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Written by Stuart Brown
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Tuesday, 06 November 2007 13:16 |
Cylinder head
Either the small intake port (ABF, 9A) or the larger intake port heads (some PL, KR) can be used, although the larger intake ported head are a better base head.
Porting and valve train
Porting and polishing doesn't hurt if done properly, and there are a few companies out there that do a bloody good job of it. One of the best are CNC heads, but a 16v head will set you back £750!
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)
The 35mm ABF valve guide is shorter than the 38mm 9A/KR/PL, hence causes less air restriction
Camshafts and Vernier Pulleys
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)
It's also possible to modify an exhaust camshaft to use as an inlet cam. This will give you a further 1mm lift over the KR inlet camshaft, but retains the same duration.
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
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Last Updated on Tuesday, 10 June 2008 19:17 |
16v Turbo conversion 
