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7.3 Performance
What you REALLY wanted to know about SOI.
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[QUOTE="Power Hungry, post: 244882, member: 1375"] [b]Part 2: The tuning hardware.[/b] [U][b]Part 2: The tuning hardware. Dynos, testing equipment, emulators, and how they all work together:[/b][/U] Over the last 15 years, how we tune the 7.3L Power Stroke has improved considerably. Not only has the tuning hardware and software seen significant advancements, but the diagnostic equipment has also improved and provides a much greater wealth of feedback data than anything we could have hoped for in the '90s. Tuning for the 7.3L (or any other EEC processor based vehicle) is at a distinct advantage because these ECMs can be "live" tuned. This means that we can actually make changes to the tables and functions as the vehicle is running. This [U]SIGNIFICANTLY[/U] reduces the amount of time spent tuning. When you consider that we can change in seconds what would most likely take days or even weeks to tune using the "chip" method, you can see why live tuning is the preferred method of tuning for any heavily modified vehicle and is even helpful on modestly modified vehicles. Coupled with high speed datalogging, we can immediately see how individual changes affect the vehicle performance. Later vehicles (2003+) such as the 6.0L, 6.4L, 6.7L and other applications don't offer the flexibility of live tuning (at least not inexpensively), but most can be reflashed pretty quickly with only a minute or two between dyno or street runs. However, since this thread deals specifically with the 7.3L, we're going to remain on that topic. Live tuning on the 7.3L requires, at the very minimum, the use of some sort of memory emulator connected to a PC/Laptop running a related software in which changes can be made to the memory image. Ideally, datalogging software will also be used to monitor specific parameters related to the changes being made, although for certain tuning aspects such as shifting, datalogging may not be necessary. For more involved setups, additional testing equipment may be utilized. High speed Cylinder Pressure (CP) testing equipment is used by more advanced/experienced tuners to get a clearer picture of what is happening inside the cylinders during the combustion process. On a diesel, this is especially important since there is no specific, identifiable, direct relation between the Start of Injection (SOI) and Start of Combustion (SOC) and the only way to accurately determine a proper combustion cycle is to monitor cylinder pressures in relation to crankshaft rotation. Monitoring of exhaust temps is also critical, but since most trucks have a pyrometer installed already this is generally pretty well covered. Below is a breakdown of the popular tools used in tuning: [B]The Dyno:[/B] I'm pretty sure that by now everyone knows what this is. The dynamometer (or "dyno" as it is commonly referred to) is a device that measures the acceleration of a specific mass and uses that information to generate a power curve measured in HP (or sometimes WATTS in the case of foreign dynos). There are several types of dynos available for testing: [INDENT][LIST] [*][B]Engine Dyno:[/B] This type of dyno is set up to measure HP from an engine directly at the flywheel. This requires special setups for different engines to mate the engine to the dyno, along with additional equipment for cooling, exhaust, fuel, and other requirements. The advantage to this setup is that it allows the testing facility much greater control over the testing parameters and measure the power directly at the engine without having to deal with additional driveline losses through the transmission, transfer case, and axles. This type of dyno is generally used by engine manufacturers and professional racing facilities (such as NASCAR) in order to provide accurate HP numbers for specific engine configurations. Engine dynos are typically a "load" type dyno and frequently use a water brake to apply parasitic load to the engine, although some use an eddy current load cell to provide parasitic load. See the section below on "Load Dyno" for more information. [*][B]Chassis Dyno:[/B] This type of dyno allows for a vehicle to be situated so that the drive wheels spin rotating assembly. This is what most performance shops and mobile dyno services use. Chassis dynos are available in both "Load" type and "Inertia" type, with differences explained below. The disadvantage to most chassis dynos is that the HP is measured at the wheels and will always be lower than flywheel HP by sometimes as much as %30, depending on transmission type (Manual or Auto, 2WD or 4WD) and wheel and tire configurations. Larger/heavier wheels and tires provide additional parasitic losses and will regularly exhibit lower numbers than the same vehicle with smaller/lighter wheels and tires. Also, automatic transmissions will see larger parasitic losses than a similarly equipped vehicle with a manual transmission. Obviously, the biggest advantage to a chassis dyno is that you can run the vehicle without having to remove the engine, which just isn't feasible in most situations. Another advantage is that while you may not have an accurate measurement of power at the flywheel, you know exactly what is being put to the ground. This, combined with vehicle weight, can provide a pretty reasonable idea of what your ideal 1/4 mile runs will be. One final advantage of a chassis dyno is a matter of safety. With the vehicle strapped to a dyno, it's a considerably safer place to make changes in tuning than what you'd find on even the most deserted of streets. Plus, with a load dyno you can even simulate various road and driving condition, even simulating pulling a trailer. Since chassis dynos are the most popular and prevalent configuration, this provides a fairly common platform for individuals to compare performance and power numbers. Just keep in mind that no two dynos are going to give the exact same power numbers and these numbers can vary greatly between load dynos and inertia dynos as well as numbers between different dyno manufacturers. Popular chassis dynos are [URL="http://www.dynojet.com/automotive_dyno/default.aspx"]DynoJet[/URL], [URL="http://www.mustangdyne.com/mustangdyne/"]Mustang[/URL], [URL="http://www.superflow.com/Dynamometers/Chassis/index.html"]SuperFlow[/URL], and [URL="http://www.dyno.com.au/dyno/controller/home"]Dyno Dynamics[/URL], with Mustang, SuperFlow and DynoDynamics being primarily load type dynos and DynoJet being primarily an inertia type dyno. [*][B]Inertia Dyno:[/B] In the 1990s and early 2000s, inertia dynos were the most common dyno configuration with DynoJet model 248c probably being the most popular dyno available during that era. Inertia dynos use 1 (or more) weighted drum(s) to provide a specific load against which the vehicle must accelerate. HP is measured based on the amount of time it takes to accelerate the roller(s) and then is output as a power curve over time, vehicle speed, or engine speed. For light, naturally aspirated or supercharged vehicles, this often provides accurate and consistent power numbers. However, for heavier turbocharged vehicles, inertia dynos may not be consistent or accurate as the inertial weight (usually around 4,000 Lbs.) often doesn't provide enough load to simulate a 7,000 to 10,000 Lb. vehicle. This frequently results in inadequate boost generation and lower power numbers. There is also some debate over the accuracy of these dynos at higher power numbers, but that is outside the scope of this dicussion. [*][B]Load Dyno:[/B] A load dyno can be configured as a load cell alone, or a load cell combined with an inertial mass. Most engine dynos use a load cell by itself while most chassis dynos are a load and inertia combination. Load cells are used to provide a variable load in order to test power under different situations. Early engine dynos used a water brake to absorb power while most later engine and chassis dynos use an eddy current (electrical) brake absorption unit. A load dyno offers significant advantages over a plain inertia dyno as they can be configured to accurately simulate vehicle characteristics under a variety of test conditions. Because of this, most consider a load dyno to provide a more accurate power measurement, especially on heavier, turbocharged vehicles. With additional loading, the turbochargers are more effectively utilized and a more accurate power number can be achieved. [*][B]Accelerometer:[/B] These are considerd the "poor man's" dyno. While not technically a dyno, these can be used to calculate power output based on vehicle acceleration as well as provide a pretty accurate 1/4 mile run. [URL="http://www.gtechpro.com/index.html"]G-Tech[/URL] is probably one of the most popular manufacturers of these devices and their units are pretty inexpensive at around $200.00. [/LIST][/INDENT] For a more detailed breakdown and description of dynos, there is a good article on [URL="http://en.wikipedia.org/wiki/Dynamometer"]WikiPedia about Dynamometers[/URL]. [B]Tuning Software:[/B] Realistically, without tuning software this discussion wouldn't even be possible. Without the ability to make changes to the binary images used by the PCM there wouldn't be any chips, programmers, or custom tuning. Tuning software has been continually improved and now has more feature and functionality than ever before. When you consider where the industry was 15 years ago, it's surprising that we were able to achieve anything at all. As computers and software have advanced, so did the quality of the tuning. Today's tuning software provides multiple methods of visualization, ranging from "spreadsheet" views which work with tables of data, to full, 3D graphical representations of the binary data which clearly illustrate maps and curves in a form that most people can look at and understand to a fair degree. It's partly because of these improvements in tuning software that today's tunes are more powerful and more reliable than ever before. [B]The Emulator:[/B] These devices are used to effectively replace the ROM (memory) image on the PCM with an image that is stored on a PC/Laptop. This allows changes to be made on the PC/Laptop and those changes will be directly translated to the emulator which causes the PCM to immediately run from the new changes. When making adjustments to fueling, timing, shifting, idle, or other functions, this helps to save time by effecting changes in real time and more quickly reaching the desired target values. More involved devices not only allow live changes but also provide feedback to the PC/Laptop application as to what areas of a specific map or function are currently being accessed by the PCM and the software then provides a visible indication of these locations. This is commonly referred to as the "bouncing ball" and helps to indicate where changes need to be made based on current operational conditions. Some emulators are self powered and can continue to function as a standalone chip when not connected to a PC/Laptop, which means that it can run on the last settings provided without having to actually burn a chip with the final working image. Emulators are one of the most important tools used by a tuner as it provides an exponential increase in speed and flexibility. [B]Cylinder Pressure Testing Equipment:[/B] This equipment is used to get a snapshot into the actual combustion process. It consists of pressure sensors that are mounted in such a fashion that they can record cylinder pressure (usually situated in the glow plug holes on a diesel) and extremely high speed datalogging equipment which can record thousands of samples a second to provide a very clear profile of the combustion process. This information is then used to determine the relation between Start of Injection (SOI), Start of Combustion (SOC), Crankshaft Angle, and other parameters, and then that information can be used to achieve optimal fueling and timing parameters under specific operating conditions. This equipment is extremely useful in developing calibration profiles for certain modifications such as performance injectors, modified/multiple HPOP setups, compression changes, airflow/turbo/camshaft changes, and other modifications that will have an effect cylinder pressure and SOC. [URL="http://www.tfxengine.com/index.html"]TFX Engine Technology[/URL] provides a very good package, but because this equipment is extremely expensive it is generally cost prohibitive for most tuners. [B]Datalogging Equipment:[/B] This equipment is extremely helpful in providing valuable feedback to changes in tuning, especially for fuel control changes such as Injection Pulsewidth and Injection Pressure, and should be considered standard equipment for anyone performing any kind of tuning on a vehicle. Equipment ranges from simple standalone devices such as the ScanGuage, Insight, DashDAQ, or the Ford NGS (Star Tester), to devices coupled with a PC/Laptop such as AutoEnginuity, AutoTap, LiveLink, Ford IDS, PCMScan, Eye Spy and many others. Most (if not all) of these will provide datalogging (or at least data monitoring) of critical parameters as well as reading and clearing of Diagnostic Trouble Codes (DTCs). Most inexpensive datalogging devices will have a fairly low data sampling interval, usually around 5 Hz (samples per second) and is fairly adequate for most hobbyist tuners. More expensive applications such as the Ford IDS or Eye Spy provide a much higher sample rate of around 500 Hz and yields a much more detailed image of what's going on. If you are considering getting into any heavy tuning or if your vehicle has significant modifications, you may want to consider going with a high speed setup as the resolution is much, much better. This pretty much covers the basics on tuning equipment. As you can see, getting into tuning can be a pretty expensive enterprise, and that's just from the equipment aspect. The cost of training should also be considered, and in some extreme cases, the cost of experience (ie. blowing and engine). Most diesels are pretty forgiving, but it doesn't take much tuning to cause a runaway engine. Even a simple SOI curve that is too aggressive can scatter a bottom end in short order. Yes, experience can be pretty expensive so don't overlook that. We've been fortunate in the fact that the only engine we've ever damaged on the dyno was actually from a cylinder wall failure (crack), which ultimately had nothing to do with the tuning. Every major tuner out today has had customers that have suffered engine failures while running their tuning, as evidenced by our [URL="http://engfailsurvey.phptune.com"]engine failure survey[/URL], although the number of failures has declined in recent years specifically due to improvements in tuning quality. __________ [U][b]Up next, the meat and potatoes! Part 3: Tuning Maps, SOI, SOC, and other stuff.[/b][/U] Hang tight! [/QUOTE]
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