I want to buy an RC car for control via Arduino Mega its speed and direction. I searched for something cheap.
I found this RC car but in net i found its semi-propotional... what is that means; I has a servo or not ;
Its a bit confusing..
I can't find more information.
The steering and motor power could be like 'on' or 'off', and nothing in between.
Semi-proportional could be that the transmitter is only sending 'on' or 'off', and the motor increases slowly speed if it keeps receiving 'on'. Or some other trick like that. Looking at the movie I think that the motor is only 'on' or 'off', and some trick is used for the steering.
For forward/back i have allready build my own H-bridge on and worked on other RC car, so i need now only to find a cheap RC with servo for direction 
And i cant find any info about that RC car .. only this photo
Legolas69:
For forward/back i have allready build my own H-bridge on and worked on other RC car, so i need now only to find a cheap RC with servo for direction
Yeah - it looks like that RC car has "bang-bang" steering; you would likely need an h-bridge to control the steering as well - or look into hacking the RC receiver; see this thread for ideas:
http://forum.arduino.cc/index.php/topic,86883.0.html
Something like "proportional" steering could be done by pulsing the steering as you moved forward...
But I wouldn't expect to find a "low cost RC car" with a servo for steering; you would be better off getting a cheaper car, and adding your own servo to the mechanism.
I send mail and the guy that sells it answer me:
"Hello...I checked out the car's steering, and it seems to turn fully left and right. I am not sure what it means by semi-proportional right and left steering. To me, it can only be turned right or left, what other choises can there be. If you know what it means, I would be interested to know what it means."
So i keep my current car and will program it for bang-bang with LN298. bridge 
I asked on modeling-car for car with propotional steering and told me the min value is 90euros... So i keep my 6euro car
If your current car uses a motor to actuate the steering, you might try attaching a potentiometer in such a way so that the potentiometer is rotated left/right as the wheels are turned left/right. Then hook the potentiometer up to an analog input pin on the Arduino, and read it as you move the actuator.
This will only work well if you remove the "centering spring" from the steering system, and if the motor isn't geared high to make the wheels switch from left to right quickly.
Basically what you would be doing is implementing a servo function completely in software.