Isn't the size of the prechamber different on the 1.6 NA versus 1.6 TD head? I thought I read that somewhere...
...BTW your Bieber avatar is awesome.-Malone
pre 86 the NA had a much larger pre chamber than the turbo, this was to allow a greater amount of air to be mixed with fuel to create a cleaner burn, the turbo used the same size pre chamber as the na1.5l the reason why they used the smaller pre chamber in the turbo was to try and prevent cracking between pre chamber and exhaust valve by allowing more aluminium head surface to be exposed so hot spots didn't form between the steel inserts and the head and since it was forced induction, it didn't need as much volume in the pre chamber because there was more than one atmosphere of pressure in the cylinder under boost conditions.
“During the course of the combustion chamber optimization program the opening in the cylinder head between the injection nozzle and the swirl chamber was increased from 7 to 13 mm.