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Dyno Graph - Real Wheel HorsepowerGoing beyond the dyno graph From the February, 2012 issue of GM High-Tech Performance By Justin Cesler Photography by The Author
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Spend enough time comparing dyno sheets and you will begin to wonder why so little information is normally considered enough. In the real world, most numbers come with additional data, data that is necessary to make a full decision. For example, if we said "John has been on a diet for six months and hasn't lost any weight at all," you might assume that his diet is terrible. Of course, if we continued by saying, "but he gained 15 pounds of muscle mass, can now bench three times his body weight, and finished a half-marathon on his first try," you would get the full picture, proof that John's diet and exercise plan was working well. The same can be said for the dyno. For instance, if we said, "Installing the new intake manifold and cylinder heads only picked up five rear wheel horsepower," the natural reaction would be to think they weren't worth the money. Completing that sentence with, "however, looking at the datalogs showed a 3-psi drop in overall boost, a 35-degree drop in incoming air temperature and a slightly lean condition throughout the run," we would know that the new combination was actually much more efficient and capable of making significantly more power, assuming we could get the missing boost back and add enough fuel in the tune up to compensate for the increased airflow. You see, you can't ever go off horsepower and torque alone, they just don't tell enough of the story, which is why looking at and understanding datalogs is essential.. The VCM Scanner
Through the magic of technology and glory of all things electronic, checking out an engine's vitals is just a matter of downloading the right software to your laptop and plugging into your vehicles OBDII port (OBD1 fans have a little more work to do but that's a discussion for another time). Of course, like anything else in this hobby, OBDII datalogging isn't to be treated as the end all of engine information, but using the VCM Scanner data, along with dyno graphs, track times and traditional engine tuning techniques (reading plugs), can really help reveal the entire picture, instead of just a small view into an engine's performance. Here at GMHTP, we use the HP Tuners VCM Suite for 90-percent of our OBDII tuning and scanning and we've provided links in earlier articles so that you can download the HP Tuners software to be able to open and view datalogs from our testing. This month, we're going to jump a bit deeper into the VCM Scanner and explain some of the most useful data for comparing dyno graphs to one another. As with everything HP Tuners, you can modify, tweak and expand the VCM Scanner to do a variety of things but we're just going to focus on the "must have" data that should be standard on each and every datalog you acquire. We're not going to mention RPM below but we're going to assume you know what it means and why you would need it to get any good data from a log. As with everything else in our Real Wheel Horsepower series, we are going to make these datalogs available to download (http://bit.ly/pekZ6c) and we will upload future data as it becomes available during testing. So, download this test info, check it out and email or write us if you have any questions. Spend enough time comparing dyno sheets and you will begin to wonder why so little information is normally considered enough. In the real world, most numbers come with additional data, data that is necessary to make a full decision. For example, if we said "John has been on a diet for six months and hasn't lost any weight at all," you might assume that his diet is terrible. Of course, if we continued by saying, "but he gained 15 pounds of muscle mass, can now bench three times his body weight, and finished a half-marathon on his first try," you would get the full picture, proof that John's diet and exercise plan was working well. The same can be said for the dyno. For instance, if we said, "Installing the new intake manifold and cylinder heads only picked up five rear wheel horsepower," the natural reaction would be to think they weren't worth the money. Completing that sentence with, "however, looking at the datalogs showed a 3-psi drop in overall boost, a 35-degree drop in incoming air temperature and a slightly lean condition throughout the run," we would know that the new combination was actually much more efficient and capable of making significantly more power, assuming we could get the missing boost back and add enough fuel in the tune up to compensate for the increased airflow. You see, you can't ever go off horsepower and torque alone, they just don't tell enough of the story, which is why looking at and understanding datalogs is essential.. The VCM Scanner
Through the magic of technology and glory of all things electronic, checking out an engine's vitals is just a matter of downloading the right software to your laptop and plugging into your vehicles OBDII port (OBD1 fans have a little more work to do but that's a discussion for another time). Of course, like anything else in this hobby, OBDII datalogging isn't to be treated as the end all of engine information, but using the VCM Scanner data, along with dyno graphs, track times and traditional engine tuning techniques (reading plugs), can really help reveal the entire picture, instead of just a small view into an engine's performance. Here at GMHTP, we use the HP Tuners VCM Suite for 90-percent of our OBDII tuning and scanning and we've provided links in earlier articles so that you can download the HP Tuners software to be able to open and view datalogs from our testing. This month, we're going to jump a bit deeper into the VCM Scanner and explain some of the most useful data for comparing dyno graphs to one another. As with everything HP Tuners, you can modify, tweak and expand the VCM Scanner to do a variety of things but we're just going to focus on the "must have" data that should be standard on each and every datalog you acquire. We're not going to mention RPM below but we're going to assume you know what it means and why you would need it to get any good data from a log. As with everything else in our Real Wheel Horsepower series, we are going to make these datalogs available to download (http://bit.ly/pekZ6c) and we will upload future data as it becomes available during testing. So, download this test info, check it out and email or write us if you have any questions.  IAT When comparing A/B dyno...  IAT When comparing A/B dyno numbers, the Incoming Air Temperature (IAT) sensor provides vital information. As air heats, it becomes less dense, which affects overall power production. As it cools, it becomes denser, which potentially increases power output. For consistent testing and true comparison, it would be ideal to have IATs within 1 degree, however a 5-degree variance is more typical of aftermarket testing. If a dyno test involves swapping cold-air intakes, adding methanol injection or changing an air-to-air or air-to-water intercooler, these numbers are even more important, as they will show how well each particular modification is working. Otherwise, make sure you peak at a tuners datalog to check the IAT between runs, especially if your interested in comparing a baseline run to a finished product.  MAF/MAP The MAF and MAP sensors...  MAF/MAP The MAF and MAP sensors play a vital role in the factory tuning loop, and viewing their recorded data can tell you a lot about what the engine was doing during a run and why. The MAF datalogs are normally recorded in pounds of air passing over the MAF sensor per minute (lb/min) and should generally rise smoothly over the course of a run. Big dips, noise or other inaccuracies in the datalog should tip you (or your tuner) off to a problem with the MAF unit or the routing of incoming air to the engine (or an even larger problem). Along with the MAF, Gen III and IV computers rely on the MAP sensor to monitor manifold pressure, which is alongside the MAF to calculate fueling. A drop in manifold pressure from one run to another (when switching parts) could tell you about a new restriction you’ve introduced or a increase in flow which is creating more power.  At the end of the day, with...  At the end of the day, with all of the cool technology we have and all of the data we can collect, Spark Advance and the Air/Fuel ratio are still the kings of the horsepower and torque game. Move spark advance (timing) and your engine will make or lose power, move it too much on the wrong combo and your engine will make a quick escape out the bottom of your car, but that is another story. When comparing dyno runs, you want to keep an eye on overall Spark Advance to make sure that scientific A/B testing has been completed. When tuning your own car with a new combo, expect that your tuner will adjust total timing, but if you’re checking out our A/B testing in the magazine, make sure we stick to our word and either tell you why we’re adjusting it or explain why we left it alone!
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