FIAT Doblo Cargo 06' 1.3mj & Focus 08' 1.6tdc g8db - Overboosting turbo diesel

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Fri 2 Sep 2016 12:06
FIAT Doblo Cargo 06' 1.3mj & Focus 08' 1.6tdc g8db - Overboosting turbo diesel - 3uga

Please help me understand why these conditions may apear on random ocasions and what negative efects may it have on the engines on long term to get an ideea if its a problem that needs to be taken care of as urgent as posible.

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Sat 3 Sep 2016 09:39
FIAT Doblo Cargo 06' 1.3mj & Focus 08' 1.6tdc g8db - Overboosting turbo diesel - Railroad.
A turbo is a centrifugal air pump, which when driven by the outgoing engine exhaust gasses increases the flow rate of air into the engine air intake. The faster the turbo spins the more air is blown into the air intake. This greatly increases engine power, and without it your engine wouldn't pull the skin off a rice pudding.

But that's not the end of the story. Too much turbo boost can seriously damage the engine, even to the point of total destruction, and so the turbo boost must be correctly controlled.

Turbo boost pressure is measured by a Manifold Absolute Pressure (MAP) sensor. This tells the ECM what the turbo boost pressure is so the ECM can fuel the engine correctly for all engine load conditions.

Turbo boost pressure is controlled in one of two ways. Either a wastegate valve in the turbo opens to dump any excess pressure directly into the exhaust once the maximum pressure has been reached, or the turbo vanes are variable, which means the ECM controls the turbo boost throughout.

If your engine is overboosting then the means by which the boost is controlled is not working correctly. This will have to be investigated, but likely causes are a faulty turbo actuator, split vacuum pipes, or stuck wastegate valve or vane ring.

The ECM will have a safety protection against overboosting by reducing engine power to prevent damage should this occur. Limp home mode is itself not a fault, but rather a protection against something that is.
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