Lakedude,

I would like to challenge you about number 8). I keep reading posts that recommend slow acceleration, or driving slowly up hills, to save fuel. It is true that the instantaneous milage will be higher, the slower you accelerate. But the average milage might not.

What matters most for fuel economy is the efficiency of the engine, or rather of the whole drivetrain. For most ICEs, efficency is highest at full throttle. So, when accelerating hard on a highway ramp, the fuel consumption will of course be high, but the fuel will be best used to take the car up to speed. As long as you can use the speed after the acceleration, average fuel economy will not be affected, or might even be higher. Only if you have to brake right after the acceleration, will your fuel economy be reduced.

This is also the reason why a pulse and glide technique can save fuel. The engine will run less, but with more open throttle - increasing efficiency.

Also important for the fuel consumption is to keep the throttle steady. Whenever the position changes, the control unit takes some time to adapt, and often also injects some extra fuel, thus reducing economy. Rapid changes of throttle position waste fuel even more. The fuel-saving features of the Civic hybrid, such as the adjustable valve timing and the possibility to turn of one or several cylinders, probably also requires a steady load to work optimally. Steady throttle position would be number 8 on my list.

Please comment. I will try to back this up with some testing, when my car arrives.

Regards,
Rolf

 

One variable that complicates the "how fast to accelerate" question in hybrids is the fact that if a driver accelerates at a more open throttle positoin onto freeway onramps etc, followed by long steady cruising, they may deplete the battery enough to require direct charging off the engine, which could hurt the average. Very gradual acceleration all the time would tend to minimize IMA use. In city driving though, where there are necessary stops, this extra overhead would be "paid back" by regenerative braking sooner or later.

 

I want to challenge this theory as well. A lot of people argue that charging the battery while crusing on the highway, hurts milage. I can agree that WHEN it is charging, milage will go down. But look at it this way, when you add load to an engine that is already in a low load condition (=mediocre efficency), you will get the extra power at very high efficiency. Meaning, you will get a lot of extra energy, by spending only a little extra fuel, since a lot of fuel is already being spent at just keeping the engine turning.

The energy is stored in the battery for use later, when needed better. You will of course not get it all back, the overall efficency for power generation, storing in the battery, and then returned to the IMA, is probably less than 80%.

I admit that one weak point in this argumentation is that the Civic hybrid engine is not a normal ICE, it has a lot of tricks, such as being able to shut down cylinders, close valves completely, adjust valve timing, and firing the double spark plugs in sequence.

But still, I wouldn't be too worried about charging the battery when cruising on the highway, unless I knew that I was approaching an extremely steep and long downhill slope, after which the battery would anyway be completely charged.

Again, I don't have personal experience of driving a hybrid, yet. Please tell me that I'm wrong, and why.

 

RGX

Acceleration is a much debated topic. I personally take off a lot quicker than most of the other hypermilers but we all agree that WOT is NOT the way to get the best mileage. I'm sorry I lack the understanding to explain why mild acceleration is more efficient. Perhaps WOT would be fine if you still hit your shift points? In other words if you shifted as soon as the next gear would be just above idle? While I might not be able to tell you why WOT does not get the best mileage I can tell you that we have tried many combinations and WOT is not the answer. We have yet to agree on what is the answer but WOT is not it.

An engine sucks in a certain volume of air every time it goes around while it is running. A certain volume of gas must be added to the air. If you add too much gas the engine will run rich and if you add too little the engine will run lean. Because of the roughly fixed ratio of air and gas, the way to burn the least gas is to have the engine turn around as few times as possible thereby sucking in less air and burning less gas. The way you do that is to keep the car in as high of a gear as you can.

 

I agree 100%! To try and sum it up and expalin what LakeDude was trying to explian: Basically anytime you accelarate you are using lots of fuel and getting poor mileage. If you accelarate slowly you are using lots of fuel for a longer period of time while you are getting up to speed. However, if you accelarate somewhat faster, not going at WOT, you are burning even more fuel but for a shorter period of time. The differance in fuel consumed between accelarating with little throttle and more throttle is not as not nearly as bad as the length of time use up the fuel. If I explained that correctly.

 

Ok I just broke 80 calculated my last tank for the first time but.......

It doesn't count because it is clearly a fill mistake. Calculated was 80.1 but displayed was only 77.5. Displayed is normally higher than calculated so something is fishy.

Which really sucks because that likely means I'll pay the price next tank and so far the next tank is at 87.8displayed!!!!! I love warmer weather! The really cool thing is that the 87.8 (or was that 88.7?) was cruising by the RTP (Round Trip Point) so it is totally legit.

If I get high eighties displayed and under eighty calculated I'm going to be so steamed.

Chances are it will cool off or something else will ruin the tank but OMG high eighties dispalyed!!!!! Looks like it time to charge the camera batts.....I feel sorry for anyone behind me, they are getting no slack if I'm on a record pace.

Who can hit 80 first (for real)?

 

Lakedude, congrats! That's quite an accomplishment!

I have a question regarding FAS (for any hypermilers out there!). I made a true effort to research this procedure using the advanced search. I read through many posts, and tried (unsuccessfully) to view some videos on the process, but it's all confusing! Seems there are significant differences between HCH I and HCH II ... there are also differences between MT and CVT. Can anyone tell me how to do FAS in my HCH II? I'm looking for a simple instruction. What speed to do it at... instructions on how to initiate the procedure (turn key off... wait 2 seconds... return key to position 2?)... how to restart the ICE ( do I just step on the gas to restart?)... ways to avoid damage to the CVT... etc., etc.

I have read and fully understand ALL of the safety warnings regarding FAS. I'll only use it on desolate roads! Thanks for any info you can provide... or sources you can refer me to!

 

Thanks,

Sorry I can only tell you about FASing a MT car. I really don't suggest you do it in a belt and pulley CVT based hybrid. If you choose to anyway....

Check out HG-2004's technique:

https://www.greenhybrid.com/discuss/...72.html?page=1

and X's detailed advice:

https://www.greenhybrid.com/discuss/...77.html?page=1

 

Those are two of the threads I had read through... but none of the posts relate to the HCH II. Has anyone perfected the FAS technique in an '06? I'd love to try it, if it isn't going to mess anything up on my new car!

 

Perhaps you will be the next generation experimental hypermiler. Give us "old timers" a run for our money.

The HCH 2 should be similar to the CVT HCH 1 no?