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Tuning the VW 1.8 Turbo engine

"T,T,T,T,That's all Volks!"

VAG 1.8T engine Volkswagen/SEAT/Audi: 150-240 bhp from the factory.

The 1781 cubic centimeters in this 20 Valve turbo charged engine represents what must be one of the most tunable engines around today. The 20 valves are arranged as 3 intakes and 2 exhaust valves per cylinder. (The exhaust valves are larger and the intake design makes the engine an efficient one). The compression ratio is set to 9.5:1, but,  in the 170bhp engine compression ratio is 9.3:1 and a slightly lower 9:1:1 in the 240 bhp versions, which although high for a turbo gives plenty of low down torque.

Technical information of this engine: Bore size of 81mm (3.19in) a Stroke of 86.4mm (3.40in) and a Rod Length of 144mm The peak power band is between 2000 and 5000 rpm, and delivers good fuel economy as well around 34-38mpg. The turbo delivers a boost pressure of 8.7 psi or .6 bar on most variants of this engine although the 180bhp engines run 11.6 psi from 2002. The standard cast iron engine block can handle power up to 240 in factory tune and many owners have reported much higher power gains than that. The most common turbos fitted are the KO3 (150-180 bhp) and KO4 (210-240). A remap on a standard engine will typically yield around 40-50bhp increase, and, with the addition of a higher capacity turbo, a freer flowing intercooler and efficient induction and exhaust design, power gains to around 300-350bhp are possible. Expect to have to upgrade the clutch when increasing the power of the engine or the clutch life will be dramatically reduced. The pistons are forged aluminium Mahle, with fracture split forged steel connecting rods mated to a forged crankshaft which is capable of handling far more that the mild 150bhp tune. 

Volkswagen 1.8T engines represents one of the most easily tunable engines today.

The engine code is found at the top part of the engine near the valve cover on the side etched into the head. The engine codes are

Small Port size head Engine Codes: ADR, AMB, AMU, APT, APU, ARG, ATC, ATW, AWM, AWP, BEA
Large Port size Head Engine Codes: Typically 97-99: AEB, AGU, AFY 

An obvious upgrade path for KO3 turbo owners is to swap in a KO4 turbo. The software take a lot of getting right for the maximum power gains but interestingly most people report that the KO4 turbo runs fine on the standard manufacturers ECU Map. It is usually easier to remap the standard KO3 engine and set the boost to 1 bar but the KO4 changes the characteristics of the engine and gives a more rewarding drive pulling hard even when the KO3 runs out of steam around 5000rpm the KO4 still delivers good power. You may think the KO4 is more prone to lag but this is not the case and both are very similar as far as low down low boost power goes.

Weak spots - the engine oil must be fully synthetic and changed at the correct service intervals. Use of the wrong type of oil will cause the oil pump to seize causing a catastrophic loss of oil pressure and engine failure. The engine takes 4.35 l of fully synthetic 5w-40 oil  either castrol 5w40 synthetic or motul 5w40 synthtic depending on engine code. (Interestingly the Audi variants of this engine require 5w30 fully sythetic oil.)

Some users have reported problems with early coil packs but most of these will have been replaced now and newer coil packs do not seem to have any problems. The ecu will not appreciate a blow off valve venting to the atmosphere and this will cause an error code to appear on a diagnostic. Partially venting BOV's are available but we have not had any feedback on their effectiveness on the VAG 1.8T engines.

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2 Responses to “Tuning and performance modifications for VAG 1.8 SO3 and SO4Turbo engine.”

  1. jack says:

    Hi, I wish to know about the Audi TT petrole engine 1.8 Turbo 5 (year 2000)
    are used in what other Cars models by VW & Audi,Thanks.

  2. Mhd albaali says:

    thanks for the useful information, though i would like to ask: if replacing a KO3 turbo with a KO4 only would be useful to an AGU unit and how much hp could be gained from that?….. many thanks in advance!

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