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Common rail diesel discussion thread
baldur Offline

Posts: 365
Joined: Dec 2013
Location: Iceland
Common rail diesel discussion thread
It has been requested that I open a thread to discuss and share information about common rail diesel injection.
I am in the process of developing a controller to run solenoid controlled injectors, and plan to create a different power supply for piezoelectric injectors.
The difference there being that the solenoid injectors require high current and low voltage, although a moderate voltage (80 volts nominally) from a charged up capacitor is used to boost them during the opening phase to get a faster current rise. To keep them open requires only on the order of 6 volts.
Piezoelectric injectors on the other hand need a couple hundred volts to open, with high initial current and this voltage must be maintained to keep them open, at negligible current. Then in order to close them they require an inverse current as the piezoelectric element has internal capacitance that must be discharged.

Common rail is unique to most other injection control systems in that you have control over injection quantity and injection duration independently. Only other control system that offers this is hydraulically actuated unit injectors. Other solenoid controlled systems such as cam actuated unit injectors and injection pumps while allowing exact control of injection start and end do not have any way to control the rate of delivery  during the injection.

One advantage offered by direct electronic injection control that is not possible with rack controlled injection pumps is the ability to have multiple injection events during the combustion cycle. This feature is not unique to common rail but is also possible with some solenoid valve controlled unit injectors and some solenoid valve controlled injection pumps.
The primary advantage of this is being able to use pre-injection to heat up the air prior to starting the main combustion event, as this accelerates ignition of the fuel injected for the main combustion event and thus reduces diesel knock which is caused by a too abrupt ignition of the fuel (too much fuel is introduced before it is able to ignite in the chamber)

I will add more information to this post later. Feel free to ask any questions.
Baldur Gislason

01-13-2019, 01:50 PM
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firen456 Offline
TA 0301

Posts: 64
Joined: May 2016
Location: europe
RE: Common rail diesel discussion thread
I wanna know something more about the EDC15/16 ecus from OM613/648. It seems that EIS, ESL, TCU and DAS and some ABS/ESP stuff is needed. The EIS will send a crypted can message to the ecu to start the engine. So we'll have to keep the EIS because it's to complicated to reengineer the crypted message. It seems there are two options to deal with the rest. First: Deleting all the DTCs in the ecu regarding ELS, DAS and TCU like wheelspeed and missing can bus devices and modify the ecu to start without them (gearlever in N or P for example). This seems to be the harder way. The easier solution might be to emulate all the can meassages the ecu wants do see via a can controller. Maybe something arduino based. There will of course have to be deleted some DTCs in the ecu because we don't want to run ELS, factory TCU, DAS and ESP. We must have a W210/211 car to reingeneer the can bus. To start the engine the gearleaver must be in N or P position. What other signals will the engine need to start? Maybe there can be found something in the WIS. Searching for some opinions or a little help from people who run these ecus in older cars.
01-14-2019, 02:24 AM
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barrote Offline

Posts: 1,514
Joined: Dec 2011
Location: Portugal
RE: Common rail diesel discussion thread
As of me, i'm dealing with changing mechanichal properties of bosch CRD system to operate under higher pressure and higher flow and reliable for the tunning fans.
Electronically, as discussed a stand alone ECU without the vehicle electronics seem a lot viable. One feature must be present , the box must be switched in same socket as a EDC16 or have a kind of adapter. For the users without edc16 cars(loom) does not really matter which conector to work on.
Injection opening resolution is of atmost importance weather the coil or the driver , need to be in line with needs.
As there is no point using a diff nozzle if opening is not within 100's of milisecond. As example.
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01-14-2019, 03:50 AM
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