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Dyno Testing and Tuning

Book Review

by Ryan King

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If you think that bolting on a set of headers, an exhaust system, an intake, or any other part means you will make more power, then this book is for you.

Tuning doesn't just mean changing carb components, or injector flow, and adjusting ignition timing until driving glitches go away, or it simply "feels good," it requires quite a bit of information about how an engine is running to get it right. In order to get that information, you need quite a few tools, but of all the equipment used in tuning, one is key: the dynamometer.

That's where this book comes in.

As the authors explain it, a dynamometer is a complex, but very useful tool for tuning — especially if you want to effectively and efficiently improve performance and drivability. They also point out that the key to making it useful is understanding how it works and how to go about the meticulous process of tuning.

The information contained on these pages isn't only useful for engineers, dyno operators, or "tuners," it's highly useful for any serious performance enthusiast — either pro or amateur — who is, has, or is going to install performance parts, build performance engines, or attempt to improve the factory tune for a little more power.

It isn't that the well-informed engineer, automotive professional, or enthusiast hasn't heard a lot of what is contained in this book, but it's the context that really makes the difference. When the concepts such as accuracy, repeatability, cylinder wash, and intake air temp are explained, placed in the right situation, and are part of a methodological process, their importance really starts to become clear. That clarity turns into vivid understanding when they delve into the process of tuning. They also fill in many smaller pieces of the puzzle so that you are left with a complete picture that will help you as you start to modify, test, and tune your engine and vehicle.

As a huge bonus, the book is filled with sidebars that point out important facts and tips related to dynamometers, tuning, and performance. There's also sections at the end of the book for terms, source material, and resources for dynos and tuning.

The following is a summary of what you'll find in this book.

The Book

Chapter 1: Introduction to Dynamometers

Chapter 1 starts with a brief explanation of what a dynamometer is, before going into a look at the history of how they came to be. After the history lesson, the authors look at dynamometer principles as well as the two most common power absorption methods used in modern dynos: water brake and eddy current. After power absorption, they discuss how chassis dynos work as well as the functionality of the two most common types: power absorption and inertia. They then finish the chapter by explaining the basic principles of Force, Work, Power, Torque, and Horsepower — all of which make up how an engine functions, what a dyno measures, and what is extrapolated from those measurements.

Chapter 2: Types of Power Absorbers

This chapter is broken down into two major sections. The first covers the many different types of dynamometers. The second discusses the testing methods used with dynos, which includes constant-speed, constant load, acceleration, and inertia.

Chapter 3: Numbers and Formulas

I really enjoyed this chapter. Yes, it's about theoretical math. Yes, I'm a geek. I've been taught or have studied the sciences since at least the age of three, which are my earliest memories of it. As the authors point out, proper use of a dyno and applications of the dyno numbers require an understanding of the theoretical physics involved. Also, as the authors note, the math isn't terribly complex, but it is necessary. As a matter of course, they spend this chapter explaining those equations, the appropriate applications, and how to use them in vehicle development. The chapter finishes with the effects exhaust, cooling and cylinder pressure have on power output, how those equate to theoretical numbers, and how to configure an engine on a dyno for the best real-world results.

Chapter 4: Goals and Objectives

In Chapter 4 the authors cover quite a bit of ground, however, the omnipresent theme is that planning and preparation are the most important factors for a successful test session or sessions. Planning, as they point out, starts by writing out the goals and objectives of the testing sessions in detail so that you can keep your eye on what you need to do to reach them. Then they spend the rest of the chapter explaining — in detail — what to do in preparation for a dyno test session and what you are trying to gain from testing sessions — data — as well as how to get it accurately. They also explain what to do with that data, once you've obtained it and give quite a few tips to make sure you get the data you need, and aren't left with holes you will need to fill with subsequent and costly test sessions.

Chapter 5: Let's Test

As the authors state, dyno testing should be considered an exact science, which means serious preparation as well as methodology. That's the first thing the authors explain in this chapter. They spend the rest of the chapter covering safety and the testing needs. Those needs include testing equipment as well as engine components. They also look at how these pieces of equipment and components need to be working during the various testing procedures for a productive and accurate test session.

Chapter 6: Tuning

This chapter covers the basic tuning factors as well as the order in which tuning should occur for methodically repeatable and accurate data. It also has an important side bar that discusses how to shape a torque curve for best use in a car.

Chapter 7: Testing Tips on How to Use a Dyno

Chapter 7 takes a close look at some specific points to manage while tuning as well as how to test for mileage, which may save some considerable track time if you are building a race car that has to compete with a limited fuel supply.

Chapter 8: Accuracy and Repeatability

This is what it's all about. I know, you'd think dyno tuning is all about numbers...and ultimately, yes, it's about the test data you get in the end, but it's the accuracy and repeatability of that data that shows its quality and it's the quality of the data that counts more than the data itself. Without accuracy, the information you just paid a hefty chunk to receive is worthless. In Chapter 8, the authors explain what accuracy and repeatability are, and how to go about getting them.

Chapter 9: Correction Factors: Problems and Procedures

Throughout Dyno Testing and Tuning, the authors make reference to correction factors that allow the uncorrected measurements taken during the dyno run to be changed to a standard that allows comparison with other dyno sessions where variances in temperature, humidity, barometric pressure, and the like effect power output. However, there are quite a few different corrections to change the numbers taken during the test session to different standards. This chapter helps to explain those differences as well as the equations themselves, so that you can better compare your test to others.

Chapter 10: Troubleshooting

If you've ever done any serious diagnostic work, then you know how valuable a systematic approach is to the process, as well as how it can make it SO much easier. There are, of course, several ways to go about coming up with a corollary diagnostic list: You can gain a great deal of experience with whatever it is you are working on, figure out all the ins and outs to come up with a list of protocols; you can also study the basic details others have found that make up whatever subject you are working on so you can, again, come up with a list on your own; or you can go right to source information for the diagnostic routines already devised by experienced people in that field, and use their knowledge. The last one is what this chapter provides.

Chapter 11: What to Look for in a Dyno Facility

Just like everything else that has to be done right, finding a quality dyno facility is necessary. In Chapter 11 the authors give you some very helpful tips to find a competent shop to test and tune your engine. As with the rest of the book, they look at the details of dyno testing and explain what kind of dyno facility can provide the data you are looking to get. They also give you an idea of what to look out for with dyno facilities that don't make the grade, so you don't expend valuable resources getting substandard data on your engine's performance.

Chapter 12: How to Read a Dyno Sheet

This chapter gives you insight into the information displayed on a dyno sheet. It lays out the common variables tracked during dyno testing as well as the necessity to record the type of dyno runs being made. It also explains how to approach analyzing the data you've gotten from the session(s). The last section explains the differences between engine and chassis dyno data. Additionally, there are two very useful sidebars: the first looks at Lambda and its correlating air/fuel ratios in gasoline, diesel, and methanol; the second looks at gasoline and the way its different aspects effect performance.

Chapter 13: Tuning with Dynamometer Data

Chapter 13 takes you beyond the dyno room (albeit, briefly) and shows you how to apply the data you gained from testing to real track performance. This key facet is important for being able to recreate dyno performance in the real world where conditions will be different than those you've tested in.

Appendix A

This is a pretty cool little bonus — a dyno break-in sheet that gives you a checklist of information as well as the process for breaking in a freshly built engine on a dyno.

Appendix B

Appendix B features two nifty dyno aids — a dyno log for recording basic information on the series of runs you've made with an engine, and a pre-run checklist to help you make sure you've gotten all your ducks in a row before you fire your engine and possibly ruin it.


As with any process, there's no replacement for experience, but trying to figure out as complex a process as dyno testing and tuning without having a basic foundation is both foolhardy and a waste of time — especially since Harold Bettes and Bill Hancock have done a great job making the information easily available to anyone who is interested in performance and tuning.

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For more information contact CarTech Books on the web at www.cartechbooks.com, by phone 1.800.551.4754, or by email at info@cartechbooks.com.

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