do you have any experience about chemi car competition?

Example Reactions

Some ideas for chemical reactions have been using pressurized air(creating oxygen through a chemical reaction and allowing it to build pressure) or using electricity created by the dissolving of metals in certain acids(basic battery). One clever idea by Cooper Union Hall is to use a fuel cell[4] (a cell that converts fuel to electricity via an electrochemical reaction) to power their car.

Winners in this competition aren't determined by whether their car is faster or more powerful, but how accurate their chemical reaction to stop their vehicle is. This is quite difficult, especially when the weight of the car, and distance it has to travel are unknown until the day of the competition. So teams must find a method that is flexible enough to fit a range of payloads and distances, and reliable enough so it doesn't fail with real world variables (temperature, humidity, ect.). Winners in the past have had a variety of ways of dealing with this problem, such as an "iodine clock" reaction[1]. This reaction works by using two clear solutions (many variations) that change color after a time delay (the exact time can be found experimentally). When applied to the car, the team used a simple photo sensor that could tell when the solutions changed color, at which point the cars power would shut off by cutting the circuit[5]. While the process itself is somewhat simple, accounting for the unknown variables like the payload and distance would be quite difficult.