kelp

This is normal. It is however exaggerated under certain conditions as you mention. It is further exaggerated to the point of undrivability by very lightweight flywheels and large cams.

The timing alternates between base idle spark and the normal spark table, a datalog will show this exactly. At low throttle % positions the VCU seems to alternate between these. You can solve this by matching the timing in the two tables in these areas: 1. below the 1000 RPM and low gm/cyl area on both tables, and 2. more closely approximate the two areas from 1200 to 2000 and up to 0.77 g/cyl or thereabouts. A tuner can do this for you also. It will smooth it right out.

HotZ06

Thanks for that. I think I still have a problem as tuners are a bit thin on the ground in Saudi. However, I'm at a track day in Bahrain on Friday and will see if there are any facilities in the neighbourhood. Ruf have just built a massive complex there but I don't think they are open yet. Just for interests sake, why do they change the timing? Emissions?

kelp

Well, maybe. It certainly runs better most stock conditions, unless you experience those occassional resonant conditions. I would leave it alone unless it drives you nuts. For me and a 13 lb flywheel and a 247/256 cam, things are a bit more eccentric.

BTW when you comprimise your idle timing, try not to go over 25 degrees. You might consider getting HPTuners. It is enjoyable to see the adjustments you can do. Start small and work your way up as you get familiar.