Senior Design: Improving the Performance of a Go Kart

We first brain stormed some ideas on how we could improve the go kart before we fully repaired it. We know we wanted to improve the performance of the go kart so we considered improving either the straight line or cornering performance. Due to the skills, time, and resources we had at our disposal, we decided to improve the straight line performance in terms of acceleration by modifying the engine to produce power.

After conducting some research on getting more power out of go kart engines, we found various forms of modifications such as fabricating a performance air filter, adjusting the timing of the camshaft to increase the intake valve lift duration, removing the governor, re jetting the carburetor, fabricating a high flowing exhaust, and increasing the compression ratio.

However, we found that we had no feasible way of generating more power due to limitations on budget and resources. If you look at the graph on the left, you'll see curves for torque and horsepower. The Honda GX160 has a rev limit of 3600 rpm. At the end of the limit, the horse power curve is still going up which means that engine's breathing capabilities are already maximized. We compared the GX160 to the next engine in its family, the GX200. The only difference between the two engines is that the GX200 has a longer stroke to generate more power. With this knowledge, we knew that our options in getting more power out of the engine were limited.

The slide show to the left shows the final go kart after all the necessary repairs were made. In the middle of preliminary test runs, the brake mount on the go kart came off so we had to create a new brake mount as seen in slide 3. Slide 4 shows a SolidWork model of the brake mount. The last slide shows the items that would come with the drive train kit if we were to sell it which includes a driving gear, a chain to accommodate for the size of the larger gear, and a chain breaker to make chain adjustments easier. The kit cost $43.09 before tax.

We tested the go kart from 0-100 feet 10 times with the original gear set, and 10 times with the modified gear set. We did all testing in the same direction on the same day with me as the driver for all recorded data. We marked up the straight away from 0-100 feet with 10 foot intervals. We recorded the timing for when I crossed the 10 feet marks by mounting a phone onto the go kart frame and having it record each run I made. We then took the video footage and recorded timings for every 10 feet by using Avidemux. To do so, we played the videos frame by frame to get timings of when a certain distance was met.

The slides to the left show a sample video of one of our test runs. You will also see the analysis we conducted with all the data that we obtained from all of our videos. Initially, the go kart had a gear ratio of 5.5:1. The modified go kart had a gear ratio of 6:1 which in theory should increase the go kart's torque by about 9%. Though the torque did increase by that amount in certain parts of test runs, the marginal difference in acceleration could only be seen from around 0-30 feet.

Due to different timings of when the governor limited how high the engine was completing revolutions, aerodynamic drag, and rolling resistance, the speed at which both karts reached at the end of the test distance were similar.

To improve this project further, we could potentially implement a gear train of 2 or 3 gear sets to allow access for a wider range of torque and speed. Bigger gears provide substantial torque which is beneficial for starting races and, accelerating out of corners while smaller gears complete revolutions faster which is beneficial for top speed in straight lines. We used Matlab to complete our analysis and, create the graphs seen in the slides for this section. To see the code, click here.