'90 SYNCRO Caravelle GL 112 hp with 16" wheels

[Trundler]

Hmmm interesting points all...

My quattro is actually a non-turbo one with basic non-mappable ignition and no knock sensor. I think its tolerance of the low octane fuel might be to do with the Schrick cam - increased valve timing overlap means cylinder pressures are not so high as 11:1 compression suggests?

I don't think I'll advance the timing on the Syncro as it seems lively enough for a campervan and with LPG consumption between 14 and 17mpg I do run out of gas and end up running on petrol quite often!

[HarryMann]

My quattro is actually a non-turbo one with basic non-mappable ignition and no knock sensor. I think its tolerance of the low octane fuel might be to do with the Schrick cam - increased valve timing overlap means cylinder pressures are not so high as 11:1 compression suggests?

Thats a good point, and one that isn't so obvious, though there will be a region where cylinder filling will be better than std (if that cam earns its money), probably higher up the rev-band pressures will not be so high as torque is actually falling. The critical region for detonation, maybe max torque, will then as you say, probably be filling less well than with the production setup (timed to avoid detonation).

The ignition is I should think, electronic and though not re-mappable, would have accurately defined curves taking into account measured engine parameters sufficient unto the moment

It also speaks volumes about good comb. chamber design...

[FBIVW]

A couple of new pics.