[vanir]

Actually the 605D/C2-C3 fuel was first fitted to preproduction prototypes for the 109K, was adapted for MW50 (DM motor) then evolved firstly into the D-2 using either B4 or C3 and finally into the DB and DC variants which entered production (MW50 standardised for both). No "DM motor" entered production, but the D and D-2 entered production for development purposes.

Here is the specifics for analoguous comparison between AS/A motor, and ASB/DB or ASC/DC motor.

Climing condition (standard 30min setting, no MW50 use)
AS 1275PS with 1150PS @ 7.8km
ASM 1250PS with 1150PS @ 7.8km
AM 1275PS with 1250PS @ 5.8km

ASB 1430PS with 1285PS @ 6.9km
DB 1430PS with 1285PS @ 6.8km

ASC 1400PS with 1285PS @ 6.8km
DC 1370PS with 1285PS @ 6.8km

Full Throttle Height performance/MW50 use
ASM 1500PS @ 6.4km
AM 1700PS @ 4km

ASB 1600PS @ 6km
DB 1600PS @ 6km

ASC 1800PS @ 6km
DC 1800PS @ 6km

Rated altitude
AS/ASM 7.8km

A/AM 5.8km

DB/DC 6.8km

ASB/ASC 6.8-6.9km


So the figures clearly stipulate the AS motor is a supercharger alteration to the A motor. Whilst the ASB/ASC motor is a supercharger alteration to the DB/DC motor.
Documentation says the AS was developed by mounting the 603 supercharger to the 605A. One can reliably infer the ASB/ASC was this same method applied to the 605D which was done in 1945, using the figures provided for engine performance between the 605 series in full.

It also makes a great deal of sense, considering the reliability and serviceability issues when applying MW50 boost to the A motor, which were not a problem with the D motor.

But again I must ask, what are your sources for holding such reservations about D motors using 1.98ata?
And a new question, what leads you to think the ASB/ASC are constructed from an A motor base like the AS, rather than the D motor base in current production in 1945? It would seem a rather backwards step would it not?

edit.
I should add for prosperity the stipulation of 603 supercharger fitment lay in the cruising conditon of the ASB/ASC compared to the DB/DC, which is a kilometre higher for the same output.
The D series obviously had a larger supercharger casing than the A series to begin with, which blurs the line between it and the AS, combined with increased flow dynamics through the cylinder heads which can alter performance outputs at altitude as well, hence an easier handling of higher pressures in the standard settings.
The lines between DB/DC and ASB/ASC are really very blurred until you examine cruising condition, where the larger supercharger fitment is clear.