The VAG 1.8 Turbo 20V is an engine that doesn’t stand out as particularly special when compared to six-cylinder or V8 powerhouses from other German automakers. However, it has great historical importance and powered many of the modern classics which are on the verge of becoming iconic, such as the Audi TT.
The 1.8-liter turbocharged engine is geared towards offering performance in a small package, hence the 5 valves per cylinder. However, it found itself under the hood of 16 cars of the VAG range, back when you called it that and not Volkswagen Group. Some of these cars basically made their debut with this engine, like the TT, but also the SEAT Leon Cupra and the Skoda Octavia RS.
Although not as common in Europe as the 1.9 TDI, these relatively powerful turbocharged engines are still easy to find for not a lot of money. The four-cylinder was introduced in 1994 and evolved continuously until being discontinued in 2010. There are many different versions of this engine with specific engine codes relating to power output and parts fitted. It’s not to be confused with the later 1.8 TSI that you might know from modern Jettas and Audi A3s.
For a whole generation of enthusiasts in the late 90s, and early 2000s, this was THE affordable German performance motor. It basically started the whole addiction to turbocharged four-cylinder units which are still going strong today. The 20V was also one of the first small turbo engines worth tuning.
The internet is filled with advice on how to tune these engines. Although the power ranges from 150 to 240 hp stock, the most common versions make 180 and 225 horsepower, and apparently can be pushed to 300 horsepower on stock internals.
Audi 1.8T 20V history
The roots of the 1.8 Turbo are, ironically, with Mercedes. The premium automaker developed the M118 four-cylinder engine which was first used by early Audis like the 60, 75, and 80 after the company was sold to Volkswagen. It had really high compression ratios, up to 11.2:1, for power and efficiency, but it wasn’t reliable enough. High compression also made these engines quite noisy.
Audi made its own version of the water-cooled 4-cylinder, which was more reliable. It had an iron block and an aluminum head. The EA111 made its debut in the 1974 Audi 50, and because Volkswagen owned the company they stole everything to make the Polo. This early layout evolved into turbocharged series like the EA827, the EA113, and the modern EA888, which means we have a 48-year-old lineage.
This basic layout was used all the way into the modern era. The 20V features an iron bottom end with five main bearings and a twin-cam top end. What makes this an iconic tuning engine is the standard forged crankshaft on almost all versions. Aluminum forged pistons were fitted to many versions, although it’s best to check your engine code and know for sure.
Story of two blocks
There are many differences between these engines which span 16 years of production, most are split by the engine block. Early EA827 versions of the 1.8T 20V had what’s known as the 058 blocks, while cars made after 2000 use the EA113 engine with the 06A block.
The old engines had an intermediate shaft driving the oil pump and a water pump driven by an accessory belt. On the other hand, the later models have a chain-driven oil pump manipulated by the crankshaft.
Why 5 valves?
These engines are famous for having DOHC and five valves per cylinder instead of the usual four. This was done to maximize the breathing of the engine which is pretty limited by the 81mm bore. The tech was only possible due to port injection and this is why modern Audi/Volkswagen EA888 engines had four valves.
The three 27mm intake valves are driven by a chain at the back of the head linked to the exhaust cam, a very unusual DOHC layout. The two larger 29.9 exhaust valves are driven by the belt.
While the 1.8T can be tuned and still daily-driven, it’s not as bulletproof as modern engines and it requires careful maintenance. The oil pan is pretty small, so checking the levels constantly is best. If you’re going to add power, it’s best to change the oil every 5000 miles and use the expensive stuff.
Using the smaller K03 turbocharger, you can make about 14 pounds of boost reliably. After that, it’s best to swap in the bigger K04 if it’s not fitted or even do a hybrid turbo.
For making big horsepower numbers, it’s best to do a full engine rebuild and have all-forged internals. The rods are perhaps the biggest issue on normal 1.8T engines, but this teardown and rebuild by popular VW mechanic Charles Sanville covers everything you’d want to know. As we said, the 20V is one of the easiest modern engines to tune and build.