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Mk2 Golf 1.8T Conversion Hints and Tips

Although other aspects of the Mk2 20vt conversion are relatively straight forward, the following has been complied from our experience and should be helpful.

Coolant System

The proximity of the top radiator hose top to the 20v intake manifold makes the use of the original GTi radiator difficult, though it is possible. The G60 type radiator, with the hose outlets at the opposite end is an excellent choice. However, this conversion actually used a Mk2 1300 radiator which has worked well and has the added advantage that the 1300 top hose is a direct fit to the 20v engine. If you are going to use an engine more powerful than the AGU, or plan to do any track work then a bigger unit will be needed.

With regard to the bottom hose, joining the engine end of the 20v hose to the radiator end of the 1300 hose with a length of suitably sized aluminium or steel tube is reasonably neat solution.

With suitable trimming, the 20v rubber heater hoses will fit the Mk2 heater matrix.


For a low hassle direct fit, obvious choices of intercooler are the Rallye Golf and Golf G60 (w/out aircon) units. However, if cost and availability are an issue then the more resourceful may want to look elsewhere and the Mercedes Sprinter unit has proved effective in many cases. Another low cost option is to obtain a suitably sized intercooler from an HGV and use the core as the basis for a custom unit. When choosing a suitable core, only the length and width are of importance, since the unit can be cut ‘across’ to the core to achieve the desired depth. Depending on the suitability of the original end tanks, new tanks can be fabricated as required and welded on.

In most cases it should be possible to use the 20v charge pipes to connect the intercooler to the engine, adding universal pieces as required.

Click for more information on intercoolers

Fuel Evaporation System

The 20v engine is equipped with a fuel evaporation system that is not required when fitting the unit to the Mk2 Golf. The whole system, including the purge valve, can be removed, though the pipe stub on the top of the throttle body must be blocked

Exhaust Downpipe

It is possible to utilise the 20v downpipe for the conversion, though it does require a large amount of modification. Cut off the cat and use what's left, along with some additional straight pipe, to make something suitable. Be sure to include some sort of flexible joint to avoid cracking through engine movement.

Retain Lambda sensor and mounting boss and, for later cars (post ’92), a catalyst  will be needed for MOT's.

Engine Mounts

Although the Mk2 GTi engine mountings bolt directly to the 20v engine they are particularly soggy and it is well worth fitting uprated units during the conversion. The G60 items offer increased stiffness with little increase in noise transmission, though any uprated items can be used.

AFR Meter

It is highly recommended that an air/fuel ratio (AFR) meter be fitted during the conversion. The importance of a correct AFR to the longevity of a high performance turbocharged engine cannot be overstressed. Simple LED AFR type meters are both cheap and easy to fit and can be connected to any standard 3-wire lambda sensor, as found on any petrol car manufactured after 1993. When running at full throttle and boost, the meter should always show a ‘rich’ AFR. Operation under these conditions with a lean AFR can lead to engine failure in a matter seconds and generally points to a problem with fuel supply system, such as a failing fuel pump or blocked fuel filter. If in doubt contact us .

Throttle Cable

Due to the position of the throttle body on the 20v engine, the original GTi throttle cable is too short, though a Mk2 1.6/1,8l carburettor cable is a suitable replacement. However, the use of a Mk2 type cable on the 20v engine requires that the cable mounting bracket on the intake manifold be turned round 180° and ‘tweaked’ slightly to ensure correct alignment.

Oil Temperature/Pressure Sensors

Since the 20v engine has only 1 oil pressure switch, it is necessary to add a T-piece to one of the tappings in the oil filter bracket in order to use the twin oil pressure switches from the 8v engine. Alternatively, one switch can be used, for >2000rpm operation, and the cylinder head (Bulb check) sensor left disconnected – This is not, however, recommended!

The oil temperature sensor from the 8v engine should also be used and can be connected as usual.

Power Steering Pump

The 8v PAS pump is a direct fit if used with the 20v mounting bracket and pulley

Next follows a step by step guide to the engine conversion, the vehicle used in this example is an '91 model year 8v Digifant so bear in mind that there may be differences depending on your choice of vehicle and engine .

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