[zoltiz]

So my first tank with my neutral coasting is making me very happy. It's been pretty representative mix of my trips to work (7 mile one way), a couple of 20-mile trips through metro Atlanta, even some awesome downtown Atlanta traffic.

Best I could do with in-gear coasting was close to 41-42MPG...

 

[Redzed]

Coasting in neutral down hill is the opposite of hypermiling tactics. Going down hill one should accelerate since gravity will give you a boost and less energy will be used. Let off gas up hill and glide towards stoplights and stop signs but do it in gear. I get 50+MPG in the city and never coast in neutral. Read up on hypermiling tactics and you will get an easy 50 in city and an easy 40 on the hwy.

 

[zoltiz]

Coasting in neutral down hill is the opposite of hypermiling tactics. Going down hill one should accelerate since gravity will give you a boost and less energy will be used. Let off gas up hill and glide towards stoplights and stop signs but do it in gear. I get 50+MPG in the city and never coast in neutral. Read up on hypermiling tactics and you will get an easy 50 in city and an easy 40 on the hwy.

I've read up on hypermiling quite a bit in the past and try to use some of the tricks, but not being the only car on the road makes it a challenge. Accelerating downhill is a good idea, except when you end up breaking the speed limit and end up with a ticket. Letting off gas uphill also works like a charm except when you have people behind you and they don't appreciate you going 10 below the speed limit when they have places to be. 50MPG is probably doable with FAS, but I wouldn't call it "easy" unless it involves being a complete selfish ass on the road.

Update on the first tank with neutral coast - calculated 45.6MPG (vs. my average of about 41MPG) - looks like 9 gallon (US) fill-ups at 400 miles will be the norm from now on. Cool.

 

[eufo]

I just got my 2013 CR-Z 6MT about a week ago and am trying to figure out exactly the best way to treat stopping... neutral coast or regen. I'm the kind of manual driver that likes going into neutral WAY before I need to stop and let my car coast forever and a day.

If I somehow must stop sooner than anticipated or misjudge my coasting speed I will go ahead and stick it into gear to get some engine braking regeneration going on, but I would think that neutral coasting is far more efficient.

 

[thoughtsimple]

I'm a little confused on how neutral coasting is helping gas mileage in the 6MT CRZ. When I neutral coast with the MID on the screen that shows the engine/IMA status, it shows fuel use when coasting. Is this not the case for others here? I don't know what the CVT does but in my 6MT the only way to get fuel shutoff seems to be to leave it in gear.

 

[zoltiz]

Yes, the only way to get the fuel shutoff is to be in gear, BUT you can coast for miles in certain scenarios while in gear you'd make it 200 yards before slowing down to a socially unacceptable speed and will have to accelerate again, using even more fuel.

I have a spot in my commute that's almost level and I can coast for about a mile in neutral @ around 45mph. Same spot in gear and I'm at 30 in 100 yards.

 

[cyeung]

I drive a CVT, and what I have been doing lately is coasting in D, but with my foot on the accelerator pedal just enough to keep the mpg gauge at 100 mpg and the charge bar at almost nothing. That has been yielding some gains in fuel economy for me. I don't know how well that would work on MT, though.

 

[msingell]

^ bingo. There is a sweet spot where you have the slightest input on the throttle and it keeps up the cars momentum and boosts mpgs.

 

[thoughtsimple]

I drive a CVT, and what I have been doing lately is coasting with my foot on the accelerator pedal just enough to keep the mpg gauge at 100 mpg and the charge bar at almost nothing. I don't know how well that would work on MT, though.

Yes that same technique is what I use on my 6MT. That is why I was confused. I wonder under what conditions it would be better to have idle fuel use over fuel shutoff. Zoltiz earlier claimed a MPG boost by coasting for about a mile in neutral. I don't know how often that really comes up in normal driving.

I'm skeptical that needing enough fuel to keep the engine running in idle really beats momentum turning the engine over with nearly 0 need for fuel while in gear. At least in most circumstances. If the engine turned off while neutral coasting, that would be different. And if engine regen is occurring, that also would make a difference but that seems easy enough to avoid with a little practice.

 

[JasonCRZ]

What I do is charge the battery full until it doesn't charge then I coast it in neutral, but this only works if you have a huge hill in the commute like my route.

If not, I use the "sweet spot". Although I never seen much gains coasting in neutral vs the sweet spot. The highest MPG I had, I didn't neutral coast.

 

[Varmint]

I don't know what the CVT does but in my 6MT the only way to get fuel shutoff seems to be to leave it in gear.

I am not convinced this fuel shutoff thing really exists. I know the HID graphic shows no fuel going to the engine, but I am skeptical that the engine is truly shut off.

More on this later, but I gotta run to a :staffmeeting:

 

[JasonCRZ]

I'm 100% sure the engine doesn't shut off but cuts fuel supply to the bare minimum. I got to the point where the car wouldn't charge even if I hit the regen while lightly braking. Hypothetically if the engine did cutoff then we would be running full electric and the bars will drop quickly (our packs aren't that strong)

If the engine did shut off we would be at 0rpms in neutral. But we can also argue that at 1k (or idle rpms at neutral), electric is running the engine. Which in that case would deplete the battery.

I'm no expert but I think that's how it works

 

[Varmint]

We know the MID graphic shows no fuel leading to the engine on the diagram. This happens while coasting in gear at a speed that allows for 3 bars or more into charge mode. That certainly suggests that the car has shut off the fuel supply.

Does anyone have documentation explaining how it does that?

First, let's take care of the obvious. Whether the engine is running or not, we know the pistons are reciprocating. (Otherwise the car would not move while in gear.) The pistons will only move when fuel is being consumed, or when the engine is being powered by an outside force - like the wheels turning the axles, which turns the crankshaft, which turns... In short, the wheels are driving the engine instead of the other way around.

We know the engine does not have a VCM mode for the VTEC head. It will not fully shut down the valves to reduce pumping losses. So, that's not how it happens.

A more likely option is that "something" in the fuel line shuts down. The wheels drive the pistons causing engine drag (pumping losses). That seems reasonable. However, when the driver's foot returns to the accelerator, there is no perceptible shutter when the engine comes "back to life". Nor is there any flicker or disruption in the car's electronics. I realize the engine is not going from a stop to a start, so the shutter should be minimal. However, I've looked and never felt or heard anything. Going from some fuel being consumed to zero fuel and back again should result in a perceptible change. At the very least, the degree of engine braking should be reduced when fuel is added back into the mix.

I suspect the MID is telling us the engine is getting almost zero fuel. Perhaps the fuel pump is shut down, but fuel is still being sucked by vacuum pressure. (File that under Varmint's crazy notions.) Whatever it does it seems like there's not a complete fuel cut-off.

 

[eufo]

I finally saw on my screen what was being described here earlier. My screen does indeed stop showing fuel going to the engine when I'm coasting in gear and allowing for regen. Obviously you can't coast as far in gear, so I'm not sure if this is necessarily better even if the fuel is indeed cutoff. I'd be interested to hear confirmation on this.

 

[supercrz]

After reading this thread, I've tried the coast on neutral, since I've only done coasting in gear.

I've been trying different variations and uses of each and found the coasting on neutral is effective on flat surfaces and coasting on gear is effective on down slope.

If you look on the gauge above the MID, both will reach up to 100 mpg regardless of what method is used.

Using the coasting in gear will however charge the IMA, but it will not get any further compared to using coasting in neutral.

What do you think?

 

[eufo]

I think every situation is different and the best course of action will depend on that, so I like your idea of staying in gear while coasting downhill.

My natural reaction when I see red lights far down the road is to instantly go to neutral and "see what happens". It is a simple action and requires no feathering of the accelerator or any kind of staring at the display, so I believe it is probably the safest action as far as avoiding accidents.

If neutral ever feels "too fast" for whatever stop I'm anticipating I will put it back in gear and let the engine help slow the vehicle down.

I'm not sure what is the most fuel efficient. As funny as it sounds, we have a hybrid hybrid since it is a manual transmission. Most documented fuel efficiency tips I can find for hybrids have nothing to do with manual transmissions since most hybrids have some form of CVT.

Maybe it's up to us to start testing and experimenting on how to get the most out of the car.

 

[JasonCRZ]

After reading this thread, I've tried the coast on neutral, since I've only done coasting in gear.

I've been trying different variations and uses of each and found the coasting on neutral is effective on flat surfaces and coasting on gear is effective on down slope.

If you look on the gauge above the MID, both will reach up to 100 mpg regardless of what method is used.

Using the coasting in gear will however charge the IMA, but it will not get any further compared to using coasting in neutral.

What do you think?

The way I coast is once my battery is full it goes into neutral IF I won't lose any speed. If I lose speed, I hit the sweet spot and just go from there.

I see you're in Reno I really want to try this on the 80. Probably coming from NV back to CA since it will be mostly downhill. I'll post an update when I come up there and see what happens

 

[thoughtsimple]

Coasting in neutral to a traffic light or stop sign is probably not what you want to do for the best overall MPG. The car only charges the battery when in gear. Even the brake regen happens through the IMA so it only works when in gear. Much of the benefit of a hybrid is using the regen recover some of the kinetic energy when slowing down instead of losing it to heat.

So even though the instantaneous MPG meter shows the same 100 MPG when coasting in neutral as when slowing in gear, the reality is you are losing all of your kinetic energy instead of recovering some of it for later use down the road.

 

[eufo]

It's not entirely that simple (no pun intended) since you can coast in neutral for usually a MUCH further distance so you avoid a bit of extra fuel use for the difference.

The battery seems to never need much regen when stopping anyway. Mine has a tendency to regen to nearly full while cruising.

I wish there were some numbers out there to solve this quandary.

 

[thoughtsimple]

I think it is pretty clear from this discussion and the variation that you can see on people's MPG signatures, that there is no simple answer. What works for some might not be optimal for others.

For example, you state that you see nearly full battery while cruising. I'm almost always at just above 1/2 battery when cruising. That's were I want it since it means I'm getting quite a bit of boost from the battery. Everyone has different driving habits and different road conditions to contend with.

S. Florida vs. Boston Metro West really are going to create different driving conditions. Hills and traffic patterns are completely different not to mention the weather. Experiment until you find what works best. But keep in mind, physics are the same for everyone. If your CR-Z is not in gear, it is not charging the battery. If you get more use from the kinetic energy from coasting to a stop and don't need to apply your brakes, then you should coast. On the other hand, keep in mind that 100+MPG on the gauge in neutral is not the same as 100+MPG on the gauge while in gear.

I'm really enjoying experimenting with this car and trying different techniques for high MPG. I just went one whole tank in Econ mode nearly 100% of the time. Now I've switched back to Sport mode nearly 100% of the time to see if there is any appreciable difference.