Turbocharging a VW 16V motor

Turbocharging a VW 16V engine

This page describes the various paths that can be followed in the process of turbocharging a VW 16V motor, from mild to wild. The information is arranged thematically, with no guarantee of its accuracy.

Engine block

The 16V motor comes in various flavours:

You can get a tall-block, 236mm high with 159mm long rods, in the form of a 2 litre ABF
Or a standard block, 220mm high and 144mm conrods, with 2 different capacities:

1.8 litres, 86.4mm stroke, 81mm bore, in the form of KR and PL
2.0 litres, 92.8mm stroke, 82.5mm bore, in the form of 9A (and Audi 6A)

The tall-block ABF comes with 60-2 trigger wheels on its crankshaft, while standard blocks use camshaft triggering mechanisms
Connecting rod dimensions for 6A/9A/KR/PL:

C-C length: 144mm
Big end bore: 50.6mm
Big end width: 24.9mm
Pin diameter: 20mm
Small end width: 24.9mm

Connecting rod dimensions for ABF

C-C length: 159mm
Big end bore: 50.6mm
Big end width: 24.9mm
Pin diameter: 21mm
Small end width: 24.9mm

Stock internals have been proven to be reliable at high output levels, with the rods being the weak link if detonation is avoided. At elevated power output, detonation will be unforgiving towards the stock 16V cast piston. Various options to use for the bottom end are:

Stock rods and pistons, which usually yields a volumetric compression of around 10 in the various permutations of the 16v motor
Stock rods and pistons, with 2 metal head gaskets, will lower the compression by approx 1 point
For the 1.8 litre engines only, stock rods with 81mm Audi ADU/3B/AAN/ABY/RR pistons (pic 1, pic 2), yield approx 9:1 compression ratio with the 5cc dish of the piston. Pistons seem to be forged, and will take a lot of abuse before melting, possibly due to their large top-land area
For the tall-block 2.0 litre engine only, stock rods and 2.0-8V pistons (e.g. 2E, AGG, ABA, ABT, etc), yielding a compression of approx 8 due to the large 16cc dish. Some valve clearance MAY be required. Some more modern 2.0-20v pistons (e.g. Audi A4) MAY need machining to reduce the compression height, in addition to adding valve reliefs
For the tall-block 2.0 litre engine only, stock rods rebushed to accept 9A/6A pistons (which use 20mm pins), yielding a compression of approx 9, and maintaining good squish compared to the 2.0-8V pistons above
For the 1.8 litre engines only, stock rods (or 1.8T rods) with modern 81mm 1.8T 20 valve pistons. Must check piston to valve clearances after assembly, since no personal experience of this combo.
Aftermarket forged steel rods, with forged aluminum pistons. Bore size up to 85mm possible if the block is crack-free, but for turbo avoid more than 84mm bore. TDI 95.5mm crankshaft can be added with this combo, but not recommended for the standard height blocks.

Engine block ancillaries:

2.0 oil pumps supposedly higher flowing than 1.8 ones, so preferable
ABF crank pulley can be used to convert to serpentine accessory belt system, or alternatively a 2.0-8v crank pulley can be slightly machined to correct any belt alignment issues
Crankshafts with 60-2 trigger wheels attached (e.g. ABF) are only found on 2.0 tall-blocks, so an external wheel+sensor must be fabricated for the standard height blocks if crankshaft trigger is required (e.g. waste-spark coils)