The problem with building a current limiter (essentially a speed controller) is a circuit diagram is only part of the solution; the physical layout of the board is just as important due to the extremely "noisy" environment. Even putting it in a metal case or changing the separation between tracks can have unwanted effects; you really need full PCB artwork as well as a schematic.

Being a driver I think that the limiter slows it down a great deal because at the catapult events or drag races our old car passing wind flew going at speeds up to 45mph by now it would be 50 or 55

thats the idea of a current limiter. we didnt use one on passing wind because it was a dragster and the car isnt in use now because the series was discontinued

thats obvious as you would of wanted to go the fastest

So does anyone have any ideas? I am completely stuck.

I know a schematic is only part of the idea, but it's a start...

I've only seen circuits that can handle 3-4A, and GP needs 20-25. I was thinking also being able to change it from the cockpit, according to motor temperature.

You will probably be better off with a full Motor Speed controller. A current limiter would be very similar in design and cost to a full Motor Speed controller.
So you would probably be better off going for one of these giving you more flexibility.

Hi all, i am also in the process of developing a current limiter for use in our car this year. Has anyone got a basic schematic that they could send me or publish...? It would prove very helpful and id be extremely grateful!
Thanks, Joe.

I don't have a circuit for a basic current limiter, but the circuit for RR's speed controller is on our website. This would require an additional PIC/Atmel to control it though. It would do current limit or full motor speed control. Might be worth a look for some ideas. Alternatively, with no programming required, you could use something like Sandback's UC3845 in place of the driver chip. Both could use a variable resistor to set the current limit.