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A Guide to Building Your VW/Audi 1.8T 20V Engine for High Horsepower

IE's Complete Guide to Building Your 1.8T 20V for Power and Avoiding Engine Block Failure

This in-depth article will educate you on the 1.8T bottom end in stock form, how to upgrade it correctly to meet your performance goals, and what IE offers for your 1.8t build.

SECTION 1: EVERYTHING YOU NEED TO KNOW ABOUT THE STOCK 1.8T ENGINE

First launched in 1996, VW's 20-Valve 1.8L Turbocharged Engine has become an icon and popular engine for tuning and building horsepower. Lovingly referred to as the 1.8 20v turbo, this engine has spanned many variations across generations of VW and Audi platforms. Popular vehicles include:

  • VW MK4 GTI
  • VW MK5 Jetta
  • VW MK4 GLI
  • VW B5 Passat
  • Audi 8N/MK1 TT
  • Audi 8L A3
  • Audi 8L S3
  • Audi B5 A4
  • Audi B6 A4
  • And more

1.8T 20V 058 & 06A BLOCK TYPES

The 1.8T 20V has been mounted transverse and longitudinal in many VW/Audi models, receiving dozens of updates and different engine codes. However, they can all be dialed down to two main generations of engine blocks, 058 and 06A.

EARLY 058 ENGINE BLOCK

The first generation longitudinal 058 blocks are found in early Audi B5 A4, and VW Passat produced from 1996 until midway through 2000. 058 blocks have an internal intermediate shaft that drives the oil pump, and these use an external water pump driven by an accessory belt.

LATE 06A ENGINE BLOCK

The second generation 06A block was introduced in mid-2000 and mounted longitudinally (A4, Passat) and transverse among many VW and Audi models. Model years 2000.5 and newer use 06A block.

This new generation received many updates, most notably the timing belt-driven water pump and eliminated intermediate shaft. The oil pump was also updated to chain driven by the oil pump drive gear located on the crankshaft snout.Watch the video below on how to identify your 1.8T 20V block type:

1.8T 20V STOCK MAIN CAPS

Both the 06A and 058 1.8T 20V use 5 two-bolt main caps. There are 4 outer main caps and one center main cap that contains crankshaft thrust bearings (also commonly called thrust washers). Factory main caps MUST be reinstalled in the exact location and orientation as removed.

NOTE: All 1.8T 20V main caps use M10 threads, however, the main stud lengths vary between 06A and 058 engine blocks, as noted below:

06A main bolts - M10x80mm

Manufacturers Part Number: N90130001

058 main bolts - M10x65mm

Manufacturer Part Number: N10263801

1.8T 20V STOCK CRANKSHAFT

All 06A and 058 crankshafts are manufactured with an 86.4mm stroke. Crankshafts found in 06A platforms are forged or cast iron. 058 crankshafts are cast iron only.

The timing belt drive gear and crankshaft damper are attached via a 4-bolt interface. The crankshaft trigger wheel is partially used with the crank sensor to determine engine RPM.

NOTE: 06A and 058 Crankshafts have different trigger wheels and can not be interchanged.

06A blocks use a thin slotted-style trigger wheel.

058 blocks use a thick dented-style trigger wheel.

1.8T 20V STOCK CONNECTING RODS

All 06A and 058 connecting rods measure 144mm in length on the center-to-center dimension and have a big-end journal width of 24.90mm. The connecting rod wrist pin size and taper vary depending on engine codes.

A tapered 19mm wrist pin (144X19) is the most common connecting rod size in 06A engine blocks.

225HP 06A models (Audi TT & S3) have a non-tapered 20mm wrist pin (144X20).

058 1.8T engines are most commonly found with a non-tapered 20mm wrist pin (144X20).

1.8T 20V STOCK PISTONS

All 1.8T 20V engines feature a stock bore size of 81mm. During its long run, 058 and 06A 1.8T engines featured factory-cast and forged pistons ranging from 9.25:1 to 9.3:1 compression ratios.

NOTE: None of these factory pistons were designed for high horsepower, cast, or forged, and they are much less robust than forged aftermarket pistons.

SECTION 2: BEARINGS, BOLTS, & TIMING UPGRADES

UPGRADED ENGINE BEARINGS

Rod bearings, main bearings, and thrust bearings must be replaced anytime you remove them or replace their components (rods, crank shaft, main caps). We highly recommend using a performance main bearing and rod bearing as power levels increase. The main advantage of performance bearings is their tri-metal composition to withstand added bearing loads and the ability to withstand crankshaft flex. Performance bearings are also treated with specialty coatings to reduce friction and wear further. 

NOTE: All IE 1.8T 20V Connecting Rods are only designed for tanged style rod bearings. Tanged bearings locate and lock into the journal, reducing the chances of bearing spin and less chance of bearing failures.

1.8T 20V ONE-TIME USE ENGINE HARDWARE

Much of the factory main bolts, head bolts, crank bolts, etc., are one-time use stretch bolts and must be replaced with either new factory replacements or aftermarket upgrades once removed. New stock bolts are adequate up to the 300+ range. At 400HP and higher, we recommend upgrading with IE/ARP hardware options. Common one-time use engine block hardware:

  • Head bolts (10x)
  • Main studs (10x)
  • Flywheel bolts (6x)
  • Crank damper bolt (1x)
  • Crank damper pulley to timing gear bolts (4x)

1.8T 20V UPGRADED ENGINE HARDWARE

Upgrading your engine bolts is a good practice with any performance build. However, it is highly recommended if you plan on pushing your car further than 400HP. As an added bonus, ARP hardware is reusable and does not need to be replaced if removed.

1.8T 20V TIMING SYSTEM UPGRADES

The 1.8T timing belt system is a concerning weak point at just about any power level. The most common timing failures occur at the timing belt tensioner and drive gear. A failure at either location can result in immediate timing loss and a complete engine failure. IE timing solutions are engineered to strengthen these interfaces and help protect your newly built engine investment from an unfortunate loss.

SECTION 3: BUILDING YOUR AUDI/VW 1.8T ENGINE FOR POWER

A large aftermarket for the 1.8T 20V engine ranges anywhere from subtle stock engine 30HP ECU remapping all the way up to big turbo builds generating 500+HP -or more! To help you determine the best combination of parts for your power goals, we have separated each section and part upgrade recommendations by horsepower levels.  

300-400HP CONNECTING ROD UPGRADE W/STOCK PISTONS

The factory connecting rods is the primary concern and weakest point around the 300-400hp power level. The most common practice at this point is to perform a mild build with IE forged connecting rods and retain the stock pistons. This is an affordable, proven, and reliable combination for this power level. The weak points of the factory connecting rods come down to two main design limitations:

  1. Very narrow beam design that leads to bent rods under increased torque.
  2. Inferior metals (stock rods are usually made from sintered iron) compared to aftermarket forged rods. These weak alloys lead to broken connecting rod beams.

NOTE: In high mileage or worn blocks, upgrading with overbore aftermarket pistons may be necessary if the piston-to-wall clearances can not be set correctly.

IE CONNECTING ROD OPTIONS FOR STOCK PISTONS

  • 144X19 Drop-In H BeamThis connecting rod is engineered with a tapered 19mm small end for use with the stock pistons found in most 06A blocks. Not compatible with Audi TT and S3 225HP models with 20mm non-tapered wrist pins.
    IE part number: IERHVA2
  • 144X20 H Beam The early 058 blocks, along with 06A TT and S3 225HP engines, will typically require a non-tapered 20mm small-end rod to be used with stock pistons. Common 20mm wrist pins engine codes are AEB, AGU, AMK, AMU, APX, ATC, ATW, AWD, AYP, and BEA.
    IE part number: IERHVA1


400-500HP CONNECTING ROD UPGRADES

To ensure reliable operation at power levels exceeding 400HP, replacing the connecting rods and pistons with high-performance forged upgrades is necessary. All 1.8T aftermarket piston & rod combinations offered by IE use a non-tapered 144x20mm connecting rod for robust strength.

  • H-beam 144x20Proven reliable, lightest weight
    IE Part Number: IERHVA1
  • Tuscan I-beam 144x20 Our highest quality connecting rod. Strong and reliable, superior strength-to-weight ratio, included rifle drilling for extended wrist pin life. 
    IE Part Number: IERTVA1

400-500HP PISTON UPGRADES

Choosing the correct piston forging for your build depends on what you will use the vehicle for most of the time. Stronger material forgings excel under constant cylinder pressures, such as during extended track use. Still, they can have more expansion resulting in rattles during cold starts and increased blow-by on daily driven or weekend road warriors.

NOTE: IE always recommends a slight overbore 0.5mm piston to ensure proper piston-to-wall clearances.

  • Mahle pistons The perfect option for street builds and daily drivers. Features a strong, yet quiet piston operation with tight piston-to-wall clearances due to the low expansion alloy.
  • JE pistons IE's choice for heavy track and some road use. These tough 2618 alloy forgings are available in many compression ratios and bore size options.
  • Wiseco pistons An affordable yet good quality option for track and street use that also features a tough 2618 alloy.

500HP+ Connecting Rod Upgrades

When building past 500HP, that power is only spread across 4 cylinders, subjecting each rod to extreme pressures. The difference between reliable power and a window through your block is a rotating assembly that can withstand these loads.

IE's Tuscan connecting rods have been engineered with a unique I-beam "egg" shape, which lowers stresses by as much as 20% compared to less evolved designs. This also evenly distributes the high compressive loading from high boost pressures onto the connecting rod beam, reducing piston stress and providing a stable foundation for the rod bearing.

  • Tuscan I-beam 144x20IE's highest quality connecting rod offering a superior strength-to-weight ratio, tested over 1000BHP!
    IE Part Number: IERTVA1

500HP+ STROKER PISTONS (06A ONLY)

Building past 500HP on a 1.8L engine requires spooling a huge turbo, which can result in severe turbo lag, even on modern "fast spooling" turbochargers. Combining 83mm overbore "stroker pistons" with a 92.8mm stroker crankshaft results in an increased displacement of 2008cc (2.0L). A stroker build yields more horsepower and torque on the same boost pressure, less chance of detonation due to lower peak cylinder pressures, faster spool, and produces more power on lower octane fuel.

  • IE Spec Mahle Pistons IE has teamed up with Mahle to design the ultimate 1.8T stroker piston set. These pistons deliver OEM fitment, OEM-like wear characteristics, ideal compression ratio, and very stout wrist pins.
  • JE Stroker Pistons Recommended for serious track/drag use, these pistons feature a lower 9.5:1 compression ratio and strong forgings ideal for extreme boost.
  • IE Race Spec JE Stroker Pistons The ultimate stroker piston used in all IE race engine builds. Features upgraded oil ring support, tool-steel wrist pins, FSR "short" skirts for reduced weight, and more!

500HP+ TOOL STEEL WRIST PINS

Why did we create a section just about wrist pins? We have seen endless builds fail due to under spec’d wrist pins.

Many piston manufacturers use a lighter spec pin that works for lower horsepower builds, however, with higher HP levels and raised cylinder pressures you need a stronger wrist pin. For any build using JE pistons, we recommend upgrading to the tool steel wrist pins. NOTE: Be sure to always check the material specifications and wrist pin wall thickness to avoid any pin failures!

500HP+ STROKER CRANK (06A ONLY)

Our forged stroker cranks begin as factory-new VW/Audi 2.0 FSI crankshafts. The crank is modified with a specialty press-fit oil pump drive gear in-house to fit your 06A 1.8T block. This modification produces a drop-in 2.0L crankshaft solution that requires no engine block modifications to install.

500HP+ BILLET MAIN CAPS (06A ONLY)

The stock main caps are cast and lack the rigidity required for a reliable, high-powered build. As an upgrade, we offer billet steel main caps that are far more rigid and will help to reduce main bearing wear.

NOTE: Requires specialty machine work. Check with your machine shop before ordering to ensure they can align bore and hone main caps.

Conclusion

This concludes our complete parts guide on building a VW/Audi 1.8T engine. Thanks for reading! If you have any questions or need help putting together your build, IE's Horsepower Specialists know these motors inside and out; please contact sales@performancebyie.com

Common VW/Audi 1.8t Engine FAQs

Is the Audi 1.8 Engine Reliable?

Yes, the Audi 1.8T engine is generally considered reliable, especially in its later iterations. It's a well-regarded engine in the Volkswagen Group's lineup, known for its balance of performance and efficiency.

Like any engine, its reliability heavily depends on proper maintenance and care.

What Audi Has the 1.8 T Engine?

The 1.8T engine has been used in various Audi models over the years. Some notable ones include:

  • Audi A4 (B5, B6, B7): The A4 was perhaps the most common model to feature the 1.8T engine, particularly in the B5 and B6 generations.
  • Audi A3 (8L, 8P): This compact model also featured the 1.8T in both its first (8L) and second (8P) generations.
  • Audi TT (8N): The first-generation Audi TT (1998-2006) also sported the 1.8T, contributing to its reputation as a fun, sporty car.
  • Audi A6 (C5): Though less common, the C5 generation A6 also had the 1.8T engine as an option in some markets.

Why Is the Audi/VW 1.8T So Good?

The 1.8T 20v engine earned its reputation for these reasons:

  • Performance: With its turbocharged setup, the 1.8T engine offered a good power and fuel efficiency balance. It was capable of delivering strong performance for its displacement, especially with some tuning.
  • Tuning Potential: Enthusiasts love the 1.8T engine for its tuning potential. With relatively minor modifications, such as ECU remaps, intake, and exhaust upgrades, it can produce significantly more power.
  • Durability: Despite being a small displacement engine, Audi/VW’s 1.8t 20V turbo was built with robust internals, allowing it to handle higher levels of boost and power when modified.
  • Fuel Efficiency: The turbocharged design allowed for good power output without excessive fuel consumption, making it a popular choice for those who wanted both performance and efficiency.

What Is the Weakness of the 1.8T?

While the 1.8T engine is generally reliable, it does have some weaknesses:

  • Oil Sludge Issues: Early versions of the engine were prone to oil sludge buildup, which could lead to further issues if not addressed. This issue was largely resolved with proper maintenance such as the use of high-quality synthetic oils and regular oil changes, however.
  • PCV System Problems: The Positive Crankcase Ventilation (PCV) system on the 1.8T can be problematic. Replacing the PCV components may be necessary as the engine ages.
  • Ignition Coil Failures: The 1.8T engine experienced some degree of coil failures, which can cause misfires and rough running. Audi issued recalls and service bulletins to address this, meaning most 1.8T engine equipped vehicles should now be fixed. If they aren’t, then replacing the coils with updated versions is typically a fix for this potential issue.
  • Timing Belt Maintenance: The timing belt on the 1.8T needs to be replaced at regular intervals.

Overall, the 1.8T is a strong engine, but like any performance-oriented engine, it requires routine maintenance to keep running smoothly.

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