Not all hybrids created equally

[MasterAlex]

I was just wondering if anybody knows the sure answer for this or not.

I've heard that all hybrids do EOC automatically. Does anybody have any proof for this because I know for a fact that my 2005 HCH does not, do I still need to put it in neutral and turn off the engine to get better results?

[SVOboy]

I'm pretty sure only the prius and the FEH stop the engine automatically, but I haven't been up on the new two-mode stuff in all the GM trucks.

[Red]

Far as I know the only way for a Gen 1 or 2 IMA system to EOC is if you are in neutral and are below 18-20 MPH. Anything faster and the ICE stays on

[jamesqf]

Originally Posted by Red

Far as I know the only way for a Gen 1 or 2 IMA system to EOC is if you are in neutral and are below 18-20 MPH. Anything faster and the ICE stays on

Not strictly true, at least in the Insight. You need to be below the ~18 mph speed for the engine to stop, but if you're on a hill you can then coast up to a fairly high speed (45 mph is as high as I've been), I think until brake vacuum drops.

Coincidentally, I was just doing this tonight on the way back from the lake. There's about 10 miles of 6% downgrade, which is being repaved so there's a 40 mph limit in the one-lane sections. I normally go about 55-60 down it, in gear with regen. With the paving, there were a couple of spots where traffic stopped (or nearly so), which put me in autostop. When it started moving, I just eased up on the brakes, and soon was rolling along at 40, still in autostop.

I don't think it's much of a gain, though, since I normally would have been in fuel cutoff, and getting regen. This is probably true of most hybrids - you may coast a little further, but OTOH you don't get regen - and in these parts most hills are steep enough that you can be in gear with regen, and still need to brake a bit.

[MetroMPG]

Coasting is still more energy efficient than regen. Regen is more efficient than friction braking.

[MasterAlex]

Originally Posted by MetroMPG

Coasting is still more energy efficient than regen. Regen is more efficient than friction braking.

well if you have a battery like mine you have to recharge it after you turn on the radio practically.

This goes back to that 100 hypermiling tips (the one about breaking) wouldn't it be more efficient to break and keep it charged then try and accelerate later while the car tries to recharge it?

[PaleMelanesian]

If you can avoid assist on the accelerations, you don't have to regen to recharge it. I know how hard that is, though. Honda was very aggressive on the assist logic. You think about pressing the pedal, and it assists from the battery pack.

I believe the GM 2-mode hybrids to have a electric-only mode (mode 2). That puts them in the same class as the Toyota and Fords.

The 06+ Honda hybrids have a very low friction mode that the engine goes into instead of completely detaching it from the IMA. It's maybe halfway there to a full electric-only mode, and a definite improvement over the first gen system.

[MetroMPG]

Originally Posted by MasterAlex

This goes back to that 100 hypermiling tips (the one about breaking) wouldn't it be more efficient to break and keep it charged then try and accelerate later while the car tries to recharge it?

That ranking was based on the assumption that you had a fair amount of control over how much you were pulling OUT of the pack, so you could use it sparingly (and therefore have to recharge sparingly). I've only driven the Toyota system, personally. From what PaleMelanesian says, maybe your car's system is harder to control.

But I'd still bet that if we had two of your cars, and one driver maximized coasting while the other employed regen, the coaster would get better MPG, regardless of when & how the computer decided it needed to recharge.

[PaleMelanesian]

43) The most efficient way to slow down

When you *have* to slow down, here's an approximate heirarchy of methods, from best to worst.

1) coasting in neutral, engine off (ie. roll to a stop);
2) coasting in neutral, engine idling;
3) regenerative coasting (hybrid vehicles)
4) regenerative braking (hybrid vehicles)
5) coasting in "deceleration fuel cut-off" mode (in gear, above a certain engine RPM)
6) conventional friction braking (non-hybrid or hybrid)

Choosing the right method depends on traffic conditions (following vehicles) and how quickly you need to stop.

I didn't say it earlier, but I do agree with this ranking.

[MasterAlex]

that brings be to another question then, EOC is dangerous (not going to do it on the freeway) but how bad is it for your car and what about just putting it in nuetral?

Also, will the scangauge monitor while the engine is off?

[PaleMelanesian]

Scangauge will monitor while the engine is off if you set the fuel type to Hybrid.

Putting it in neutral is usually a good thing - the engine is turning at idle rpm, below 1000, instead of much higher and burning extra gas just to keep itself turning over.

I don't know how your CVT likes EOC. Check the manual's instructions about towing.

It's not dangerous if you're not foolish. Obviously, try it out in a quiet place first. Hybrids like yours have electric power brakes and steering, so those work just as well with the engine off.

[MasterAlex]

Originally Posted by PaleMelanesian

It's not dangerous if you're not foolish. Obviously, try it out in a quiet place first. Hybrids like yours have electric power brakes and steering, so those work just as well with the engine off.

Mine doesn't, brakes and steering go when the power is cut.

Also, just so I know what to look for, when talking about towing, i should see if it will allow it to????

[PaleMelanesian]

Here's an example from my 2004 Odyssey. 4 wheels on the ground towing is allowed below 35mph and for up to 50 miles. Anything below those marks is fair game for EOC.

Some will simply say you must tow it on a dolly, or only at "low speeds for a short distance". In that case, you don't want to EOC, except maybe rolling up to a stop.

Originally Posted by MasterAlex

Mine doesn't, brakes and steering go when the power is cut.

Ah, sorry about that. I must be thinking of the 06+ version, then. I believe the Insight has electric as well.

That said, they do both work, it's just a matter of being harder work on your part. Some are worse than others. My civic's steering is almost the same, while my Odyssey has Incredible Hulk steering with EOC. Brakes on both are good for 3-4 applications, then they start going the Hulk path themselves. I make sure I don't get into that situation by leaving myself a reserve or by restarting if I start running low.

[jamesqf]

Originally Posted by PaleMelanesian

2) coasting in neutral, engine idling;
3) regenerative coasting (hybrid vehicles)
4) regenerative braking (hybrid vehicles)

I disagree. #3 should be more efficient than #2, under most circumstances. If you are coasting in neutral with the engine idling, you are still using fuel. If you're doing regen, you usually (unless it's cold, when the ECU tries to keep engine temps up) will be in fuel cutoff mode, using no fuel AND getting some charge in the battery.

Of course this may vary depending on terrain, too. Even with full regen, a 6% downgrade will put me over 60 mph.

[PaleMelanesian]

Well, a 6% downgrade is pretty severe. The nearest one of those to me is a good 1000 miles away!

You also have to balance out the lost momentum from regen against the power reclaimed. On the much more common flat-ish land, coasting comes out ahead for this very reason. You do use a little fuel idling the engine, but it's more than counteracted by the momentum not lost to engine braking.

[jamesqf]

Originally Posted by PaleMelanesian

Well, a 6% downgrade is pretty severe. The nearest one of those to me is a good 1000 miles away!

Which shows the problem with a general statement like that list. Maybe true in the flatlands (I don't have enough experience to say), but most definitely not true in these parts :-)

[MasterAlex]

I was doing some tests and I found that with the HCH1 the regen only occurs when the engine is on and in drive. IF the engine is on it will find the correct gear for that speed. So basically putting it in neutral is good unless you are going slow enough for the car to realize that it was going slow to put it in neutral.

Does that make sense?