I think I could get much better highway mileage by disabling IMA on the '06 HCH, though I'd have no idea how to go about doing that. My problem is how the car uses regeneration even when the accelerator pedal is pressed; it really hurts mileage and when driving on the highway a while I'd rather just turn it off and rely on the gas engine. Pressing the gas pedal harder eliminates it but also runs more gas to the engine so it's pointless.

I'd like to be able to disable IMA (both motor and regeneration) after getting on the highway, re-enabling it when getting off or slowing down or going downhill, etc. A simple switch.

Does anyone think they can figure out how to do this?

Hi CGameProgrammer:

___This should get you started …

FAS, it works!

___Good Luck

___Wayne R. Gerdes

But I'm not trying to coast; that would slow me down. When maintaining a fixed speed, foot lightly resting on the accelerator, the car often activates regeneration. It turns it off if you accelerate or just press harder on the gas pedal, but that wastes gas. When staying at a steady speed, it turns regeneration on and lowers FE.

I guess you've never test-driven an '06 HCH. The car disables IMA when the battery is cold, and it disables regeneration specifically when the battery is 100% full, but only 100%, not even 90%. And it's never been 100% full except when I went down a 4000' gradual slope.

It only disables constant regeneration at 100%!? That's quite ridiculous, I know the '03 model goes to constant-regen at 40%-50% charge, but doing so at 90% charge is absurd. (this actually comes up for me every day as I have an 850' hill climb in my commute with several stop signs on it)

Anyway, this is yet another reason I wish I understood enough about electrical engineering to implement the MIMA system from the Insight on the HCH...

The regeneration level decreases as battery level goes up, but depending on how light your foot is on the gas pedal, it still often uses 1-2 bars of regeneration at a high battery level. Maybe not 90%, come to think of it... maybe that's only when coasting... but I know, even at 50% battery, it still uses regeneration when the gas pedal is pressed and it's annoying.

I may try experimenting with "S" mode. From very brief tests on regular roads, it seems to use alot of regeneration but very little assist, so maybe I can use it to accelerate onto the highway without using too much assist, so I won't be hurt with the regeneration later... I'll see.

I would hope/guess that Honda's engineers would have a good reason for this, possibly the battery will last longer if fully charged. Also, you are simply storing energy that will be used later. I'm probably naive, but I would think if Honda could eak out a couple of more miles/gallon by disabling it at speed on the highway, they would have. I barely notice it on the highway, seems like it regeration occasionally comes on for a few minutes, but is mostly off, unless the battery charge gets low from a lot of city driving.

CGame, are you SURE the regen at hwy speeds lowers the real-time MPG? Because on the 2004 manual tranny HCH it does not. At least not noticably on the real-time meter. Do you actually see the real-time meter go lower when it goes to regen at hwy speeds?

I'd be surprised if a single bar of regen has a measurable effect on tank mileage based on my measurements of its effect on coasting distances, but it would be interesting to find out for sure. The manual IMA mod looks very interesting, but I'm not sure how much work would be required to adapt it to the HCH.

Well since both regen and mileage are dependent on gas pedal pressure, it's hard to measure the exact difference since any any given time either regen is on or it's off, I can never toggle it while keeping everything else constant. But when I've driven on the highway without regen, I definitely appear to get higher mileage than with it on, and that's logical, isn't it? I can definitely feel when regeneration is on, even a little. It's alot more enjoyable when the car just glides.

But guess what? I figured out a way around it using 'S' mode! I'll post more about it when I have a chance to collect more data, but with S it's easy to accelerate using just a high-revving ICE and little to no assist. I was able to drive on the highway at 80 miles per hour with a completely full battery; when I got to the exit, the friction brakes were mostly used with barely any regeneration since the battery was full.

Unfortunately I don't have very useful MPG figures. I had 14 miles of 34 mpg on the trip meter when I began a 20-mile highway trip that brought it to 41 mpg going mostly 80 miles per hour (some traffic made it 70-80). But that had a bunch of downhills. On the way back, with a reset trip meter, I got 40 mpg from 0mph to 0mph, but not only was it mostly uphill but there was a headwind... weather.com says 12 miles per hour but it felt like more... anyway hopefully sometime I can do a more fair test and compare the two driving strategies.

Clearly S is less fuel-efficient in the short term but over a decent-length highway drive like the one I did, it definitely helped alot.

Hi CGameProgrammer:

___You simply asked for a way to disable IMA regen and Assist. I showed you a way. If the BCM activated Forced Charge at steady cruise, your SoC is more then likely at a level where the BCM has deemed a Forced Charge necessary. Steady state cruise with a high SoC has never given a Forced Charge to any IMA I have ever driven? A low SoC can however.

___I am very interested in your S-Mode ops however. Accelerating w/out assist is what I have asked of the other HCH-II owners with little to no success.

___Good Luck

___Wayne R. Gerdes