In 2012, Audi revealed the EA824, a four-liter twin-turbo V8 that has been used in the flagship A8, as well as the S6, S7, and RS7. The 4.0t came in a range of power outputs, with different turbos and intake setups depending on the model. Older cars featuring this engine are becoming very affordable. Given the massive power these motors are capable of, they are a performance bargain.
If you just picked up a new-to-you Audi powered by the first-gen 4.0t, you might be wondering what the upgrade path for this platform looks like. In this article, we are going to go over the best upgrades for the 4.0t, and what power figures you can expect.
The second generation 4.0t, the EA825, has powered the A8 and RS7 since 2019, and more recently, the RS6 Avant, SQ7, SQ8, and RS Q8, as well as some Porsche, Bently, and Lamborghini models. This engine is significantly different from the first generation, and we will be covering the best upgrades for it in a future article.
The 4.0t Engine is a twin-turbocharged V8 engine featuring a “Hot-V” turbocharger layout. On traditional turbocharged V8 engines, the turbos hang off the side of each cylinder head, and the intake manifold sits on top of the motor.
Hot-Vee engines are reversed. The exhaust ports are facing inward to the center of the engine, while the intake manifolds are where the exhaust would normally begin. The turbochargers sit in the “V” created by the cylinder heads, and the exhaust travels from the top of the engine down the back and around the transmission.
Hot-V turbo setups decrease turbo spool-up time by shortening the distance air needs to travel. A faster spool results in better throttle response and allows peak torque to be achieved earlier in the RPM range.
This guide will be split into two parts. The first half will cover the upgrade options for lower output 4.0t, and the second will look at the path for the high output version found in RS cars and the S8.
The low-output version of the 4.0t came in the S6, S7, and A8. Smaller turbos and less aggressive software from the factory led to a power output of 450 horsepower and 444 lb-ft of torque.
The upgrade path for the low-output four-liter engine will be very familiar to those who have modified smaller engines from the Volkswagen Group, like the 2.0 TSI.
As with other forced induction engines, the absolute best bang-for-your-buck upgrade is an ECU tune. Audi left a lot of power on the table, and a simple remap with no additional hardware can yield gains of 80 horsepower and 150 torque depending on the fuel used. Running E-85 can result in even more impressive power gains.
Please be aware, upgrading your vehicle’s downpipes should only be done if your car is being built for track use only! You will not pass emissions tests with downpipe upgrades, and in some areas of the country, they are illegal for use on public roads.
To get more power from the stock turbos, the exhaust needs to be modified. High-flowing downpipes, paired with the software are the next major upgrade resulting in significant gains. This combination can result in gains near 90 hp and 180 lb-ft of torque depending on the octane and tuning company.
After doing downpipe upgrades, the stock turbos are maxed out. To push the car further, they need to be replaced with bigger ones. Similar to other bolt-on OEM turbo upgrades on smaller four-cylinder engines like the 2.0 TSI (think IS38 or K04), the low output 4.0t does not need any internal upgrades when moving to RS Turbos. The engine’s stout rotating assembly can easily take the additional power and torque they produce.
Upgrading to RS turbos is not a very invasive process. Instead of replacing the entire turbo, the stock “cartridge” (the compressor housing and turbine wheel) is removed from the exhaust housing. Turbo cartridges from an RS7 are installed in the original exhaust housing.
Upgrading to RS turbos allows your low-output 4.0t to make the same power or power above an RS car depending on the tune. With RS Turbos and downpipes, you can expect over 650 hp and 630 lb-ft of torque.
If you want to use RS Turbos and keep your car street-legal, they can be used with the factory OEM downpipes.
You may pick up a few horsepower and torque from the exhaust, but it won’t be enough for you to feel while driving.
When looking at upgrading an RS7 or S8, you are starting with larger turbos. Factory, this version of the 4.0t makes between 560 and 605 horsepower (the RS7 Performance and S8 Plus get the full 605). The upgrades are going to be the same as the low-output engines up to the point of turbos.
Just like on the low output engine, a stage one provides the most gains for your dollar. Depending on the octane used, you can see over 110 horsepower and 130 lb-ft of torque gained without any other modifications.
Adding downpipes to free up exhaust flow and pairing them with a stage two ECU tune can yield 40 horsepower and 60 lb-ft of torque over Stage 1 on this platform.
This upgrade applies to both the low-output and high-output versions of the 4.0t. Manufacturers like Weistec and TTE take the factory turbocharger housings and retrofit turbine and compressor wheels. These “hybrid” turbos (meaning they retain OEM fit while providing the power output similar to a custom big turbo setup).
The amount of power you can achieve from a hybrid turbo setup varies significantly. In general, you can expect to see over 800 horsepower at the wheels, with some systems from TTE capable of over 1000 horsepower.
At all stages, you can add additional modifications for appearance, sound, and some modest power gains. No piece of hardware will have as much of an impact as downpipes on this generation of the 4.0t, but these supporting mods will enhance your driving experience.
Tuning your transmission won’t provide any power gains, but it will optimize and enhance the way your transmission operates. You can expect faster acceleration, better shift points, and more control over the transmission when in manual mode.
There is a range of intake options available for the 4.0t. An intake will allow better airflow to the engine, increase the turbo and induction noise you hear while on the throttle. The 4.0t’s twin intake tracts will look pretty awesome when you pop the hood.
The first gen 4.0t is utilized to heat air to water heat exchanged to reduce air intake temperatures. When your car is running higher boost pressure and making more power, upgrading to a larger, more efficient cooler can help prevent heat soak.
While upgrading downpipes leads to more power, they do not do much in terms of improving the sound of the engine. Installing a cat-back exhaust system can give you a much more aggressive sound, ranging from a slight rumble to earsplittingly loud, depending on your taste.
If you are ready to start modifying your V8 Audi, give Alex’s Autohaus a call and speak our tuning experts today! Our team will give you advice on the software and hardware to achieve the goals you have for your car. Give us a call or stop in at our shop in Midvale, Utah today!
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