Thanks for the link. I read the first couple of pages, and the discussion makes sense to me. Except for one thing, and I'd hate to read all 25 pages in case the answer is not in there.

People were finding they could get regeneration while slowing by shifting into "L" between the maximum and minimum EV-only speeds.

But no one described what happens in the '05-'08 FEH between the EV max and min speeds, in "D", and they apply the brake pedal. From the discussion, it sounds like most or all of the braking would be done with the mechanical brakes in that situation. This can't possibly be true, can it? That would mean that without using the "L" trick and between about 40mph and 8mph, there'd be little or no regen. That would be a huge waste of energy. But if it isn't true, then why are people with the '05-'08 shifting into "L" to get regeneration while slowing?

On the post '08's, in "D" in the same situation, and you apply the brake pedal, the system looks after getting as much regeneration as possible, and applying the mechanical brakes as little as possible. Above or within the EV range.

So in the post '08's, there's no reason to use "L" to slow unless the stopping/slowing situation is so extreme you know you're going to exceed the battery capacity. Using "L" in that situation causes the engine to spin, which wastes energy, delays filling the battery, and so reduces use of the mechanical brakes. Turning on the A/C has the same effect, but much less pronounced.

Therefore, wouldn't the post '08's be better suited for mountain driving or trailer towing?

 

In L on the early models there is a greatly reduced need to ever even engage the brake pedal when slowing. My morning commute is normally bumper to bumper in town interstate traffic. I shift into L as soon as I get on the interstate and only infrequently use the brake pedal.

 

Not necessarily, remember the 05-08 have disc brakes all around which dissipate heat well. It's also interesting to see that on an earlier model, the rear brake pads normally wear faster than the fronts because the regen does so much of the normal braking. I haven't been able to fade the brakes even when riding them a lot at highway speeds down mountains but I suppose it's possible if you push hard enough.
Some early model drivers have had their front discs/pads rust or corrode because of non-use and wet conditions. I sometimes throw the shifter to N while braking to turn regen off and get the brakes hot to clean the pads/rotors.

 

I often descend hills that are so steep and long, such as down 3000 vertical feet in 10 miles, on gravel. These roads are pretty crude (old logging roads up the mountains) and you have to come down them around 50kph/30mph.

The traction battery is full by the time I'm a quarter of the way down, so the rest of the descent is in "L" for some engine braking, plus using the mechanical brakes. At the bottom the front discs are always warmer/hotter than the rear drums. The brakes are hot if I come down too fast, warm if I come down slower.

I'd like to know if the AWD engages the rear axle during regen in this situation, because sometimes these descents are on ice or slippery snow. I'd rather have balanced braking to both the front and rear wheels, rather than regen just acting on the front wheels. Which strikes me as inherently unstable.

At highway speeds down big descents usually the wind resistance is enough to keep things under control.

Because of how this FEH is used, and given that the mechanical brakes always activate below 3mph, that may be enough to keep them polished. But as you say, it can take some doing to heat them up. Good idea how you force them into use.

 

That's an interesting capability. Maybe it was so different from non-hybrids that Ford decided to make things work more like ordinary cars.

The Mitsubish PHEV comes equipped with a control to select 6 different levels of the sort of regen braking you describe.

 

"Infrequently" might have been a bit too strong...substitute "noticeably less frequently".

 

Here's a couple of questions on 2007 braking behavior that I've asked on this forum before, but never gotten a answer:

1) If I'm decelerating to a stop in "L", does lightly depressing the brake pedal (no mechanical braking) increase the amount of regenerative braking?

2) If I'm decelerating to a stop in "D", does lightly depressing the brake pedal (no mechanical braking) generate less regenerative braking than if I was in "L"?

I'm sure there are subsets and permutations of the above two questions having to do with speed and state of charge, but I'm just interested in the general case.

Any thoughts?

 

I thought of another aspect of this, and this consideration makes it simple for me to decide which system I prefer.

Since FEH's of any year lack really effective engine braking, and since the load on the mechanical brakes increases once the traction battery is "full", then what happens if you have a mechanical brake failure?

I realize this is vanishingly uncommon, but for my usage a brake failure would be like a runaway train and would be uniquely dangerous with an FEH. On the roads we drive, such a failure would have a high chance of being fatal. The only other "out" would be to turn into the uphill side and end up rolling.

Disc brakes can't be used as parking/emergency brakes. So cars with rear discs have little drum brake systems in the rear hubs. The earlier FEH's would be so equipped, while the later ones, with rear drums, already have rear drums.

If you're in a "runaway" situation, all you have left is the parking brake. I'd much rather have full-size rear drums in this situation than the tiny ones used as parking brakes with discs.

Rear brakes don't take much of the braking load. I've never heard of the '09+ rear drums overheating anyway, so I don't think their poorer inherent cooling compared to rear discs would become an issue to begin with. And I appreciate the option to race the engine to waste energy and reduce the load on the brakes, by shifting into "L".

 

Disc brakes every day of the week. The chances of "runaway" brake failure are so remote, I'll take better brake performance. It's not just cooling. it's better wet performance as well. Going to drums was strictly a cost saving measure.

 

Probably rear discs cost more than rear drums because they need small drum brakes for parking brakes anyway. How do rear discs work better than rear drums, since rear brakes don't have enough work to do to overheat?

The cost savings extend to maintenance, since drums are cheaper to maintain than discs. Especially rear brakes, where discs exposed to crud flying off the front wheels degrade faster than drums that are self-enclosed.

I guess which rear brake is best for an FEH owner depends on the type of driving they do. I'll take the drums.