After working on a quite a few VW 16v engines and being able to quantify their character after optimizing them, the desire to find what makes these engine respond differently has arisen once again. Time and time after tuning up an ABF motor it can be observed that this engine does indeed respond quite well once the factory airpath, fuelling and spark advance has been fettled. We have discussed on here many times about heads and camshafts. About the long connecting rods and about piston dwell at TDC. But I convinced that as a package the character of the ABF engine is a hard one to beat. If only VW had the need to design a vtec cam system for this engine this would have left Honda owners quaking. We know from previous discussions that there are 3 common variations of 16v heads the 027 133 373 E , 051 133 373 and the 051 133 373D. The first two are fitted to early and later KR engines as well as post 94 9A and early 6A motors. The latter can be found on ACE, ABF and ADL motors. Having tested both types of KR engines it has been observed that the torque curve is more or less the same between 051 and 027 heads. The same happens but at a higher magnitude when the engine is a 9A or 6A with inlet cam 027109021AH fitted. This response changes somewhat when the engine is a Seat or VW ABF motor fitted with K jet, just to keep things equal. There seems to be more lower torque pre 3000 and even a bit more come 5500 then slowly the torque starts descending until it gets to near 6400 rpm before making a rapid crescendo. So whats responsible for this? Well if one was to remove the dress kit, i.e. the exhaust system , inlet manifold and intake tract and examine the head and block there many hidden improvements over older 16v motors. I was speaking to one of our german suppliers who was a VW enthusiast himself and after a bit of discussion of the above he gave a list of OEM camshafts for the VW 16v range. I will share them for all to see. 16v camshaft (Nockenwelle) for ABF, 9A and PL and KR engines. All Measurements at 1mm valve lift IVO= inlet opens IVC= inlet closes EVO= exhaust opens EVC= exhaust closes PL= peak lift. KR Inlet # 027 109 021 AH IVO 3 ATDC IVC 35 ABDC Duration -3 +180 +35 = 212 PL 9.6mm PL/9A pre 94 inlet # 027 109 021 AL IVO 1 ATDC IVC 21 ABDC Duration -1 +180 + 21 = 200 PL 8.8mm Exhaust cams for 027/051 103 373E/NC NC =* Not classified or No letter Exhaust # 027 109 022 G EVO 43 BBDC EVC 3 ATDC Duration 43+180+3 = 226 PL 10.2mm ABF Inlet # 051 101 or 051 019 021B IVO 1 BTDC IVC 38 ABDC Duration 219 PL 10.8mm ACE/ADL and late post 94 9A Inlet # 051 109 021 C superceeded by 051 109 021A as of 010304 IVO ? IVC? Duration ? PL ? Exhaust cams for 051 103 373D heads found on ABF,ADL, ACE and post 94 9A Exhaust # 051 102 or 051 109 022B EVO 39 BBDC EVC 1 ATDC Duration 39+180+ 1= 220 PL 10.8mm As the cylinder head is the mechanical brain of the engine, could it be that the 27mm exhaust valves and valve seats with subtly improved ports ( very small valve guide protrusion from factory), higher valves lifts an in the case of the inlet valve even more duration than older engines cause this ABF engine to respond quite well to tweaks. Is it that all of these interactions help to reduce pumping losses. ABFs cam sets seem to have a 1 of over lap vs 0 for KR camset. Let discuss to see if there is more learned. I will aslo add that I have seen a similar pattern on 1.8T engines where a series of engines with the same type of head have the inlet cam changed only.