Ever since the release of the game-changing 1.8T in the B5 A4, Audi has produced some of the most tunable and mod-friendly cars in the world. As technology and performance has increased with innovations like gasoline direct injection, improved chassis construction and design, as well as an increasingly complex and capable computer system, Audi has upped their game with every new release and iteration of forced-induction engines.
The MLB-based 3.0T-powered B8 Audi S4 and B8.5 S4 and S5 are some of the very best offerings from Ingolstadt to date. They occupy a sweet spot, offering dynamic performance, refinement, and understated but classic good looks that have continued to age well, ever since the original S5 was released in 2008. As good as these cars are out of the box, there are several effective modifications to improve the acceleration, braking, handling, and overall looks. Here are some of the top five modifications for your 3.0T S4 or S5.
Audi S4 Suspension Mods
There are few areas where a change can impact a car’s performance, like in the suspension system. Upgrading components in the suspension can improve handling, acceleration, and braking, as well as improve the looks. Even small changes can be very effective at making your S4 more fun to drive and stand out from the crowd.
Audi S4 Lowering Springs
Sport lowering springs are probably one of the easiest and most common choices when it comes to suspension upgrades. There is no denying that a lowered S4 or S5 has a decidedly purposeful look. Sport springs come in many varieties, from mild to wild, so it’s important to consider what kind of roads you drive on and how you drive the car, as these can impact what the best choice will be for your S4 or S5.
A mild drop is ideal for use with factory struts, especially if your car has the Audi Adaptive Suspension. Eibach’s Pro-Kit sport lowering springs are among the most well-known and best-performing spring kits on the market. Lowering is rated at 0.8” front (20 mm) and 0.6” rear (15 mm), which is enough to notice in terms of aesthetics but not enough to ruin the ride or the handling.
If you want something just a bit more aggressive, check out the Dynamic+ springs from 034 Motorsport. Offering 1” (25 mm) of lowering, the Dynamic+ springs provide a noticeable but not excessive reduction in ride height and are designed to offer an excellent ride quality with improved handling over the factory springs. Plus, the 034 Motorsport Dynamic+ are specifically designed to be used with factory dampers.
If you want to go low on a budget, H&R Super Sport springs may be what you’re looking for. Offering up a large 2” (50 mm) drop, these will give you an aggressive look, but at the expense of ride quality when it comes to larger bumps. They’re best matched with upgraded shocks and struts, as the factory shocks are not going to last as long at that low ride height.
Audi S4 Shocks & Struts
Speaking of which, your struts and shock absorbers are a crucial component of your S4 or S5’s suspension. Depending on your car’s mileage, you may want to replace them when you install your sport lowering springs no matter which set you get. They will provide better performance, better ride and handling, and save you labor in the long run.
The Bilstein B8, aka Bilstein Sport, is one of the most proven sport dampers around. A high-pressure monotube design, these durable shocks are designed to be used with a lowering spring, helping to retain a decent ride even at lower ride heights. Damping rates are increased over the factory shocks and struts, but not to the extent that it negatively impacts comfort or how the car handles. You will see a benefit with upgraded dampers whether you’re cruising down the highway or taking laps at a local race track.
Audi S4 Coilovers
If you’re someone who wants a more aggressive, lower, style, or you’re just picky about the ride height and the handling performance of your S4 or S5, an adjustable coilover suspension may be the right choice for you. Coilovers are height-adjustable, with threaded perches allowing you to fine-tune your look or weight balance of the car down to the millimeter. Many kits also offer adjustable damping, which enables you to make the shock absorber either more or less firm. This can be used to give the car a more or less compliant ride, or it can be used to help change the balance of the car by controlling weight transfer.
Pricing and features of coilover suspension span a range of budgets, so if you find yourself more interested in these over springs, fear not. They also have the added benefit of often having an improved ride and better handling over the factory suspension, thanks to higher quality dampers and perfectly matched spring and damper rates.
The range-topping Sachs Performance coilovers offer an excellent combination of ride and handling for your B8 S4 or S5. Featuring inverted monotube dampers, the Sachs Performance kit utilizes much of the same technology as the ZF Race suspension used on our GTI TCR race cars. Advanced valving and adjustable damping combined with high strength means unbeatable responsiveness on the street or track.
If you’re looking for a suspension that is a bit less costly but still uses the highest quality components, one of H&R’s many coilover suspensions is a great choice. H&R arguably invented the street coilover as a product, and their Street Performance coilover suspension uses inverted monotube dampers, similar to Sachs Performance and Bilstein, but without adjustable rates. You can still fine-tune your ride height, but thanks to reduced complexity, these come in at a significantly lower price while still offering superb handling. H&R Street Performance coilovers offer between 1.0” and 2.2” of lowering. If you want to go lower, their Ultra-Low kit has all the same features of the Street Performance kit but offers 1.5” to 2.7” of ride height reduction for that perfect stance.
If H&R isn't exactly what you're looking for, it's hard to argue with Bilstein's offerings in the segment. Bilstein's quality is well-known which makes them a solid choice if you have the extra cash to spend. We highly recommend their Street Performance PSS10 B16 Suspension Kit for any street or dual-purpose car.
When your S4 or S5 has Audi Adaptive Suspension, it is important to note that replacing the shocks or installing coilovers that are not AAS-compatible will result in fault codes in multiple systems of the car, including the ABS and stability management systems. If you do choose to replace your dampers with an aftermarket set, and AAS-defeat kit, such as the one produced by KW Suspensions, will be required for the best results.
Audi S4 Wheel Spacers
Adding on a set of wheel spacers to your factory wheels, combined with a lowered stance, can be a great way to transform the look of your S4 or S5 with minimal cost compared to a set of aftermarket wheels. Fitting spacers will require longer lug bolts, and it’s important to use high-quality spacers with both hub and wheel-centric fitment. Poor quality spacers that don’t fit tight to the car’s hub or the wheel’s hub center bore will result in vibration at highway speeds. As we all know, if you improve your car’s looks but it has a huge negative impact on the driving experience, is it really an upgrade?
Audi S4 ECU/TCU Reflash/Pullies
Audi S4 ECU Tune
There is no better bang for the buck for horsepower on a 3.0T than a performance tune for the ECU. Utilizing the on-board diagnostic (OBD) port, tuners such as Unitronic, APR, and others, can make changes to the fueling, timing, and boost parameters to increase horsepower and torque. Like most other Audi engines, the supercharged 3.0T is overbuilt from the factory. This means that there aren’t any other required parts to achieve a major increase in the power from the engine. When properly maintained, you shouldn’t see any reduction in long term durability or reliability either.
A ‘Stage 1’ tune is likely to require no other parts and makes no requirement other than the use of a certain octane of fuel. For example, with a Unitronic Stage 1 tune, power is increased to 392 horsepower and 351 lb-ft of torque with 91 octane fuel. Rated for 91 octane fuel, you can use anything 91 or higher, but not lower. Although this is a simplified explanation, basically, the higher the octane, the greater the resistance to pre-ignition, and the more power can be made. That same tune in Stage 1+, 93 octane spec, makes 415 horsepower and 360 lb-ft of torque. That is a gain of 82 horsepower and 35 lb-ft of torque over factory power numbers with absolutely zero other changes to the car. Best of all, the Unitronic flash can be performed at home in your driveway with only a laptop, battery tender, and an internet connection, thanks to the Uniconnect OBD flash cable.
Audi S4 Supercharger Pullies
A large part of the reason you can gain so much power with the 3.0T is due to an increase in the boost from the supercharger from the performance ECU software. Upgrading to an aftermarket supercharger pulley, crank pulley, or both, will spin the charger faster and allow it to make more boost, and therefore potentially more power. A corresponding ECU tune has to be installed along with a pulley change. Depending on the tune and exact parts being used, such as a free-flow intake and exhaust, or cooling components, a dual-pulley 3.0T can make close to 500 horsepower on standard 93 octane fuel. That’s an outstanding 160 horsepower gain over the factory 333 horsepower rating, all without touching anything inside the engine or compromising the engine’s overall reliability.
Audi S4 TCU Flash
If you happen to have an S Tronic dual-clutch transmission, you will want to upgrade the transmission control unit (TCU) software when you upgrade the ECU. While not required for most basic Stage 1 tunes, the S Tronic transmission will offer smoother and improved performance when it is remapped to optimize the increased power from the engine. Performance TCU software optimizes shift points, increases clutch clamping power, increases the speed of the shifts, and offers an improved manual-mode experience.
Audi S4 Brake Mods
Whenever you increase power beyond a factory level, it’s important to consider the other systems that are designed around that power output. As easy and fun as it is to increase horsepower, and therefore speed and acceleration, it’s arguably more important to make sure you can stop just as quickly. Upgrading components of your factory braking system is an easy process and will ensure you can stop with confidence, even with a big increase in power over the factory S4 and S5.
Audi S4 Street Brake Pads
Of all the components that improve braking performance, nothing is as effective as upgrading your brake pads. Not only can you see improved stopping power, but very often lower amounts of brake dust levels compared to the OEM brake pads.
Ate Ceramic Brake Pads are an excellent choice if you’re looking for the best street performance with a huge reduction in brake dust over the factory brake pads. If you have a modified S4 or S5 and want a significant increase in stopping power with a little more dust than the Ate, check out the Stoptech Sport brake pads. These offer improved pedal feel, reduced dust, and improved braking performance under demanding driving conditions and work just as well commuting as they do hitting backroads or participating in a local autocross.
Audi S4 Track Brake Pads
If you have plans to really push things to the upper limits of power or attend track days, but still plan on daily driving your car on the street, we suggest looking at the Ferodo DS2500. This is one of the best all-around brake pads you can buy; a true “street and track” capable pad. The DS2500 offers amazing on-track braking performance, excellent modulation, and great wear rates for both the brake pad and the brake rotor. Best of all, while it does dust a bit more than the street sport pads from Stoptech or Hawk, they are still less dusty than the stock brake pads and don’t suffer from the extreme noise that usually accompanies a track-ready brake pad.
Audi S4 Brake Rotors
You should always install fresh brake pads with new brake rotors. Simply installing a fresh set of Zimmerman blank discs with new pads will go a long way to ensuring the best performance and even brake wear. The brake pads make more of a difference in stopping power than brake discs, so when it comes to budget, it’s better spent on better pads. There are sport brake discs that do offer some limited improvements over plain rotors.
Sport brake discs typically come as either slotted, cross-drilled, or both cross-drilled and slotted. Each design has its advantages and disadvantages. Slotted brake rotors are going to offer an improved initial bite when you apply the brakes but at the expense of being a little more aggressive in terms of brake pad wear. The slots also help to keep the pads clean and wearing in an even fashion. The last benefit is that they help with braking in the wet in particular, as it aids in water evacuation between the pad and the disc.
Cross-drilled discs offer some of the benefits of a slotted disc, such as a strong initial bite and water evacuation in the rain, but there are some considerations for drilled rotors and extreme use. First, they can wear the brake pads in a less-even fashion that slotted or plain discs due to the arrangement of the holes. Secondly, during ultra-high performance use such as track days, the holes create additional areas of stress around the disc. Brake disc quality and the manufacturing process is extremely important when it comes to drilled discs, so choosing German-made discs like the Zimmerman Sport discs is highly recommended.
In the most extreme braking conditions, poorly made cross-drilled discs are more likely to crack and experience brake disc failures. That’s not to say they are a bad choice, drilled rotors look great and offer some benefits over a plain disc, but it’s important to consider how you use the car when purchasing. Both slotted and cross-drilled discs can result in a little more physical brake noise than a plain rotor, which is another key consideration when deciding which style of brake disc to use on your car when you’re upgrading brakes.
Audi S4 Brake Lines and Fluid
The two final components of an upgraded stock braking system are the brake caliper lines and the brake fluid itself. Upgraded to braided stainless steel brake lines in place of the basic rubber units will give you a firmer pedal feel and increase confidence and the ability to modulate the brakes better at the limit. While any standard DOT 4 brake fluid works well, upgraded to a racing brake fluid such as Motul RBF600 or Liqui Moly LM20156 will give your braking system the temperature capacity it needs for aggressive street or track driving. Racing brake fluids also usually have less compressibility, again improving pedal feel and performance.
Audi S4 Big Brake Kits
A big brake kit is another way to increase braking performance on your S4 or S5 substantially. While they tend to be costly, a BBK is going to offer a number of benefits if it’s in your budget.
First, an aftermarket big brake kit will feature a multi-piston caliper, usually with either 4 or 6 pistons, which not only looks super cool but also has a lot of advantages over the stock single-piston sliding caliper. Multiple pistons offer more even pressure on the brake pad, more cooling air is able to circulate around the pistons, and allows the brake to cool more effectively. They also usually have a larger and thicker brake pad, and more physical pad area equals more potential braking performance.
Adding to the benefits of a multi-piston caliper, as the name implies, a big brake kit will usually have a much larger brake disc than the factory unit. The stock front brake disc on an S4 or S5 is 345mm, while most BBKs will have 355 mm, 365 mm, or even 380 mm discs. These discs typically have a directional design, which means they cool more effectively than the stock discs. They are also usually 2-piece, with a lighter ‘hat’ or ‘bobbin’ center, typically made out of aluminum, and the actual friction surface is the only thing made of cast iron. This means that not only does a BBK offer better performance, it’s also usually lighter as well.
Two of the best brands for big brake kits are Stoptech and Brembo. Both offer a range of options depending on size, budget, and use, and have a wide range of replacement parts and brake pad compounds available thanks to their availability and well-known quality.
Audi S4 Intake & Exhaust
Upgrading your intake and exhaust system is one of the cornerstones of performance tuning. Making power is all about moving air in and then back out of the engine in the most efficient manner possible. A performance intake also has the added benefit of giving the engine a little bit of a more aggressive sound. If you’ve heard a 3.0T engine with a nice intake, you know how cool it sounds with the bark of that intake and the whine of the supercharger.
There are typically two kinds of aftermarket intakes for the 3.0T, closed, or open airbox. A closed system typically has some kind of baffling to enclose the air filter more completely, ensuring less hot air is entering the system from the engine bay, and helping to improve power while still damping the sound a little bit. Basically, you get the power without a lot more noise, so the car retains some of its refined character. AWE Tuning’s S-Flow carbon fiber intake is a good example of closed-box design.
As you might guess, an open-intake will usually have a heat shield, but no complete airbox surrounding it. This really opens up the sound of the supercharger and you can hear the whine as you accelerate through the RPMs. An open-intake also tends to be a bit less expensive, so you can see power increases and get that aggressive intake sound for less money than a closed system. Integrated Engineering’s 3.0T intake system provides an aggressive sound with an increase in power, with gains of up to 15-20 horsepower on a tuned 3.0T S4.
Just like the intake, performance exhaust systems for the 3.0T S4 and S5 range from refined but sporty to race-car loud. AWE Tuning is one of the top brands of performance exhaust for Audi, as well as Volkswagen, Porsche, BMW, and many other makes. AWE Tuning’s range of products allows you to fine-tune the performance and volume of your 3.0T with their Touring or Track exhaust systems, as well as either resonated or non-resonated downpipes.
First, the downpipes connect the catalytic converters to the rest of the exhaust system. The resonated downpipes will be quieter and have less of an edgy tone, with less of a rasp, compared to the non-resonated version. Power will be unaffected; it’s just the sound that’s being changed.
For the exhaust system, the Touring version is louder than stock but offers a smooth and inoffensive tone at light throttle. When you put your foot down it will open up and get a bit more aggressive, but it's still totally reasonable. The Track edition has two modes - loud and even louder, so it’s not the best choice if you have neighbors that will try to run you out of town for having a loud exhaust. For our money, non-resonated downpipes with a Touring exhaust gives the best combination of bark and bite, without giving you a migraine on the way to work every day.
The AWE Tuning exhaust systems are available with a wide range of exhaust tips, with different sizes, materials, and finishes allowing you to make your S4 or S5 look and sound exactly how you want it to.
Audi S4 Bushings, Inserts, and Motor Mount Upgrades
While many major components are easy to upgrade and yield more power and better handling, many smaller items can be added or upgraded to refine your S4 or S5 further. Removing slack from a bushing or improving the control of an engine mount may not seem like that kind of thing that makes for a major change in your driving experience, but you’d be surprised how small changes in the right areas can do just that.
Audi S4 Control Arm Bushings & Ball Joints
Control arm bushings and ball joints on the B8 chassis are a common wear item and, depending on the mileage, are the components most likely to need replacement in the suspension of the S4 or S5. Rather than replacing these with OE control arms, upgrading to a set of 034 Motorsport’s Density Line control arms will yield improved control and performance, thanks to higher durometer 75A solid rubber bushings without adding a lot of harshness or penalizing ride quality. If you’re planning on hitting the track, or if you have a significantly lowered ride height on your S4 or S5, the 034 Motorsport billet adjustable Density Line control arms allow you to fine-tune camber and caster. This can improve handling, ensure even tire wear, and set your alignment for your exact use.
Audi S4 Bushing Inserts
One of the best and most affordable means of increasing the feedback and improving response in the chassis of your B8 S4 or S5 is to utilize bushing insert kits. They’re available in billet aluminum, such as those from 034 Motorsport, and polyurethane, offered by Powerflex and other brands. These inserts are designed to fill the voids and air-gaps designed into the OEM engine, drivetrain, and chassis bushings. Since you’re not having to replace any of the bushings or mounts themselves, the labor costs are much lower than complete replacement performance parts.
The 034 Motorsport driveline insert kit provides aluminum inserts for the transmission and differential mounts. It removes the driveline slop, and limits movement for more direct shifting, better launches, and a more connected feel on the road. It also offers these benefits without a huge penalty when it comes to noise, vibration, and harshness. So, just because you see better control doesn’t mean the car will be less comfortable despite the improved performance.
Similarly, 034 Motorsport offers a rear subframe insert kit, which limits movement in the rear subframe mounts and has two benefits. First, by limiting movement in the subframe, the rear suspension geometry is more stable and provides better handling performance. Second, with a more solid connection to the chassis of the car, the rear differential is able to work more effectively, as less movement means more positive power delivery.
Powerflex’s polyurethane inserts offer the same benefits of the billet 034 Motorsport designs at substantial cost savings. At the same time, the 034 Motorsport aluminum parts are more durable and able to be easily removed and resold should you ever want to do so.
Audi S4 Engine Mounts
Finally, upgrading the engine mounts themselves is a great way to increase response and reduce drivetrain movement for a better, more direct driving experience. The 034 Motorsport Street Density Line mount is great for daily drivers and mildly upgraded S4s and S5s, providing increased control without any additional NVH. The Track Density Line mount is a little more firm but provides a significant increase in driveline control and reduced engine and transmission movement. This is ideal not only for better performance off the line, but reduced movement in the driveline on throttle transitions and braking means less weight transfer in the car, and a more stable platform.
If you want something a little more aggressive and flexible, the line of engine mounts from Black Forest Industries offers Stage 1 or Stage 2 polyurethane mounts which offer better control and billet aluminum housings for the best durability in extreme use conditions.
Without a doubt, the B8 3.0T S4 and S5 are some of the best German sport-luxury buys on the used-car market today. With a few of the upgrades from this list, you can turn either of these great cars from Audi into a more powerful, better handling, and more engaging vehicle. Perhaps best of all, with the massive number of performance parts and upgrades on the market today, you can choose to make your 3.0T S4 or S5 as wild as you want. All it really comes down to is your budget and what you want your 3.0T S4 or S5 to be to you.
If you haven't yet purchased an Audi B8 S4 to modify yet, check out our B8 S4 Buyer's Guide below.
If you have questions about what mods are best for your car, or have suggestions that we might have left out, leave them in the comments section below. If you’re looking for more Audi guides, DIYs, news, and features, visit our Audi hub at audi.fcpeuro.com.
