The 5 Best Mods for the Audi B8/B8.5 S4

Audi came out with the B8 S4 (fifth generation) in 2008 and introduced an all-new 3.0L TFSI Supercharged V6 engine. This engine was made much smaller with only 6 cylinders and was able to still match the numbers put out by its predecessor, the B7 S4. The new 3.0 TFSI V6 puts out an impressive 329hp and 325 lb-ft torque out of the factory. There are two transmissions to choose from on the B8 S4: a 6-speed manual and a 7-speed S-Tronic automatic transmission. Audi has been able to put out many tunable and mod-friendly cars and the 3.0 is no exception. If these B8 S4’s get the right mods, they can be putting down up to 500hp easily

Before jumping into the mods, check out the most common problems on the B8 S4.

Ignition Coils & Spark Plugs

We always like to start these mod guides off by suggesting replacing all of the ignition coils and spark plugs to ensure you’re getting the most power out of your mods. All it takes is one bad coil or spark plug to make the engine have a misfire and you won’t be able to tell what the mods have done. With that being said, before spending money on expensive mods, pony up the money on some fresh spark plugs and coils, so you aren’t disappointed with the gains. We’ve all been there and it’s better to be safe rather than sorry!

Buy Here: Audi B8/B8.5 S4 OEM Ignition Coils
Buy Here: Audi B8/B8.5 S4 OEM Spark Plugs

The 5 Best Performance Mods for the B8/B8.5 S4

To make your Volkswagen B8 S4 tuned machine, you will need to add these aftermarket mods:

1. ECU Tune or Flash
2. Supercharger Pullies
3. Heat Exchanger
4. Intake
5. Exhaust

Aside from the supercharger pullies, the mods listed above are basic bolt-on and should be able to DIY. We want to mention that there are MANY aftermarket brands out there that create mods for the B8 S4, but we will be going over our favorite. This is OUR opinion and we highly advise doing your own research because everyone has a different preference when it comes to vehicle performance, sound, and spending.

1. B8 S4 ECU Tuning

An aftermarket ECU tune or flash will most likely be the biggest bang for your buck. Often the stock ECU doesn’t optimize the engine’s full potential because not every consumer wants to have a hp monster out of the factory, believe it or not. There are many benefits to a tune or flash besides performance gains such as it makes your engine more efficient, can fit your driving needs, provides a cleaner burn, and is easy to install depending on the company.

APR ECU Upgrade

We’ll start it off with APR’s tune. We are big proponents of APR because of not only the R&D they put into all of their products but all of the data they provide consumers. They are known for building high-quality aftermarket parts for German vehicles. This tune is no exception. It features performance gains, program switching, increased fuel economy, and many more.

Stage 1 Power Gains 91 Octane: +84hp & +61lb-tq or 427hp & 370 lb-ft
Stage 1 Power Gains 93 Octane: +98hp & 72lb-tq or 441hp & 375 lb-ft
Stage 2 Dual Pulley Power Gains 91 Octane: +100hp & +80lb-ft or 445hp & 412 lb-ft
Stage 2 Dual Pulley Power Gains 93 Octane: +120hp & +97lb-ft or 465hp & 428 lb-ft

Price: $599.95 + Free Shipping

Unitronic Stage 1 ECU Flash

Next is Unitronic’s ECU flash. Although it may be a little more inconvenient to take your B8 S4 to a local dealer to get flashed, it is well worth it. Unitronic is another aftermarket company that is known for making parts for German parts. This flash is directly through the OBDII port of your vehicle and takes 10-15 minutes. Improved fuel efficiency, perfectly optimized power throughout the power band, and more.

Stage 1 Power Gains 91 Octane:  +42hp & +12lb-ft or 392hp & 351lb-ft
Stage 1+ Power Gains 93 Octane: +67hp & +26lb-ft or 417hp & 365lb-ft
Stage 2+ Power Gains: +101hp & +49lb-ft or 451hp & 388 lb-ft

Price: $1,100.00

2. S4 Supercharger Pulley Upgrades

This may be a strange aftermarket part to have on the list but they actually do a lot more than you think. As you can see in the graph below, provided by APR, you can see how upgraded pulleys increase the rotational speed of the B8 S4’s supercharger. More rotational speed = More boost & power. The stock pulleys are not optimized to get the most out of the superchargers.

APR Upgraded Crank and Drive Pulleys

APR made it on the list 2 more times because we believe their products, although on the expensive side, are superior to many of the companies out there. There are options to do a single pulley or dual pulley and an aftermarket belt, pictured above. The dual pulley and belt will result in the supercharger spinning ~26.4% faster than the stock pulleys and belt. The kit is fully bolt-on and no changes will be needed for fitment.

Price: $607.95

Unitronic Pulley Upgrade Kit

With the Unitronic flash, it makes sense to go with Unitronic pulleys. With the single pulley, this will put your B8 S4 to Stage 2+, which puts down a whopping 450hp. However, if you decide to go with their dual pulley configuration, this will push the B8 S4 to an astounding 493hp.

Price: $2,000.00

You read that right. After TWO parts, an ECU tune or flash and upgraded pulleys, the B8 S4 pushes close to 500hp. However, without the mods listed below, it may not run as efficiently or be near as reliable. 

3. Heat Exchanger Upgrade

This may be a hot take, but heat exchangers are well worth the money if you are looking to go 500hp+. A heat exchanger is like an intercooler because it lowers the intake air temps (IATs) and reduces the hp killer, heat soak. Typically these aren’t viewed as a performance mod, but more so a reliability and efficiency mod. The longer a vehicle has been running, the more susceptible it is to heat soak because of how hot the engine is. When heat soak occurs, power essentially falls off slowly, but you’ll be able to feel it.

To reiterate, this is not a performance mod, this is mainly for engine efficiency and reliability. If you are looking to go stage 2 or higher, we highly suggest spending the extra money to ensure the extra power is supported with better engine cooling.

AWE Tuning Coldfront Heat Exchanger

AWE Tuning is another popular brand in the aftermarket space that makes parts for many different OEMs. However, don’t think that they don’t make quality products because they don’t focus on just German vehicles. Their patented ColdFront system reduces high IATs by up to 15°F and reduces coolant temps by 24°F. They also offer an extra reservoir which increases supercharger coolant capacity. We would suggest going with both the heat exchanger and the reservoir, but a heat exchanger alone will make a big difference.

Price: $899.00
Extra Reservoir: $549.00

APR CPS Radiator

APR’s heat exchanger is 140% larger than the stock unit which means there is more surface area for cooling. On top of this unit being easy to maintain, it is fully integrated into the OEM cooling circuit.

Price: $1,103.95

4. Performance B8 S4 Air Intakes

Air intakes and exhausts are almost always viewed as a waste of money, but not to us. Compared to the OEM units that come in the 3.0 TFSI, aftermarket intakes are far less restrictive. Meaning airflow is dramatically increased, which in turn means more power. There may not be much of a power benefit, but other perks from intakes are less pressure drop, a “whoosh” noise from the engine we enthusiasts love and gives the engine a better aesthetic.

Some may say, why not just use a drop-in filter. You will not receive near the benefits seen from an aftermarket system because of the stock intakes restrictive properties.

AWE S-FLO Intake System

AWE’s S-FLO intake provides 34% more airflow to the engine than the stock intake. It claims to make 15hp & 11lb-ft of torque to the crank, which may be accurate with the proper supporting mods. Not only do we like the aesthetic the intake gives the engine bay, but we like the variety they offer with this product. You can get a system for only $229 if you don’t care about the carbon look.

Price: $229.00 – $549.00

APR Closed Carbon Fiber Intake

APR’s intake provides roughly 35% more airflow than the stock intake. It claims performance gains of 17hp, but that is at Stage 2. If you are around Stage 1 or don’t have a tune, you can expect around a 3-5hp gain. We like the variety APR provides in having the ability to choose from an open or closed intake system and providing a rear inlet pipe that further increases airflow. Our ideal setup with this system is the open system with the rear outlet pipe to get the most out of your money.

Price: $387.95 (Open) – $535.95 (Closed)
Rear Inlet Pipe: $260.95 (Adds a few more HP)

5. S4 Upgraded Catback Exhaust System

Aftermarket exhausts don’t provide much of a power benefit, however, don’t you want an aggressive sounding B8 S4? Sound aside, aftermarket exhausts do provide some benefits such as reducing backpressure because of the increased diameter in the tubing over stock exhausts. Now we’ve included downpipes in this portion as well because most of the aftermarket exhausts have an option to include them. Downpipes are where you will get the most power out of your exhaust, especially if your B8 S4 is tuned.

AWE Touring Edition Exhaust and Downpipe

AWE offers a Touring and Track edition 2.5″ diameter set up. The touring is street legal and will not affect emissions devices, but the track edition is not “street-legal” but is the least restrictive. On top of providing two types of systems, it offers downpipes with and without resonators and black tips or chrome silver tips for the catback exhaust system. They really allow the consumer to get the system they want by providing so many options. On top of the options, they claim 8hp and 9lb-ft torque for both the touring and track edition.

Touring Edition Price: $1,495
Track Edition Price: $1,045
Non-Resonated Downpipes: $649
Resonated Downpipes: $899

Milltek Turbo-back Exhaust

Milltek offers aftermarket parts for many different OEMs but has been around since 1983, so they have a great reputation for creating great quality products. They offer a turboback exhaust resonated or not, and with four different tip designs: black ovals, black quads, polished ovals, and polished quads.

B8 S4 Turbo-back Edition Price: $2,039
B8.5 S4 Turbo-back Edition Price: $2,146

Conclusion – B8 S4 Mods

Once again, there are many other aftermarket brands out there that supply great products, but we just posted about our favorites. If you’re going for a 500hp B8 S4, you’ll need an ECU tune or flash with aftermarket dual pulleys and push for stage 2+. It’s that easy. Let us know your setup in the comments below!

If you want to read up on more Audi content, here is a post for The Most Common B9 S4 Problems.