Audi A8 Quattro Supercharger Assembly Replacement Cost

internal combustion engines (ICEs) function by sucking air and fuel into a cylinder, compressing it with a piston, and ignition the mixture with a spark. This forces the piston back down and that piston causes the crankshaft to spin with great force. Once basic concept of creating more power is to force more air and fuel into the same sized cylinder, so when the fuel and air burns, the piston is pushed down with much greater force. This means the crankshaft will spin with much greater force, and provide more power to drive the vehicle. To accomplish this feat, a supercharger is used to push air into the cylinder instead of depending on the air to be sucked into the cylinder.

Superchargers are driven components, just like an alternator or power steering pump. They use a crankshaft driven belt to spin an internal air pump that sucks in air from the air filter. When the air is sucked in from the air filter, the supercharger will compress that air and pump it into the intake manifold. This means there is now much more air being pushed into the engine, so the engine control system is now able to introduce much more fuel as well. With all of the added fuel and compressed air, the engine will have a much more powerful burn inside the combustion chamber, and the piston will turn the crankshaft with much greater force.

Since superchargers main function is to increase power output, a failing supercharger will cause the engine to lose power. This is because the amount of air being pumped into the engine is no longer substantial, and the engine can no longer create those more powerful combustion events. Also, many superchargers will rattle when they are failing, but this may not be accompanied by reduced engine power. Finally, if the supercharger is not pumping sufficient air, or air pressure is being lost before it arrives in the combustion chamber, the check engine light will also illuminate, and the on-board diagnostic (OBD) codes will reference manifold absolute pressure, mass air flow, and a rich running condition. Finally, while not as common, the exhaust may have a black tint due to incomplete combustion of fuel inside the combustion chambers.

Supercharger failure can lead to other failures. Rich running conditions will lead to early failure of oxygen sensors and catalytic converters in the exhaust and emission control systems, carbon buildup in the combustion chamber may foul spark plugs, and shavings from the supercharger may enter the engine causing damage to mechanical components. Least of all, fuel mileage and power will be greatly reduced, and the vehicle may move into a safe driving mode. It is safe to say that supercharger failure should be repaired immediately.

Superchargers do fail, but not very commonly. Most supercharger failures will be aftermarket superchargers for engines that are purpose built for extreme power. Factory superchargers are typically modest in their compression rates, and will be serviced several times throughout the vehicle's useful life. Unfortunately, supercharger failure is not common enough to estimate the frequency of failure, but rest assured they have few moving components and tend to last the lifetime of the vehicle when properly serviced.

Supercharger gear or coupler noise is obvious to the trained technician, and this is the most common failure type with superchargers. In order to diagnose the cause of the noise, the technician will remove the supercharger front housing to inspect the coupler and drive gears. The damaged component, front cover, and oil will be changed. For superchargers that produce low amounts of compressed air, the technician will ensure the mass airflow sensor (MAF) and the manifold absolute pressure sensor (MAP) are working properly first. Afterwards, if they are functioning properly, the rate of flow and absolute pressure will be compared to specifications, the supercharger will be checked for leaks, and the supercharger may be removed to inspect for clearances, damage, or bearing failure. If the supercharger fails these inspections, it will be replaced.

Replacing a supercharger is much like changing an intake manifold. In fact, they bolt directly to the intake manifold in nearly every case. First, the supercharger belt tensioner and pulley will be removed, and any cooling lines or driven components will be removed. The air inlet or intercooler piping must be removed, and, finally, the supercharger mounting bolts or nuts can be removed to free the supercharger unit. Note that some vehicles will require extreme deconstruction of the vehicle or removal of the engine to remove or inspect the supercharger. This is because some transverse mounted engines in front wheel drive vehicles will have the supercharger mounted underneath the intake manifold.

Many aftermarket kits are available to spin the supercharger faster than originally designed. This increases power and intake pressure, but will reduce the service life of the supercharger. While the supercharger may still last a significant amount of time, the supercharger drive gears and coupler, which is typically a composite, non-metallic material, will likely fail prematurely. We here at RepairPal do not recommend altering the functionality of the supercharger without consulting the original equipment manufacturer. Note, it may also void the warranty for the supercharger and other components.

Some superchargers drive other components like a secondary air pump for emission control or an engine coolant pump. In some European models these secondary drive assemblies fail quite frequently, and should be inspected far ahead of schedule. Also, it is absolutely imperative that the engine be maintained according to manufacturer guidance for a supercharged vehicle, especially the replacement of oil, coolant, and spark plugs.

The skilled DIY mechanic can handle the diagnosis and replacement of most superchargers. This is often done with the vehicle on the ground, with only basic hand tools and a torque wrench, and within only a few hours. The inexperienced DIY mechanic should leave this to a professional or get assistance. This is because the supercharger may need to be checked for clearance, shaft play (bad bearings), and cracks to the housing.