The Audi S5 V8 engine with its perfect blend of power and refinement is another testimony to how good German automotive engineering can be. The V8 engine in the Audi S5 propels it from 0-60 mph in approximately 4.9 seconds, with a driving feel that few vehicles can match. The high-revving NA V8 sound is music to the ears of any enthusiast, and the way the car hauls itself from any speed is satisfying in itself.
The Audi S5 V8 engine for sale here is not just about power; it showcases reliability and longevity. It's built with the precision and quality that Audi is known for. Whether you are cruising the highway or driving spirited backroads, this engine delivers.
Engine Overview: Audi 4.2 FSI V8
The Audi S5 V8 is the 4.2 FSI V8 engine (engine codes BNS and CAUA) that powered the B8 chassis Audi S5 Coupe and Cabriolet from 2008 to 2012. Specifications:
Detail
Description
Feature
Specification
Engine Codes
BNS (early B8) and CAUA (later B8)
Configuration
V8 90° DOHC 32-valve
Displacement
4.2L (4,163 cc)
Bore x Stroke
84.5 mm x 92.8 mm
Compression
12.5:1 (high compression NA)
HP
354 HP at 6,800 RPM
Torque
325 lb-ft at 3,500 RPM
Redline
7,200 RPM (high-revving)
Aspiration
Naturally aspirated (NOT turbo or supercharged)
Fuel System
FSI direct injection
Fuel Type
Premium 91+ octane mandatory
Timing
Timing chain (tensioner = primary service area)
Production
2008-2012 (US B8 S5)
Critical Disambiguation: B8 S5 V8 vs Post-2012 Supercharged V6 S5
This is the most important purchasing distinction for the Audi S5. The Audi S5 model name covers TWO completely different engines across generations:
Performance: 0-60 in ~4.7 seconds (slightly faster despite less HP due to torque)
For replacement applications: verify which engine your S5 has. The V8 and supercharged V6 are NOT interchangeable.
The VW-Audi Group 4.2 FSI V8 Architecture
The Audi S5 V8 is part of one of Audi's most important performance V8 engine families. The same fundamental 4.2 FSI V8 architecture powers:
Audi S5 V8 (This Listing)
Application: B8 S5 Coupe and Cabriolet (2008-2012)
HP: 354 HP
Character: Refined sports coupe tuning
Audi RS4 B7 (2006-2008)
Application: RS4 B7 sedan and Avant (wagon)
HP: 420 HP (the more aggressively tuned variant)
Character: RS-tuned for maximum performance
Differences: Different ECU, intake, exhaust, and supporting components
Audi R8 V8 (2007-2015)
Application: R8 V8 supercar
HP: 420 HP (R8-specific tuning)
Character: Mid-engine supercar configuration
Differences: Different ECU, intake/exhaust, oil system for mid-mount, supporting components
The shared 4.2 FSI V8 architecture means all three engines use the same fundamental block, heads, FSI system, and basic V8 design , with Audi RS / R8-specific tuning for higher output. For replacement applications, the S5-specific variant should be matched (BNS or CAUA engine codes for the S5).
FSI Direct Injection Technology
The "FSI" in 4.2 FSI V8 stands for Fuel Stratified Injection, Audi's direct injection technology:
What FSI Does
Fuel injected directly into combustion chambers (not into intake ports)
High pressure injection (200+ bar)
Multiple injection events per combustion cycle
Stratified charge operation at part-throttle for efficiency
Homogeneous charge operation at full-throttle for power
Benefits Over Port Injection
Higher compression possible (enables 12.5:1 in 4.2 FSI V8)
More power from same displacement
Better fuel economy at part-throttle
Lower emissions with optimized combustion
Trade-Off , Carbon Buildup
FSI direct injection doesn't wash intake valves with fuel (port injection does)
Result: Carbon builds up on intake valves over time
Symptoms: Reduced low-RPM power, rough idle
Service: Walnut blasting at 60,000-100,000 miles
Cost: $1,500-3,000 for proper service
Vehicle Applications
Audi S5 Coupe B8 (2008-2012)
The original 4.2 FSI V8 S5 application:
Body style: 2-door sports coupe
Drivetrain: Audi quattro AWD standard
Transmissions: 6-speed manual, S Tronic 7-speed DCT, Tiptronic 6-speed automatic
Performance: 0-60 in ~4.9 seconds
Production: 2008-2012 US market
Audi S5 Cabriolet B8 (2010-2012)
The convertible variant of the V8 S5:
Body style: 2-door soft-top convertible
Drivetrain: Audi quattro AWD standard
Transmissions: S Tronic 7-speed DCT or Tiptronic 6-speed
Performance: 0-60 in ~5.1 seconds (slightly slower than coupe due to weight)
Production: 2010-2012 US market
Common 4.2 FSI V8 Service Items (Honest Disclosure)
The 4.2 FSI V8 has several significant documented service areas that buyers must understand:
Timing Chain Tensioner Failures (THE PRIMARY 4.2 FSI V8 CONCERN)
This is the most well-documented and concerning service area for the 4.2 FSI V8.
What Happens
Audi 4.2 FSI V8 uses timing chains at the rear of the engine (between engine and transmission)
The chain tensioners (multiple) can fail over time
Failed tensioners allow chain slap and eventual chain skip
In severe cases, complete engine destruction
Symptoms
Cold-start rattle from rear of engine
Persistent timing chain rattle
Check engine light with cam/crank correlation codes
In severe cases, engine no-start or running poorly
Why It's Severe
Engine-out service required: The chains are at the REAR of the engine
Transmission must be removed to access the chains
Significant labor: 25-40+ hours typical
Service cost: $4,000-8,000+ when performed properly
Audi TSB and Updates
Audi issued multiple updated tensioner designs throughout production
Later production examples may have updated tensioners
Replacement engines should have current updated tensioner design ideally
Our Inspection Approach
Cold-start rattle assessment: Listening test for tensioner symptoms
Cam/crank correlation check: ECU scan for timing-related codes
Engine code documentation: BNS vs CAUA for service history context
Honest disclosure: We disclose any concerns identified
Common rate: 1 quart per 1,000-3,000 miles at high mileage
Causes: Piston ring wear, valve seal wear
Mitigation: Regular oil top-off, quality 5W-30 or 5W-40 synthetic
Severe cases: May indicate need for piston/ring service
Water Pump Failures
Service interval: 60,000-100,000 miles
Service: $500-1,000 typical
Cost includes: Coolant flush, thermostat often replaced together
Coil Pack Failures (8 Coils)
Symptoms: Misfire codes, rough running
Service: $80-150 per coil
Multiple failures: Common across engine lifetime
High-Pressure Fuel Pump (HPFP)
Service area for FSI engines: Documented HPFP failures
Service cost: $1,000-2,000 typical
Vehicle Compatibility
Direct Fit:
Vehicle
Compatibility
Audi S5 Coupe (B8 chassis)
2008-2012 with 4.2 FSI V8 engine (BNS or CAUA engine code)
Audi S5 Cabriolet (B8 chassis)
2010-2012 with 4.2 FSI V8 engine (CAUA engine code typical)
NOT Compatible
Post-2012 Audi S5 (B8.5 facelift 2013+, B9 generation 2018+) which uses 3.0L supercharged V6 (different engine entirely)
Related Architecture (NOT directly interchangeable)
Audi RS4 B7 (4.2 FSI V8 at 420 HP, different tuning), Audi R8 V8 (4.2 FSI V8 at 420 HP, mid-engine configuration), other Audi 4.2 V8 applications , all share fundamental 4.2L V8 architecture but with Audi RS / R8-specific tuning, ECU, intake, exhaust, and supporting components
Condition and Inspection
Engine code verified (BNS early B8 or CAUA later B8)
Donor vehicle confirmed (S5 Coupe or S5 Cabriolet)
B8 S5 V8 vs post-2012 supercharged V6 distinction verified
All 8 cylinders compression tested
Oil pressure verified at idle and operating speed
Timing chain tensioner condition SPECIFICALLY assessed (the primary 4.2 FSI V8 service area)
Timing chain condition assessed
Cam/crank correlation ECU scan performed
Cold-start rattle assessment performed
Carbon buildup on intake valves assessed (FSI direct-injection typical service)
Oil consumption indicators inspected (documented service area)
FSI direct injection system tested (HPFP + 8 direct injectors)
High-pressure fuel pump function verified
8 direct fuel injectors function verified
All 8 coil packs condition assessed
Water pump function verified
Head gasket condition verified (both banks)
All-aluminum block condition inspected
Cylinder head condition assessed (both banks)
8 spark plug condition documented (iridium plugs)
Coolant system function verified
Front and rear main seal condition checked
Oil leak inspection
Miles from donor vehicle documented where available
Engine code correctly identified (BNS or CAUA, both are 4.2 FSI V8)
V8 90° DOHC 32-valve, naturally aspirated, FSI direct injection
Engine Codes
BNS (2008-2009), CAUA (2010-2012)
Manufacturer
Audi AG (VW-Audi Group)
Configuration
V8 90° (longitudinal mount)
Displacement
4.2L (4,163 cc)
Bore X Stroke
84.5 mm x 92.8 mm
Hp
354 HP at 6,800 RPM
Torque
325 lb-ft at 3,500 RPM
Redline
7,200 RPM
Compression
12.5:1 (high compression NA)
Aspiration
Naturally aspirated
Fuel System
FSI direct injection
Fuel Type
Premium 91+ octane mandatory
Valvetrain
DOHC, 32 valves, chain-driven
Block Material
All-aluminum with iron liners
Head Material
Aluminum (DOHC)
Timing System
Timing chain (tensioner = primary service area)
Production Years
2008-2012 (US B8 S5)
Direct Fit
B8 S5 Coupe 2008-2012, B8 S5 Cabriolet 2010-2012
What is the Audi S5 V8?
The Audi S5 V8 is the 4.2 FSI V8 engine (engine codes BNS and CAUA) that powered the B8 chassis Audi S5 Coupe and Cabriolet from 2008 to 2012. Specifications: Type: V8 90u00b0 DOHC 32-valve, naturally aspirated Displacement: 4.2L (4,163 cc) HP: 354 HP at 6,800 RPM Torque: 325 lb-ft at 3,500 RPM Compression: 12.5:1 (high compression NA) Fuel System: FSI direct injection Redline: 7,200 RPM (high-revving) Production: 2008-2012 US market The 4.2 FSI V8 is part of the broader Audi 4.2 FSI V8 architecture shared with the Audi RS4 B7 (420 HP variant) and Audi R8 V8 (420 HP variant).
What's the difference between B8 S5 V8 and post-2012 S5?
Two completely different engines under the same S5 model name: | Feature | B8 S5 V8 (2008-2012, This Listing) | B8.5 / B9 S5 (2013+) | | --- | --- | --- | | Engine | 4.2 FSI V8 (BNS/CAUA) | 3.0 TFSI V6 supercharged (CGWC/CREC) | | Cylinders | 8 | 6 | | Displacement | 4.2L | 3.0L | | Aspiration | Naturally aspirated | Supercharged | | HP | 354 HP | 333-349 HP | | Torque | 325 lb-ft | 325-369 lb-ft | | Character | High-revving NA V8 sound | V6 with supercharger whine | | 0-60 | ~4.9 sec | ~4.7 sec | | Redline | 7,200 RPM | 6,800 RPM | For replacement applications: verify your S5 has the V8. The V8 and supercharged V6 are NOT interchangeable. For the post-2012 supercharged V6, see our separate Audi S5 3.0 TFSI listing.
What are the engine codes BNS and CAUA?
Both are 4.2 FSI V8 engines for the B8 Audi S5: BNS (2008-2009) Early B8 S5 production 4.2 FSI V8, 354 HP, 325 lb-ft Slightly different supporting electronics CAUA (2010-2012) Later B8 S5 production (and B8 Cabriolet) 4.2 FSI V8, 354 HP, 325 lb-ft Updated supporting electronics For replacement, match your specific engine code for proper ECU and supporting component compatibility.
Is the Audi S5 V8 turbocharged?
No, the 4.2 FSI V8 is naturally aspirated (NA). This is an important point of distinction: Audi S5 V8 (This Listing) Naturally aspirated , no turbos, no supercharger High compression: 12.5:1 High redline: 7,200 RPM Sound: Classic NA V8 character Power delivery: Linear, builds with RPM Other Audi V8 Engines (Different) Audi RS6 (4.0 TFSI): Twin-turbocharged V8 (different engine, batch 48 Bentley V8 listing reference) Audi RS7 (4.0 TFSI): Twin-turbocharged V8 Audi S6/S7/S8 (4.0 TFSI): Twin-turbocharged V8 The 4.2 FSI V8 in the S5 is the NA V8 , one of the last great NA V8 engines from Audi before the move to turbo V8s in 2012+.
Is the Audi 4.2 FSI V8 the same as the Audi RS4 or R8 engine?
Same architecture, different tuning. All three engines share: Same fundamental 4.2L V8 block and heads Same FSI direct injection technology Same 90u00b0 V8 layout Same DOHC 32-valve architecture Differences | Feature | S5 V8 (This Listing) | RS4 B7 V8 | R8 V8 | | --- | --- | --- | --- | | Years | 2008-2012 | 2006-2008 | 2007-2015 | | HP | 354 HP | 420 HP | 420 HP | | Redline | 7,200 RPM | 8,250 RPM | 8,250 RPM | | Application | Sports coupe | Sedan/wagon | Mid-engine supercar | | ECU | S5-specific | RS-specific | R8-specific | | Intake/Exhaust | S5 routing | RS routing | R8 routing | | Tuning | Refined sports car | Aggressive RS | Supercar | For replacement applications, the S5-specific variant (BNS/CAUA) should be matched to your S5. Cross-installation from RS4 or R8 is theoretically possible but requires extensive supporting changes.
What is the timing chain tensioner issue?
The primary 4.2 FSI V8 service concern. Critical to understand before purchase. What It Is The 4.2 FSI V8 uses timing chains at the rear of the engine Multiple chain tensioners maintain proper chain tension Tensioners can fail over time, causing chain slap and eventual problems Symptoms Cold-start rattle from rear of engine Persistent timing chain rattle Check engine light with cam/crank correlation codes In severe cases: chain skip, engine no-start, catastrophic damage Why It's Severe Rear-mounted chains: Located between engine and transmission Engine-out service required: Transmission must be removed for access Significant labor: 25-40+ hours typical Service cost: $4,000-8,000+ when performed properly Audi Response Multiple updated tensioner designs throughout production Later production may have updated tensioners Our Approach Cold-start rattle assessment Cam/crank correlation ECU scan Honest disclosure of any concerns identified Buyer expectation: 4.2 FSI V8 owners should specifically budget for potential timing chain tensioner service.
Does the Audi S5 V8 need premium fuel?
Yes, premium 91+ octane (95 RON) is mandatory. The combination of: High compression ratio (12.5:1) FSI direct injection Performance tuning Requires high-quality premium fuel. Top Tier gasoline is strongly recommended for FSI direct injection cleanliness. Never run regular 87 octane , this will cause severe detonation and potential engine damage.
How is fuel economy on the Audi S5 V8?
Modest fuel economy , this is a performance V8: EPA City: 13-14 MPG EPA Highway: 22-23 MPG Combined: 16-17 MPG Aggressive driving: 10-12 MPG Gentle highway: 24-26 MPG possible The 4.2 FSI V8 prioritizes performance over fuel economy. Modern turbo S5 V6 supercharged is more efficient (~18-21 combined) , one reason Audi moved away from the V8 in 2012.
15 Day Replacement Warranty
Covered:
Internal defects discovered at delivery (broken connecting rods at delivery
Failed bearings at delivery
Cracked block
Cracked head
Broken pistons at delivery
Complete loss of compression at delivery
Broken crankshaft)
Not Covered:
Timing chain tensioner failures developing after delivery (the well-documented 4.2 fsi v8 service area
Buyers should expect potential tensioner service in engine lifetime
With $4,000-8,000+ engine-out service cost)
Carbon buildup on intake valves developing after delivery (fsi typical service)
High oil consumption developing after delivery (documented 4.2 fsi v8 service area)
