Ok, the 'fight' has been started, but lets move it to its own topic and quit hounding the discussion of the HCH passing the Prius in FE. I believe the question that started the discussion was weither Honda's IMA system was scalable and wether or not Honda could improve on its city milage enough to make it competition for the Prius in that arena.

1: Is the Honda System Scalable?

YES! The IMA system is very scalable. With a larger Flywheel motor and the addition of Electric AWD the IMA system could generate more than enough Horsepower to propel an H2 (or small house, your pick ) down the highway, and plenty of torque to pull that boat. The problem with scaling the IMA system in such a way is how to control it. With an automatic this is easy enough, when starting let the rear wheels do all the work, if the pedal's at the floor start the I.C.E. up and let 'er rip. With a MT the problem becomes much more complicated for maximising FE. They COULD have an EV mode for those in city crawls, perhaps an EV gear setting? But making it useful and controllable for the 'idiot' masses will prove to be a big challenge for them and I for one, am interested to see how they solve it. They do however HAVE TO solve it before they can scale it in such a way. Following Honda's philosophy in car design, leaving out a MT would be heressy.

2: Can Honda match or beat the HSD in city?

YES! Honda can! The next generation IMA will likely have a more intelegent autostop function that will allow it to shut the engine down at far faster speeds and far more intelligently. It will also likely have a VCM system that will shut down two of the four cylinders and use the flywheel motor to balance out the torque (like in the Insight). Add in direct injection allowing 65:1 lean burn...thats very little fuel needed to run the engine..but also little power. A slippery COD will likely follow suit to allow for these crazy low fuel consumptions. Honda will also eventually figure out the EV only issue from above. Adding Electric AWD is the obvious answer, but controlling it AND following Honda's car philisophy poses a major challenge, but it can be done.


This of course in no way faults Toyota; Toyota is an amazing company with a bright future. I am simply atempting to put to rest the 'rumours' that Honda is behind and its hybrid system will die out. Just drive what you drive cuz you want to drive it. Toyota is going in a direction that will get you from point A to point B without any notice/events...its movement has been described as a 'sterile' driving experence. Now dont take this as a bad thing at all, many people are searching for this. Honda has decided to keep the driver and the drivers experience at the forefront of there products. Let the driver has as much control and feel as posible. It is this fact that has kept there system 'behind'. They're working on it, and when they figure it out...it'll be fun as heck to drive.

Cheers, Steven

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lakedude's 2c

The Toyota is nothing short of amazing. The HSD is going to be hard to beat for the 80% of drivers that prefer an automatic or CVT style transmission.

Honda's technology is better suited for a manual transmission. In fact a manual is impossible with HSD as the heart of HSD is the split power device which is a CVT.

Because of advanced features like pumping the hot coolent into an insulated container and the Atkinson cycle engine IMO Toyota is ahead. However Honda could improve their hybrids to include such features and still be using IMA technology.

IMO IMA is no better or worse than HSD but also IMO Toyota is a little ahead (currently) with the Prius. Still personally I prefer a manual so that rules the Toyota and HSD out for me.

HSD engine: 13.5 : 1 expansion ratio (because it can use Atkinson cycle).
IMA engine: 10.8 : 1 expansion ratio (because it can't use Atkinson cycle).

Which is the major reason why...

HSD engine: 36% peak thermal efficiency
IMA engine: 30% peak thermal efficiency

HSD engine can always run at full throttle and hence close to peak efficiency.
IMA engine is almost always throttled during normal driving, so running at substantially less than peak efficiency.

So HSD can extract at least 20% more energy from each gallon of fuel than IMA, hence it is the more advanced.

What can Honda do to catch up? Leapfrog Toyota and go series hybrid with a proper Atkinson cycle engine. (not simulated Atkinson cycle as used in the Prius engine)

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"They COULD have an EV mode for those in city crawls, perhaps an EV gear setting?"

It's my understanding that IMA can't have EV mode. The gas engine HAS to propel the car (if it doesn't spin, you don't go) with the electric motor on the same driveshaft as the gas engine, thus an 'assist' hybrid.

How will Honda do an EV mode when they currently don't have a large enough battery/motor combo, no way to make electricity on the fly (only regen), and no separate drive from the electric motor?

IMHO, it makes HSD clearly superior.

'04 Seaside Pearl #7. Fumoto oil drain, mudflaps, rear bumper scuff protector & rear warn system, compass mirror, EV mode button, 8" subwoofer in right rear cubby & 6" subs under seats, power lumbar in the front seats, Coastaletech hitch w/ Aspen bike/snowboard rack. iPod2car, 2 amps, Alpine component speakers, and DVD video, solid 47 MPG @ 70000 miles.

You assume they can't get a better battery/motor combo and they couldn't use clutches to disengage the motor from the engine. It will be interesting to see what the next gen IMA system will be like. Considering the disadvantage IMA has over HSD you would think it would be doing worse in a head to head comparason of mpg.

If you look at the civic hybrid with a pretty much first gen IMA system and compare it to the first gen prius system it seems honda isn't doing too bad.

One thing that will be interesting is to see what honda has planned for IMA in the future. Maybe the next gen civic hybrid will give us an idea.

My hydroponics experiment

You ever notice how hard it is to lip read cartoon characters?
"Crazy is what the sane call Delta Flyer"

It seems like one clear way that Honda could improve the IMA system while still keeping a single drive-shaft is to have a clutch positioned between the IMA and a electric motor that could disconnect the engine when crusing around at slow speeds or coasting, so that it would not be a source of friction/resistance. For coasting down hills, that clutch could be released to allow the regen alone to control the speed of the car, and collect a lot more energy in the process without wasting it with engine friction. If the IMA alone were not enough to control speed safely (such as the battery being full), the engine coudl be re-engaged automatically.

While this type of EV mode woudl not be as powerful as the prius, it would allow a driver in stop-and-go traffic to roll along at slow speeds.

Another thing would be to allow more control, such as a way to manually force an "auto-stop" without using the ignition to restart. Another thing would be the ability to adjust the aggressiveness of the assist logic, such as favoring heavy assist (for a short, steep incline coming up) or disabling all but minimal assist (long gradual climb). There could be a few "modes" that the driver could select for those different scenarios. A cruise-control that woudl automatically lock in a certain gas throttle level, then vary assist/regen alone to maintain steady speed would also help FE.

Doing this alone would probably increase MPG numbers by a noticable amount.

My hydroponics experiment

You ever notice how hard it is to lip read cartoon characters?
"Crazy is what the sane call Delta Flyer"

Intriguing and genius idea. With advances in the Nox trap, perhaps lock it into lean burn for extended periods and have the IMA control speed more, either in cruise or not. I think a mode option like you say would be best for driver control and FE maximization, and those that dont want to mess with it doent have to.

You also leave out the possibility for an electric AWD system, the motors that drive the rear wheels could word to gain electricity while moving and to move the vehicle in an electric only mode.

Hidden Views Photography

"You also leave out the possibility for an electric AWD system, the motors that drive the rear wheels could word to gain electricity while moving and to move the vehicle in an electric only mode."

You mean like the Highlander Hybrid? The current IMA is not set up to do EV mode...but a future system similar to HSD would enable EV mode.

Also the clutch thing seems to complicate things (installing a clutch to "disengage" the engine from the electric motor, thus enabling EV mode). HSD is just so simple in design and function. No torque converters, no clutches, all gears/parts constantly meshing, no shifting. Smooth and efficient power distribution. Now that's what innovation is all about.

'04 Seaside Pearl #7. Fumoto oil drain, mudflaps, rear bumper scuff protector & rear warn system, compass mirror, EV mode button, 8" subwoofer in right rear cubby & 6" subs under seats, power lumbar in the front seats, Coastaletech hitch w/ Aspen bike/snowboard rack. iPod2car, 2 amps, Alpine component speakers, and DVD video, solid 47 MPG @ 70000 miles.

I doubt Honda would ever adopt a powesplit device (PSD) - purely because it would be an admission of technical inferiority to Toyota. In terms of patents too, while the PSD itselft is not the problem (it was invented decades ago, and not by Toyota) there would be an issue in that Toyota owns the IP relating to its integration with two electric motors. Ford realised this setup was best for them, so just coughed up the royalties - but Honda would rather eat dirt than do that!

So I think the next step for Honda is not IMA or HSD, but whatever the next generation is after both of these.

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