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Servicing Hybrids: What Your Shop Needs to KnowPosted 6/11/2009
Hybrid models are constantly changing.
This December the ACDC Honda Insight will be 10 years old. That is old by most standards for a car, let alone a hybrid car. I have been actively involved with hybrids for a decade. You may have lots of experience with hybrids or none at all but they are here, all 1.5 million of them in North America and they are not going away. Let's examine the differences that hybrids bring to the eight certification exams ASE lists on its Web site. The eight certification exams are Engine Repair, Automatic Transmission/ Transaxle, Manual Drive Train and Axles, Suspension and Steering, Brakes, Electrical/Electronic Systems, Heating and Air Conditioning and Engine Performance. We will take them in order and see what hybridization adds to each category. Engine repair
All original equipment manufacturer (OEM) hybrids sold in the United States have a gasoline internal combustion engine (ICE) but that will change. Diesels, CNG, LNG, ethanol (most any liquid fuel) will find their way into a cylinder but for now it is petroleum. Look for late intake valve timing (LIVT), a modified Atkinson cycle design in some Toyota, Lexus, General Motors Corp. and Ford Motor Co. vehicles. Some hybrid electric vehicles (HEV) use 0-20 oil. It was installed for fuel savings and lots of low-friction tooling is built into the ICE to remove friction. The starters are three-phase AC brushless motors with some hybrids also having a 12-volt starter as a backup. The 36-volt belt-alternator-starter (BAS) system uses brushes but the rest don't. Overfilling the crankcase with oil can result in a no start, driveability problems and poor fuel economy. Perfection is the rule. GM 2 mode systems use a V4 mode in their V8 ICE, and Honda shuts down all of its cylinders during coasting and braking in the new Insight and current Civic HEV. Timing belts are being replaced with chains, and belts of all types are losing their place in line. The new HS250h Lexus and 2010 Prius are beltless. Even the ICE water pump is driven with an electric motor. The internal combustion engine is not going away but it is being used for what it was designed for - moving a wheeled vehicle down the road. Electric motors can do the rest. Automatic transmissions (ATs)/Transaxle
There are three types of transmissions used in hybrids - two continuously variable transmissions or CVTs and the traditional automatic. The Honda Accord Hybrid (2005-2007) used a five-speed automatic with torque converter but Honda had to add an electric motor to pump the fluid so that the AT is alive during idle stop (this is the time when the ICE is off and the car is on). The Saturn hybrids and Malibu HEV also use a convention AT, also with a 12-volt pump. Honda only provides hybrids with belt and pulley type of CVTs currently. They do not use a torque converter but instead have a start-clutch that allows the engine to run and the CVT to be engaged but not move the car as the output shaft can be disengaged by the start-clutch. Be cautious on this CVT as any contamination of dirt or sand can break the steel belt. Once that happens, the CVT is economically totaled. The warranty is 36 months or 36,000 miles, so be kind when servicing this CVT. The most popular and unusual CVT is a planetary system pioneered by Toyota in its 1998 Prius first sold in Japan. This design is similar to the Ford CVT used in the Escape and Fusion (Mercury and Mazda have clones). Nissan uses the Camry HEV (hybrid electric vehicle) system. The CVT with a planetary set or power split device is deserving of your attention. GM also uses three planetary gear sets and two electric motors in its two-mode CVT automatic. Manual drive train and axles Hybrids have axles and that hasn't changed much. If you bought the first hybrid sold in the United States, it was a stick shift (2000 Honda Insight). The model year (M/Y) 2003 Civic HEV was sold with a CVT or five-speed stick. One hybrid feature was a first gear switch that gave a command to "Start your engines." It was really only one engine, so when you shifted out of neutral into gear during idle stop, the ICE would fire up. Other than that, in 2006 we saw the last original Insight roll off of the assembly line and manual transmissions were gone from the hybrid world. Suspension and steering
The suspension systems just need to be sprung a bit stiffer as hybridizing a gas car adds weight. For example, the Gen I Civic HEV has thicker springs and damping is modified as well. Steering, of course, is electric - which means no pump, lines or hydraulic fluid. Some early GM hybrid trucks used an electric-driven pump but not anymore. Alignments are still done the same way but if you replace the power steering (PS) computer, rack or column, make sure your scan tool can reset the torque sensor. If not, the electronic power steering (EPS) light will illuminate and you will not have assist. Once you get the hang of electric-powered steering, you will most likely feel the way I do. It is a much simpler and easier system to work with than what we had in the old days. OEM tires are designated as energy efficient or having "low rolling resistance." If changing from factory tires, make sure the customer understands it may affect the mpg in a negative way. Brakes
Brakes are the same on the wheel end but how and when the fluid gets there is a new world. This is a simple explanation but should help you get the idea. The master cylinder still produces pressure but added to it is a brake simulator and a pressure transducer. The simulator is there to give your foot the proper feel. The transducer sends a signal to the brake ECU. A "G," Yaw, stroke, VSS and other sensors all report to the brake-by-wire ECU. This in turn steps on the brake for you. This is done by using an advanced system, similar to an antilock braking system (ABS), that can slowly apply each individual wheel brake. As the driver requests braking, the ECU delivers a combination of regenerative braking (all electric) and hydraulic. In ABS mode, it is pure hydraulic. In an emergency, it resorts to a conventional system. This is a big subject and will require more training. Electrical/electronic systems A new word - "mechatronics" - was coined to describe a mechanical part that needs a sophisticated electrical control to work. Sounds like a hybrid car to me. Mecha_tronics, of course, is where a lot of changes have taken place, not the least of which is the high-voltage systems in the car. When the first hybrid came to America, it sported 144 volts and one high-voltage motor. Now we have 330 volts on board with up to four high-voltage, three-phase electric machines powering the wheels (front and rear), air conditioning compressors, starting the internal combustion engine, controlling internal automatic parts and making high voltage to recharge the batteries. John Deere has added a hybrid tractor to its lineup, the E-Premium 7430 and 7530 series. ACDC played a small part in John Deere bringing it to market. Com_puters are more important than ever and there are a lot more of them on board. Insulated Gate Bipolar Transistors (IGBT) - a lot of words for a power transistor - are key to inverters that produce three-phase alternating current for the motors and IGBTs also help the DC-DC converter step down high voltage for a 12-volt supply, even with the gas engine off (what is called idle stop). AC to DC is already done but DC to AC? That is a new trick. Inverters do it over and over. Don't stop learning as this stuff is not beyond our ability to understand, service and repair. Want a challenge and interesting work? Well, here it is. Heating and air conditioning
Installed on the 2004-2009 Gen II Prius was a stainless thermos bottle (deleted in 2010) that requires special handling in regard to flushing the cooling system and personal safety. Make sure you read up on this before servicing the system. What do you do for heat when the combustion engine shuts off during idle stop on a 10 F day? The heater core will cool down within 20 seconds if more hot water isn't pumped into it. A 12-volt pump is fitted to a heater hose to keep that water moving. All hybrids, except the original Insight (2000-2006) and the first generation Civic HEV (2003-2005), have such a pump. It is commanded by the ECU for the heater and A/C system. The engine block holds a considerable amount of heat energy so you have a lot of cabin heat available even if the ICE is off. As far as the air conditioning system is concerned, most of it is familiar. The big changes are in the compressor. Many of the older hybrids used a belt-driven compressor so nothing new there, but in M/Y 2004 the Prius was fitted with a Denso all-electric design.
Now high voltage was a factor in servicing them. Honda uses a belt/electric Sanden unit on some HEVs but not all. GM partnered with Mitsubishi for an all-electric compressor. Ford has just introduced electric designs on its Fusion HEV. What do you need to know? Careful with a recharge as special oil is required by the OEMs. Introducing polyalkylene glycol (PAG) oil into any high-voltage (HV) compressor will require a major job of replacing most of the parts. My firm, Automotive Career Development Center (ACDC), is doing research for the aftermarket with Heat Exchanger Cleaning & Applied Technologies (HECAT) to find a better way. It looks promising. Engine performance So what do you do with a hybrid no start? What about keeping the engine running long enough to find a misfire? This is an area that really requires a new strategy.
I was teaching a class in Michigan recently and a tech had struggled for hours with a 2002 Prius (the boss's car) with a misfire. Turned out to be a bad injector. The engine kept shutting off during the diagnosis. If you want to keep the ICE running all of the time, such as during a fuel injection cleaning or coolant flush, there are factory procedures that will keep "idle stop" from happening. Note: Idle stop is commanded by the powertrain control module (PCM) to save fuel by shutting down the ICE when the hybrid comes to a stop. The OEMs do not agree on what to call that procedure. The universal term ACDC uses is "Service Mode." The ICE is still used in hybrids but it's leading the way to plug-in hybrids and then the ICE will be removed, a heating system is added and presto, an electric car! Internal combustion will never go away; we will just find a more sustainable liquid fuel, but pure electric cars may end up being cheaper in another decade. Time will tell We are part of a changing industry. A decade ago most techs had never heard the word "hybrid car," and now it is part of our daily life. Keep studying, learning and be safe. Photos courtesy of Craig Van Batenburg.
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