Yes, I know the 2006 HCH can go EV only.

The virtue of the IMA is it's simplicity. Allowing it to go into an EV mode would seem like a simple mod.

You have a crankshaft with gas engine > electric assist > transmission (or so I think). Why not add a simple clutch between the ICE and the electric assist? In EV mode, the ICE is disengaged.

I would not necessarily expect the Honda EV mode to be as robust as the Prius EV mode, but it would still be a great improvement for many drivers such as myself. Just allow EV at sub-10mph stop-and-go traffic jams. Also allow it for leaving the driveway getting up to 30-40mph. I realize it would require more batteries, but regenerative braking has improved.

If I understand the IMA concept correctly, the assist is centered around an efficient ICE. Just allow the ICE to work mainly at a cruise and reduce the low-speed ICE usage. The same concept would apply in a fuel cell vehicle with an IMA.

This enhanced IMA design would allow the use of a 5-speed. Automatic transmissions have improved a lot over the last thirty years, but it still does not seem like they match a standard tranmission's efficiency.

61.5mpg lifetime - 82mpg in recent months

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"fanatic" is what the lazy call the dedicated

You'd need a separate starter on the engine to do it. Either that or two IMA's with a clutch between them. It's doable; mainly just a matter of economics. The reason Honda chose IMA rather than the Prius' more complex but theoretically superior design was cost. There's also the issue of insufficient engine bay room for a second clutch and/or IMA thanks to the transverse layout, but there could be ways to work around that if you had a good enough reason to, for example using a VR4 or V-4 layout to shorten the width of the ICE.

The bottom line is simply the transition from EV to ICE mode. In the current setup, since the ICE is always spinning, it's always ready to run. Just turn on the fuel injectors and you're off to the races. With a fully disengaged engine, you need a way to spin it up to the proper speed then rev-match it and engage to the EV drivetrain. Honda already claims the losses from running with the intake and exhaust valves are 90% lower than the old design where the valves were not disengaged. This implies the ICE loss is now extremely small since you're generating no manifold vacuum and doing no exhuast pumping. The force needed to compress the air that's in the cylinder already is largely made up on the downstroke.

Learned something - I did not realize Honda released the valves to reduce the load on the ICE.

61.5mpg lifetime - 82mpg in recent months

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"fanatic" is what the lazy call the dedicated

The Prius folks are laughing at our IMA whining now, I'm sure. I'd have to agree that it would be great to have EV-only mode in a traffic jam (i.e. from a stop, something the HCH II doesn't do). I don't even mind having the ICE take me up to speed (30-40 miles per hour); that can be done relatively efficiently. Nothing burns me worse, though, than wasting a perfectly good autostop to travel a few car lengths in heavy traffic.

Speaking of that (stop and go traffic) I was in some of that yesterday when I was leaving the Cardinals/Seahawks football game.

I managed to run the hybrid battery in my manual tranny HCH apparently ALL THE WAY DOWN, or just about all the way.

I had been turning the car off to conserve gas rather than let it run, because my battery level was below AutoStop level, and one time, after I had turned it off at a red light, the car would not immediately restart.

I felt it act like maybe it was trying to use the REAL starter motor, instead of the hybrid starter generator, but it would not really turn the real starter over completely either. It was almost like the computer was confused as to which start method to use.
After about two short tries, it finally restarted, and I did not kill it again until I had some charge bars back in place !!

Anyway, that is a long-winded way of agreeing with Robby about wasting good autostops. Too bad the new IMA system will not allow stop-and-go EV mode, which I think we all agree would be very nice to have.

That's new for 2006 only.. the pre 2006 did not disengage the valvetrain.

so are you guys saying if i'm stuck in traffic going like 20 km/h tops then the civic's ICE will always run right? While the prius would be only EV mode, does this account for the prius I as well? I thought when honda meant "can run on ev alone" is for that kind of situation.

i got around 20 km a liter when i drove a civic 5 spd using advanced hypermiler techniques
and now I drive a salvage nwh20 prius that gets almost to 25 km/l with 192,000 km to date.

philmcneal,

I had the misfortune tonight of spending 45 minutes in bumper-to-bumper traffic in my Insight. After awhile, the autostop no longer works, probably because the catalytic converter has cooled off. Even worse, this is when a recal is most likely to happen and it did. Over 360 miles of travel, my mpg dropped from 75.2 to 73.0.

Realistically, I probably would have taken a hit even with an EV mode, but it would have been softened in this extreme case.

61.5mpg lifetime - 82mpg in recent months

Best Run >
www.cleanmpg.com

"fanatic" is what the lazy call the dedicated

No, the thread is about the physically turning of the ICE's crankshaft, not the "running" of the engine, i.e. consumption of fuel. The Civic's engine always turns when the vehicle is in motion, regardless of if there is any fuel injection or not. They did realize this inhibited FE to a certain extent and so new for 2006, at speeds between 10-30mph (16-48km/h) the 3-stage VTEC lets the valvetrain freewheel, thus cutting virtually 100% of the loss from cam resistance against the valvesprings and more importantly, eliminates pumping losses. That's almost as good as the engine not turning at all.

So then, what keeps the engine spinning? After a prolonged low-speed cruise, could it conceivably run out of rotational momentum and require reengagement of the valvetrain and fuel injection? I hope this doesn't telegraph my utter ignorance of car mechanics. I'm more of a people mechanic.