No regen on downshift

Tranquility · 08-19-2006, 05:06 PM

I know this isn't a new topic because I've seen it mentioned in passing, but I'm curious what the logic might be behind it - 'cause it isn't making sense to me.

I can "force" regen after a downshift during decelleration by tapping the accelerator, but why wouldn't Honda want to take advantage of the regen opportunity that is there? Maybe the car would act quirky if we downshifted for added acceleration, such as up a hill, and got a momentary regen in the process? It doesn't seem like it'd be an issue. I'm generally slightly into the accelerator as I'm releasing the clutch if I'm downshifting for added power. So it would seem that there wouldn't be a quirky problem with hitting regen, then acceleration. Maybe I'm wrong though.

Just seems like it would be nice if we could just downshift through the gears, regenerating all the way, until we hit autostop speed. Tapping the accelerator, though brief, does put a surprising amount of hamper in the regen - downshifting process. I lose a lot of regen opportunity. Not to mention it's just combersome.

Thoughts?

Rick · 08-19-2006, 06:23 PM

I noticed on mine if you took too long to down shift it would not regen unless you blipped the gas, but it did regen normally with a downshift. You might try different down shifting techniques and you might get a different result.... and maybe the software in your 06 behaves differently than what was in my 02.

kapps · 08-19-2006, 09:59 PM

It will regen after a downshift if your not on the brakes while your downshifting. This means serious loads on the syncros if you don't double clutch. Fortunately, the Insight is very easy to double clutch if you learn how.

Tranquility · 08-19-2006, 10:23 PM

It may be a thing with the new control modules, I don't know. If I downshift I lose regen. Maybe I'm waiting too long? I tried downshifting from 5th right into 3rd at 60 mph. Regen kicked in and remained on, but only until about 30 mph. I did it again, this time with the brake on, forcing full regen, and it still kicked out at about 30 mph - far above the ~1100 rpm regen kickout. I'll keep playing with it. Shift into third, and then into second at maybe 40 or 35 mph. Maybe it will pick up regen again if it has a higher potential. Maybe the new control modules are just protecting the batteries against a too rapid recharge and I really shouldn't be trying to get around it?

I know coasting down in 5th, then to 4th, is useless. There is never any regen after the downshift unless I tap the accelerator. It's too bad. A nice long coast down through the gears in fuel cut and with regen, then right into auto stop would seem to be optimal.

Does it behave this way for you others with the late models?

Dougie · 08-20-2006, 12:51 PM

I think the best thing to do is let the charging system do what it wants to without trying to force it. I usually just stay in whatever gear I'm in, say 4th or 5th, and keep the clutch engaged until the engine is down to 600 rpm or so--below its normal idle point. That way the fuel is shut off during the whole coast down time. I bet you use more gas downshifting than you save by getting that extra second or so of charging...

Tranquility · 08-20-2006, 08:47 PM

I got to play around with downshifting a little bit today. It seems I'm just not being agressive enough to kick in the regen. If I downshift each gear sooner I'll get the regen. I think 4th is too close of a ratio to 5th to kick in regen if the car is allowed to coast down any in 5th.

I too am cautious about persuing a regen where the car normally wont. But then I'm looking at it as maybe I'm just not driving how Honda want's me to drive it. Perhaps a downshift that is a little more agressive than I was doing is the best way. If the computer thinks the batteries shouldn't be getting a regen, be it because of temp or SoC, it would seem no amount of aggressive downshift would initiate regen. I'm still using every gear; not skipping any. I'm just staying in each gear for a shorter period.

I'll play with it some more and see what I come up with. One thing I don't like about running the rpms down in fifth is that regen kicks out when engine rpms reach idle rpm: ~30mph. And I'm learing that regen is soo important in stop and go. I've been doing all city driving the past couple days and I'm maintaining ~60 mpg in the city. The FCD is bouncing between about 58 and 61 with about 30 miles of stop and go. I think if I can get a good regen - accel routing going I might be able to pick that number up at least a little. Who knows! It's fun experimenting and learning even if I don't improve the mileage.

kapps · 08-21-2006, 02:16 PM

Yeah, you're learning. In traffic, regen is VERY important to keeping mileage up.

Dougie, your not in fuel cut once you get below 1k rpm. Even if you don't see the mileage bar drop, be sure, there is fuel going to the engine so that it won't stall. That's why I tend to do a 5-3 downshift (double clutched, of course) so when regen dies in 3rd at 20 mph, I can go right into auto stop.

Dougie · 08-21-2006, 11:18 PM

You're probably right; the engine will try to keep itself at idle speed. This is particularly noticeable in second gear, which will "drive" along just fine with no gas pedal at all...

ethicalpaul · 08-23-2006, 02:28 PM

Hmm, I don't see regen as the key to good mileage.

I see it far behind, real far behind low maximum speed, and also behind the practice of not accelerating needlessly. In my opinion, regen is mostly a parlor trick, like idle stop.

Also Kapps, are you saying the proper idle speed of our Insights is 1K?

Tranquility · 08-23-2006, 05:19 PM

I think idle stop is useful. It hard to argue against the efficiency of an ICE that isn't running.

The IMA does well what it should - allow a small efficient ICE without the poor accelleration of same.

It would be interesting to see in town mileage differences with and without the IMA - see if it's hurting or helping. Though I'm still working on it, I'm having trouble getting decent regenerative braking which would seem essential for the IMA to be a benefit to fuel economy over and above allowing a smaller ICE.

Even if it detracts from the best possible mileage, I don't know if I would like the car too much without the IMA. Mileage is awesome; getting no response from the accellerator isn't.