Kart Racing Lap Timer and Tachometer

Hi my name is Carson

I am new into Arduino and i do kart kart racing. i'm wanting to know what i need to make a tach and to count lap times. You can buy them online but they are $500+ so i think it would be cheaper to make one. you can look them up a very popular on is the "MyChron" i am wanting to put a small LCD on my screen to show all the data. i would like it to show, RPM, Lap time, water temp, speed. if i was able to save the data and look at it later better on a lap top later too. the motor I have is 125cc Rotax kart engine on the top of the motor the is a spot to screw in a temp sensor. for the RPM i think i could wrap some wire around the wire that goes to the spark plug.

For the Lap time there are magnet strips in the track but there can sometimes be more then one strip so it be nice if i can tell the Arduino how strips there are. i think a hall effect sensor would work for this. and for the speed i can put a magnet on my axle and use a hall effect senor

i'm only 15 so i need help with how to wire this all up and and other ideas would be great too

I hope this is enough info

Are there magnet strips in the track, or a magnetometer? Big difference. As for speed and lap time, why not use a GPS? Speed is measured very accurately, and if you set the coordinates of the startpoint, you ought to be able (with a little navigational math) to determine lap times.

Ya they cut a line in the track and place them inside the the cut that they have made I think GPS we'll be harder to do then Hall effect sensors