Please pardon my ignorance on this... I know the Asst meter stands for assist, but in terms of the car performance, does it mean the electric motor is active and assisting the gas or is it the other way around? I am just not sure what the Asst meter is telling me. Is it a good thing for MPG when that meter registers or is it bad??? Also, I have seen a number of people talk about avoiding the brakes and coasting to benefit MPG and avoiding stopping. How does this benefit MPG? Don't the brakes regenerate the battery? When stopped, doesn't the autostop save fuel? Thank you.

 

I am not sure if the Asst means the electric motor is active, or if it means current is being drawn from the batteries. My thought has always been that the motor is active when gliding (zero Asst, zero Chrg, zero gallons/mile), but it is only consuming the juice generated by the ICE and not drawing from the battery so it shows no Asst bars.

All things considered, I try to use assist only when accellerating. If I see white bars when cruising, I adjust the gas (usually by backing off) until the bars go away. This is because draining the battery below 4 bars puts you in forced regen mode which is considered (around here) to cost you overall FE.

Regarding the avoiding brakes comments, you aren't really avoiding the brakes so much as maintaining your momentum. The worst thing for your FE is accelleration. If you are able to slow down to 30mph, avoid stopping, and then accellerate back to 45mph, you are better off than accellerating from 0-45mph. This is true in any car--not just hybrids.

In terms of brake regen, you are recovering about 30% of the energy you spent to accellerate. That's much better than the 0% you get in a normal car, but with a 70% loss, you are better maintaining your momentum than stopping and starting.

 

no dumb questions here - only the ones not asked Actually this is a good set of questions.

Many thoughts and opinions on this, but here are mine:

The assist meter may show positive assist (white bars), regen (green) or neither (no assist nor regen).

- When it is assisting (white bars), the battery is sending current to the IMA motor which is attached to the gas engine. This helps the gas engine with power needed to accelerate, climb hills etc. It is fine if this is registering - thats what its there for - to help out.

- When it is in regen (green bars), the motor generators are sending current back into the battery (recharging it). This may happen when you are braking, going down hills or just slowing down by letting foot off gas. This is also fine as you are capturing some of the energy you had in the battery versus just heating up the brakes. Later, when you use the IMA (and the Battery), you get some of this energy back as it helps the engine out - which saves gas.

- Avoiding the using brakes as much as is practical - and coasting instead, is beneficial. Every time you use the brakes you only get part (under 50%) of the energy sent back to the battery and you waste energy heating up the brake pads. If you plan ahead, you may not have to even stop at a light, let alone brake for it. This also helps avoid having to rev up the engine to get you going from zero mph back to what you were running at.

- Certainly, autostop saves fuel. Otherwise your vehicle would burn fuel just idling at the stop. This is not as efficient as avoiding the stop altogether though.

 

Here is yet another opinion, but has worked for me. I am always learning new things about how to get better FE, and my experience over the 5,400 miles I've driven the car has shown I keep doing better. The 10 tanks I've used since getting the car average is 46mpg (my wife killed the mpg on the first 3 tanks sitting at 38mpg), but my last 5 tank average is 51mpg, and my current tank is about 53mpg. I am in no way an expert on the HCHII, and am still trying to figure out how some of these super hypermilers get 70+mpg!

There are 2 forms of assist - ICE Assist and EV-Assist. The first is using gas, the second is not. Here is when each is used:

ICE Assist - When you are at 0 and accelerate from a light or stop sign, depending on your battery state of charge (SoC) you will see the white assist lights appear - any variation of 1 to 8 bars depending on how hard you are accelerating as well as the battery SoC. You are using gas at this point... the assist is increasing your torque to help accelerate, with the major portion of acceleration coming from the ICE. Also, you will see the assist lights appear if you accelerate say from 40 to 50 depending on how quickly you are trying to accelerate, or when you're going up an incline. ICE Assist can be a quick drain on your SoC.

You will hear 2 sides of a story around here 1) Accelerate quickly to your cruising speed then let off the gas and coast/cruise. This will use the ICE Assist to it's fullest to get you up to speed. 2) Accelerate gradually keeping your RPMs under 2,000 (1,500 if your good). I use the latter because I can keep the iFE above 40mpg while accelerating gradually. Plus if I see the next light turn red, I let off the gas and coast to the light without having to waste the gas getting up to the speed limit! I have tried #1 and the iFE sits at 5-10mpg and I can sit and watch my current mpg drop quickly.

EV-Assist - When you are at the speed limit or cruising speed and you can "switch" to EV mode (valves closed/ICE disengaged, iFE pegged at 100mpg, no fuel being used), you can use the assist lights to help maintain speed, or help reduce your deceleration. You will only be able to get up to 4 assist bars. If you try to go above 4 assist bars, the ICE will engage and you will be using fuel again and your iFE will drop. There are some circumstances where you can get a 5th assist bar while in EV mode, but you probably won't be able to do it under 55mph.

I do avoid using my brakes as much as possible. You get better battery regeneration if you let off the gas and see the green assist lights vs the same number of lights when pressing on the brakes. I am constantly watching the traffic lights ahead of me... if one turns red, I take my foot off the gas and coast to the light. 7 out of 10 times I never have to stop completely - I will get down to 15 or 30mph and coast in behind the car in front as they are accelerating from the now green light. Also, LEARN YOUR DRIVING ROUTE WELL. What I mean is I can guarantee I know when at least 4 lights are going to be red on my route. I know how I can beat them (by accelerating from 45 to 48), or know I don't need to get up to the speed limit because there is no way to make them, so why waste the gas. It's hard with some of the small street lights to know if they are going to turn on you, but major cross street lights are usually on a "less-variating" timer based on time of day and traffic. Nights and weekends don't always apply because they can be set for "first come-first serve traffic". I drive 7 miles each way to my regular job, and up to 25 miles to my side jobs. In my 7 mile commute I hit 4 stop signs and have 12 traffic lights to hit or miss. At the stop signs, I put my car in D2 when I'm at 10-12mph which will stop the engine from going into Auto Stop. Auto stop is good as long as you will be stopped for more than 6-10 seconds (this buffer is needed to make up for the fuel used when restarting the engine from Auto Stop). I have most of the lights timed pretty well. When I'm at work I have to get the mail at the post office so I drive about 3/4 mile each way to and from the post office. I then occasionally take a short 1-2 mile trip to get lunch. You'll hear a lot of people around here say "If you do short distances, you won't get good mpg". I think I'm doing pretty darn good for all my short distances, not to mention the slight hills and all the stop and start at the lights. You can too!

Search for my other posts where I have put in some helpful information. And also be sure to read the HCHII Bible - I mean Tarabell's HCHII writeup!

 

For the two schools of thought on acceleration portion, Tarabell, who wrote adapting hypermiling techniques to the HCHII did the tests and determined it is best to keep the RPM's as LOW AS POSSIBLE to maximize FE

 

They don't live in Sacramento... let alone any part of California

 

I think one of the HCH2 drivers with highest FE does live in CA, down the road from you - Kenny is at 64 something lifetime...

Tarabell, who wrote the great FE article on the HCH2 and blows away the EPA FE regularly, lives near LA I think.

Carl

 

[EV-Assist - When you are at the speed limit or cruising speed and you can "switch" to EV mode (valves closed/ICE disengaged, iFE pegged at 100mpg, no fuel being used), you can use the assist lights to help maintain speed, or help reduce your deceleration. You will only be able to get up to 4 assist bars. If you try to go above 4 assist bars, the ICE will engage and you will be using fuel again and your iFE will drop. There are some circumstances where you can get a 5th assist bar while in EV mode, but you probably won't be able to do it under 55mph.


Is there something you need to physically do to "switch" to this mode or does the car do it automatically???

Also, I am still a bit unclear -- are the assist bars good for fuel economy or bad???

 

[quote=GNiel9;138312Is there something you need to physically do to "switch" to this mode or does the car do it automatically???[/quote]

The car will do it automatically... when you do the right foot motion on the gas pedal. It's like flipping a switch with your foot. The accelerator is extremely sensitive. Even wearing a different pair of shoes can produce different results! Many have gotten used to this procedure while barefoot so you can fell what part of your foot is actually touching and applying pressure. You can read my short description on how to do it here: https://www.greenhybrid.com/discuss/...695#post131695 . The extended, in-depth detail version is in Tarabell's great writeup on the HCH.


It depends on how you use the assist bars. Many will say if you see assist bars, then you're using the electric assist which is saving gas that would be used by the ICE. Most use it for acceleration assistance and swear by keeping the SoC from 6-7 bars all the time to avoid forced regen which reduces FE. I hardly use the assist bars for acceleration because I do it slow and smooth. My SoC average is 5 bars. After I'm up to speed I use the EV-Assist for maintaining speed between lights which is where I feel you will get the most benefit from the electric portion of our Hybrid. When you're in EV-Assist mode, you're getting 100-150mpg using no fuel (valves are closed). Since the 20hp electric engine cannot propel the HCH by itself like the Prius's can when under 35, you have to switch on EV-Assist whenever you can to get the most out of your mileage around town. You do have to find the right balance of EV-Assist vs Regen time so you're not going into the SoC 4 bar range which will force a regen. If I do drop into forced regen, I still can get 60+ mpg to show on the iFE so it's not too much of an FE killer for me. Again, I have about 4 posts in the thread I linked above so read the whole thread.

 

Thank you, that is very helpful. Can you feel the difference when you "switch" into that EV Assist 100+ MPG mode?