Audi RS5
The CFSA is Audi's farewell gift from the naturally aspirated V8 — 8,250 rpm rated speed, 450 PS without a turbo. The character is the opposite of a BiTurbo: the engine demands revs and rewards with a sound no production family car offers any more. Double throttle body in the intake: soft down low, sharp up top. Direct injection (FSI) is the structural weakness: without fuel washing over the intake valves, their backs coke up from blow-by oil vapour. Walnut blasting every 50,000–70,000 km is mandatory. The variable intake manifold with flaps tends to rattle from oil deposits — bolts can come loose and fall into the engine. Timing chain fundamentally robust, needs clean oil and short change intervals.
RS5 Coupé — NA V8 in the best-looking B8 body
Same 450 hp V8 as the RS4 B8, but in a coupé. Visually the most beautiful high-revving Audi, acoustically a revelation. Heavier than necessary, not as sharp as an M3, but the sound compensates. The coupé is the more fitting body for this engine than the wagon.
Engine Weaknesses 9
CFSA uses simplex chains on the gearbox side. Although more robust than the BBK predecessor, tensioners and guides are wear items. Engine removal mandatory for a full repair. Significantly more durable with regular short oil change intervals.
Symptoms: Rattle on cold start, timing chain noise at low revs, engine warning light
The CFSA revs to 8,250 rpm as a high-revving naturally-aspirated engine. Con rod bearings are under extreme stress. Neglected oil changes or poor-quality oil risk bearing wear. Preventive replacement at 80,000–100,000 km is discussed.
Symptoms: Knocking from the engine at operating temperature, increasingly loud rumbling at high revs, oil pressure drop
Four camshaft adjusters on the CFSA are more heavily stressed by high-rev operation up to 8,250 rpm than a normal V8. Oil quality and short change intervals are critical for longevity.
Symptoms: Rattle on start, camshaft fault codes, limp mode
The flaps in the variable intake manifold stick due to oil deposits from crankcase ventilation and begin to rattle. In the worst case screws or flap fragments come loose and are ingested by the engine — piston and valve damage can result.
Symptoms: Rattling or clattering from the intake area at idle and low revs, rough idle, individual cylinder misfires.
FSI deposits on intake valves documented from as early as 32,000 km, especially severe with urban use. Walnut blasting costs 600–900 € for RS4/RS5. Regular cleaning every 40,000–60,000 km recommended.
Symptoms: Power loss (up to 40 hp), rough idle, poor throttle response at low revs
RS4/RS5 with CFSA shows elevated oil consumption due to high revs and spirited use. Valve stem seals and piston rings wear. 1–2 L/1,000 km during spirited driving is normal.
Symptoms: Oil level drops noticeably, slight blue smoke after full-throttle sections, oil consumption above 1 L/1,000 km
CFSA water pump is heavily stressed in RS4/RS5 high-performance use. Failure after 100,000–140,000 km. Replace thermostat at the same time. Tight engine bay in the RS4 B8 means higher labour costs.
Symptoms: Coolant level drops, temperature fluctuations, coolant smell after driving
The FSI high-pressure pump in the CFSA can fail after 80,000–100,000 km. In the RS4/RS5 with high-performance demands this is particularly critical. Expensive replacement due to cramped engine bay.
Symptoms: Starting problems, severe power loss, hesitation under load, fuel smell
8 ignition coils in the CFSA are particularly prone to failure due to high-rev use. Motorsport-oriented use increases wear. Complete coil replacement 300–700 €.
Symptoms: Misfires, engine warning light with misfire code, hesitation on acceleration
Vehicle Weaknesses 17
The 7-speed S-tronic DL501 is prone to judder when pulling away and when shifting, especially under load or at low temperatures. The cause is usually a worn dual-clutch pack or a faulty mechatronic valve block.
The mechatronic unit of the 7-speed S tronic is a known weak point. A fault message indicating a gearbox problem points to the mechatronic in 99% of cases. Repair requires gearbox removal.
The S5 8T has an elaborate four-link front axle made of aluminium. Control arm bushings and ball joints wear prematurely under spirited driving and motorway use. Replacing all four control arms per axle involves significant cost.
On the optional sport differential the end caps of the driveshafts do not seal permanently. Heat build-up from the exhaust system creates internal pressure that overcomes the adhesive joint. Audi TPI 2025572/1 exists.
Early S5 8T models (pre-facelift 2012) developed rust blisters at the sill-to-wheel arch liner transition and on wing edges. Audi frequently covered repairs under goodwill. Paint quality improved after the facelift.
The optional CDC chassis uses electronically controlled Sachs dampers. After approximately 150,000 km, leaks or reduced control response are reported. Drive Select between Comfort and Sport makes little noticeable difference.
The MMI 3G/3G+ is prone to complete failure caused by overvoltage, moisture in the Bluetooth control unit or a defective radio module. A MOST-bus interruption takes down the entire system.
The thermostat on the 3.0 TFSI supercharged V6 (CAKA) fails and stops opening the main coolant circuit. Despite coolant temperatures reaching 110°C no fault codes are stored. Replacement requires removing the supercharger.
On S5 8T models with the Bang & Olufsen sound system, blocked drains or a leaking rear screen washer can cause water damage to the amplifier in the boot. Audi provides a free protective cover.
The hydraulic DRC control valves on the RS5 8T rattle audibly and the dampers develop leaks. An Audi-internally known problem that could not be fully resolved. Repair at dealer with special tooling.
The RS5 8T has two separate oil circuits at the gearbox; the drive axle circuit requires an oil change every 30,000 km. Even Audi dealers are often unaware of this. Neglect causes damage.
The optionally available carbon-ceramic brakes are due after 100,000–150,000 km and cost over €10,000 to replace. At low temperatures and in wet conditions they only reach full effectiveness after warming up.
Dirt accumulates between the plastic underbody panels and wears through the corrosion protection. Rust forms at mounting points and weld seams. Annual removal and cleaning is considered essential.
A characteristic whine or squeal occurs at full lock. The cause is excessive hydraulic pressure at maximum steering travel or wear in the power steering pump. Incorrect fluid level can make the problem worse.
The S5 sport brake system (340 mm front) requires specific pads and discs. Under sporty driving pads can be due after 30,000–40,000 km. Only one side has a wear sensor.
The Milano leather on the side bolsters of the S5 sport seats is considered too thin. Friction when getting in and out causes noticeable wear on the outer bolsters from around 80,000 km.
Electric window regulators fail over time and must be replaced completely. Affects older high-mileage vehicles more frequently.