Can the piezo injector, stuck in opened position, be the cause of hydro blow? Let’s calculate!Ī) lets start with the situation – the engine is started and runs. Accordingly, around 20 ml is considered as critical fuel amount, which can damage the engine.ģ. The volume of each cylinder of N43/53 is around 0,5 liter, the min volume of the combustion chamber (compression 12:1) is around 40 ml. From the other side, if the combustion chamber is filled for 50%, compression will be around 20:1 – that could be considered as max allowed leakage. It’s clear, that in a situation when the combustion chamber is full with fuel, the hydro blow is inevitable. What is the amount of fuel, which has to leak in the combustion chamber, will damage the engine? Accordingly – continuously opened piezo injector during time X (for example, 1 second) will inject 6 times more fuel than injector of “old type”! Accordingly – there is some reason to worry.Ģ. If we take in account, that, for example, for N52 series engines (with rail pressure around 3,5 bar) the opening times of injectors in idle are around 2.5 ms, but an N43/53 series engine with rail pressure around 200 bar: only 0.4 (2 X 0.2) ms. Additionally, the piezo element “feels” only changes of the voltage, which means – if the injector receives signal to open, it will stay open, until the signal to close will be received! For this reason, it’s not allowed to disconnect injectors, while the engine works problems can also appear, if suddenly the supply voltage, for example for DME, disappears when the engine runs.Īdditionally, the engines, in which piezo injectors are used, has much higher rail pressure, also the flow-rate of the injectors – higher. The injectors are “closed” by the piezo element itself, changing its size. Piezo injectors, intended for petrol engines, don’t have the spring anymore. The spring was comparingly “strong”, even wear of the moving parts or a micropart, stuck in the injector, were not able to keep the injector open. “Old type” injectors in a closed position were held by the spring. Piezo injector stucks in opened position – is such situation possible? In the image: the structure of piezo injectorġ. In the image: the structure of “regular” injector Till then – I will very make very simple calculations, is such hydro blow possible or not. To keep the intrigue, I will tell about my experience at the end of this entry. It’s clear, that the damages of such type can be very hard, with high possibility – the engine is irreversibly damaged. Fuel, leaked in the combustion chamber (which cannot be compressed as air or correct fuel mixture) can create hydro blow – connecting rod can be damaged, the piston, possibly, can be broken, the walls of the engine block can be damaged etc. I believe many of you have heard, that you have to be very careful from the situation if the piezo injector stucks in opened position – the engine can be irreversibly damaged.
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