Austin Dillon, grandson of Championship NASCAR car owner Richard Childress wheels a dirt l
What does your circle track program have in common with a NASCAR Nextel Cup (NNC) team or a Formula One team? You may think that the only answer is that all the cars have four wheels. I am sure that Smokey would tell you that we all have limits to our time and money. He would also tell you that the best teams always use their available resources most effectively.
For the sake of this article, we will define resources as money, man hours or material that you spend on your racing program. From NNC to your shop, having a plan and working that plan is the most important thing we have to do. You may think that a NNC team has no resource problem. However, look at the current "merger" trend in Cup racing. Both Roush Racing and Evernham Motorsports have sold a part of their teams to investors, for sources of additional funding.
You have heard the clich that circle track cars don't burn fuel, they burn money and time. Well, in many respects, this is true. The best teams, from NNC to your local circle track, spend their money on what is most important. Or at least they should.
With that said, a good question is "What is most important?" And, with respect to that, how important is engine performance? "Having worked with NNC teams for the last seven years, I always ranked the five most important elements in Cup racing as follows," says Charles Jenckes. (You may want to consider these as your own priorities):
* Team/Resource Management
* Aero/Mechanical Grip
* Pit Performance/ Race Strategy
ASA Late Model Challenge Champion Travis Dassow (on left) discusses his practice laps with
"I am an engine engineer, yet I ranked engine performance Fifth...unless they break. When an engine failure occurs, it is unrecoverable." In many cases, a severely-damaged car can be returned to the track to gather points, but an engine failure is final. For example, the #8 car missed the Chase in 2007 because the team suffered five engine failures. It was not because of poor car or driver performance. Now let's examine the list.
The Driver The driver is the competitor and, in many cases, the data acquisition system. Without good feedback from the driver, making adjustments to the car is very difficult. Whether at a short-track or a Cup event, it is the driver's ability to ascertain what the car needs and his (or her) ability to communicate this to the crew that often represents the difference between on-track success and failure.
"Natural talent cannot be learned. We have all seen how a talented driver can make a mediocre car look good," says Jenckes. "For these reasons, I rank the driver as the most important element in the majority of race programs."
Does the team with the biggest budget always win? Well, David sometimes slays Goliath. So, in racing, how does this happen? It happens when a team works together and uses all of its resources most effectively.
Even in Formula One, where teams annually spend the equivalent of the gross national product (GNP) of a third-world country, there are limits to their resources. No matter how much money they have, no one can purchase time. Time is the great equalizer. All Cup teams today have big budgets. And, all teams have large staffs. Because of their vast resources, Cup teams have more combinations to test than they have time to test them. The teams that recognize what to test and use their time most efficiently will have the most success.
In the 2007 Cup season, the car of tomorrow (COT) was a perfect example of how resource management can make the difference in winning or losing. The teams that emphasized development of the COT performed significantly better than those that did not. Simply stated, think about how you'll spend your time, well in advance of when it gets spent.
Bill Elliott won the 2002 Brickyard 400 even though he was down 50 horsepower to others in
Clearly, circle track racing is not drag racing. It is all about turning left. In 2002, Bill Elliott won the Brickyard 400 beating Rusty Wallace. NASCAR ran all of the top cars across a chassis dynamometer immediately following the race, and Elliott's was down 50 CBHP (corrected brake horsepower) to the best car. By any account, Indy is a "horsepower track." But Elliott had the best corner exit speed of any car on the track that day. That day, corner exit speed was worth more than 50 horsepower! Imagine a drag race where one car has a head start. It takes a considerable amount of horsepower to chase someone down.
Aerodynamic performance is a key aspect of any motorsport involving speeds that reach triple digits. At speeds over 100 mph, down-force becomes as important as mechanical grip (traction). As speeds pass 150 mph, down-force becomes more important than mechanical grip, and aerodynamic drag is interchangeable with engine power.
Here's an example: The pitch (nose attitude) of a NNC directly affects the drag. An optimal pitch would have the front valance sealed against the ground, thereby providing the minimum frontal area and preventing air from passing beneath the car. As the nose rises, more area is presented to the air (effectively increasing frontal area) and air passes underneath the car. In acceleration from 165 mph to near 200 mph, an increase in valance height of only two inches equates to a loss of 50 horsepower. The importance of aerodynamic performance increases as the square of vehicle speed. If you do the math, this is significant.
In Cup racing, it's many times easier to pass on pit road than on the racetrack. A team can often make up seconds on pit road. This is very hard to do on the track. How many horsepower would it take to make up a second on the racetrack?
Pitting at the right time can also play a significant role. On tracks where passing is difficult, passing in the pits may be the easiest pass you can make. The best example of how important pit strategy can be is seen in Formula One. Because of the aerodynamic configuration of these cars, the only way to pass is often on pit lane.
Engines last on the list of priorities? Well, we said unless they break. Smokey was an innovator, but he always knew that you had to finish. In 2003, Matt Kenseth won the Cup Championship. From NASCAR's chassis dynamometer we know that the Roush cars were 25 CBHP down (compared to other major teams) all season. Engine power was clearly not the deciding factor in claiming this Championship. However, note that the #17 car had only two engine failures that season, one of which was after Matt had clinched the Championship. Reliability was the key engine performance feature for winning the Championship that year, not power. By the way, Matt Kenseth and his Ford finished Second at Indy in 2003, despite the power deficit.
|CHART A|| |
| ||HP & TQ ||TQ ||RPM |
|Peak HP to baseline ||3.3% ||0.0% ||1.2% |
|Peak TQ to baseline ||1.8% ||2.2% ||-1.2% |
|Maximum RPM ||9,200 ||9,200 ||9,900 |
Engine performance becomes more critical when the percentage of on-throttle time is high; e.g. at tracks with long straights and during qualifying.
How do you evaluate how important your engine performance is to your racing?
First, start with the track or tracks where you race. Break the track down into the percent of lap time that you spend at wide open throttle (WOT) vs. what percent of the lap you spend in the corner and off the throttle. Clearly, if most of your lap is spent in the corner, then this is your area of concern.
Let's look at an example: Graph A shows engine speed (blue) and throttle opening (red) for a Cup car at Atlanta Motor Speedway. Atlanta is one of the fastest tracks in Cup racing, if not the fastest. This track should emphasize engine performance.
The shape of the power and torque curves shows the difference.
Even at Atlanta, it is interesting to note that the throttle was wide open only 58 percent of the time. By way of comparison, 42 percent of the time, the driver was off the throttle. Clearly, Cup cars spend almost as much time off the throttle at Atlanta as they do on the throttle. Since Atlanta is arguably NASCAR's fastest track, you can clearly see from this data why getting on the throttle earlier can be more important than engine power.
In most cases, the shape of the power curve is more important than peak numbers. Over the history of racing, engine speeds have increased. When the engine speed range is reasonably tight, engine speed and gear ratio beat shaft torque, almost every time. You can make more torque at the tire contact patch with gear than is possible with the crankshaft (flywheel torque). To demonstrate how this works, we will compare the power curves of four engines and see how they accelerate a vehicle (Chart A, and Groups B and C).
The comparison shows how four engines accelerate a vehicle (similar to a NNC car) from 165 mph to a distance of 3,300 feet. This would be similar to a straight on a typical 1.5-mile track, comparable to Lowes Motor Speedway.
The first engine is the baseline. The second makes more torque and more power but has the same engine speed range. We will label this second engine "HP & TQ." The third engine makes significantly more torque than the baseline but the same peak power and has the same engine speed range. We will label this engine "TQ." The fourth engine has a small power increase and less peak torque than the baseline, but has greater RPM capability and allows for more gear. We will label this engine "RPM" as shown in Chart A and Graphs B and C.
Actually, these engines are dramatically different. Which engine will accelerate a racecar faster? Well, you may be surprised. A computer simulation program was used to compare how each engine would accelerate a NNC-type car for 3,300 feet, starting at 165 mph.
The data shown in Graph D compares to a car running the baseline engine. The X-axis represents the baseline car and the Y-axis shows by how many feet the other engines would lead or trail the baseline car.
You can see that when all engines were run with a 3.70:1 final-drive gear ratio, the performance was as you would expect. The "HP & TQ" engine, with the +3.3 percent power and the +1.8 percent torque increase, would be fastest. After 12 seconds of acceleration, "HP & TQ" was 13.1 feet ahead of baseline. "TQ" was 2.9 feet ahead of baseline and "RPM" was 4 feet behind baseline. The results are shown in Chart B (next page).
Perhaps the only surprise is that a 2.2 percent increase in peak torque yields only a 2.9-foot lead after 12 seconds of acceleration. Clearly, torque at the expense of power is not always the best solution. The "RPM" engine performed poorly in this test, but the "RPM" engine's extended speed range cannot be favorably used without a change in final-drive ratio Let's install a 4.10:1 and rerun the data. The results may again be surprising.
After 12 seconds of acceleration, the results are dramatically different as shown in Graph E (next page).
The effect of the gear can clearly be seen. Not only does the "RPM" engine with the 4.10 gear jump out to a significant early lead, but it maintains that lead for the entire acceleration run. This is surprising, considering the "RPM" engine is down more than 2.0 percent on peak power and 3.1 percent on peak torque (compared to the "HP & TQ" engine), but the increase in final-drive makes all the difference. Increasing the final drive of the "HP & TQ" engine may help it. Obviously, we can't use as much of an increase as we did with the "RPM" engine because we would hit the rev limit before the end of the run. Now, we'll increase the final-drive ratio to 3.76:1 for the "HP & TQ" engine. The results appear in Graph F (next page).
The increase in final-drive ratio helped the "HP & TQ" engine significantly, and now the increased power of this engine is clearly evident at the end of the acceleration run. From this exercise we can note the following:
1. Gear ratio and engine speed may provide a performance gain in some (but not all) situations.
2. Optimizing final-drive ratio for each engine combination is critically important.
What is right for your track depends on the type of racing you do. On tracks that are very slick and with reasonably long straights, a higher rpm engine with the appropriate final-drive ratio may be fast. On short tracks with lots of grip, a higher torque engine may be best.
The purpose of this part of our series is to have you consider and plan what is best for your circle track effort. Be honest about the resources you have. Rank what are the five most important things for your type of racing, and spend your resources wisely. Remember, when you get passed from the flag stand to the corner, it is not necessarily killer power that got you. It is more likely the driver had a higher corner exit speed. Ask yourself what type of engine combination is best for your track, and make sure you optimize the final-drive ratio.
This was a beginning, intended to focus on the importance of engine performance and related elements in a winning combination. You'll need to step back and apply the information shared to your particular racing efforts. Determine priorities and rank them, not necessarily as provided here but in a similar fashion, according to how they fit into your scheme for winning-and then stick to them for consistency. If you allow priorities to change in the short-term, you'll have difficultly evaluating your original pecking order.
Next month we'll begin digging into the essentials of building a solid engine foundation, including parts longevity, bore/stroke relationships, and the essentials of good component selections and most important aspects of good oiling systems. You'll make some definable progress.
|CHART B |
| ||HP & TQ ||TQ ||RPM ||RPM |
|Baseline with 3.70:1 rear gear ||w/3:70 ||w/3:70 ||w/3:70 ||w/4:10 |
|Distance ahead of (or behind) |
baseline (measured in feet)
|13.1 ||2.9 ||-4.0 ||18.3 |
As we begin this "Technology Transfer" series, here's the plan Charles and I intend to follow. While each of us is an automotive engineer, we come from different sides of the track, so to speak. And, quite frankly, that's part of what makes this combination of experiences valuable to you. As such, it's possible for us to present the "what's" that work in concert with the "why's" that support the reasons. In this fashion, you'll be able to assemble some new "tools" for your racing program by benefitting not only from our previous experiences in designing and building engines and components but Charles' hands-on involvement with both Cup and (more recently) F1 powertrain development. To put all this in motion, we'll begin rather simplistically, but you can expect technical detail and depth to increase as the series is developed.
Where appropriate, you'll find data and graphs that support the concepts and ideas presented. And in every instance possible, we'll be linking this information with what is appropriate for racers engaged in just about any form of circle track racing, literally at the "racer level" where it counts. All reader comments and suggestions are welcome. By so doing, you'll help Charles and me provide you the most applicable and useful information for your racing experience. Enjoy the series.
Jim had a storied career in the automotive performance industry, beginning in a variety of editorial roles at Hot Rod magazine. For 19 years he served as Vice President/R&D for Edelbrock Corporation where he oversaw the design of automotive induction and exhaust systems, camshaft/valvetrain components, and cylinder head development, while having extensive interfacing with exhaust emissions controls regulatory agencies, including the U.S. EPA and CARB. Over his 42 years of experience, he has worked for and consulted with some of the biggest names in the automotive industry.
SEMA's "Person of the Year" Award recipient in 1985, McFarland is the author of over 300 automotive technical/feature articles including SAE Papers, general performance automotive publications dealing with the motorsports, RV, outdoor and truck markets. He has won numerous awards, is a member of the SEMA, International Drag Racing and Hot Rod Magazine Halls of Fame, and was elected to "Fellow" grade of the Society of Automotive Engineers' Institute for the Advancement of Engineering.
Charles holds two masters' degrees in mechanical engineering with his primary field of study in thermo-fluid science. He has worked in engine and fuels research at both the OEM and supplier level and has completed leading-edge work in the mathematical modeling of high performance four stroke spark-ignited engines. In Motorsports, he has contributed to championships in IMSA, NHRA, and NASCAR Nextel Cup as well as two Daytona 500s. He most recently served as Technical Director for Dale Earnhardt Inc.'s Engine Department.
Now based in Europe and working as a consultant in Formula One and Moto-GP, Mr. Jenckes has authored articles and technical papers on a wide range of engine topics from combustion and emissions to the use of CAE (Computer Aided Engineering) in engine development. He has received numerous awards for his work and presentations from the Society for Automotive Engineers (SAE).
Photo by Jeff Huneycutt
Over time, a considerable amount of material has been written about the merits of horsepower in a racecar. And, likely in an equal period, the value of optimizing power has also been banded about. Of the points advanced in Part I of this series, one we should focus on is where in the engine's speed range power occurs and how this relates to on-track performance as it pertains to final-drive gearing. Although power gains in a two-stroke-cycle engine are linked to an increase in peak rpm, a measure of this logic can be applied to four-stroke-cycle powerplants. But first, let's have a clear understanding of torque and horsepower.
By definition, torque is the measure of a twisting force, absent motion. Grasp a locked door-knob, apply a twisting force and motion (torque) only impends, but it's measureable. Suddenly, unlock the knob and the applied twisting force causes motion, measured as horsepower. Simply stated, horsepower is torque acting over time. In other words, torque is an "independent variable," and horsepower is a "dependent" variable, the amount of which is based on torque input and rpm. Conventional wisdom suggests torque accelerates a racecar, horsepower makes it fast. So, the placement and amount of torque in an engine's speed range becomes critically important, particularly when proper gear ratios are selected-as pointed out in the text of Part I in this series.
Years ago, during the development of multiple intake manifold designs, we developed design tools that enabled torque curves to be "shaped" in a fashion that provided power where it was needed, not relative to peak numbers. These techniques proved quite valuable for applications that included short- and medium-length circle tracks where corner exit speed (torque) was critical and did not relate to peak power. Plus, the ability of an engine to accelerate through its speed range (some have called this "transient" horsepower) adds to the benefit of corner exit speeds, for example.
However, as track length increases and throttle on-time correspondingly grows, a reliance on horsepower and higher rpm becomes of value. Note the fact that peak super-speedway engine rpm is now in excess of 9,400, whereas only a few years ago this cap was in the low-to-mid 8,000s. Much of these recent gains in engine speed have come from higher rpm-capable valve trains. As the series unfolds, we'll be talking more about this issue and how it relates to weekend racers.
Meanwhile, understand that peak horsepower numbers aren't the singular goal in building a successful circle track engine. Hopefully, this evolving series will help you understand the logic and reasoning in support of that statement.