Definitive Guide to Building The Early 1.8T Engine For High Horsepower

Guide to building your 1.8T 20V engine block

Integrated Engineering's complete guide to avoiding engine block failure

Popular Audi & VW Models that have the 1.8T (1995-2005)
  • MK4 GTI
  • MK4 Jetta GLI
  • B6 A4
  • B5 A4
  • MK1 Audi TT
  • And many more

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 has to offer for your build. If you have any further questions feel free to contact us or leave a comment below.

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If you’re looking to upgrade your 1.8T engine, you have come to the right place. Integrated Engineering (IE) offers a large product line spanning 1.8T engines to modern day platforms... Additional guides pertaining to 1.8T cylinder heads or other engines can be found in our engine building guide blog section.

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  • Blocks – there are two styles of 1.8T engine blocks, 058 and 06A.

  • 058 blocks are found in vehicles produced from the beginning of production until year 2000.5.

  • Model years 2000.5 and newer use 06A block.

  • Model year 2000 was a split production year so both 06A and 058 blocks are found in that year.

  • 058 blocks have an internal intermediate shaft that that drives the oil pump and use an external water pump driven by an accessory belt.

  • 058 blocks are only found in the early longitudinal Audi B5 A4 and VW B5 Passat.
  • 06A blocks do not have an intermediate shaft and use a water pump driven by the timing belt. The oil pump is chain driven by the oil pump drive gear located on the snout of the crankshaft.

Watch the video below for more information on how to identify you 1.8T block type:

Mains Caps & Bearings

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Like most other VAG 4 cylinder engines, the 1.8T uses 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). The stock main caps are cast iron and can be upgraded to IE's billet steel versions as power output increases.

The block side of the main caps have M10 threads but the lengths between 06A and 058 vary as noted below:

Crankshaft

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All 1.8T stock cranks have a stroke of 86.4mm.  Cranks found in the 06A can be found forged or cast iron. Most 058 crankshafts are cast iron. The timing belt drive gear and crankshaft damper is attached via a 4 bolt interface. Also on the crankshaft is the trigger wheel which is used in part with the crank sensor to determine engine RPM.

  • 06A blocks use a slotted style trigger wheel.

  • 058 blocks use a dented style trigger wheel.

Rods & Bearings

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All 1.8T connecting rods measure 144mm on the center-to-center dimension and have a big-end journal width of 24.90mm. With the common measurements out of the way, that leaves the wrist pin size, which vary depending on engine codes.

  • Most 06A 1.8T engines employ a 19mm wrist pin (225 horsepower models use 20mm).

  • 058 1.8T engines typically use a 20mm wrist pin.

Pistons

18tpistons Some 1.8T pistons are cast rather than forged, which results in a fairly weak piston. Some engine codes did have forged pistons but they are not designed for high power levels, and still not as robust as forged aftermarket pistons.
  • All stock 1.8T pistons have a bore size of 81mm.

  • Factory published compression ratios tend to vary but from our experience actual compression ratios range from 9.25:1 to 9.3:1.

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This section will be separated by different horsepower levels. Our goal is to point you in the right direction and make your build a success.

300ug

300HP+ Connecting Rod & Piston Upgrades

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At 300+ hp we often recommend using a set of IE connecting rods with stock pistons. This proven combination works fine as long as the piston skirts and cylinder walls are in good shape. In high mileage or worn blocks,  larger bore aftermarket pistons should be used so piston-to-wall clearances can be set correctly. It is fairly common knowledge at this point that 1.8T connecting rods are the weak point in the bottom end, since they were designed for only 150-225HP depending on the model.

Two main factory connecting rod weaknesses:

  • Very narrow beam design that leads to bent rods under increased torque.

  • Inferior metals (stock rods are usually made from sintered iron) compared to aftermarket forged rods.  These weak alloys lead to broken connecting rod beams.

There are two possible solutions if you are planning on using upgraded rods with stock pistons connecting rod options:
  • 06A blocks will typically require 144x19mm connecting rods that have a tapered wrist pin (with the exception of 225hp engines). There are many engine codes that accept these rods with stock pistons. (availabe with rifle drilling) IE part numbers: IERHVA2, IERHVA2-RD

  •  058 blocks or other high-output (225 HP) 1.8T engines will typically require 144x20mm connecting rods to be used stock pistons.  Common engine codes that use 20mm wrist pins are AEB, AGU, AMK, AMU, APX, ATC, ATW, AWD, AYP, and BEA. (available with rifle drilling) IE part numbers IERHVA1, IERHVA1-RD

Connecting Rod Rifle Drilling

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Rifle drilling is an oiling hole that travels the length of the connecting rod beam from the big end to the small end of the connecting rod. Additional pin oiling has been shown to greatly extend bushing life on daily driven or high mileage applications.

300HP+ Engine Hardware

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At these power levels the stock hardware, such as main bolts, are adequate. One important fact that enthusiasts often overlook however is that many stock bolts are stretch bolts and thus are one-time use only.  Stated another way, once the bolts are removed from your engine, they must be replaced with new/unused units.

Common OE bottom end hardware that are one time use and should be replaced are:

  • Flywheel bolts (6)

  • Crank damper pulley to timing gear bolts (4)

400ug

400-500HP Connecting Rod Upgrades

18ttuscanbuiltrods   To ensure reliable operation at power levels exceeding 400HP upgrading to aftermarket pistons and rods is absolutely necessary.  All 1.8T aftermarket piston & rod combinations offered by IE use a non-tapered 144x20mm connecting rod with a matching 20mm aftermarket piston.
  • H-beam 144x20- Proven strong and reliable IE Part Number: IERHVA1

  • H-Beam 144x20 rifle drilled- strong and reliable with added wrist pin longevity from rifle drilling IE Part Number: IERHVA1-RD

  • Tuscan I-beam 144x20- our highest quality connecting rod: strong and reliable, superior strength-to-weight ratio, included rifle drilling for wrist pin longevity IE Part Number: IERTVA1

400-500HP Piston Upgrades

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  • Mahle pistons- a great option for street builds and daily drivers, quiet piston operation, tight piston-to-wall clearances due to low expansion alloy. Explore pistons

  • JE pistons- a great option for street or track use, uses a tough 2618 alloy piston forging, with tons of compression ratios and bore sizes available. Explore pistons

  • Wiseco pistons- a great option for street or track use, affordable yet good quality, uses a tough 2618 alloy piston forging. Explore pistons

400-500HP Crankshaft Timing Gear Interface

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The 1.8T timing belt system is a major weak point. The most common failure point is the timing gear located on the snout of the crankshaft. As a solution, we have developed a crankshaft timing gear that is far stronger than the original unit and also an ARP crank bolt that increases the amount of force holding the gear on.

For 06A applications, we offer a press-fit timing gear along with an IE Spec ARP crank bolt.

For 058 applications, we offer a dowel-pinned OEM timing gear, along with an IE Spec ARP crank bolt.

  • IE dowel pin kit (This kit allows you to drill and ream a hole in the end of the crankshaft, which allows a hardened steel pin to be installed) IE Part Number: IEBEVA6

400-500HP Engine Bearings

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We highly recommend using a performance main bearing and rod bearing as power levels increase. The main advantage of performance bearings is due to a tri-metal composition they are able to withstand added bearing loads and are better suited to withstand crankshaft flex.

400-500HP Engine Hardware

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At this power level, the stock hardware is typically sufficient as long as it is never reused. If you plan on pushing the car further in the future you may want to consider to upgrading to ARP engine hardware. As an added bonus, ARP hardware is reusable and does not need to be replaced if removed.

1.8T 06A ARP Hardware:

1.8T 058 ARP Hardware: Also, be sure to check out our complete ARP hardware kits for 06A and 058 engines.

400-500HP Main Cap Upgrades

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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. Be sure to check that your machine shop can align bore and hone mains before ordering.

500ug

500HP+ Connecting Rod Upgrades

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    • H-beam 144x20- Proven strong and reliable IE Part Number: IERHVA1

    • H-Beam 144x20 rifle drilled- strong and reliable with added wrist pin longevity from rifle drilling IE Part Number: IERHVA1-RD

    • Tuscan I-beam 144x20- our highest quality connecting rod: strong and reliable, superior strength-to-weight ratio, included rifle drilling for wrist pin longevity IE Part Number: IERTVA1

500HP+ Piston Upgrades

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  • Mahle pistons - standard Mahle shelf pistons unfortunately come with fairly weak wrist pins in most 1.8T applications. At this power level, you should consider using our 1.8T Mahle Stroker custom pistons, which include a very stout wrist pin. Explore pistons

  • JE pistons -a great option for street or track use, manufactured from tough 2618 alloy piston forgings. Tons of compression ratios and bore sizes available. Explore pistons

JE 1.8T Custom Spec Pistons

 

Integrated Engineering knows these motors inside and out, we can help determine the custom specifications to design the exact piston to meet your project's goals. Contact sales@performancebyie.com to order custom spec pistons

  • Any bore, compression ratio, and several crankshaft strokes available.

  • Thermal dome coating - reflects heat away from the piston. Commonly used in high HP turbo builds or nitrous applications.

  • Anti-friction skirt coating -  Commonly used in endurance applications to increase piston skirt longevity.

  • Oil-shed coating - used to minimize rotating assembly weight, generally in high RPM naturally aspirated applications.

  • Upgraded wrist pins - options range from small and lightweight to stout and strong for turbo high HP turbo builds.

  • Lateral gas ports - ensures superior piston ring seal by increasing gas pressure behind the rings. Only recommend for race use as lateral gas ports generally become clogged quickly and wear rings quickly in street applications.

500HP+ Crankshaft Options

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Some stock 1.8T crankshafts are made from cast iron. At a certain point, it is a good idea to upgrade to a forged crankshaft. For that reason, many serious 1.8T builds use a forged 2.0L crank to convert the 1.8L block into a 2008cc 2.0L stroker engine. (Requires stroker pistons)

  • 2.0T FSI 92.8mm Stroker Crankshaft -This factory forged 2.0 FSI crankshaft is modified with a special IE oil pump drive gear which makes it a drop in 2008cc crankshaft for 06A blocks. IE Part Number: IESKVA6

500HP+ Crank Damper Options

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At this power level using a crankshaft damper such as Fluidampr can increase main bearing life by absorbing crankshaft vibrations. We generally recommend one of the two following options. 06A block only

If you do not already own any 4 bolt components we would recommend using the following 6 bolt components for added security at no extra cost.

500HP+ Main Caps & Girdle Plate Upgrades

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At this point the main caps should be upgraded at minimum to prevent excessive main bearing wear. As power levels increase you should consider using billet main caps and a main bearing girdle kit.

  • IE 06A standard main caps & IE girdle kit - Standard main caps are the simpler solution as they use spacers on the top of main caps. The spacers are then machined to form a level oil pan surface that the girdle plate will sit on. IE Part Number: IEBEVA9

  • IE 06A tallboy main caps & IE girdle kit - Tallboy main caps, an Integrated Engineering innovation, require complex machining to be installed installed. Instead of using spacers on top of the main caps, the main caps stand proud of the deck and then must be machined flat. In the end they are the better solution as they provide a more stable, and flat, mounting surface for the girdle plate. IE Part Number: IEBEVA13

  • IE 058 standard main caps & IE girdle kit - Standard main caps are the simpler solution as they use spacers on the top of main caps. The spacers are then machined to form a level oil pan surface that the girdle plate will sit on. IE Part Number: IEBEVA12
  • IE 058 tallboy main caps & IE girdle kit - Tallboy main caps, an Integrated Engineering innovation, require complex machining to be installed installed. Instead of using spacers on top of the main caps, the main caps stand proud of the deck and then must be machined flat. In the end they are the better solution as they provide a more stable, and flat, mounting surface for the girdle plate. IE Part Number: IEBEVA14

500HP+ Crankshaft Timing Gear Interface

18timingface500hp The 1.8T timing belt system is a major weak point. The most common failure point is the timing gear located on the snout of the crankshaft. As a solution we have developed a crankshaft timing gear that is far stronger than the original unit and also an ARP crank bolt that increases the amount of force holding the gear on.

For 06A applications, we offer a press-fit timing gear along with an IE Spec ARP crank bolt.

For 058 applications, we offer a dowel-pinned OEM timing gear, along with an IE Spec ARP crank bolt.

  • IE dowel pin kit (This kit allows you to drill and ream a hole in the end of the crankshaft, which allows a hardened steel pin to be installed) IE Part Number: IEBEVA6

500HP+ Wrist Pin Upgrades

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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. Be sure to always check the material specifications and wrist pin wall thickness to avoid any pin failures!

500HP+ Engine Bearings

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We highly recommend using a performance main bearing and rod bearing as power levels increase. The main advantage of performance bearings is due to a tri-metal composition they are able to withstand added bearing loads and are better suited to withstand crankshaft flex.

500HP+ Engine Hardware

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At this power level, the stock hardware is no longer sufficient. With the increased levels of load, it is very highly recommended to upgrade to ARP engine hardware. As an added bonus, ARP hardware is reusable and does not need to be replaced if removed.

1.8T 06A ARP Hardware:

1.8T 058 ARP Hardware: Also, be sure to check out our complete ARP hardware kits for 06A and 058 engines.

This concludes our overview on building a 1.8T 20V bottom end. If you have any further questions, please contact us or leave a comment below. Thanks for reading!


27 comments


  • J Lawless

    Hi i’m doing an engine swap from a 150bhp AUM to a 225bhp BAM. My plan is to rebuild the AUM engine for high horse power, what is the most i can get from this engine ? I’m looking to go over the top with this build and use only the best parts for a street/track car. Can you give me a list of parts and prices ? It’s a high mileage engine at 240k.

    Thanks.


  • Bruce Kapanda

    What is the piston ring size which can b used on a 1.8t 20v engine?


  • Scott Oliver

    Can I run a 058 engine in a 2001 A3 I have already built a decent motor from a 98 a4 but the body its no good also bad wiring


  • Admin

    Brandon,

    Yes, it will, all 1.8T heads are interchangeable, no problem!


  • Brandon

    Hi there, soo I’m wanting to tear down my 02 gti awp 1.8t and my head is warped I believe. My buddy offered me a atc head instead of spending money on getting my head resurfaced. Will the atc head fit on my block and work with my cams, valves, seals, etc.?
    Thank you, I hope you guys are able to help.


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