As I continued reading about the engineering that went into Toyota's hybrid effort, many of my preconceived notions were turned completely on their ear, especially where battery technology and engine management are concerned. Every little feature I read about the Prius seemed to have undergone some really brilliant thinking in its development. It was clear that there were a lot of good minds in the customer base, too. Several sites and forums pointed to obscure, tech-heavy but very excellent papers that explained many of the principles. Forum archives and various owner sites offered plenty of reverse-engineered hypotheses about Toyota's hybrid designs, and I began finding myself quite in awe of the things that modern automotive engineers need to think about. It was very informative to look back ten or fifteen years in various patents and see how some of the design thinking had evolved, and how many of those ideas had obviously been adopted in the Prius too. It's often hard to stay awake through something as dry as patent text, but in this case it was worth it. The "Hybrid Synergy" drivetrain is actually beautifully simple from a mechanical standpoint. Nothing ever physically shifts -- the two motors and gas engine are linked through a planetary system that always remains meshed. Everything else about power allocation is done electronically, by simply playing a torque-balance game between engine demand and motor loads. Even "Neutral" is just an electrical state -- no mechanical disengagement of anything. And the motors are fairly simple 3-phase machines with permanent magnet rotors -- no moving contacts or screwing around with induction and phase slip, and exactly the right thing for producing plenty of regeneration power. Almost like big stepper motors with tight position feedback. Another major change in my thinking came concerning batteries. From the old school viewpoint of ni-cads that often had to be "zapped" back into life to remove that infamous memory effect, Toyota's approach to battery management seemed completely strange. "Deep-cycle" capacity isn't even mentioned -- instead, it turns out that modern nickel-metal-hydride chemistry will provide a much longer useful service lifetime if it is *never* deep-cycled or overcharged. Thus, the battery management deliberately ignores a certain amount of capacity and keeps the state of charge between 40 and 80 percent, centering around 60. This keeps the battery chemistry in a very stable region, but still allows room for a useful amount of either driving energy or regeneration overhead at almost all times. The electronics surrounding the battery are designed to keep *very* close tabs on charge state and communicate it accurately to the rest of the system, unlike a lot of cell phone and laptop packs that seem to rapidly drift away from reality and kill their own cell chemistry in a couple of years despite periodic "recalibration" attempts. What this means is that the stock battery pack is sized so that that's only good for 2 or 3 very gentle miles on a "full", i.e. 80%, charge. This isn't going to golf-cart you around through a full day's shopping, even if it did allow itself to run all the way down -- the Prius is not an EV, although many people like to think of it as one. The battery is for temporary energy storage, not primary propulsion. But for moving between parking spaces or something, running solely under electric power is absolutely the right thing to do -- avoid the rich-mixture hit of cold engine startup if you don't need it. The car's brain can't predict where you're *going*, and sometimes needs a little help making the decision. Very early in the study process I read about the "EV button" hack that several people added to their cars, for which it turns out that the functionality is already there and all that's needed is a switch to momentarily ground one of the pins in the controller and enable it. That immediately went on the list of pending mods, of course, assuming that the functionality would also be present in other hybrid vehicles. If a cold engine startup does happen, the effects are mitigated in a really entertaining fashion -- at the prior shutdown, the hot coolant is pumped off to a thermos-style holding tank that can stay hot for something like three days, and then all pumped back in around the cylinders just before starting up. Like a built-in block heater. Certainly not enough to bring a cold block completely back up to running temperature, but it still gives a head start on heating, to reduce startup friction and fuel consumption and make emissions reach a low level that much sooner. Cold start engine management emphasizes getting the catalytics warm as soon as possible so they can begin working right. And even more thermal efficiency comes from the Atkinson/Miller cycle engine, which uses a variable intake-cam offset hack to allow different compression and expansion ratios. It's very similar to a standard Otto cycle engine but winds up extracting more energy from each charge of fuel, at the expense of a little bit of torque. Toyota's hybrid-adapted engine can set the valve timing on the fly under computer control with the VVT system, and thus best tailor the compression/expansion to demanded output. And they even decided to slightly offset piston axis from the crank axis to allow a more "straight-down" shot on the power stroke, reducing sliding friction and piston-skirt wear. Spark generation is done directly at the plug, using an integrated "igniter" containing the coil and switching electronics, mounted directly over the plug. A low-voltage pulse triggers it. Thus, no spark plug wires, external coils, distributor, etc. The igniters sit down in deep wells in the head cover, probably reducing EMI as well. Coil-per-plug has been around for a while but seems to be appearing in many more engines these days, because really, it just makes sense. Toyota's approach also utilizes normally wasted space down in the plug holes to contain the electronics. I had never realized before digging into all this that an engine's efficiency *increases* under load. But here I was, facing the possibility that my usual method of babying a car might actually *reduce* gas mileage, and that better gain might have come from pushing it a little harder! Another old notion scrapped, and with that came the realization that traditional cars all have engines sized to handle *peak* demands which actually don't occur that often in normal driving and certainly not in steady-state cruising. Thus, they all have an oversized engine loafing along at partial loads most of the time, but still needing to crank a significant volume of air and fuel through themselves to stay running. Even if you drive like a total butthead, you can't be placing a high demand on an engine *all* the time. That's one of the main reasons for crappy mileage in most vehicles -- overpowered, yet having to accomodate widely varying power demands. Fewer worries with a hybrid system, though, since the engine can be much smaller and engine management and electronic throttle control should try to keep it nominally loaded when it's running and much closer to its efficiency sweet-spot, or eliminate the entire problem by shutting down and consuming no fuel at all. Of course having a hybrid system eliminates the alternator and starter motor, two frequent sources of automotive headache, and moves all that functionality into a protected, lubricated, and cooled environment. No more G-r-r-r-r-r and klunky solenoids trying to chip teeth off the flywheel -- instead, the engine is spun up to 1000 RPM or so and confirmed to be turning *before* any gas and spark are applied. This eliminates the traditional method of using combustion [and associated low-RPM lugging, knocking, and connecting-rod stress] to bring the engine speed up the rest of the way. A brief burst of battery current, and suddenly it's magically running. This happens whether the vehicle is moving or sitting still. And on shutdown, the motors are actually used to reposition the engine in a way that optimizes forces and timing during the next restart. Three relays are used in the main battery pack -- one on each terminal, and a third to connect the positive side through a resistor long enough to charge the filter capacitors in the inverter more slowly and avoid high inrush currents before bringing in the main contactor. Standard technique for electronic devices with large capacitors such as power amps, but amusing to now find in a car. A fused safety plug connects both halves of the battery pack together in the middle, disabling the whole deal if it's pulled out. Toyota refers to this often in the emergency-response info hung out on their website, making it very clear how to completely disable the high voltage side of the hybrid system when needed. Toyota evidently had to take a bunch of lessons from the Japanese bullet-train control systems and design their own switching transistors from scratch, to achieve sufficient current-handling capacity and breakdown resistance. They're mounted in the inverter module on a cold-plate that gets its own coolant loop along with the motors themselves. This makes things a little harder to work on since that coolant loop must be drained first, but it gives plenty of heat-removal capacity to protect the inverter electronics. Braking is done as regeneratively as possible, resorting to physical brakes only on high stopping demands or at very low speeds when the motors aren't turning fast enough to produce useful zoobs. [Yes, that's a technical term..] There are lots of electronics involved in modern braking already, when systems like ABS and skid-control and traction control are taken into account. So we already have hydraulics passing through many little solenoid valves under computer control. With the newer hybrid system, Toyota simply decided to merge *all* of that functionality into one place and went with a fully electronic braking system in which each wheel is independently controlled and front/rear proportioning, ABS, etc just happen as a natural consequence of how the braking computer responds. Including to apply little or no physical braking at all if gentle stopping is requested and things are stable and within comfortable margins -- at that point it can *all* be regenerative using the main electric motor, and the braking controller keeps itself out of the picture until really needed. If the electronic braking fails somehow, there is still a physical hydraulic path between the foot-controlled master cylinder and the front wheels, giving a reasonable safety backup and allowing the brakes to function when the car is not powered. The various elements of control software appears to take *rate of change* of inputs into account. Some of this is described in the patents dealing with the brake-by-wire system. Sudden hard braking, e.g. quick pedal travel, causes different response than slow braking, even if the same final braking amount requested is the same. Similarly, a sudden step input to the accelerator yields a temporarily higher surge of engine output power, if it's running, assuming that the driver thought it was needed. Or it encourages the system to start the engine in the first place. This allows a *little* more explicit control over run/stop via quick blips on the accelerator. I have always been a very "predictive" driver and thought down to the level of d(input)/dt with regard to throttle and brake, based on terrain and surrounding conditions. So I'm all in favor of a control system that is also aware of such things and responds in a reasonable manner. In general, the more I read the more it was evident that Toyota had really made a strong bid for reliability, reduced stress, and carefully staged startup in many design areas. Which also happens to totally match my own approach to handling gear and using technology, because I understand many of the real-life analog effects and how to minimize the deleterious side of them. Anyone who's heard my lamp-preheat or hard-drive-warmup rants can attest to this. The more I kept discovering the little stuff like this that they'd thought of, the more it made me want to throw money at them. Some people are uncomfortable with the idea that a car engine can randomly start and stop itself when it sees fit. But do you specifically turn the furnace in your house on and off? No, you set the thermostat and forget about it, and it fires up and shuts down automatically when needed. Often that's under computer control too, especially in larger complex HVAC systems. Heck, any other car has a high number of automated systems too -- radiator fans, for example. Did I begrudge the old wagon's automatic decision to spin them when the coolant was too hot? No, but I *would* let them finish cycling before shutting down the engine -- but that's just me and my usual hyper- awareness of what's going on under the hood. Numerous factors affect a hybrid system's decision to run the engine -- not just propulsion demand, but batteries needing to be charged, a call for cabin heat or cooling, and sometimes just to keep itself and the emissions system properly warm. In general it's making the right choices, although there are still times when the human can help beneficially sway the decision. Now, as some people are quick to ask, what about computer failure? Think about how many lines of code you're already running to read this, or to make a call on your cellphone, use a camera, or in fact to drive most cars nowadays. Concern over the reliability of dedicated processing devices goes down as their ubiquity rises. Let's face it, almost *any* car on the road today has at least one reasonably complex electronic control unit [ECU] of some sort, without which the engine doesn't run, period. The industry has gotten way beyond those days of fire-breathing carburetors and bimetallic choke actuators and centrifugal timing advance and brute-force points and spark coils, however brilliant some of the work in that arena may have been at the time. Embedded control is everywhere, and increasingly is the *least* likely component of a system to break. Many of those early growing pains of semiconductor-based automotive control are over -- they've gotten much better about dealing with device and power stability, input and thermal protection, and even software design. Now that it's a well-known and fairly proven approach for engines themselves, designers are going after the larger concepts of how the entire powertrain works together. Better efficiency tweaks can be done entirely in software, as well as early detection of potential problems ... and in general it *is* working out for the better. Yeah, I thought *I'd* never be saying that. The downside, of course, is that when components do fail, they're wicked expensive to replace and for the most part infeasible to D-I-Y fix. Exceptions to robustness may arise if those means of control are allowed to converse arbitrarily with the outside world. Here is a rambly but important digression about computer security and reliability in actively hostile environments, which is not only a major concern on the desktop but also a concern in the embedded-control world -- whether anyone's really aware of it or not. Part of my research had also more or less become a crash course to update my knowlege of modern engine-control systems, and while computers are rapidly numbering the days of the traditional weekend car mechanic, one only needs an OBD-II scan tool and the newer control modules could pretty much tell you the cause of any given problem right up front. People are way too scared of that "check engine" light, but all it takes is the equivalent of plugging a serial terminal into the device in question and issuing a few commands to figure out what's going on. Having maintained routers and firewalls for several years, I can certainly relate to that -- as long as the *protocol* is well-documented. The cars with parts simple enough to get apart and scrape the gunk out of with a Swiss Army knife or even [in the words of an old buddy] a plastic fork from McDonalds to get running right again were already fading into fond memory. The new plastic fork is something almost as ubiquitous nowadays -- a laptop or a PDA. The old carburetor-tweaker in me was slowly, grudgingly coming to grips with this. Therefore, the other item on the shopping list was an interface for my laptop to plug into the diagnostic port on a car and pull out the trouble codes and other info. In parallel with all the ongoing research I had also dug into OBD-II somewhat, and discovered that by now there are something like five different interface "standards" that can appear at that little plug under the dash and a vast array of parameters and pathologies that can be reported through it. *Sigh*. So much for those golden Saturday afternoons fooling with the little screws on the side of the carburetor and listening to how the engine changes. If I was going to do my own diagnostics and implement the list of hacks I had already started forming in my mind, I'd need that modern-day plastic fork -- and not just for a hybrid, but to help me diagnose any other late-model car including the existing wagon. The newer Toyotas all speak Controller Area Network [CAN], which is supposedly slated to be THE standard for new vehicles by 2008 or so, but vehicles using other protocols will still be around for some time so it's good to be versatile. The tool I settled on was Alex Peper's "CarCode" with a CAN-compatible interface, the installation instructions for which amounted to "unzip into some directory and run OBD2.EXE to start it up". A very nice philosophy -- no hidden DLL conflicts, no turds in the registry -- could run in the same very cut-down windoze environment I use for running lights, using generic display and serial-interface calls without a lot of broken Microsoft fru-fru. So I liked this guy's style, at least at first. More on him later. If I'd had such a kit six months earlier and some of the newly-refreshed knowledge I was sponging up about control systems, I could have pinpointed and possibly fixed the "check engine" light that came on in my parents' car while I was visiting for the holidays. But they wound up taking it to the Toyota dealer, and getting shafted. Mere posession of a diagnostic tool doesn't ensure that the person wielding it actually knows what they're up against, as I explained to them quite after the fact: I also happened across descriptions of typical EGR valve problems, such as what supposedly went south in your car. There is a strong chance that it was merely due to needing the carbon deposits scraped out of the little pipe that connects between exhaust and intake -- that's a very common cause of that "insufficient flow" sort of problem. But of course the dealer will seize any opportunity to sell you $450 worth of parts you probably didn't need yet. I was rather stunned by those guys' obstinate unwillingness to actually *diagnose* what the real problem was, instead of blindly parts- swapping it away. Even with cars the way they are now, if one digs in a little, genuine problem causes can still be ferreted out. Unfortunately that level of dedication/interest isn't cost-effective anymore, but I still think it was a rather telling indictment of their ability to think. Thus, I was totally unafraid of the electrical maze I would inevitably face. That's what service manuals are for, and once I found that they were available for a nominal download fee at techinfo.toyota.com, I felt much more confident about it all. One thing that the CAN bus or other diagnostic interface provides is more than one option for adding instrumentation. Numerous sites show how people have gone the "pure" digital route, especially on the Japanese-only prius-hacking sites, designing embedded systems to query the ECUs and show figures on a small LCD display. Alternatively, one can read analog signals straight from various sensors in a more traditional fashion, or design something with a mix of both methods. My own forte is more on the analog side, so that's the way I would generally head. And whatever form it would take, I really wanted to get started on the rest of the learning experience. Somehow. Perhaps a mild sense of desperation had set in? I found email addresses for a few dealers in the group archives, and started trying to ask some of them directly if they knew *anything* about the Estima or a US-market equivalent. Well, dealers are evidently the *last* people to find out any real info about new or future vehicles, so that was pretty useless. They also have about zero influence back up the chain to Toyota corporate. I found myself sending *them* URLs to good info resources because of all the things they didn't know. One of these guys was relatively local but never answered the email, so I decided to just try calling him one afternoon. That would be Gilles Labelle, at Westboro Toyota. And it turned out to be a very enjoyable conversation, because we seemed to be on the same page about the whole reduced-consumption concept in the first place and he's got genuine passion about it. By the end of that call I had agreed to haul down there and visit him in person. Not that he knew anything about Estimas either, but that was rapidly becoming immaterial.Next