite complex. The rail pressures are very high, the flow volumes are very low, the working fluid is incompressible, and the pump output flows must be continuously varied and corrected at a very high frequency rate.
High pressure CR diesel pumps are mostly variable displacement piston pumps. With the displaced volume (per cycle) being controlled by a PW modulated, high-frequency solenoid inlet valve, and a check valve on the discharge side.
Rail pressure control is critical with these very high pressure injection systems, since a small change in relative rail pressures (ie. 26KSI versus 28KSI) can have a huge impact in injector nozzle mass flows. Rail pressures, nozzle orifice diameters and edge geometries, all can have a big impact on fuel mass flows when the injection pressures are 28KSI.
Diesel engines don't require the stringent A/F ratios that a gasoline engine needs. But they still have very sophisticated ECU's and software control laws. A modern piezo-actuated diesel automotive injector is capable of producing up to five separate injection events per cycle, at over 180 bar. Thus each injection event must occur in less than 0.20 milliseconds and is sequential. Pretty impressive.
The typical diesel DI injector control basically has two parameters: Beginning of Injection (BOI) and injection duration (PW). These parameters are controlled by the ECU which uses sensor inputs such as engine temps, air temps, engine speeds, engine loads, manifold pressures, rail pressures, etc., and calculates the correct injector driver values based on mapped software tables, algorithms, and control laws. Some of the more sophisticated ECU's are even capable of modifying these values based on data acquired over the life of the engine.
High pressure CR pumps are basically operating with the same controls as the injectors. The main difference between diesel injection controls and gasoline injection controls, is that gasoline injection systems really require a closed loop type system. Where there is instrumentation feedback from devices like O2 sensors in the exhaust, and air mass flow sensors in the intake, to correct the A/F ratios.
Hope that helps.
Terry
RE: Fuel injection timing of Common rail engines
Are you suggesting that I can change the start of injection in my common-rail diesel by altering the cam or crank timing signal???? Is this really a sensible suggestion?
RE: Fuel injection timing of Common rail engines
The computer reacts to input from the sensor. Moving the sensor or trigger will tell the computer the crank is in a different position so the injector timing will still be correctly timed relative to the sensor, but at a different crank position. That is if a crank or cam position sensor is used
Regards
Pat
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RE: Fuel injection timing of Common rail engines
This will probably do something bad ...
One thing that has not been asked: What is the motivation for tinkering with the injection timing? If there is some sort of fault with the engine, perhaps that would be better addressed by fixing the underlying problem rather than attempting to cover it up.
RE: Fuel injection timing of Common rail engines
RE: Fuel injection timing of Common rail engines
RE: Fuel injection timing of Common rail engines
Most current diesel ECU systems are still open loop with regards to firing pressures. They avoid excessive firing pressures only through careful mapping and use of control laws with inputs coming from measurements of various temperatures, crank speeds, various pressures, and load demand. In the near future, production engines will close this firing pressure feedback loop with pressure sensors built into the glow plug: htt
Four stroke engine controls (gas or diesel) always require two separate angular position feedbacks (one on the crank and one on the 1/2 speed cam drive) so that the engine knows whether it's on the power stroke or intake stroke.
Good luck.
Terry
RE: Fuel injection timing of Common rail engines