Incredible project: Audi A4 with an aviation turbine continues to break everything in its path
If there is a project that perfectly embodies the phrase “because race car,” it is Kelby Krahn’s Audi A4 with jet forced induction. The B5-generation Audi A4 has long since strayed from its factory roots thanks to a very clean VR6 engine swap, but Krahn did not stop there. Instead, he added one of the most unusual parts imaginable: an aviation gas turbine system designed to feed boost into the engine. The only problem — it just keeps breaking everything around it.
How does it work?
First, let’s break down how exactly this works. The turbine is not a turbocharger. Turbochargers use exhaust gases to spin a compressor, which forces compressed air into the engine. Add some fuel and you get extra power. Krahn’s turbine is a real auxiliary power unit (APU) from an aircraft, and unlike most “jet cars” you have seen, this one does not create thrust to move the car.
More: The company behind your robot vacuum cleaner attached rockets to its electric car, claiming 0-62 mph in 0.9 seconds
Instead, the turbine simply creates boost, which Krahn then feeds into the VR6 itself. Why do this? “It scratches an itch in his brain,” says Krahn. Well, and as he tells Carscoops, to “completely eliminate turbo lag.” Since the turbine does not run on exhaust gases, it can create boost regardless of what the engine is doing.
The complete opposite of turbo lag
Krahn could technically just add an output shaft and drive the car using the turbine, but as he notes, “the turbine weighs 320 pounds and makes 60 hp, but provides air for 1500 hp.” In other words, this B5 A4 has no concept of turbo lag in any sense. In fact, it has the opposite problem. Even with the throttle wide open, the throttle is too small, and the boost pipe maintains 12 psi.
In his latest update, Krahn once again faced the consequences of immense power. While the turbine supercharging system continues to do its job, the rest of the Audi is forced to withstand stress levels that its original engineers almost certainly never imagined. Most recently — he broke an axle shaft. Before that, a subframe bolt tore out of the frame, and even earlier, second gear decided it had had enough.
The real challenge isn’t the jet engine
Here is perhaps the craziest part of all this. Even without the turbine setup, this Audi would be notable. The VR6 swap into a B5 A4 is a significant undertaking on its own, requiring serious fabrication and engineering. Most builders would have stopped after installing the engine and getting it running properly. Of course, the biggest challenge may simply be keeping the rest of the car alive.
Such projects often fail because the experimental technology does not work as intended. In Krahn’s case, the opposite is happening. The jet-inspired supercharging system continues to do its job, while the Audi keeps discovering new mechanical weak points, one component at a time.
This project is a vivid example of engineering audacity clashing with physical limitations. Krahn is not just upgrading a car — he is testing the strength limits of every element, from axle shafts to the transmission. And while the turbine works flawlessly, it is the “ordinary” parts that become the weak link. It serves as a reminder that even the most powerful engine is useless if the rest of the car is not ready for such a load. Perhaps the next step will be strengthening the drivetrain or even building a fully custom chassis capable of handling this insane power.