APR - FIT0003 - S8 ADAPTER -- Audi (D4/D4.5) S8 -- 4.0 TFSi engines



APR - FIT0003 - S8 ADAPTER -- Audi (D4/D4.5) S8 -- 4.0 TFSi engines


S8 Adapter

The Audi S8’s factory catback exhaust system is located in a slightly different location compared to other models. As such, the APR Adapter is required for proper fitment with the factory catback exhaust. The fit kit consists of two OEM clamps and extension pipes. The system bolts directly between the APR downpipes and factory catback pipes.


for use with:

APR Cast Downpipe Exhaust System for the 4.0 TFSI

+25-59 Horsepower

+32-95 FT-LBS of Torque

Cast Bell Mouth Inlets

Full 76mm Stainless Steel System


APR is pleased to present the ultimate Cast Downpipe Exhaust System!

The APR Cast Downpipe Exhaust System replaces the restrictive factory catalyst cross pipes and resonators with an upgraded 76mm stainless steel mandrel-bent system, featuring port-matched cast inlets, high-flow catalysts and various other features. Expect better throttle response, more horsepower and an intoxicating exhaust note, while remaining civilized during normal daily driving. It’s the best performance upgrade for the 4.0 TFSI following the APR ECU Upgrade and it’s all designed and assembled in-house, using premium materials and world-class manufacturing techniques few can match.

Quick facts:

  • More power and better response
    Expect a decrease in turbo lag with power and torque gains as high as 59 HP and 95 FT-LBS of torque over APR Stage I!
  • Full 76mm downpipe system
    The APR system is a full downpipe upgrade as it replaces the kinked 60mm catalyst cross pipes and resonated midpipes with straight through, 76mm mandrel-bent tubing.
  • Port-matched investment-cast downpipe inlets
    The factory inlets are restrictive. APR’s cast system allows for massive, port-matched inlets that smoothly neck down over a long distance. The result is improved flow, better response and more power.
  • Dual, high-flow catalysts
    GESI’s encapsulated catalysts are known for their strength and performance. Expect lower emissions, reduced noise and less exhaust smell compared to catless setups, all without negatively impacting performance to over 1,000 HP. Furthermore, with the catalyst moved, expect a cooler engine bay!
  • T304L stainless steel construction
    Premium grade T304L stainless steel resists corrosion and stands the test of time.
  • Argon back-purged TIG welding
    Clean, strong and attractive welds both inside and outside the pipes.
  • OEM-style low-profile slip-on clamps
    The APR slip-clamps are easy to use, resist leaks and pipe deformation better than swedged setup, are lower profile than vbands and flanges and don’t require replacement gaskets.
  • OEM-style internally-corrugated flex sections
    APR’s flex sections are internally corrugated to increase flow and prevent failures common with braided flex sections.
  • Investment cast secondary oxygen sensor bungs
    APR’s obsession to details resulted in investment cast oxygen sensor bungs that sit on top of the piping, preventing material from protruding into the exhaust stream, disrupting flow.
  • Compatible with the OEM catback exhaust
    Bolt-on and go! The system is fully compatible with the factory catback exhaust.
  • Designed, assembled and quality controlled in-house
    All critical aspects of the system are handled internally to ensure the highest quality fit and finish.
  • All hardware and instructions included
    New OEM gaskets, oxygen sensor harnesses, clamps, brackets and install instructions are included to make the install as headache free as possible.
  • APR Stage II ECU Upgrade price waived
    With every APR downpipe purchase comes a free upgrade to Stage II from Stage I, saving consumers hundreds of dollars!
  • Limited lifetime warranty
    The best system on the market also carry the best warranty in the industry!
Downpipes Inlets

Cast Downpipes Inlets with 76mm Tubing

The factory downpipes are less than desirable from a performance standpoint. Both pipes quickly neck down from the massive turbocharger outlet to small and resistive 60mm pipes that are kinked in many areas before twisting and dumping into catalytic converters. APR greatly improved upon this design through the use of investment-cast and port-matched downpipe inlets. Each pipe gradually reduces to the larger and straighter 76mm piping, with the hot catalyst moved further down the exhaust stream to keep under hood temperature down. 

The cast inlets, piping and other components are made from the the high-nickel content, premium-grade stainless steel known as T304L. This material was chosen for its excellent corrosion resistance, strength and appearance. The castings are tumbled to smooth and de-burr any imperfections, and all piping is brushed clean before entering the CNC controlled mandrel benders. TIG welding is used at all connection points, and was chosen for its strength and appearance. Each weld is argon back purged during assembly to increase strength and consistency of the welds. The gusseted brackets are CNC laser cut and bent to provide strong mounting points to the factory mounting hardware.   

APR Stage II Calibration Report
Vehicle NAR Fuel ROW Fuel Max HP Max TQ Max HP Gain
Over APR Stage I
Max TQ Gain
Over APR Stage I
- Max increases are based on APR's actual measured stock values and not those reported by VAG. | RON = ROW Fuel Grades | AKI = North American (RON+MON)/2 Fuel Grades.
- Reported wheel figures measured using APR's AWD Dynapack and APR UK's AWD Dynojet dyno with multiple vehicles, using SAE correction and an average of multiple runs for all figures. Stage II included a high flow downpipe. Crank figures are estimated based on the measured wheel figures. Results may vary depending upon environmental conditions, vehicle, transmission, vehicle health, operating conditions, temperatures, fuel grade, dyno type, dyno setup, other variables and other modifications.
Audi S6/S7 (C7) 91 AKI 95 RON 575 HP 669 FT-LBS +56 HP @ 3,850 RPM +82 TQ @ 3,350 RPM
Audi S6/S7 (C7) 93 AKI 98 RON 586 HP 694 FT-LBS +52 HP @ 3,950 RPM +73 TQ @ 3,500 RPM
Audi S6/S7 (C7) 100 AKI 104 RON 602 HP 713 FT-LBS +59 HP @ 4,050 RPM +83 TQ @ 3,500 RPM
Audi S6/S7 (C7) 104 AKI 108 RON 614 HP 717 FT-LBS +71 HP @ 4,250 RPM +91 TQ @ 4,000 RPM
Audi S6/S7 (C7.5) 91 AKI 95 RON 567 HP 648 FT-LBS +35 HP @ 3,950 RPM +61 TQ @ 2,400 RPM
Audi S6/S7 (C7.5) 93 AKI 98 RON 588 HP 684 FT-LBS +36 HP @ 3,850 RPM +58 TQ @ 2,300 RPM
Audi S6/S7 (C7.5) 100 AKI 104 RON 613 HP 689 FT-LBS +25 HP @ 4,300 RPM +50 TQ @ 2,350 RPM
Audi RS6/RS7 (C7) 91 AKI 95 RON 679 HP 703 FT-LBS +40 HP @ 4,950 RPM +74 TQ @ 2,450 RPM
Audi RS6/RS7 (C7) 93 AKI 98 RON 712 HP 751 FT-LBS +44 HP @ 5,050 RPM +77 TQ @ 2,500 RPM
Audi RS6/RS7 (C7) 100 AKI 104 RON 761 HP 793 FT-LBS +43 HP @ 4,700 RPM +85 TQ @ 2,500 RPM
Audi RS6/RS7 (C7.5) 91 AKI 95 RON 687 HP 777 FT-LBS +42 HP @ 2,700 RPM +83 TQ @ 2.600 RPM
Audi RS6/RS7 (C7.5) 93 AKI 98 RON 709 HP 797 FT-LBS +42 HP @ 2,700 RPM +83 TQ @ 2,600 RPM
Audi RS6/RS7 (C7.5) 100 AKI 104 RON 730 HP 811 FT-LBS +49 HP @ 4,950 RPM +94 TQ @ 2,650 RPM
Audi RS6/RS7 (C7.5) 104 AKI 108 RON 759 HP 889 FT-LBS +49 HP @ 2,750 RPM +95 TQ @ 2,650 RPM
Audi S8 91 AKI 95 RON 672 HP 691 FT-LBS +30 HP @ 4,700 RPM +36 TQ @ 4,100 RPM
Audi S8 93 AKI 98 RON 688 HP 727 FT-LBS +28 HP @ 4,750 RPM +32 TQ @ 4.500 RPM
Audi S8 100 AKI 104 RON 710 HP 751 FT-LBS +32 HP @ 4,200 RPM +41 TQ @ 4,100 RPM

The APR Difference

The Engineering and Designing Phase

In the past APR worked with other manufacturers to develop a limited range of private-label exhaust systems outside the scope of APR’s internal development and manufacturing capabilities. Understanding the limits of such a program, combined with APR’s desire to deliver higher-quality products in a timely manner with better customer support, APR invested in internalizing the program. With the release of this exhaust system and the others like it, APR is pleased to present our first systems fully designed and engineered in-house from the ground up! 

Design and development begins with the use of APR’s professional grade in-house coordinate measuring machines. APR’s engineers have full access to a Romer Absolute arm with integrated laser scanner, FaroArm and Creaform 3D laser scanner for collection of special constraints surrounding the factory exhaust system. The engineers scan the vehicles and create detailed 3D maps of their design environment while designing each system in PTC Creo 3.0 CAD software.

Using APR’s in-house stereolithography 3D printer, rapid prototypes are created for fitment on the vehicle. The design is easily and quickly verified, and if necessary, changes can be made. Once adequate clearances and fitment is confirmed, especially in areas that move under load, physical quick-cast prototypes are created and fitted for final verification through real-world use.

APR’s world-class manufacturing partners from around the globe are responsible for manufacturing each component that falls outside of APR’s internal capabilities. Working closely with each manufacturer, APR’s engineers supply CAD models, materials specs, and other design specifications and work hand-in-hand with the manufacturer to develop the components. The end result is a collection of components, wholly unique to the APR name, awaiting final finishing, assembly and quality control at APR’s 78,000 square foot facility in Opelika, Alabama in the USA.


Application Guide
Vehicle Engine Drivetrain Part Number Price  
Designed for Left Hand Drive (LHD) vehicles only. Right Hand Drive (RHD) vehicles require slight clearancing.