Very good observation. When the engine is charging the battery, it is consuming extra fuel to produce electricity for storage at the same time it is trying to accelerate the car. I would bet the best fuel economy would be had if you can manage to consistently isolate those two demands (acceleration vs. battery charging) from each other.

 

My take off varies depending on what is ahead of me and traffic conditions. I always attempt to give a moderate take off then let up for good FE or glide if possible. So far the tank I am on using this is at 52.9mpg and 327 miles. This will be my best tank so far if I keep it up. Never had a car be at half tank and over 300 miles before.

 

I find accelerating too slow, trying to keep the iFCD at 40mpg doesn't help much because you'll never get up to speed that way. Once you're at speed it's easy to stay at atleast 60mpg. I usually have some assit up to 30mph or so, but after that I can continue accelerating without it.

 

I think you guys are making this too complicated.
When I accelerate from a stop I *never* look at my assist LEDs, Fuel Consumption Display, tachometer, or the state of charge of my battery.

Yet I have the highest MPG of the all of the 2006 HCH2s in our database, 60.6 MPG.
My HCH1 had the second highest MPG in that database, 60.1 MPG.

When I accelerate from a stop I am a creeper.
I go as slowly as I can tolerate, especially if nobody is behind me.

Frequently if people are behind me I'll creep but put my turn signal on and change lanes as soon as the next lane opens up to let the people behind me pass.

If I'm taking off from a red light and there is a bus stop ahead on the right I'll even creep into the bus stop space to let the cars rush past, and then I'll pull back into the lane.

I'm ALWAYS thinking ahead about how I can conserve momentum and change my speed, up or down, as gradually as possible.

 

It sounds like he does the same technique I do, which is basically, a strong acceleration to get up to about half-assist or so, maybe a little more if I'm on an incline, then backing off the throttle as soon as the tach hits about ~2650 rpm. Above that point, efficiency seems to drop. The key that has helped me is when I start from a stop and need to go uphill. Rather than accelerating slow, then needing to accelerate while going up, which would send me well over 3000rpms, I accelerate harder at the beginning, sometimes even at full assist for a moment, then continuously back down on the throttle so that I can hold the ~2500 rpm range on the engine the whole climb.

Also, another thing to keep in mind is that if you are acclerating faster, and need to stop again very soon, this will end up being worse, as it will essentialyl increase your average speed (incurring a drag penalty) but not save any time (this would be the same though as accelerating slowly but to a faster top-speed to achieve the same average speed). However, if oyu are accelerating onto a freeway slowly vs swiftly, it shuold average out to nearly the same, so long as you are not at one extreme or the other (full throttle or absolutely minimal acceleration)

 

Slower acceleration is better.
If I'm on a level road and traffic permitting I'll use Assist up to about 30-35MPH, then accelerate @ about 60MPG. That lasts up to about 45MPH, which is fine if the speed limit is 45.

My last tank:



I traveled 935.1 miles but the FCD cheated me. I pumped 12.7 gallons up to the rim (Last fuel bar had just gone out) for 73.6MPG

This would not be obtainable in any way other than slower acceleration.

 

mmrmnhrm, I had the chance today to do some more driving. I love driving this car by the way! And I noticed that my tach was between 2500-2600 rpm when I would use my assist technique. I did noticed that if I used slightly less assist, just under 50%, the tach would be about 2000 rpm. I understand that there is a power curve for the ICE with a range of maximum power and there is a also relatively flat power curve for the IMA. What is the ideal range of rpm for power?

I do like trying to get better gas mileage. And I like trying a set of techniques for a whole tank so that I can compare the mpgs on a tank by tank basis. The hard part is waiting between fill ups! A tank has been lasting me about 16 days so far.

Mark

 

Meggert, I've got no idea what the ICE torque curve looks like, but if I remember my machines class (why it's called that in an EE program, I don't know), an electric motor's torque curve was a function of mag flux, which is dependent on current, so the more boost/regen involved, the greater the torque either direction. There might also be a limit on how quickly the IMA controller can switch between windings, so beyond a certain rpm, the IMA may become useless. There's quite a car following here in CTown, and while I'm sure the racing board I'm on could give me the dyno hookup, I'm not sure if we'd be able to get a realistic trace considering the CV transmission. No idea what the ideal rpm range for us is, I just based my accellerating style on the "what's the point if you can't give it more air" theory. That said, I plan on following the K&N filter thread closely A very simple mod for what may result in a respectable accelleration and overall mpg boost.

 

From what I ahve read, the combined torque peak is 1500rpm. When starting from a stop, RPMs seem to jump right up there and stay there. I'm not sure what the peak power curve is, but I do know that the assist works big time to prevent RPMs from exceeding 3000, even on steep freeway inclines it's rare to see as high as 4000 (which is quite good considering a lot of 1.8L cars I've been in rev as fast as that in a similar situation).

I believe someone did a pulse and glide experiment a while back and found around 2400rpms was the most efficient, as far as minimizing pumping losses, even when the battery became depleted and it was the engine alone.

It seems a cold-air intake system would be a benefit for people who do a lot of acceleration in that powerband, such as drivers with hills, as it should be able to increase the amount of power avialable within that "sweet spot" -- a much better alternative than raising the RPMs to a more inefficient range.

 

2400 seems high... I've been getting better than average mpg over the past couple of days by using foot instead of cruise, and my sweet spot seems to be right around 1500@48mph, and 1700@53mph.

And yes, I've gone ahead and done it. I've asked the racing crew if it's possible to separate the IMA torque from the ICE torque on a dyno, and if it's possible to even get accurate measurements with our CVTs.