Over the winter I rebuilt my 1.6 EW into a 1.8 GTI and have a few questions about proper setup for ignition timing and the dizzy vac source. I do have a Bentley, but it's a US copy and doesnt cover carbureted cars. I also have a Haynes PDF that dose, but some of the information is mismatched. First the details of the engine. EW block & con rods, DX Pistons, G60 Crankshaft, G60 Head, Techtonics 272* cam, Weber 38/38 carb, Dual outlet manifold off G60, Techtonics downpipe, MSD Blaster coil, Eurospec lightened flywheel I'm using the stock 1.6 dizzy with the vac advance coming from the back of the Weber not the manifold. So I have no advance at idle and have confirmed this with my timing light. But my question is Ive read on this forum that the if your running a GTI cam you should have the timing set at 6* not 18* like I have now. Can somebody confirm this and maybe explain why? I understand that the GTI cam opens the valves further and keeps them open longer but I don't see how it has such a big effect on timing. Thanks in advance
the discrepancy is down to how you set the ignition timing on carb and k-jet gti cars. with the carb you set it with the vacuum pipe connected, with the gti one you set it with the pipe disconnected and plugged. the gti dizzy is best as the ignition curve will match the cam better
Ok I get that, but if the standard 2E carb uses the vac advance on the manifold and has vacuum at idle. And Im running the vacuum from the back of the carb and have no vac advance at idle would I still set the timing to ~18* or the GTI setting of ~6*
I would start at about 6 degrees and experiment from there. It's impossible to be exact about it, because it's a modified engine, and I think you might be in the US, from what you've said, so your fuel is different. The Tim Stiles Golf GTI book says they ended up leaving the vac advance off of a lot of modded engines (presumably it was causing pinking at low throttle openings.) Once the throttle is wide open, the vac advance doesn't do much anyway - the centrifugal advance takes over.
