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Practical Diesel Tuning: Advanced Sensors

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Advanced Sensors

04.08

00:00 - The sensors we've mentioned up to this point are really all we need to get up and running and start making tuning changes to a diesel engine.
00:06 And these will be sufficient for 95% of tuners.
00:09 Of course there are plenty of additional sensors that you may want to consider if you're planning to push your diesel engine to the limit and we'll cover those in this section.
00:16 For example, if you're wanting to maximise the performance of a specific turbocharger, then it would stand to reason that having the ability to monitor the turbo performance in more detail would be beneficial.
00:26 Two great additions here include a turbo speed sensor and an exhaust back pressure sensor.
00:31 The exhaust back pressure sensor is plumbed into the exhaust manifold pre turbo and measures the back pressure between the turbine wheel and the exhaust valves.
00:37 This sensor gives you a lot of information about the restriction being presented to the exhaust gas flow by the turbocharger and this becomes something that's a bit of a compromise as you go to smaller wheels or smaller exhaust housings.
00:50 The small exhaust wheel and turbocharger and the smaller exhaust housing both help provide great boost response and will build boost quickly at low RPM.
00:58 The problem here is this sort of turbocharger basically chokes the engine at high RPM hurting power and dramatically increasing exhaust gas temperatures.
01:07 Variable geometry turbochargers go a long way towards giving us the best of both worlds.
01:12 However as we start modifying an engine and pushing boost pressure to its limit, we'll get to the point where back pressure begins to spiral out of control.
01:20 We normally get some hints that the exhaust back pressure is becoming excessive because we'll start to see the gain in engine performance fall away as we add more boost.
01:28 However directly measuring it is the best way to know exactly what's going on.
01:31 This in itself is a little tricky since we can't just go and fit a pressure sensor directly to the manifold.
01:37 It won't last very long with the high temperature of the exhaust gas.
01:40 The solution is to remotely mount the sensor and run a length of copper tube to the manifold.
01:45 The copper tube will dissipate the heat, ensuring the sensor gets a long life and reliability.
01:49 The other sensor that's invaluable to optimising the performance of a given turbocharger is a turbo speed sensor.
01:54 This sensor is fitted to the compressor cover of the turbo and outputs a signal as each blade of the compressor wheel passes it.
02:00 Once calibrated for a specific blade count on the compressor wheel, it will tell us what the turbo speed is.
02:07 This information, along with the compressor map can help us figure out exactly how efficient the turbocharger is at a given mass flow and pressure.
02:15 These sensors are quite tricky to fit to a stock turbocharger and require some pretty fiddly and precise machining.
02:21 If you're at the point where you're considering a turbo speed sensor then there's a pretty good chance you're already dealing with an aftermarket performance turbo and fortunately both Garrett and BorgWarner are now offering turbochargers with mounting provisions for the speed sensor already cast into the comp cover, making our lives much simpler.
02:36 The other two sensors on the engine here are useful for monitoring engine health and can become valuable for heavily modified engines.
02:42 The first thing is a coolant pressure sensor which allows you to monitor pressure in the engine's cooling system.
02:47 The reason why we'd want to fit one of these sensors is that it allows us to see the telltale rise in pressure that occurs if a head gasket begins leaking combustion pressure into the water jacket.
02:57 This can be used to provide the driver with warning which can potentially give you enough time to prevent more serious damage to the engine in the cylinder head.
03:04 Some standalone ECUs can incorporate the pressure sensor directly into the control strategy and automatically provide safety features such as reducing boost or limiting engine RPM or power.
03:14 The last sensor I'll mention here is the crankcase pressure sensor.
03:17 This monitors the pressure in the engine's crank case and can be used to monitor how well the rings are sealing.
03:22 This sensor is more useful to provide a historical trend of ring seal over the life of the engine rather than being used as an absolute value we can rely on.
03:30 What I mean here is that if we data over a period of 10,000 to 20,000 miles or 10 to 20 hooks over a season, then we can see if the ring seal is deteriorating which would cause a rise in crank case pressure.
03:43 Interpreting the data from a crankcase pressure sensor does require a little care though, as the pressure will vary with RPM, boost pressure and even with engine temperature.
03:51 So when you're comparing historical data you need to make sure you're comparing apples to apples.