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1.8T engine block guide

The tuning setup of the 1.8T engine block
Bartek Bartoszewicz
Tuning Professional

1.8T Tuning: Block and connecting rods

Here you'll get all the info you need to get to 500 PS and beyond with your 1.8T engine block and connecting rods. We show you where the engine is installed, how the block is built, its bearings, crankshaft, pistons and connecting rods and more! You'll also learn which tuning parts you need for your 1.8T engine to get the maximum performance out of it. There's something for every performance goal.

What cars have a 1.8T engine?

The following vehicles were equipped with the 1.8T engine:

  • Golf MK4 GTI (1997-2005)
  • Audi TT 8N (1998-2005)
  • Audi A3 8L (1997-2005)
  • Seat Ibiza (1999-2001)
  • Seat Leon Cupra (2001-2005)
  • Skoda Octavia (2000-2001)

The engine block of the 1.8T engine

There are two different engine blocks. The 058 engine block was installed up to the production date of May 2000. In the Audi B5, it is longitudinally mounted only. It has an internal intermediate shaft and an external water pump. 06A engine blocks, on the other hand, have no intermediate shaft, and the water pump is driven by the cam belt. They are installed in all vehicles with transverse engines.

1.8T engine main bearing/bearing shells

All four-cylinder engines have five main bearings. The main bearing shell is additionally equipped with two thrust washers. The main bearing shells are made of cast iron and can be upgraded to billet steel versions depending on the performance set-up. The threads of the main bearing shells are M10; the lengths vary between the 06A and the 058 engine, though.

The crankshaft of the 1.8T engine

All 1.8T crankshafts have a stroke of 86.4 mm. They are made of cast iron or are forged. There are two different wheels used to determine the engine speed.

The con-rods in the 1.8T engine

All 1.8T con-rods have a length (hole center to hole center) of 144 mm and a width of 24.9 mm.

  • 06A engines have a 19 mm piston pin (except 225 PS models that have a 20 mm piston pin)
  • 058 engines all have a 20 mm piston pin

The 1.8T piston

All 1.8T pistons have a bore of 81 mm and a compression ratio from 9.25:1 to 9.3:1. Some pistons are cast, making them relatively weak. The forged ones are considerably more rugged. Our innovative compression ratio calculator allows you to filter according to your engine code, and the compression ratio is automatically displayed.

This is how the upgrade to 300+ PS will succeed.

As of a desired performance of 300 PS, we recommend the use of upgrade pistons and con-rods. This combination only works when the cylinder walls are in good condition, though. You get matching combinations of pistons and con-rods for your 1.8T engine from us.

Con-rods with oil drilling hole:

The oil drilling hole is a hole that is present from the small to the large side of the con-rod (riffle drilled). Thanks to this additional oiling, the piston pin has a considerably longer service life.


As with all performance levels, bolts and studs should be replaced. Since many bolts are stretch bolts, they cannot be reused. Our ARP studs are more stable and reusable.

What you need to upgrade to 400+ PS

In order to guarantee reliable operation from a performance of 400 PS and up, it is absolutely necessary to modify con-rods and pistons. A 20 mm piston pin with matching pistons must be installed.

1.8T cam belt system:

The cam belt system of the 1.8T engine is its great weakness. Often, the original belt pulley veers off, resulting in disastrous engine damage. To avoid this, our range includes a matching pulley with a high-strength guide pin. You also get from us reinforced ARP crankshaft bolts and our complete high-performance cam belt kit.

Main bearing

We strongly recommend replacing main bearings and con-rod bearings with our 1.8T race main bearing shells. The advantage is the tri-metal composition, which withstands the high loads on the bearings.

Main bearing supports

The main bearing supports of the 1.8T engine are cast and have an increased engine movement compared to the upgrade IE billet supports made of high-strength alloy steel. In addition, they reduce the wear on the main bearings. (For this, the bearing line of the crankshaft must be honed again in the block.) 

This is how you successfully upgrade to 500+ PS


The crankshaft is made of cast iron. As of a certain performance, it makes sense to upgrade to a forged crankshaft. The engine is converted to a 2.0L through a change in the stroke to 92.88 mm. Take a look at our 1.8T stroker kit.

Vibration dampers

With a fluid damper, e.g. our harmonious vibration damper, you achieve a long service life of the main bearings. It reduces the vibrations in the whole crank drive.

Piston pins

The piston pins are often neglected in conversions. From the aforementioned performance upward, it is important to use a specially reinforced piston pin. Piston pins that are too weak can break and result in severe engine damage.

Important: Products from previous upgrades are also needed.

You will find appropriate articles for your upgrade here:

Do you have more questions about 1.8T tuning?

Our team knows a thing or two about the tuning of 1.8T engines and is happy to answer your questions. Just contact us by phone or e-mail.

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Please leave us a comment.
Tim French
08.02.2024, 07:43 Uhr
What do you folks do about installing cracked rod bearings, I have been building engines for over 40 years and haven't ever seen lock tangless bearings, is their a special way to install the shells in the rod
Pierre Hollinde-Hoffmann
02.05.2023, 16:29 Uhr
Guten Tag Kann ich in meinem App Motor eine Kurbelwellen vom ein 1,9 tdi mit 96,5 hub verwende
Bartek Bartoszewicz
Tuning Professional
His first car was a Polo Mk1 with a 40 Weber twin carburetor and 129 PS (95 kW). His second was an Audi 50. Today Bartek tunes Lamborghinis to 1000 PS (735 kW). Even as a young boy, Bartek disassembled vehicles and put everything back together better. He wrote his high school diploma with oil on his fingers. The trained automotive mechanic with a focus on engines and gearboxes was determined to go into motorsports. In his 10 years in Formal 1, he supervised 73 races, including as engine mechanic for Ralf Schumacher at Toyota. Since 2010, he has dedicated himself fully to his company BAR-TEK® and helps his customers to bring VW and Audi engines to peak performance.
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