Audi B8 VS B8.5 Engine Comparison

Audi B8 VS B8.5 Engine Comparison

Audi has produced several models and series, usually luxury vehicles. One of them is the A4 series, a compact luxury sedan with a competent engine. The company also produces the high-performance version called Audi S4.

From exterior and overall features, you may not see much change because Audi uses the same base. However, it would help if you looked closely at under the hood as the S4 model utilizes the high-performance one. It is called B8 S4, with the capability to boost a powerful powertrain.

The company launched the B8 S4 in November 2008 as the 3.0-liter TFSI Supercharged V6. This one utilized an Eaton Supercharger that had been implanted in the engine block. Moreover, it also used water-cooled intercoolers to balance the temperature and heat, including a cooling area.

Audi claimed the B8 S4 engine could reduce vibration, noise, and harness. The performance improved significantly after they installed this engine. The car delivered a powertrain of approximately 329 horsepower and torques 325 lb-ft based on the official claim.

B8 S4 delivered more power and stability with six cylinders that evenly matched the B7 as the predecessors.

The S4 received the update as in 2012. It was not just appearance but also technical upgrades. You can tell the difference after hearing the sound due to the improvement was very significant. Moreover, two S4 B8 from 2008 and 2012 will show a solid distinction after this upgrade. It means Audi puts too much effort into boosting every aspect, especially the performance. This engine brings the S4 series to full capability.

Audi B8 S4 Common Problems

Some drivers and owners experienced transmission failure, carbon build-up, misfire, water pump failure, and excess oil burn. To know more about them, check the following sections.

Transmission Failure

Reports showed that 20% of the B8 S4 would have transmission issues, especially failure.

 The number is quite high among the old cars that still use the first generation of the B8 S4. The mechatronic unit cannot control the oil system, leading to the next issue on the circuit board.

From this point, you can see why the transmission does not work as it supposed to be. The oil and board react to produce the heat that disturbs shifting gear, especially when you try to get second gear from the first one.

It seems the issue is common after the owners drive their Audi S4 up to 220k miles. When the car reached more than such limit, you can imagine what will happen to the transmission. On the other side, the probability of encountering before the 20k miles is relatively high.

The upgrade in 2012 was a significant improvement because Audi put the new generation of DSG transmission to overcome the mechatronics failure.

Another factor is the gearbox malfunction because the sensor is susceptible. You will see this issue from the sign on display. The situation is less common, but the owner must know as soon as possible. The effect is difficult to get the intended gear smoothly.

How to fix B8 S4 Transmission Failure? To overcome this problem, you replace it with a new impeller. It sounds simple and easy, but the plastic one might have a reliability issue.

Audi does not produce custom spare parts, which means you will have the same quality as the original one. You do not want the problem to appear again in the future. In this situation, using a metal impeller seems to be the right choice.

PCV Valve/ Excess Oil Burn

The B8 S4 also has another issue called PCV valve failure. PCV means positive crankcase ventilation as the part that controls gases from the combustion chamber.

The engine emits gases that can be hazardous and toxic when releasing directly on open air. You may not see much gas in the latest car except the very old one. The PCV valve has the job of obtaining all gases and putting them into the combustion chamber to be burned down. The issue is the engine produces more carbon buildup that will harm many components.

When this situation happens, the engine has lower performance, and even the car cannot accelerate after adding new oil and fuel. It seems the engine consumes more fuel but does not deliver more power. Another side effect is oil consumption becomes less efficient. One liter of oil only takes at least 2,000 miles, even less than 1,500 miles.

Carbon Build-up

The Audi S4 utilizes direct injection that is different from the stratified one. When using this feature, fuel goes to the cylinders directly, not via the intake valves. To do such a thing, the sprayer must use high-pressure to get the right direction. This procedure has pros and cons.

Engine B8 can produce more power quickly, and the car will accelerate faster than the A4 series. That’s the main purpose when having a high-performance model. However, the fuel’s risk will be less clear and clean due to direct injection does not go to the valve for cleaning.

The intake valve on this engine has a risk for carbon build-up as gunk. It is not an issue when the amount is fewer, and the car will work without hassle. Unfortunately, the carbon buildup disturbs airflow and decreases volumetric capacity.

The engine becomes stuttering, rough idling, and dreaded misfires. More carbon will bring the engine into a complete failure. That’s the price you must pay after using excessively to deliver more power and speed.

Fixing this issue is easy, but you must maintain the schedule. The intake valve receives cleaning with a walnut blast after the car reaches up to 50,000 miles. The performance might not show significant differences because the situation does not happen accidentally. It takes slowly and smoothly, and then you see the difference after the cleaning is done.

Water Pump Failure

The next problem is water pump failure that occurs on the B8 S4 engine. The percentage of this issue is relatively low because the issues can fix it without much hassle. The problem is divided into two types; the water pump pumping more fluids or does not work.

All engines for vehicles must use the cooling system to maintain the heat. The B8 S4 utilizes the water pump with an impeller. This component has the responsibility to do pumping the fluids from the pump into the cooling. The problem arises after an impeller cannot work as it must be because it is broken.

Audi produced an impeller from plastic material due to more practical and easy to do the job. However, such a thing is sensitive when working in a highly pressurized environment. When you drive the car often, the work becomes more exhausted because the cooling system works excessively. In that case, the pump will be no longer capable of supporting anymore, and the engine becomes overheating. As a result, your car will stop and wait until the temperature inside the engine room is down to normal. That takes time, and the risk is more parts will be malfunction.


Misfire also happens on the B8 S4 because of a bad coil, injectors, or both. The engine uses a coil pack to ignite the plugs with electricity. With this process, it creates combustion, and the car is started.

However, the packs might not work due to several factors, and the plugs do not power. In that case, the cylinder is out of the ignition, and more fuels are pre-detonated without additional process.

The worst situation is no detonation at all, which means the car is still idling. You replace coils packs after at least 40,000 miles regularly. This task is done easily on your own at home.

Audi B8 vs. B85 Reliability

You compare between the B8 and B8.5 regarding reliability. Audi decided to upgrade the engine B8 because of many failures. The most significant one is transmission caused by mechatronics. You get the better version of this engine in the B8.5 with more reliability and capability. Moreover, the new DSG transmission becomes standard for the latest model.

The car in your garage still uses the B8. Unfortunately, you cannot replace the transmission with the new model. You must pay more when replacing the mechatronic unit. It is considered expensive unless you rely on a non-genuine spare part. The risk becomes higher even the problem more severe. As the car owner, you cannot do such a thing.

Water pumps, coil packs, and thermostats are other issues that often appear on the B8. Keep in mind that it does not mean the B8.5 will not have the same problem at all. The probability of having the failure becomes lower, and the engine works better. In general, the B8.5 is much more reliable with upgraded transmission and excellent components.

Final Word

From the above explanation, you know the issues when having the B8 S4. This car is definitely more powerful than its compatriot A4. On the other side, you must ready to experience some problems such as transmission, water pump, misfire, and carbon buildup. Each problem has its own causes that you must understand before fixing it. The good news is the B8.5 contains an upgrade version of the B8 with better reliability.

Audi B8 Engine Specifications

Production years2009-2016
Cylinder block materialaluminium
Cylinder head materialaluminium
Fuel typegasoline
Fuel systemFSI
Number of cylinders6
Displacement, cc2,995 cc (182.8 cu in)
Power, Horsepower329 Hp
Torque. lb-ft325 lb-ft
ApplicationsAudi A4, Audi S4, Audi S5, Audi A6, Audi A7

Pictures: Audi

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