Reprogramming Fuel Injection

Transcript

Technical REPROGRAMMING FUEL INJECTION – PART TWO: Dynojet’s Power Commander III-USB I by Mark Barnes map, but instead “trim” it by nudging the ECU’s instructions to the injectors, either richer or leaner, at certain combinations of throttle position and engine speed. The term “piggyback” refers to the way the module is insufficient by itself, and has to be used in conjunction with the map in the ECU. For the sake of clarity from here on, we’ll reserve the term “map” for what’s contained in the ECU, and we’ll use the term “trim table” for what’s contained in piggyback modules. (Note: this terminology distinction doesn’t apply Not So Fast! elsewhere; manufacturers and conOkay, before we jump in, and before sumers commonly refer to a piggyback anyone invests in an expensive EFI tunmodule’s trim tables as “maps.”) ing module, two procedures—Throttle Before we get to what information Position Sensor (TPS) calibration and resides in the trim table cells, a quick throttle body synchronization—can sigprimer on terminology is in order. nificantly improve driveability if the The time-frame (in milliseconds) associated hardware is out of whack. during which an injector is open is With a couple of special tools, these are called the Injector Pulse Width (IPW). fairly simple adjustments definitely Derivative of that figure is an injector’s worth doing first on any bike (consult Duty Cycle (DC), which is the IPW your shop manual). When we checked divided by the time required for the them on our Super Duke, the TPS was (four-stroke) engine to complete two within spec, but the throttle bodies were crank revolutions at a given rpm, quite out of balance, probably because Dynojet’s Power Commander III-USB, ready for the radically different aftermarket air- installation. Note ground wire and large plugs for expressed as a percentage. In other words, an injector opens once during box/filter had changed flow through insertion in-between the halves of KTM’s BGC. each sequence of four piston strokes each throttle body to differing degrees Connectors for other bikes will be different. (intake, compression, power and (we believe flow was less symmetrical exhaust), which requires two crank revonationwide network of tuning facilities in the stock setup, and the throttle bodies lutions. An injector’s DC is the percentage using their own branded dynamometers. had been balanced properly for that of time it’s open during the total time Dynojet was quick to jump into the EFI condition). Balancing yielded slightly required for those two crank revolutions. tuning arena, though an increasing numsmoother acceleration right off idle. Note: So, if an engine running at 3000 rpm takes ber of manufacturers are entering the fray. Physically adjusting the TPS on the bike 40 milliseconds to complete two crank At this point, Dynojet appears to offer the is different than calibrating a module’s revolutions, and an injector is open for 10 broadest selection of EFI-related prodsoftware to read the TPS signal properly of those 40 milliseconds, its IPW is 10 and ucts, and they still have that big network (part of a module’s initial setup). its DC is 25 at that engine speed. of tuning centers going for them. We If you don’t already own the voltmeter Getting back to the trim table contained won’t even try to list the other options and manometer usually required for these in the PC-III, its cells contain numbers here; there are just too many. Google checks and adjustments, you may want to indicating the amount of change “motorcycle fuel injection tuning modwait until you’ve read the next installment ules” and scroll away… in this series. In it, we’ll show you another (expressed as a percentage), and the direcThis article isn’t about how the PC-III tuning option that has built-in diagnostic tion of that change, to the IPW in the corstacks up against its competition. Instead, capabilities that allow for these operaresponding cell in the ECU’s map. Hence, we’re simply going to explore how this tions—and much, much more—for less the trim table cells contain zeros where no type of unit works, and introduce you to than you’d pay for the aforementioned modifications are to be made. A 5% richer what can be done with such a tuning tool. special tools (maybe a whole lot less). mixture would be represented by a 5 in While there are certainly differences the trim table, while a 7% leaner mixture between brands, most of the principles would appear as a -7. A picture really is Dynojet Power Commander III-USB we’ll cover apply across the board—not worth a thousand words; if you glance at Founded in 1972, Dynojet has been a only from one module manufacturer to the related illustrations, all this verbiage leading—if not the leading—tuning another, but also from one make/model will be much easier to understand. resource among motorcyclists for of motorcycle to another. decades, having established its reputation Remember that the percentage in a trim Piggyback EFI tuning modules like the and a large following with its extensive table cell is not a Duty Cycle, but rather PC-III don’t change the ECU’s resident array of model-specific jet kits and a the percentage difference between the N THIS INSTALLMENT, we’re going to jump right in to an examination of perhaps the most commonly used option for altering an EFI map: Dynojet’s Power Commander III-USB (PC-III). The PC-III is a “piggyback” module that plugs into the bike’s wiring harness and modifies the instructions sent to the injectors by the ECU. We credit the PC-III with remedying the surging and hunting of our test mule KTM 990 Super Duke’s stock setup. 24 JULY 2012 ● MOTORCYCLE CONSUMER NEWS BGC is infamously vulnerable to water entry, it’s a good idea to pack any bike’s electrical connectors with dielectric grease while you’ve got them apart. The stock oxygen (O2) sensors must also be disconnected for the PC-III to exert its influence across the entire rpm range (see sidebar). Simply unplug the sensors from the wiring harness, and insert Dynojet’s O2 Sensor Eliminators in their place. These plugs “fool” the ECU (by way of resistors) into thinking that the O2 sensors are still connected, avoiding illumination of the EFI warning light on the dash. The disconnected O2 sensors can then either be left in place or removed from the exhaust pipes to tidy things up. Of course, if the sensors are removed, their mounting bungs must be plugged (18mm thread x 1.5mm pitch x 9mm deep). K&N sells weld-on O2 sensor fittings that have this plug but we found some at an industrial pipe and hose supply house. Anyone wanting to simply run the PCIII’s preloaded trim table is now done. He can take off without ever loading the accompanying software on his computer, much less using it to access and modify what’s in the module. To whatever extent the preloaded trims “correct” deviations from ideal in the ECU’s map, the bike will run more smoothly and more powerfully. Note: This may make the bike technically illegal in some places, which is why modules often carry a disclaimer that they’re for “off-road” or “closed course” use only. If, on the other hand, a user wants to alter the PC-III’s pre-set trim tables to optimize fueling for his bike’s unique The Throttle position sensor (TPS) should modifications, he’ll have to install the be checked before any trim adjustments aforementioned software on his computer are made. With its fixing screw loosand hook up the PC-III with its (included) ened, the TPS housing is rotated until USB cable. Tip: Don’t bother using the voltage output is within spec. table in the CD that came with your module; the program on it has probaECU’s instruction and the trim bly been updated since your unit was instruction coming from the PC-III. packaged. Most manufacturers have Such piggyback modules are sold the latest versions of their software for specific bikes to accommodate available for free download on their different wiring harnesses with difwebsites; get yours there. ferent connectors. So you can’t just For example, Dynojet offers an buy any module and load it with a alternative trim table for Super Dukes trim table for your bike. This also that have been fitted with freer means Dynojet can sell a PC-III with flowing air filters and aftermarket a trim table already installed for use exhausts. This trim table, which was with a particular motorcycle. As we already loaded in our Super Duke’s discussed in Part One, stock EFI PC-III, was specifically developed for maps are often less than ideal for a BMC air filter and an Akropovic full performance because they must exhaust system, but it’s also “in the accommodate noise and emission ballpark” for our SuperDuke with regulations, creating the lean conditions that lead to surging and hunt- Throttle body synchronization involves using a vacuum similar modifications. It may be possible to find a trim ing. So, even an unmodified machine gauge while adjusting the throttle linkage. The goal is might run better with some mapping to make both (all) vacuum readings equal. This should table for a bike modified exactly like tweaks. Piggyback modules gener- be done before any tuning is attempted. ally come preloaded with trim tables optimized for all-stock hardware. Installation To simply “plug and play” the PC-III using its factory-installed trim table requires very little effort. The Super Dukespecific module’s wiring consists of a simple ground connection (a single wire with a ring terminal) and a pair of large plastic electrical plugs (matching male and female) that insert the PC-III, electronically speaking, between the ECU and the bike’s wiring harness. On the KTM, these plugs, known in KTM-speak as the BGC (Big Gray Connector) happen to reside near the front of the engine bay. So the PC-III’s cable gets routed from there back to the under-seat tool tray, where there’s room for the PC-III module. Other bikes have different lengths of cable and different connectors. Tip: Although KTM’s PC-III trim tables are laid out just like ECU maps, but with modification percentages in their cells. Engine running, shown in green are current TPS percent open, rpm, trim value currently in effect for each cylinder and each injector’s current Duty Cycle. (Note: cell highlighted in blue was randomly selected.) Visit us at WWW.MCNEWS.COM ● JULY 2012 25 Technical the inner cylinders in an inline-four need to run a little richer overall (similar to “staggered” jetting on carbureted bikes), perhaps due to uneven temperature or airflow, this adjustment can be dialed in easily in the software. Alternatively, with the aid of a dyno or wide-band sensor, completely custom-tailored trim tables for each cylinder can also be created. The PC-III also has a handy “Map Compare” function that highlights the differences between two trim tables, and can create a third that averages those two. Various accessories are available for the PC-III, including a separate module that allows trimming of the ECU’s igniLeft: Stock O2 sensor removed and plug installed in the rear cylinder’s header. tion maps (as the stock ignition advance is Right: O2 sensor eliminator plugs allow closed loop control across the rpm range. often restrained to avoid detonation in very hot climates), a yours somewhere other than quick-shifter that cuts fuel to the manufacturer’s website, but the engine to allow full-throttle always consider the source—or clutchless upshifts, and an LCD rather your inability to really display module that shows data know that source. Maybe it was from the PC-III (e.g. throttle developed by an expert tuner, but position, rpm, trim value, etc.) in it also could have been devised by real time while riding. These are someone with very faulty ideas. connected by way of an expanA poorly-designed trim table can sion port in the PC-III. cause major engine damage, so be Other features that can be actisure to download and install only vated without any additional ones that have received consishardware include an “Acceleratently good reviews from others tor Pump” function that supplies with bikes just like yours. Also, the engine with a user-defined keep in mind that they don’t call it burst of extra fuel during accelthe World Wide Web for nothin’. A trim table that works great for a In the author’s hand is the stock narrow-band O2 sensor, just eration, and two features just Belgian-owned bike with a Euro- removed. Note the difference to the wide-band sensor that’s for Harley-Davidsons: “Rev Xtend,” which raises the rev spec fuel blend may be inappronow installed in the exhaust pipe for tuning purposes. limit, and “Start-up Fuel,” which priate for a US-spec machine. enriches the mixture during starting. also be saved in versions along the way, A comprehensive description of all PCYou may be thinking, “That’s all very just like any computer file. III features won’t fit here. Instead, we’ll nice, but I still don’t know what numbers The PC-III also allows the further give you the highlights. First, without any to put in those trim tables!” Ah, there’s trimming of individual cylinders. So, if connection to a computer, three buttons on the PC-III’s faceplate allow for gross adjustments to the lower, middle and upper thirds of the rpm range. Those with carb-tuning experience might be tempted to think of these ranges as roughly equivalent to air screw/pilot jet (low), needle taper/height (mid), and main jet (high) changes, but these external adjustment ranges on the PC-III are for engine rpm, without regard to throttle position, which is the basis for those carb-tuning ranges. A column of LED’s shows, in 2% increments, how much change in trim is being selected via manipulation of the buttons. In this way, modifications can be made— leaner or richer—out on the road, testing by the seat-of-the-pants, on top of whatever is already in the module’s trim table. If a change proves to be an improvement, On multi-cylinder engines, the PC-III allows trimming of separate cylinders, relative it can then be permanently incorporated to the base trim table (setting shown was selected at random for illustration). into that table when the PC-III is again Entirely new trim tables can also be custom tailored for each cylinder. hooked up to a computer. Trim tables can 26 JULY 2012 ● MOTORCYCLE CONSUMER NEWS don’t know what AFR is ideal. And, even if you had an AFR target in mind, you still wouldn’t know how much to change any given trim value to achieve it, at least not without a lot of practice. While there’s obviously a great deal of science involved, tuning is still an art, and different tuners will have differing opinions about what’s best, taking into account a host Buttons on the PC-III allow roadside adjustment of fuel mix- of variables—including ture for each third of the rpm range. LED on left indicates some about the rider, 6% richer is being selected for the lowest third (left button). such as skill level, prefDoes the seat-of-your-pants tell it improved matters? If so, erences, etc. Factors you can refine the trim tables based on speed range tested. like expected traction available and the relathe rub. The PC-III gives you the capabil- tive priority of fuel economy, among othity, but no guidance in making any modifi- ers, can also influence a tuner’s decisions cations to your bike’s fueling. If the about what’s best. So, the PC-III can produce real improvefactory-installed map or an alternative downloaded from Dynojet or elsewhere ments without a tuner, but even more is doesn’t suit you perfectly, you could start likely possible with professional help. Our dabbling with the trim table and try to get bike used the Dynojet-issue trim tables for it right by the seat-of-your-pants using a modified Super Duke. And without any those faceplate buttons out on the road. But, additional tuning, we believe it resolved given all those trim table cells and your some of the EFI problems we had experiinability to keep track of exact throttle enced, like throttle snatch, hunting and hesposition/rpm combinations while riding, itation. The previous owner’s feedback, a host of similar reports on KTM internet your chances of getting it right are nil. This is where a professional tuner comes forums and comparisons with unmodified in. He can insert wide-band O2 sensors Super Dukes confirmed this conclusion. into your exhaust system and assess the mixture to determine whether it’s rich or Bottom Line (for the moment) lean, and by how much. This might be So, it’s possible to make significant done with the bike on a dyno, or with a improvements in EFI performance without mobile data-acquisition device that would hiring a professional tuner. Piggyback collect information as the bike is actually modules like the PC-III usually come ridden. We know from previous testing with a model-specific trim table already that what works best on a dyno isn’t nec- installed (although it may still require essarily what works best on the street, but tweaking for your bike’s specific mods), that’s another discussion. Either way, the and some can be adjusted (to a very limited mixture readings would be paired with pre- extent) without your computer. A large cise information about accompanying number and wide variety of trim tables are throttle position and engine rpm, all gath- available for free download from various ered electronically at the same time. With sources on the internet, and these can be this, the crucial ingredients for trim opti- loaded in the module as viable alternatives mization are all present. Teaser: There’s a to piece-meal editing (caveat emptor). way to do this without hiring a tuner, but Professional tuning can take EFI map that will have to wait for a later installment tailoring to a higher level of precision, but in this series. at considerable additional cost. Estimates Of course, professional tuners would for custom mapping ranged from $200 to say—and rightly so—there’s more to trim $500, depending on the special equipment table optimization than just looking at this to be used, the degree of perfection sought, data and punching in the implicated adjust- and how the tuner valued his time. ments. First, while wide-band O2 sensors As exciting as all this may sound—and can give an indication of the actual air-to- it truly is!—other options are worthy of fuel ratio (AFR) being consumed in real consideration, too. Stay tuned for more in time, that info doesn’t tell you much if you our remaining installments. Power Commander III-USB, $359.95 –$499.95 (depending on application); Dynojet Research, Inc.—2191 Mendenhall Dr., North Las Vegas, NV 89081; 800-992-4993; www.powercommander.com (check online dealers for significantly lower prices) OPEN VS. CLOSED LOOP OPERATION The ECU bases its fuel delivery calculations on the input of multiple sensors, among them barometric pressure, manifold vacuum, air temperature, engine temperature, engine speed, and throttle position. This should be able to allow the ECU to provide the correct amount of fuel to achieve the requisite 14.7:1 air/fuel ratio needed by the catalytic convertor to achieve the lowest possible emissions—a process referred to as “open loop” operation. But, it’s also open—that is, vulnerable—to being wrong. To ensure that the engine actually gets the desired mixture, you need a feedback mechanism. O2 sensors do exactly that. The amount of oxygen (O2) detected in the exhaust after combustion tells the ECU if it has delivered a mixture leaner or richer than intended. Feedback “closes” the loop, and allows the ECU to compensate for errors it may have made and also improve future accuracy. While it might seem that EFI should operate in closed loop all the time, the majority of EFI motorcycles do so only at low speeds and small throttle openings, to prevent exceeding emission standards that focus on this operating range. Emissions drop dramatically at the stoichiometric ideal of 14.7 parts air to 1 part fuel, and even slight deviations in either direction result in rapidly increasing pollutant levels. Since closed loop operation requires strict adherence to the 14.7:1 AFR, only “narrow band” O2 sensors are needed. However, the 14.7:1 AFR is way too lean for maximum power, especially at large throttle openings and high rpm, when an AFR closer to 13.2:1 might be preferable. Note: Stoichiometric AFR are different for different fuels; 14.7:1 assumes pure gasoline. Fuel that is 10% ethanol has a stoichiometric ratio of 14.2:1, meaning that using E10 in an EFI system designed for pure gasoline would produce a mixture almost 3% leaner than intended, which—in closed loop mode, at least—was already rather lean. With a wide-band sensor replacing the stock narrow-band unit, we can measure AFR and determine the results of trimming to the stock ECU maps. Visit us at WWW.MCNEWS.COM ● JULY 2012 27