Face it, if you've made the hybrid choice then you've discovered your inner nerd. Oh, sure, some of you may think "Me? A Nerd? Not bloody likely." Well, if you've ever finessed the throttle pedal to precipitate a bit more FE, well, then you're in the nerd club and there's no turning back. Accept it and be at peace.

So, to promote the care and nurturing of your inner nerd, I offer you some interesting technical facts on the advanced technology of the HCHII. Nearly all of the information below comes from the thorough and informative HCHII Factory Service Manual which, in addition to repair information, goes into remarkable depth to explain the key features of each system and how they work. Most HCHII systems are "electric only" versus conventional vehicles that require engine-driven alternators, pumps, compressors, vacuum, etc. to operate steering, A/C, brakes, and accessories.

Here are some highlights:


Integrated Motor Assist (IMA):

IMA motor alone is a 20 hp, 76 ft-lb torque, DC brushless type attached to the engine output shaft.

Combined with the output of the internal combustion engine (ICE), the IMA delivers 123 ft-lb of torque from 1000 – 2500 rpm.

Battery pack is comprised of twenty-two 7.2V Ni-MH battery cells for a total of 158.4V.

Battery pack has an ON/OFF switch (located in the trunk) that disconnects high voltage circuits for service, maintenance, or repairs.

Battery pack module includes an advanced DC-DC converter, AC inverter, electronic controller, and thermal management dedicated to the IMA system.

IMA assist is not available when outside temperature is extremely hot or extremely cold (battery temperatures are monitored and carefully controlled in order to avoid battery damage).

The IMA electric motor is used to start the engine. A back-up conventional starter operates only if the main battery pack voltage is too low, the outside temperature is very low, or if a fault is detected in the IMA system.

HCHII has no alternator. The DC-DC converter in the IMA battery system is used to charge the back-up battery and provide 12V accessory power.

The motor power, A/C compressor power, and DC-DC converter power cables are all enclosed in aluminum tubing that runs between the battery pack in the trunk and the engine compartment. Bright orange jacketing and connectors identify IMA system wiring.


Internal Combustion Engine (ICE):

Honda’s most advanced production powerplant to-date includes a 1.3-liter aluminum block and head with 3-stage i-VTEC and advanced low-mass, low-friction bearings, pistons, connecting rods, and chain-driven valve train.

The ICE alone develops 90 hp @ 6000 rpm, 90 ft-lb torque @ 4500 rpm, and achieves AT-PZEV emissions.

High temperature, plastic resin intake manifold is used for improved airflow and reduced weight.

Engine block has no separate exhaust manifold. Instead, the exhaust passages are integrated into the aluminum engine block.

The ignition system uses two spark plugs per cylinder and eight independent ignition coils.

Intake valves are 3-stage i-VTEC (low lift, high lift, pause)

Exhaust valves are 2-stage i-VTEC (normal lift, pause)

The valve “pause” stage occurs during vehicle deceleration or electric only mode. During valve "pause", the engine valves remain shut to reduce piston pumping losses (the energy spent to force air into and out of the cylinders) in order to maximize the amount of energy that can be captured in the IMA re-generation mode (battery charging).

Electric throttle (gas pedal) operates a servo motor on throttle body.

Cruise control uses electric throttle motor system (no separate cruise control actuator)

Fuel is cut off to the fuel injectors during deceleration over 1100 rpm.

Fuel cut off occurs anytime engine speed exceeds 6500 rpm.

Fuel is cut off anytime engine speed exceeds 4500 rpm while vehicle is stopped.

Fuel cut off limits are reduced when engine is cold.


Continuously Variable Transmission (CVT):

CVT ratios are electronically controlled and infinitely variable from 2.53:1 to 0.42:1

The CVT has no torque converter. A special electronically-controlled “start clutch” provides smooth transfer of engine power to the transmission input shaft.

If the CVT electronic control fails, the system automatically switches to a back-up hydraulic-control system to ensure vehicle drivability.

‘R’ will not engage over about 6 miles per hour forward speed.


Advanced Hydraulic Brake System (AHBS):

The Advanced Hydraulic Brake System (AHBS) is electrically boosted and does not rely on engine vacuum-assist as in conventional systems. The AHBS includes a servo-controlled master cylinder, power boost unit with motor and accumulator, brake pedal pressure, and brake pedal stroke sensors. The power boost unit supplies high-pressure fluid to the master cylinder when required for maximum braking power.

The anti-lock brake system (ABS) is a 4-channel system operating on each wheel independently. This system is in addition to the Advanced Hydraulic Brakes.

If the electric brake boost should fail, the driver is warned via an indicator light and warning buzzer. In this case, braking power may be reduced and the driver should take precautionary measures.


Electric Power Steering (EPS):

The electric power steering system has no hydraulics and does not rely on engine-driven pumps for operation. The system includes a steering assist motor, motor angle sensor, steering torque sensor, and an electronic control module.


Electric Air Conditioning Compressor:

A/C compressor is a twin chamber, dual compressor that is both engine belt-driven and electric motor powered. The A/C is designed to run purely off of battery power under certain conditions (such as auto idle stop). Either compressor will operate (or both simultaneously) depending on the driving conditions and climate control demand.


Vehicle Controller Network:

HCHII includes an advanced vehicle control bus network to operate accessories and to allow high-speed communication between the various onboard computers.

F-CAN (Fast Controller Area Network) shares information at 500 kbps for real-time communication between functions such as the airbag system (SRS), powertrain control module, CVT, IMA computer, electric power steering, anti-lock brakes, and advanced hydraulic brakes.

B-CAN (Body Controller Area Network) shares information at 33.3 kbps between secondary electronic control modules such as the multifunction integrated control unit, keyless immobilizer, and climate control.

Collision Detection signal unlocks doors when airbags are deployed.


So, the next time someone asks you "How do you like your hybrid?" you'll be able to answer with authority. As I said in another post, everything else on the road, from Hummer to S-Class, is pretty much a Model T.

 

Thanks for taking the time to post this info, Chris. You rock!

 

Good post, Chris. I am going to file this one! H

 

thanks. Do you own a technical manual? If so, I think u will be able to answer a lot of questions around here

 

Did you know that the Honda/Acura system tester does not have a "list faults from all modules" function? What this means is that if a Tech does not know what system module to look at for a problem, or looks at the wrong module and does not see a fault, they might not find what is really wrong with your car if you have a problem. This is what happened to me with my Autostop saga.

BTW, since the Autostop root problem with the HVAC controller was fixed, Avg. MPG is up 26%.

 

Great post. This'll be a good place to refer to any information I may want to confirm.

"Fuel cut off occurs anytime engine speed exceeds 6500 rpm."

Do you mean that is the redline, and that the car electronically doesn't allow it to rev higher, or do you literally mean fuel is cut off above that speed?

Orient Express wrote, "BTW, since the Autostop root problem with the HVAC controller was fixed, Avg. MPG is up 26%."

Good to hear about that. Autostops adds tremendously to mpg! Or maybe the fault also caused the previously lower mpg somehow too?

 

What you are saying Gary is, Honda is not keeping up with there own technology! That is a bit of a concern. H

 

Yes, yes, and...yes. 6500 rpm is the mechanical redline and the electronic limit for fuel delivery. To protect the engine from damage, the fuel injectors shut off if the engine speed exceeds 6500 rpm. When the revs come back down below 6500 rpm, the fuel system kicks in again. This method of over-rev protection is nearly universal among vehicles with computer-controlled fuel injection.

 

Sure about this, Chris?

"HCHII has no alternator. The DC-DC converter in the IMA battery system is used to charge the back-up battery and provide 12V accessory power."

Without having checked mine carefully, I thought Honda kept the alternator as a backup. Users have reported being able to drive for days with IMA non-functional, which I have interpreted as HV circuitry completely shut down. I guessed Honda's strategy was that the HCH should be drivable without any IMA at all.

As a sidenote, I think omitting the alternator, starter, mechanical AC compressor drive and all other backup systems for IMA will be the next step. There lies a great potential in further FE improvement - and cost reduction. I see no reason that any of the IMA components should be less reliable than their 12 V predecessors.

 

Very informative, thanks, Chris. Yes, I freely admit to being a nerd. Not sure if gearhead is equivalent to nerd in this context, but self-labelling works for me.