Expert training, Italian style

Frank Massey is overseas again, but while he is there, he takes a look at ways to predict common rail pressure faults

Published:  06 June, 2018

I have just returned from Modena, delivering a two-day advanced technical training seminar to 21 of Italy’s top independent technicians. I was travelling from across Italy and beyond, attending PCB Automotive’s international training programme, focusing on gasoline direct injection and common rail diesel.  

The essence of the training was the advanced application of Pico oscilloscope to diagnose and gain predictive evidence for a repair solution. The technicians were particularly interested in the techniques of high pressure pump testing pioneered by ADS several years ago.

Attending the event were diesel and gasoline specialist and Italy’s most respected Bosch trainer. No pressure then! The session began with an explanation of the importance of scope performance when gathering data at high resolution requirements. Acquisition, storage, display, test lead bandwidth and advanced triggering with math channel analysis.

As expected Bosch had a different political agender towards our pump proof testing. It was however received with enthusiasm and great interest once its accuracy and simplicity was experienced.

The session on ignition evaluation was of great interest especially when focusing on primary current ramping and slew rate. Further discussion on burn time and slope completed the morning session.

The four-course lunch was a typical treat of local Italian hospitality and cuisine. The afternoon session included the evaluation of load request with air mass and Lambda response. By comparing response and rise time evaluation it is possible to predict and confirm complex fuel delivery and combustion anomalies.

A full eight-hour day concluded with hybrid cart racing north of Bologna, followed by the inevitable pizza and Mr Moretti’s finest.

Data and interest
Day two and common rail diesel with a similar agenda,   with a strong focus on Math analysis of pressure and volume control against fuel delivery pressure. We have accumulated a vast database of rail pressure profiles, rise and decay times across all diesel manufacturers. This was of great interest to a Bosch pump and injector repair specialist. Approving nods and smiles throughout supported our confidence in this form of diagnostic analysis.

There was great interest in the examination and influence of rail pressure and air mass response time.  Converting digital air mass into a current profile enabled delegates to understand the speed and simplicity with which a technician can determine the source of an error, either hydraulic or sensor input.
The day concluded with certificates and a photo session. Teachers usually get apples from students so imagine my joy with a bottle of wine and finest olive oil.

With a 6.30am flight in the morning and 50 kilometres back to Bologna, it was a very nice gesture from Luca my host to take me for a special evening meal at a villa outside Modena.

I found it intriguing to be asked by several of the delegates, with my international training experience, where the best technicians are to be found. I responded including them with the very best, not just because of their technical fluency, but especially their mutual respect and co-operation with each other, sadly lacking with some in the UK.

Using Math
To conclude let’s look at an example of using Math to predict hydro mechanical function against rail pressure.
The system example; Bosch cp1h, volume control single point, solenoid injectors. Sample taken from stable idle, part load snap open throttle, return to idle.

Channel a blue;
Rail pressure profile idle, snap open, rtn to idle.

Channel b red;  
Volume control valve ground duty control

Channel c green;  
Volume control valve, current vis rail pressure

Channel d black;  
Air mass meter profile vis rail pressure

Math Channel purple;  
Math duty volume control

The focus of this analysis was to establish the rail pressure hydraulic response time against air mass load signal, expressing the primary control device, volume, as current and math duty conversion.

To understand the values in this test enables an unequalled understanding of the systems capability in delivering fuel vis time.
The next challenge is to sync a second 4 channel scope monitoring compression using WPS, with the 4-stroke cycle overlay, noting the secondary pressure increase when fuel is injected. Then we really are ahead of the curve.



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