The CBEA and CJAA are essentially the same, except the CBEA has a balance shaft module. Also the 2009 CBEA cars have a couple other minor differences, most notably the one-piece DPF/catalyst and different pressure sensors.
While the G/J/B switched to the CJAA in 2010, the Audi A3 continued with the CBEA through 2014, but with the updated pressure sensors and two-piece exhaust parts of the CJAA. The A3 also uses a different fuel filter.
CBEA/CJAA use piezo fired injectors, higher rail pressure, and the dual EGR and deNOx catalysts as their only [intended] NOx controls.
They still both use the same style air-to-air charge air cooler as the previous TDIs use.
The CKRA shares hardly any parts with the other engines. It uses solenoid injectors, lower rail pressure, an air-to-water charge air cooler on the intake manifold. In addition to the dual EGR, it also adds SCR. It also has a balance shaft module. It has a different head, turbo, block, timing components, oil filter, fuel filter (like the A3's), etc. than the other engines.
While the CBEA/CJAA have more turbo problems than the older PD and VE TDIs, the CKRA's turbo problems are twice as bad as that. So bad, that a warranty extension was issued for them. They also have DEF tank heater issues, also resulting in a warranty extension. However, the SCR does afford them a wee bit better fuel efficiency, despite moving a bigger heavier car.
The CVCA, while I would not consider it a 100% clean slate engine, is pretty different from the previous versions. It is probably most closely related to the CKRA, although it doesn't really share much of any parts with it.
It has dual balance shafts, but are now in the block. It also adds variable water pump (which has been a weak spot) and variable oil pump (VAG gassers have had these for a decade or so now). The oil filter was moved back down below, the SCR system is completely revamped, with the DEF injector now being up high by the firewall. It also holds more oil.
Given the CVCA was, for us, a one year only, and we only got the "first" year, I suspect there will be a lot of teething troubles with it... some, possibly most, of which have likely been eliminated by now (2018, almost 2019, models), but we of course won't get to experience that. Some of these improvements may even be reverse compatible... so an improved water pump that say came into service half way through the 2016 model year may be able to be installed on a 2015 engine to remedy the premature failures we've seen.
But there may be other issues that will never be able to be easily gotten past. Really a shame, as I think that would have marked the final maturing process of the CR TDI, and by now would probably provide a really stellar engine for someone actually able to purchase a new one.
