Why do you think that a common rail engine will do away with re-gen? Cummins "B" series engines in Dodge pickups have been common rail since 2003 and from January 1, 2007, the 6.7 ltr engine came out and also has regen emissions equipment and DPF filter. 2013, Cummins had to switch to DEF fluid.
So were the problems with the 1.5 due to the emission equipment? I have a 2009 B3200 with the 4 cyl V1505.
Simply switching to common rail doesn't necessarily "fix" anything, and it won't do away with re-gen at all. Contrary. Read on.
On the B3350, the regen system uses what they call a reformer system. In short, it is a regular mechanically injected engine which they basically added a separate fuel injector with a separate system of running it, and a blower which work together to inject fuel and air directly into the exhaust system, which heats up the DPF so that it will "burn off" soot. Lots of extra stuff to run the reformer system.
With common rail, the injectors are electronically controlled. They run at higher pressures. With this type system, they are able to stagger injection events such that they can have up to 5 or 6 small injections of fuel at or near TDC of the engine, which does several things. Runs quieter (which apparently wasn't a concern with the early 24v ISB's), smoother, starts better, makes more torque, responds to load changes faster and more accurately. But the main thing is that the faster injectors and the system running the injectors allows them to inject fuel during or close to an exhaust stroke which makes the DPF work. Combine all of the benefits of more precise injection and you get less DPF regenerations, longer intervals between regen's, and faster regen's-and of course the other "side" benefits (quieter, smoother etc). Common rail systems (CRS) are also direct injected, where fuel is shot right into the cylinder-which helps the engine make a little more power and becomes more responsive to throttle and load changes. There's tons of benefits. BUT the downfall is fuel contamination. There should be zero contamination. Water? Dirt? Gasoline? Those will cost some money to "fix" and warranty is very reluctant to help with those cases. I've seen tractors totaled because of vandalism/contamination-if that tells you anything.
Kubota CRS is not new. It's been out for YEARS, way back in the early 2000's that I'm aware of, maybe sooner. I had to do some extensive training on the M108X back in the 2000's and we nearly burned one tractor engine up playing with the injection settings. We had the manifold and turbo glowing nearly the same color as the hood. Yes it's possible. Those didn't have DPF's but they knew that the DPF's were coming, which is why the were messing with it way back then.