Best Audi B8/B9 RS5 Mods

Though it doesn’t seem like it’s been that long, the Audi RS5 first saw American shores a decade ago in the 2013 model year. Audi had already made the car available in Europe since 2011, and Americans were salivating at the chance to get it stateside. The car certainly delivered, utilizing a 4.2 liter FSI V8 engine producing 450 horsepower and 317 lb-ft of torque. The original B8 RS5 lasted through 2015, but took a two year hiatus and did not return until the 2018 model year. Since the 2018, the current B9 RS5 has boasted a 2.9 liter twin-turbo TSFI V6 producing 444 horsepower and 443 lb-ft of torque. For those looking to get even more performance, we’re looking at the top Audi B8/B9 RS5 mods. Read on to find out how to make the most horsepower and torque from the B8/B9 RS5. 

Audi B8/B9 RS5 Engine Info

Audi only produced the B8 RS5 for three model years in the U.S., from 2013–2015. Under the hood was the Volkswagen EA824 CFSA-code engine, which is a naturally aspirated 4.2 liter FSI V8 producing 450 horsepower and 317 lb-ft of torque. Customers praised the solid power delivery, and it was an elegant but refined machine that blasted down the asphalt. 

Audi dropped the RS5 for a few years, but returned with the B9 RS5 for the 2018 model year. Introduced in 2018 and still in force today (with the exception of 2020 when no RS5 appeared), is the EA839 DECA-code, twin-turbocharged 2.9 liter TFSI V6 engine. It produces 444 horsepower and 434 lb-ft of torque. The B9 RS5 is available as either a coupe or a sportback hatch, but we definitely prefer the coupe in terms of performance and styling.

The EA824 4.2 liter V8 and EA839 2.9 liter V6 both use direct injection fueling, which helps improve fuel economy, increases performance, and reduces emissions output. The two biggest differences between the engines are their displacement and aspiration. The B8 4.2 liter V8 engine is bigger and naturally aspirated, whereas the B9 2.9 liter V6 engine uses twin-turbos to make up for the displacement loss. As you’ll notice, some of our mods only apply to one engine or the other, so make sure to confirm all fitment before buying any products. 

Audi RS5 Mods Engine Power Limits

Both the EA824 4.2 liter FSI and the EA839 2.9 liter TFSI are very reliable and durable engines from the factory. However, they are far from bullet proof, especially once you start modding. In terms of how much horsepower and torque the block and internals can take, each engine is a little different. For the older 4.2 liter V8, the internals will need to be upgraded to forged versions past 500 wheel-torque. The rods and pistons are on borrowed time past those numbers.

For the newer 2.9 liter V6, the engine is capable of handling a little more, closer to 600 wheel-torque before the internals need to be upgraded. The weak link is going to be the rods, followed by the pistons. Both blocks are incredibly solid, and can handle more than 700 wheel-torque without issue. If you plan on going past 500 wheel-torque on the V8 or 600 wheel-torque on the V6, keep in mind you’ll probably need to get aftermarket forged rods, pistons, and head studs. 

Top Audi RS5 Mods

Our top Audi RS5 mods are:

• B8/B9 ECU Tuning and E85
• B9 Intercooler Upgrade
• B9 Downpipe Upgrade
• B8/B9 Intake Upgrade
• B8/B9 Front & Rear Sway Bars
• B8 Transmission Cooler

1) Best Audi B8/B9 RS5 Mods: ECU/TCU Tuning and E85

Our first suggestion for Audi B8/B9 RS5 mods is going to be ECU/TCU tuning. The ECU is the engine control unit, and the TCU is the transmission control unit. Tuning the ECU and TCU are hands down the best ways to add horsepower and torque and improve shifting. ECU/TCU tuning is a great mod for both the 4.2 V8 and the 2.9 V6 engines and their transmissions. With just tuning alone, you can add substantial horsepower and torque without any bolt-on upgrades. There are two main types of tunes for the RS5, flash tuning and piggyback tuning.

Flash tunes are incredibly easy to install and can be done with just a few minutes and a handheld device. Flash tunes have pre-loaded engine software that optimizes engine parameters like ignition timing, air-to-fuel ratios, boost pressure, and valve timing, to increase performance. Piggyback tuning is the other option. Instead of installing software onto the ECU/TCU, piggyback tunes physically plug into the ECU/TCU and manipulate the signals before they reach the engine. This has the same effect as tuning, but is more untraceable. 

Upgrading to tuning is known as “Stage 1” on the RS5. Upgrading the tuning with E85 fueling is known as “Stage 1+.”. Ethanol adds immense increases in horsepower and torque over pump gas, because it has a much higher octane rating. This means tuners can push the engine harder without risking engine knock, which results in a lot more power. 

Best Audi RS5 Tuning Options and E85

For the B8 RS5, we have two suggestions for tunes, either JHMotorsports or APR. APR has long been one of the biggest names in the VW/Audi tuning world, and the APR Tuning for B8 RS5 is solid. With a stage 1 tune, you can add 10 horsepower and 16 lb-ft of torque without any bolt-ons. For the JHM tunes, they offer both a JHM Stage 1 Tune for B8 RS5 or a JHM Stage 2 Tune for B8 RS5. With the Stage 2 JHM tune and associated mods, the RS5 runs a ¼ mile in 11.89 seconds @ 116 mph. Compare that to a stock RS5 doing the same in 12.5 seconds at 112 mph.

For the B9 RS5, we have two options for flash tuning, either the IE Performance Tuning for B9 RS5 or once again APR Tuning for B9 RS5. The B9 responds a lot better to tuning than the B8 did. With a stage 1 tune on the B9, you can make 540 horsepower and 560 lb-ft of torque with no other bolt-on mods from IE. With Stage 1+, which only adds E85 fueling, the B9 RS5 makes a stunning 600 horsepower and 660 lb-ft of torque. That means with just E85 and tuning, you can gain 150 horsepower and 230 lb-ft of torque in just an afternoon. 

Audi B9 RS5 JB4

The other tuner is the piggyback option, the JB4 for B9 RS5. The JB4 is very popular in the BMW and Kia worlds, and their Audi products are gaining a solid reputation. The JB4 won’t add as much power as flash tuning, but it’s a more untraceable option that allows for better tweaking if you plan on adding more mods in the future. 

2) Best Audi B9 RS5 Mods: Intercooler and Heat Exchanger Upgrades

For our next Audi RS5 mods, we’re looking at upgraded intercoolers and heat exchangers. This mod only applies to the turbocharged 2.9 liter V6 inside the B9, as the naturally aspirated 4.2 V8 does not use an intercooler. The purpose of the intercooler and heat exchanger are to cool down the charged air or boost after it exits the turbo. The RS5’s twin-turbochargers generate a ton of heat. Hotter air has less oxygen than colder air, so it makes less power. In addition, hotter air leads to increased cylinder temperature and cylinder pressure, which leads to detonation and pre-ignition.

The TFSI V6 intercooler is an air-to-water intercooler, meaning it uses water to help cool the charged air. These are much more efficient than traditional air-to-air intercoolers, but they are also heavier and more expensive. The intercooler system relies on two main parts, an intercooler and a heat exchanger. The intercooler is the actual piece that air flows through on the way to the engine, and the heat exchanger is the radiator that cools down the water that flows through the intercooler. 

Water enters the intercooler to cool the boost. Then, after it gets hot inside the intercooler from the boost, it travels into the heat exchanger to shed its heat, before returning to the intercooler to repeat the process. 

Upgrading to a bigger intercooler increases the volume of air that can pass through on its way into the engine. Upgrading the heat exchanger allows for more rapid and sustained cooling of the water that powers the intercooler. 

Best RS5 Intercoolers and Heat Exchangers

Upgrading to a bigger intercooler is a must-do if you plan on tuning or adding other mods. The stock intercooler and heat exchanger are undersized relative to the power of the twin-turbos, and getting a larger and more efficient cooler/exchanger are the best way to combat heat soak. There are two main options for B9 RS5 intercoolers: either from Wagner Tuning or Merc Racing Both of them sell intercooler and heat exchanger upgrades. 

The Wagner Tuning B9 RS5 Intercooler and Heat Exchanger includes both pieces, while the Wagner Tuning B9 RS5 Intercooler only has the intercooler. Merc sells theirs apart, with the Merc Racing B9 RS5 Intercooler and Merc Racing B9 RS5 Heat Exchanger separate. The Merc units are much cheaper than the Wagner units, but they only include the cores instead of the tubing like Wagner. Both are solid options, and we definitely recommend upgrading both the intercooler and heat exchanger together.

3) Best Audi B9 RS5 Mods: Downpipe Upgrades

Next up on our list of Audi RS5 mods are downpipes. Again, this mod only applies to the B9 RS5 with turbochargers. The downpipes are the part of the exhaust that connect directly to the turbocharger. The purpose of upgrading the downpipes is to increase exhaust flow and reduce back pressure. Together, both of these work to increase horsepower and torque and make the engine louder and more responsive. Since the RS5 uses twin-turbos, there are two downpipes to upgrade.

On the B9 RS5, the stock downpipes are actually not too restrictive, though they do have a catalytic converter. Still, upgrading to aftermarket downpipes will add 10-25 horsepower and torque on the 2.9TT V6. There are two options for upgrading the downpipes, either catless or high-flow cat options. Catless exhausts are not street legal and are only available for cars used exclusively for racing. For street driven RS5s, high-flow catted downpipes are the best legal option. 

Best RS5 Downpipes

We have two options for RS5 downpipe upgrades, either the CTS Turbo B9 RS5 downpipes or the 034 Motorsport B9 RS5 downpipes. Both of them perform well, with the difference being cats. The CTS turbo downpipes use high-flow cats, while the 034 Motorsport downpipes are catless. They both make similar power, though the catless downpipes will have better flow and will also be louder. Upgrading the downpipes on the RS5 is also known as “Stage 2.”

Importantly, if you plan on upgrading the RS5 downpipes, you need to have a stage 2 tuning solution. The stock ECU programming will throw a check engine light and the car will potentially put itself into limp mode once it senses the cats have changed. The only way around this is to go with a tuning solution, so make sure you have one figured out before pulling the trigger. Driving under boost without tuning and with upgraded downpipes is a recipe for disaster. 

4) Audi B8/B9 RS5 Intake Upgrade

After upgrading the tuning, intercooler, and exhaust, the next RS5 mods we recommend are upgrading the air intake. The air intake is the first part of the intake system on both the V8 FSI and V6 TFSI engines. Interestingly, both engines have dual intakes. On the FSI, the intakes feed dual throttle bodies, while on the TFSI, the intakes feed the dual turbochargers. 

The purpose of upgrading the intake is to increase air flow and reduce restriction over the OEM unit. In addition, you can also shave some weight by using carbon fiber. The TFSI intakes are relatively short, as the turbos are mounted very close to the front of the engine bay. Intakes on the FSI are a bit longer, as the throttle bodies are located further back than the turbo inlets on the TFSI. 

Both the B8 and B9 RS5s can benefit from upgraded intakes, which will not only increase performance but also look a thousand times better than the OEM unit. However, intakes are pretty pricey upgrades that only net 10-20 horsepower, even with tuning.

Best B8/B9 RS5 Intakes

For the B8 RS5, we recommend either the Armaspeed B8 RS5 Intake or the Eventuri B8 RS5 Intake. Both of these are carbon fiber intakes that completely replace the intake all the way to the throttle body. They also both have closed airboxes, and will perform pretty similarly to each other. The Eventuri is much more expensive, but you are paying for one of the top brand names in the Audi aftermarket community.

For the newer B9 RS5, we instead recommend either the APR B9 RS5 Intake or the Eventuri B9 RS5 Intake. The biggest difference you’ll notice is that the APR intake replaces the turbo inlet pipe while the Eventuri does not. The APR will probably outflow the Eventuri unit a little more due to this, and also costs a few hundred dollars less, too.

5) Audi B8/B9 RS5 Front and Rear Sway Bars

For our final RS5 mods, we suggest upgrading the suspension. On both the B8 and B9, the stock suspension is lacking once you really start pushing the car or doing launches from a dig. One of the best ways to improve handling and traction is through sway bars. There are both front and rear sways for both the B8 and B9 RS5, and we definitely suggest getting the full kit rather than just front or rears by themselves. 

Sway bars are also known as anti-roll bars because their purpose is to reduce body roll. Body roll is when the car leans to the outside during turns, which hurts traction and forces a reduction in speed. Sway bars keep the car horizontal and planted, allowing for better acceleration through and out of turns. They are the number 1 suspension upgrade for the RS5, and they make a big difference.

Best RS5 Sway Bar Kits

For both the B8 and B9, we recommend the 034 Motorsports kits. The 034 Motorsport B8 RS5 Full Sway Bar Kit and 034 Motorsport B9 RS5 Full Sway Bar Kit are solid kits that combine both the font and rear sways together. Both kits have dynamic adjustable sway bars, which have two levels of stiffness for the track and for daily driving. If you only make one suspension upgrade on your RS5, make sure its sway bars. 

6) Audi B8 RS5 Transmission Cooler

Our final mod only applies to the B8 RS5, and it’s a transmission cooler. The B8 RS5 uses a Borg Warner DL-501, 7-speed dual clutch transmission. The transmission itself performs incredibly well in the RS5 (especially with TCU tuning), but the one flaw is the undersized stock transmission cooler. The stock cooler is known for overheating way too often, which can lead to devastating transmission failure. 

Transmission overheating on the B8 is not just limited to those who track their cars, as even spirited driving on the street has led to some failures. It’s a really unfortunate problem to have, because the transmission performs so well when it functions, and it’s really just a case of Audi being too cheap to use the right sized cooler.

Luckily the RMR B8 RS5 Transmission cooler solves the problem. The Red Mist Racing (RMR) cooler is the standard for the RS5 and it solves the problem of transmission overheating. If you plan on doing really any modding to your B8, you need to look into the RMR cooler before you risk paying a big price.

Top Audi RS5 Mods FAQ