Thanks Michael for the new information.
I was going to reply with some info on the previous thread but you beat me to it!
Simply put, the R1 injector was matched to injection pumps with the original cone delivery valves, which were derived from the diesel pumps and first used for gasoline on the 300SL pumps.
The 250SE/SL pump has the distinction of being the transition pump from cone valves, to the ball delivery valves we are all familiar with in all 280SL pumps.
The original 250 pump with cone valves is the R18, which was made Nov 1966-March 1967.
The second version for the 250's was the R18Z made from April 1967-Sept 1967. This was the first gasoline injection pump utilizing the newly designed ball pressure delivery valves.
The final version of the R18Z had a different 3D cam, but still used the ball valves from Oct 1967-Dec 1967.
The US version pump for the 250's was the R18Y, and always had the ball valves.
Even though the R2 injectors were first released in Feb 1966, they were not used on any 230SL pumps (R11).
The pump testing and calibration literature explicitly states that all pumps tested up through the R18 pumps with cone valves must use the R1 injector on the test bench.
All pumps after March of 1967 must use the R2 injector matched for use with the ball pressure delivery valves.
I have a bench with R1 test injectors used to calibrate R11 and R18 pumps, and another bench with R2 test injectors for the R18Z/Y and all R20 pumps.
In reality I have tested the same pump on both benches with no appreciable flow discrepancies, but who am I to question Bosch!
Regards,
Michael