Our previous article addressed how to collect and download data from the MYCHRON 2. http://www.scottracing.net/ The purpose of that article was to answer the question of how to use the download pen and the software provided by AIM. This article will address the question of what does it mean to the Go-Kart racer. It is by no means a comprehensive attempt to teach data analysis, which is a topic addressed by Buddy Fey in his out of print book.

Scope and Disclaimer:

Winning motor races is a difficult and challenging undertaking. Driving a Go-kart faster than someone else on a given day is important to winning, but it isn’t enough. You still have to finish, finish first and survive post race technical inspection to be declared the winner. Data analysis is useful in getting your program to be fast, but it does not provide much help in the other critical areas.

Going fast is a combination of driving, handling and propulsion. Data analysis in general is helpful in each of these areas. However, the MYCHRON 2 is most helpful in driving and propulsion with less to offer in handling. The next generation MYCHRON PRO is better suited to help with handling.

The information is this paper is the product of Scottracing experience and does not necessarily reflect the views of or endorsement by our sponsors or AIM Motorsports.

The most obvious use of the MYCHRON is in providing the driver immediate feedback as to lap times. Observing the effect of driving lines and techniques on the lap time is the best way to learn and go faster. Beacon placement is critical for the driver since the MYCHRON must be triggered at a place on the track where it can be read and understood by the driver. Try different placements until your driver is comfortable reading his lap times and not worrying about making the next corner. The MYCHRON can also be used to measure split times by placing multiple beacons, but you must be the only MYCHRON user at the track or have coordinated which side to place your multiple beacons.

Good driving information is available in the Speed versus Distance or Speed versus Time plots. You should select the TRACK, Test and Lap that you want to analyze and make sure they are properly scaled. We always use the same scaling for all data taken on a given track to make sure that we can visually compare the data. For example, our CR80 enters the fastest turn at about 83mph and the slowest corner is 30 so we always scale the data to 20 –90. Next you should make a mental connection between the plot and the track. You should be able to find and identify the fastest and slowest corners on the track. If you have a map for your track this is very easy as long as you have the same beacon location. If the beacon location for the map and the data are different, the map is still a useful reference for manual correlation.

Driving techniques that are apparent on the speed plots include braking and the effects of turning. The perfect corner looks like a "V" on the speed plot. This means that the Kart was smoothly decelerated (braked) right up to the point of acceleration with no coasting or jerkiness in between.

Coasting is time when no braking or acceleration is occurring and is wasted time that should be eliminated. It shows up as horizontal (flat) lines either before braking for a turn or in the middle of a turn. Look for coasting on your speed plots and have your driver work to eliminate them. Kart brakes decelerate quicker than Kart engines accelerate and are a big part of going quick.

Early turn-in is indicated on the speed plots by double dips at the turn. Instead of a smooth speed line through the turn you see a tiny v imposed on the plot. This is due to a turn in, than a correction, and then another turn. Double turning slows you down and usually is a handling problem with an experienced driver. The less experienced driver is probably not using his braking and apex marks consistently and seeing them soon enough.

You can estimate the quality of your braking technique by using the linear acceleration channel, which is a computed channel. You must have good speed data in order to compute it. Then use Modify/Channels/Math to bring up a window in which you highlight Linear Acceleration. It is the first in the long list, so this part is easy. Then select the scale you would like. For Braking, we use –1.0 G as the Zero scale and 0.0 G as the Max scale. Click on Compute and Exit, then go to the Data window. Use Data/Add channel to obtain a window where Linear Acceleration should now be shown. Select it and linear acceleration will show on your plot. You can use the Data window to change its plot color and to display the units on the graph. Double click on Linear Acceleration in the data window in order to display a "G" axis on the graph. You can change the color by selecting Linear Acceleration through a single click and then using Modify/Color to pick something you can see.

Once you display the deceleration plots, your driver can see the effects of his efforts to smoothly decelerate without locking the brakes. Great deceleration is high negative Gs without flat spots or ripples in the graph. Good trailbraking shows as decreasing G after a peak. Remember that Go-Kart brakes are twice as good as the engines in changing speeds, so use brakes to go faster.

Once you have a handle on braking and turning smoothly, the next thing to work on is corner speed. Obviously each corner needs to be taken as fast as possible, but the most critical corner is the one which is followed by a long straight piece of track. Compare laps using the Data/Add Lap or Data/Add test feature to provide a graphic comparison of how much better you are doing in each part of the track. Don’t get disappointed if you don’t see big changes, however. One MPH improvement in corner speed is a big deal on most slow corners and you have to work hard to achieve it.

Consistency is the next thing you can look for. If your driver is using fixed reference points for braking, hitting the same apex point each time and looking down the track far enough., then you can overlay laps in the Speed/Time plot and see almost a single line. What you should look for is differences in the times that portions of the track are reached and explore why a given lap is faster. You will usually find that your driver is getting through a combination of turns better and saving lap time.

This will be a short section as everything that was said about cornering applies to handling. The MYCHRON data allows you to see that you are taking a corner faster or slower as a result of some handling change. The only difficult part is to be sure that the change was one that allowed the driver to go through the corner faster, not the driver finding new lines or courage.

The Go-Kart is normally driven by an engine, clutch and gear system which act together to propel it. The MYCHRON data can help you assess and improve each of these subsystems.

Basic Gearing is one area where the MYCHRON has really made life easy. We use a combination of techniques to gear the Kart to a track. The first thing we do is guess at a good gear and let our driver learn the track well enough to be consistent in lap times. Then we look at the speed plots and find the slowest corner. We then use our trusty slide-rule (or previously prepared Excel spreadsheets) to find the gear that matches that corner speed at a few hundred RPM below peak torque for the motor we are running. Put that gear on and go test. Most of the time this will be close, but you now should look at the RPM curve on the longest straight. The curve will slope up linearly to near the peak and then start to flatten out. The flat part is a region of low- or non-acceleration and ideally occurs near the braking point for the next corner. If it occurs a long way before the turn, the engine is turning too fast and you need to lower the drive ratio until you can’t pull out of the corner. At this time, the MYCHRON data is not as useful as driver feedback and lap times.

The MYCHRON provides a good tool for setting clutch engagement points and checking them throughout a race. Clutch engagement shows up on the RPM versus time plot as a rapid RPM rise followed by a sharp straight drop and a short period of flat RPM. The flat part after the peak should occur where you want your clutch engagement, which is typically several hundred RPM below the torque peak. As the race progresses, this point should not change much. If it does, you probably are overheating the clutch and should take appropriate measures such as lowering the engagement point, rebuilding it or getting a stronger device.

Engine performance is the area where a lot of analysis can be done and performance improvements made.

During testing, we use the MYCHRON to establish an engine’s power band and locate the torque peak. We do this by doing "power pulls" from very low speeds up through the maximum RPM and recording this data on the MYCHRON. For clutch engines, you need to set the engagement as low as possible and also gear the engine as tall as possible. These changes remove the effects of clutch slip and aerodynamic drag.

These tests can be run on the track if you have enough straight and nobody else trying to hot lap or you can find a convenient drag strip or closed street. When using a drag strip, place your beacon at the start and remember to return slowly to the start to trigger the MYCHRON.

Power data can be analyzed by computing linear acceleration for each pull and then using the X-Y plot. Set up the acceleration using the Modify/Channels/Math and setting the Zero point at about 0.1 positive G. Set the Maximum at 1.0 G. Remember that you select compute before exiting.

Plot your data by selecting View/X-Y plot and selecting RPM in the resulting window. You will then have to go to the data window, add the linear acceleration channel and select it. The resulting plot shows a scatter plot of Linear Acceleration versus RPM, which shows you the shape of your torque curve. Engine torque is linearly scaled with acceleration and you can look up the relationship in any good engine book. However, you are better off just using the shape to determine where to put your gearing or assess engine tuning. Absolute torque using this technique is not comparable to data collected from the dyno. You can use this technique to compare engine-tuning differences such as pipes, tuned length, jetting, etc. Remember to print the plot and be sure you have good notes as to the complete configuration of your engine including the weather information required to compute relative air density.

During race tuning, you can use the lap data to see how well your engine tuning is working. We use the liner acceleration scaled as for the power pulls and compare it from session to session using the data/add test or add lap feature. You can add this data onto the RPM/ time plot to see how the engine is everywhere on the track. Remember that you will see higher acceleration in slow areas than fast parts due to aerodynamic effects including drafting. As a result, pick a few slower areas to make your comparisons.