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

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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:

o 1.8 litres, 86.4mm stroke, 81mm bore, in the form of KR and PL

o 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:

o C-C length: 144mm

o Big end bore: 50.6mm

o Big end width: 24.9mm

o Pin diameter: 20mm

o Small end width: 24.9mm

? Connecting rod dimensions for ABF

o C-C length: 159mm

o Big end bore: 50.6mm

o Big end width: 24.9mm

o Pin diameter: 21mm

o 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)

Cylinder head

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Either small intake port (ABF, 9A) or the larger intake port heads (some PL, KR) can be used. Porting and polishing doesn't hurt if done properly. Possible additions:

? Stiffer valve springs to allow higher rpm safely and to overcome the newfound positive manifold pressure

? Titanium retainers are half the weight of stock steel retainers (~20g each) to allow higher rpm safely

? Lightweight lifters from newer VW models (p/n 050 109 309 H) to save some valvetrain weight (saves ~10g each)

? With no clearance ABF camshafts are about 254? duration and about the same for the KR

? ABF camshafts have higher lift so can potentially injest more air (10,76int/10,73exh mm for the ABF and only 9,2int/10,21exh mm for the KR)

? Here are the timing figures (for 1mm lift)

o ABF : 1-38/39-1 so 2? of overlap

o KR : 3-35/43-3 so 6? of overlap

? The 35mm ABF valve guide is shorter than the 38mm 9A/KR/PL, hence causes less air restriction

? Aftermarket or customs cams with internal vernier pulley to adjust overlap can be beneficial for some setups

? Adjustable camshaft pulley can be useful to move the powerband around

Engine hardware

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? Use stock VW metal headgasket (p/n 050 103 383 A) for bores up to 83mm

? Use ARP head studs (p/n ARP-204-4204 or ARP-204-4702) to help avoid blown head gaskets. Torque to ~70-85lbft using ARP lube

? Use ARP rod bolts (p/n ARP-104-6004) to help keep the rods INSIDE the cylinder block. Can also use Ford 302 rod bolts (p/n ARP-154-6002) with some slight grinding of the head or if the bolts are pushed into the conrod hard enough. Torque to 25-40lbft using ARP lube.

Intake manifold

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Various options possible when it comes to choosing an intake manifold:

? Use stock K-Jetronic 16V manifold with custom fuel rail to accept EFI injectors

? Use ABF manifold but swap the 225cc/min ABF injectors (p/n 0 280 155 606) for some bigger 279cc/min Nissan Primera ones (p/n 0 280 155 607 or 0 280 155 611)

? Use a cut down Audi S2 manifold with 1.8T fuel rail (transverse or longitudinal will work)

? Use custom intake manifold with 1.8T fuel rail (transverse or longitudinal will work). To reuse the stock flange, CIS injector seats will need to be swapped to digifant EFI seats (p/n 037 133 555 A)

Exhaust manifold

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Various options possible when it comes to choosing an exhaust manifold:

? Use stock 16V manifold with different flange welded on (places turbo very low)

? Use stock 16V manifold with adapter plate

? Use a cut down Audi S2 exhaust manifold Audi external wastegate

? Use custom exhaust manifold (log-type or header-type), with or without external wastegate

Turbocharger

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Use anything suitable for a 2.0-16v motor running a maximum RPM of 7000. The choices are many:

? For good low-rpm response and reasonable power, a Garrett 60 trim T3 with stage 2 wheel and 0.48AR housing works well

? The next stage up would be a hybrid T3/T4 50 trim compressor with stage 2 or stage 3 0.63AR turbine housing

? A stage 3 0.82AR turbine housing will build boost at ~5000rpm and make good top end

Fueling

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The engine can be fueled in an infinite number of ways, but the recommended paths are:

? G60 Digifant I ECU and loom with custom programming and bigger 300 or 440cc injectors

? Standalone engine management with at least 300cc/min injectors, and preferably 440cc or higher

? Most stock VW fuel pumps good for just over 250hp of fuel, but an inline Bosch or Walbro in conjunction with the stock pump is the safer option

Ignition

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Most modern vehicles have very good ignition systems, and the 16V is no exception. Some recommendations:

? Use colder plugs. Stock 16V is F6DTC for KR/PL/9A and F5DP0R (platinum) for ABF. For most applications, a Bosch 5 or an NGK 7 are fine, usually gapped to 0.7-0.8mm. For higher boost, it might be safer to go with NGK 8's.

? Proper gapping of the plugs is necessary if using the stock coil. Depends on plug type (copper/iridium etc) and boost levels. For wastespark conversions, a gap of 0.8mm can usually be used, otherwise 0.7mm should be fine.

? Aftermarket ignition leads are usually a good thing as the stock ones normally tend to be old and tired. Magnecor KV85 are fine.