Interesting Reddit Discussion from r/Prius

I don't disagree that he may be wrong on more than one count, or that there may be things about his approach that get in the way of better understanding.

Still, none of that is a good reason for us to be wrong about what he is trying to say.

I think he is trying to say that he agrees engine braking happens in B mode, but does not agree it happens in D mode. I don't agree with that, but I think it's what he's saying.

If that's not what you think he's trying to say, maybe we should let him clear it up.

 

I also think that this is the core of the discussion.

Perhaps it would be a small but helpful step forwards in the discussion if he would acknowledge the fact that I have presented not just evidence, but proof that engine braking occurs D mode in the Gen 2 Prius:
The most misunderstood aspect of the Toyota hybrid synergy drive system | Page 6 | PriusChat

 

While I am always open to pleasant surprises, I am not betting that any such acknowledgment from Paul will be seen. That's a tree we've been around before. At some point the focus has to shift to "what information will be useful to other readers of the thread?".

To see that engine braking does sometimes occur in D, it is enough to review any of this evidence already long ago posted in the several threads on this topic. For an incomplete list:

• fuzzy1's report from a RAV4. No added instruments, but the tachometer included in the RAV4 HUD option.
• Fred_H's instrumented run in a gen 2 Prius. The pretty graph is nice because the region from, oh, 4220 to 4320 seconds clearly shows the engine RPM (green trace) being positive and the engine torque (yellow trace) being negative as the RPM's mirror image: as clear a signature of engine braking as it gets.
• ChapmanF's instrumented run in a gen 3 Prius. No pretty graph (sorry), but gives an example of working through the math with the MG1 and MG2 torques and RPMs to complete the picture of just how much engine braking was being done and the power flow through the transmission on the mechanical and electrical paths.
• The perennial how come my engine was howling when I went down a hill in D? questions that are continually being posted on PriusChat by people who come here just to ask and don't have prior convictions on this topic.

All of that stuff has been made available before and Paul, like clockwork, tends to come back around and say "but i haven't seen any evidence, just claims and anecdotes." It's like Paul means something by 'anecdote' that isn't what other people mean by 'anecdote'. So probably that's not going to change.

As a community, about the best we can hope for is that other readers who come along, and see what has and hasn't been presented, and see what Paul does and doesn't consider 'anecdote', are able to draw useful conclusions for themselves.