In my experiences:
The 1.8 N/A and the 1.8TD both tended to start immediately (one turn) hot or cold once the appropriate pre-heat had taken place.
The 1.9 N/A would start immediately hot or cold as well.
The 1.9 TD would start almost immediately when cold but need about 2 to 3 turns (guestimate on crank movement) when hot then it would fire up.
My thoughts on this:
1. I think the compression rate is a tad higher on the TD 1.9 vs TD 1.8 although I've not actually looked.
2. There might be a difference with the mechanical advance 1.9TD vs electronic advance 1.9TD although to be honest (based on comparing a 306 to a 406) its not noticeable for starting.
3. The 406 and Xantia 1.9TD nearly always have a Bosch pump (always electronic on 406) I understand early Xantia's were like the 405 mechanical Bosch pump
4. 306 (and I expect the ZX too!) the first shape ones had a Bosch pump for the turbo engines and typically Lucas for the non-turbo (about 80% were Lucas at a guess) , where as at shape change (late 'P' plate for the 306) 99% of TD units had the Lucas pump and all the N/A units had a Bosch pump. All are mechanical advance on these. Not going to mention the DW8 here as its not part of the discussion although I can if warranted.
5. Smaller cars with the 1.8 NA unit did not have the oil cooler fitted which may explain its 'interesting trick' of closing clearances up. I expect this combined with no temp gauge (Visa / 205 non turbo) did not help matters too much. I do note that when this unit was popped into larger cars it always had the cooler fitted though, even the non turbo units.
