AVL dynamometers simulate race conditions for key parts of race cars
How can Sprint Cup teams accurately test an engine without leaving the shop? The richest ones use an AVL dynamometer to make the engine think that it is in a car on that week's track.
For all you gamers and virtual racers out there your ultimate fantasy world just might be a Sprint Cup race shop with all of the gizmos and gadgets the teams now have available to them. They can literally run an entire race on the many different machines in their shops to test engines, transmissions, rear gears, shocks, chassis geometry and just about everything else on their race cars.The technology in the Sprint Cup series has literally gone space age and rivals NASA engineering in some areas for its complexity and creativity. One simple example would be how we used to set up the cars. We would "string" the car -- meaning we would use a stretched string to measure from as a guide in squaring up the chassis and setting up the geometry. Today they use lasers. As time has passed, the teams have added machines that can help them duplicate the performance characteristics they will experience at the different tracks where they race. For example, wind tunnel technology has played a dramatic role in making the cars more aerodynamically slick over the years. In the old days you would place a car in a tunnel and blow air by it while streaming smoke across the various areas to see how the air was moving, etc. Today's wind tunnels are far more sophisticated and can give much more definitive information to the teams. Another example would the be the "seven post shaker," which allows the teams to duplicate how a car performs under braking, cornering and accelerating through the corners. Now they can test various packages to see which one is best for a particular track. With the computerized "track mapping" being done the teams can try various race lines into the corner, different braking packages and various driveline combinations without ever leaving the comfort of the shop. That is the ultimate in virtual racing in my book. Jealous? You too can create this virtual world right there in your home for a measly couple of million -- well, maybe 50 million or so if you throw in a rolling wind tunnel and some of the other toys -- but who's counting. My personal pick for "toy of the year" [a very sophisticated and expensive toy] would have to be the AVL dynamometer that many of the teams are now using. The old hydraulic dynamometers allowed you to test your engine's horsepower and torque band on short test runs but the AVL dynamometer will allow you to do multiple things such as duplicate an entire race to measure wear and tear on the engine and drive train. When I first started hearing about the AVL dynamometer I was skeptical about all of the claims that were being made about it. But now I am a believer.AVL North America, Inc.The engine test cell operator monitors the progress of a test using an AVL dynamometer.If you want to learn as much as you can then go directly to the source, which is what I did concerning the AVL dynamometer. I contacted John Alford, who is the sales engineer for AVL in North America. Alford was very informative about the AVL dynamometer, including the fact it is built by a company that has its headquarters in an Austrian city where the "Governator" of California reportedly is from. Maybe Arnold Schwarzenegger really is a robot! "The biggest thing that the AVL brings to the table in NASCAR is that we use an AC dynamometer with a sophisticated control system for testing. This allows the teams to test the engine in a way that makes the engine think that it is in a car on that week's track," Alford said. "For example, we can simulate gear shifts, vehicle weight and drag, tire grip or lack thereof and track geometry, etc." Yes John, but can it brew a good cup of coffee? The result of all of this is the engine runs the same way during the testing as it would in the car, which allows the race engineers to assess how a given engine package will perform in a given car for a given race, Alford said. He gave the example that "some engines might be able to drive a car with a high top speed at the end of a straightaway, while another engine might allow a car to accelerate faster out of the corner." "Lap time is computed during the test so comparisons can be made to determine if changes to the engine change the lap time or not. It is important to note here that the lap time is computed based on the actual engine output. The lap time will get slower if a spark plug wire is pulled off the spark plug," Alford pointed out. In other words, they are not just replaying data that was collected at the track. "Different tests can be run to evaluate different trade-offs for each track to come up with the optimized engine package for each race," Alford noted. The teams can also test engine durability for new designs to ensure that they will survive qualifying, practice and the race. The capability of the AVL goes far beyond those of the old hydraulic dynamometers thus giving the teams far greater knowledge than was available to them in the past. That is starting to sound like space age stuff to me. Alford said another advantage of the AVL dynamometer is that it is capable of "motoring" the engine to simulate the effects of coming into a corner with the throttle closed. This allows the engineers to measure the resulting stresses that the engine experiences when it is used to brake the car into the corner.Courtesy of AVL North America, Inc.The AVL dynamometer's sophisticated control system for testing allows teams to test engines in a way that makes the engine think it is in a car on a specific track, says AVL's John Alford.Some teams use the AVL dynamometer to test the engine, transmission, driveshaft and rear end as a complete unit. Road courses, for example, have traditionally been very tough on transmissions in particular and drivelines in general so the teams can now test the various transmission packages to find the correct combination for their particular driver on a road course. The driver plays a significant role in how a transmission will perform on a road course. Eddie Wood said that with some drivers the Wood Brothers had drive for them over the years they would tear the transmission down after a race and the gears would literally fall out of the case. But when David Pearson drove the No. 21 the transmission gears would still look new after he raced a road course race. Being able to match the performance of the equipment more closely to your driver's style of racing is a definite advantage in my book. First and foremost it reduces the chances of mechanical failure at the track when precious points are on the line. Secondly it increases the driver's comfort level and confidence by improving the feel and feedback he is getting from the car. This can be a significant factor in multi-team operations. Driver selection can become just as much about driving style compatibility as personality and ego compatibility. Two drivers with similar driving styles can generate much more usable information for the equation with less effort than two drivers with very dissimilar styles. In an SI.com article by Lars Anderson in 2006, Jeff Andrews, the director of engine development at Hendrick Motorsports, said: "This machine does the same things to the engine that Jimmie [Johnson] and Jeff [Gordon] and the rest of our guys will do to it during a race. We're also able to learn more about generating power in the engine by seeing up close how it's stressed during a simulation. This has been a tremendous asset for us." Other teams have acquired an AVL dynamometer since 2006. Most notably Joe Gibbs Racing and Richard Childress Racing. That might help to explain some of Hendrick's lost dominance with the COT this year and the spectacular success of the Gibbs teams since they switched to Toyota. The Childress teams have also gained in their performance this year. In doing research for this article I found it difficult to find anyone who wanted to talk "specifics" about the AVL dynamometer. It must be producing some really good "stuff" for the teams now operating it because they don't want to talk about it publicly. It makes you want to go hmmmmmm. The AVL dynamometer also plays an important role in restrictor plate races, Alford said.AVL North America, Inc."Different tests can be run to evaluate different trade-offs for each track to come up with the optimized engine package for each race," says AVL's John Alford."It is important to be able to string together a series of small changes to create a package that is better than the competition's," Alford explained. "The more a team is able to measure the result of small changes then the better chance that team has to come up with a package that has more power." The gain of just one horsepower can have a dramatic effect on a lap time during qualifying. Plus having the ability to pass or pull away from the competition during the race separates the best teams from the mediocre teams, Alford said. AVL also makes a "combustion analysis" machine that measures the pressure in each cylinder and how the pressure develops during each engine revolution. This allows the teams to check and compare each cylinder's performance to the others under differing circumstances. Alford's example was that one cylinder might perform better with different timing. The machine allows you to measure what is happening in this regard and gives you ideas about what should be changed accordingly. Totally amazing stuff when compared with what was available just a few years ago. Instead of squinting through a magnifying glass at plugs like they did in the old days, today's engine builder can read a computer printout and gain far more information. It might not be as romantic but it is a heck of a lot more accurate. The results are evident on the track every week. Maybe we will get to see a "virtual NASCAR" some day in the future where the teams all do their shop runs and then send their results to NASCAR for evaluation and declaration of a winner. It sure would save the teams a lot of the aggravation of having to travel all those weeks. No more cramped flights. No more crowded motels. No more track food. No more beer. Uh, wait a minute on that last one! Bill Borden is a former championship winning crew chief who operated David Pearson's Racing School for many years.AVL North America, Inc.This is a combustion analysis system that all of AVL's NASCAR customers use.
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