Uncomfortable Over-Revving Sound on Long Hill

Yup, normal. Since the battery is full, the ICE is being used to burn off excess regen from the long downhill.

 

I've heard the car will do some "B mode" revving, even if B is not selected?

 

Yes, it is normal. The engine is spinning up a bit for engine braking. If you are in 'D gear', it isn't really spinning up very much, probably not much over 2000 RPM. This car-engine combination just happens to be noisy, so you hear it more than some other cars.

Try putting it in 'B' for a bit as a test -- it will spin up much faster and louder, various people have likened it to a jet engine, giant vacuum cleaner, or screaming banshee. Some of my hills push it up to 4600 RPM. But the engine is still safe. If it causes your car to slow down more than you want, then the hill isn't all that steep.

My descriptions are for Gen3. The Gen4 won't be identical, but should be similar.

While the engine braking concept in 'D' is the same as in 'B', the degree of braking is very different. On one of my occasional hills, 'D' hits 2000 RPM but not with enough braking force to stay down to speed limit, while 'B' hits 4600 RPM and can hold to speed limit.

 

When engine braking, the ICE valves are left open, which allows large amounts of air to pumped through it. This provides extra resistance to the drive train to help in decelerating, but also makes more noise.

 

I don't believe the valves can be left open. But, being variable, they are adjusted for maximum pumping resistance.

 

I've noticed after descending Seymour in our 2010, battery full to the gills, subsequently running along that rolling 60km zone, our 2010 will stay in electric-only even with the Hybrid Synergy Display bar slightly to the right of median (the typical cut-off point for electric-only).

 

It can close them, or at least one side, to reduce losses while the ice is off and spinning.

 

Does engine braking equate to high vacuum? That usually means better pulling up of oil into the upper cylinder region I think.

 

VVT-i stands for Variable Valve Timing (i for "intelligent", meaning the ECM controls it). That's the only trick it has up its sleeve. It can change valve timing within a certain range, and only on one cam (the intake). Doesn't have a way to just leave them closed, to my knowledge.

Toyota has built some engines with VVT on both cams, and some with "Valvematic", which does allow control of valve opening amount as well as timing. Before Gen 4 was announced, I was sort of hoping it would use that, but I don't think that happened. If what I read is correct, the 2ZR-FAE has it, but the 2ZR-FXE Atkinson version still doesn't, even in Prius Gen 4.

-Chap

 

Our previous Civic Hybrid had two cam lobes for each valve (again, intakes only?). The majority of time the valves were at the regular lobes, but under heavy load hydraulics would shift in the second, higher lift lobes. Doing something like accelerating up a hill you could feel it kick in.

 

If the engine is soinning, the oil pump will be too.

Perhaps I am misremembering a discussion on the butterfly valve position

Which had all my friends calling the Honda engine a V4

 

Does anybody actually look under the hood anymore?

 

Supra was a straight 6.