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• Common rail diesel and pressure evaluation 

  For this month’s topic I am going to revisit a subject which still attracts a lot of interest, but with perhaps a more forensic approach; Common rail diesel and pressure evaluation using Pico scope with WPS pressure sensor. Before we get into a detailed overview of pressure waveform analysis, let’s explore some of the other important tools at our disposal.
      
  Firstly, Communication. This is something that is becoming a lost art, especially with social media and online booking. Never overlook the opportunity to question the driver of the problematic vehicle. Note the expression ‘driver’ as often it may be booked in by someone else. Here lies the first problem, opinion, description, expectation, and cost. This is where, in my opinion, the most skilful member of your team is needed. Apart from the obvious technical information, you need how, where and when. You need to establish if they value their car, and if they do not, they will not value you.
      
  Next comes with what I call common-sense; observation. Cars cannot speak but they do tell a story. This could be the most valuable part of your forensic skills, looking for evidence of cause. Non-intrusive examination has many forms, including a thorough serial interrogation. Do not be drawn towards DTCs without knowing why. Look for adaption or correction data, deviation of reliable known values, once again note ‘reliable.’
  Reservoir
  
  All hydraulic systems, fuel, oil and water, require a reservoir of the appropriate substance. Just think about that one for a while, many do not, at their cost. It must travel from one location to another. Obvious, yes, so how are you going to check it?
      
  Pressure may be the obvious answer however, flow, and rate of change, (rise and decay time) are just as important. Let me throw a curve ball in here; Do you have one electric supply pump or several? The laws of physics dictate they consume current, so let us explore how observation of current will predict the physical environment of fluid flow.
      
  Initial inrush; How much current is required on start-up can suggest a faulty pump, a restriction in flow or incorrect viscosity. The continual current rate proves a similar conclusion; Too much might suggest a restricted filtration system or blockage. Too little may indicate a worn pump, low pressure or lack of fluid. All of this can be checked from a control fuse easily accessible and quickly. We love quick, and accurate.
      
  The hidden problem overlooked my many is experienced when relying on serial data alone or even pump current and flow rate when measured blind. Are there cavitation or voids in the flow stream? The void represents a pressure differential, my favourite subject, between supply and demand. This brings us to pressure gauges and the scope.
  
  Gauges or scopes
  Exactly why would a scope fanatic like me advocate the use of gauges? Where low pressure is concerned, they offer a definitive conclusion. Look at the gauge I designed many years ago, it embodies all the aspects I have just discussed; visual examination of flow characteristics, with isolation taps to check rise and decay, and proof pressure. Remember, a pressure below atmosphere is not a vacuum. It is pressure differential with a value below 1 bar. How can you have a negative pressure? Not possible guys. We live with an atmosphere at a pressure of 1 bar, pressure therefor flow, will always be high to low.
      
  Let us move on to the high pressures experienced with both common rail and direct gasoline injection which can be assessed in similar ways. Once again, we need to apply the same criteria as with low pressure priming and remember I did include oil and water measurement for consideration. This is where the scope comes into its own, evaluation of high-pressure response when delivered from a mechanical pump. The true essence of CR and GDI is independent control and delivery of fuel across engine load and demand. In simple words rate of change.
  
  Measurement and interpretation  
  The good news is that pressure sensors are usually accessed easily. Because they convert pressure into a linear voltage response, they are also easily interpreted with a scope. A little housekeeping first guys. You must have a scope with a minimum electronics industry standard bandwidth of 25mhz, and use a high sample rate. I suggest 10m/s or more. Do not drop the sample rate to clean up the image. You can filter once the data is in the buffer. Also, a floating measurement across the sensor will help, i.e., signal and ground. The sweep time can be up to 50 seconds or so providing you sample rate is high. As you zoom in for closer inspection you will be dividing your sample rate yet retaining enough data for accurate evaluation.
      
  Assuming all the priming tests have been carried out, you need to establish several critical functions. The rate of pressure rises from key on engine crank (KOEC), and key on engine run (KOER). There are subtle differences across systems. However, the later systems will reach 260bar plus in well under 500m/s.
      
  A bit more housekeeping; It is essential that the cranking system has been evaluated fully. Also clarify correct battery fitment, health and charge status, current consumption and rotation speed. Without battery health confirmation, KOEC HP pump tests are invalid.
      
  Then we assess the behaviour of pressure at idle speed, as this will be affected by injector faults, such as, delivery balance, atomisation, and leakage. Unstable pressure can also result from control actuator faults and adaption deviation. Also take note of combustion noise. Another topic for the future here is NVH vibration monitoring of combustion.
  
  Evaluation
  To evaluate full system pressure or proof as I call it, you must manually take control of the HP pump. This is however getting more difficult and should not be undertaken without full knowledge of how the pump is controlled. That said, we monitor rise time to peak pressure which is always 4.5v. Why? Because that is the limit of the system and sensor output. The actual pressure achieved could be much higher, we simply cannot confirm it.
      
  The final aspect of the HP system evaluation is decay time or system leakage. Some systems with Piezo injectors like Bosch should not leak while others do over a very predictable time. Therefore, you can confirm system leakage, with no intrusion, with clean hands, in minutes.
  
  
  
  
  

• Auto Service Finance rebrands as Bumper, as FT rates it one of Europe’s 100 fastest growing companies 

  Bumper, previously known as Auto Service Finance, has been rated by the Financial Times as one of the top 100 fastest growing companies in Europe.

• A reality check  

  This year’s summer was good, but as usual, was over too quickly – so back to work and a reality check!
      
  However, during my summer travels some of today’s necessities of life were conspicuous by their absence. I hired a car, only to discover that the USB connection I needed to use to charge my phone and link to my favourite music playlists didn’t work. The local radio station’s dubious choices in music didn’t help relive the tedium, but when I got to the hotel my woes were compounded when I discovered that they wanted to charge a ridiculous amount to use their wi-fi – I mean seriously, who in their right mind can justify charging hotel guests for basic wi-fi – unless the hotel is run by Ryanair (who seem to want to charge everyone for everything), which it wasn’t.
      
  So, with no wi-fi in the hotel room, I had some time on my hands, so I started thinking about the connections we expect in today’s connected world and in turn what connections are needed to run today’s workshop. This got me thinking about the problems it would face if these connections were either expensive, were restricted, didn’t work as they should or didn’t exist at all.
  
  Form over function
  Back in the 1990s I remember well being handed a new portable diagnostic tool which could connect to the internet via the mobile phone networks. Subsequently, it was able to conduct remote and bi-directional diagnostics on a vehicle anywhere in the world, when the vehicle was also connected to the internet – effectively ‘PC anywhere’ technology. However, I also clearly remember complaining to the development engineer within a couple of minutes because the functionality was too slow. He was visibly shocked and was clearly offended by my negative feedback on what was his pride and joy. Then I realised what had made me comment negatively – it was not the impressive technology, but the speed of use and the corresponding ability to run the diagnostics I wanted to conduct. In IT terms, this is referred to as system ‘functionality’ and ‘non-functionality’. Simply, the ‘non-‘functionality’ is the design of the system and the ‘functionality’ is what it can deliver. It might be easier to remember this in layman’s terms as being ‘Form over function’.
      
  When applied to the workshop, this directly applies to a wide range of electronic connections that are needed to support your day-to-day business, and if these connections do not work as needed, how this can quickly and detrimentally impact your business activities.
  
  Don’t miss the ‘bus’
  The ubiquitous Universal Serial Bus (USB) connection is a good example. A ‘bus’ within a PC are wires that transfer data between components inside the computer, or between the computer and its peripheral devices. We have all come to use this connection for a wide variety of tasks, from using it as an auxiliary power source for many different gadgets, to a vital communications port for various functions such as printers and other data transfer requirements. However, if it does not work correctly, physically or electronically, then simple tasks suddenly become major issues.
      
  This wired technology has moved on and most of us are now connected by wi-fi in the office environment, but increasingly also in the workshop to connect diagnostic tools to the internet. Data transfer speeds depend on the technology used and the latest generation (soon to be 802.11ax) is super-fast, which becomes more important as software updating of vehicles involves the transfer of massive data files. Generally, wi-fi connections work well, but when they suddenly stop working, it is more difficult to diagnose as it is not a physical connection than can be more easily tested. This may happen after a software update and a recent experience showed me how simple a problem can be, but how difficult it was to discover, when my PC was updated and a simple setting was changed. Over three hours of technical support was needed to discover that it was a simple tick-box setting which needed to be re-enabled. These wi-fi problems move into understanding the IT environment of certificates, configurations, permissions, log-in and passwords between the router and the various connected devices, without even starting to consider the wider communications providers that connects your workshop to the wider world.
  
  Have a cookie
  This leads me onto an increasing communications requirement which has become a fundamental part of our day-to-day lives, from both the personal and business aspects – the internet. If there is ever a perfect example of living in a connected world, this is it. However, if you think about the wide-ranging possibilities that the internet supports, do you ever stop to think about the technology behind what is happening to understand the control mechanisms that are needed for it to be safe and secure? If you visit a website, not only are there likely to be cookies tracking your choices and mapping your activities, but there will be certificates being exchanged to ensure secure communication. This may extend to log-in criteria and passwords, or may be implemented by the service provider whose website you are viewing. This becomes particularly important when you are paying for something online.
      
  In simple terms, all this is a form of coded access, but this works not only to ensure the correct access rights, but more importantly, to stop anyone who does not have the valid access rights from interfering or monitoring what you are doing.
  
  Control
  What then does all this lead to at the workshop level? In terms of the technology of the equipment, then it is developing to be both more reliable and faster, but the same cannot be said of the beloved OBD connector, which is not only restricted in terms of speed, but will become restricted in terms of access without the correct roles and rights authentication which requires certificates from the vehicle manufacturer. As the manufacturer controls this certificate, then it becomes ‘He who controls the connection, controls the function and ultimately the business’, so the workshop of tomorrow needs to worry most about a connection that they have no control over, but which will control their business.
    
  Time then to sign up with one of the aftermarket associations and join the fight to protect access to the in-vehicle data!
  
  xenconsultancy.com

• The shoe’s on the other foot  

  After my recent articles on tyres and TPMS systems, this month’s topic is wheel alignment, and the massive impact excessive toe-in or toe-out could have come MOT time.
      
  A lot of us can spot alignment issues a mile off. I would worry if after 17 years in the trade, that a technician such as myself couldn’t tell the difference between a tyre that had been toeing-in and a tyre that had been toeing-out most of its life. If you look at a front tyre on a car and only the outer edge is bald (and the tyre has plenty of pressure in) then you walk around to the other side and discover the same issue with that tyre, it would be plain enough to see that the wheel geometry isn’t correct.
  
  Compensate
  A car with tyres like this and wheel alignment so far out must handle like it has a mind of its own - like Herbie the Beetle. However, people get used to a car in this state and will compensate to a surprising extent. When we take the car for a test drive, we may come back to the customer and say things like; “there maybe an issue with the tracking” or “the car is pulling rather a lot to one side.”
      
  The customer then looks at us in amazement as if we are saying things just get their hard-earned money from them. We then offer a FREE wheel alignment check, and show them the virtual view on the screen. By Jove, the customer can then see with their own eyes exactly why their tyres have worn the way they have.
      
  I first mentioned toe in and toe out. This is the way the wheels ‘point’ in relation to the forward motion of the car. Look down at your feet. Now keep your heels in position, and point your toes inwards so they point towards each other. If you try walking like this you will wear off the outside of your shoes first.
      
  Do the same again with your heels, but point your toes outwards. This is toe-out and walking with excessive toe-out will wear the inner part of your nice new shoes and that’s the last thing you want. I’m sure you’d like it if your shoes wear evenly.  The majority of track cars/race cars will be running with toe-out and negative camber. This will be topic of conversation next time as wheel geometry is a large subject.
  
  Minutes and degrees
  I also mentioned minutes and degrees earlier too. A while ago I tried explaining this to another tech and he struggled to grasp the concept of the theory behind alignment/ geometry, but he knew how to set the wheel alignment up on 99% of cars.
      
  Getting your head around the actual maths is a different story. Think of it as a clock; there are 60 seconds in one minute; there are 60 minutes in one degree; and there are 360 degrees in a full turn. Our alignment set-up only works in minutes and degrees as it is really sensitive so no need for seconds-it would be worthless. The wind could blow and move the car slightly and that’s enough to make you panic and pick up your spanners again.
      
  Once the alignment is set-up correctly and you’re happy with the end result, your customer will in turn be very happy. Remember, in the end they are the ones paying our wages, not just your boss. It does help if you have a happy boss too of course.
  
  
  
  
  
  
  
   
  
  

• CSC comes into focus at REPXPERT training session 

  The Schaeffler REPXPERT technical team has two more ‘Tea-break training’ sessions coming up, this this time focused on concentric slave cylinder (CSC) replacement.

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