Vehicle Velocity Problem

I have a car with mass=1000 and I use SetTorque(1000) to speed it up. Its velocity reaches 20 (i get that speed value with getVelocity() function) but i want much and much more speed. When i use a torque over 1000, the car speeds up to 16 and then it begins to speed down.
What should I do to reach 70-80 value of speed? (I had a look to Newton's vehicle demo and F1 car's speed value reaches 80 but while printing it to screen it is multiplied with ~2.5 and we see 200 miles/hour) What do I do wrong? And what factors affects the speed of the vehicle? I tried several things but they didn't no difference. (changing several values like mass,torque etc.)
By the way sorry for my English!

1. more friction between tires and ground helps.

2. simulating an engine torque curve + gearbox helps a lot. my vehicles in Stunt Playground can accelerate to over 160 km/h no problem.

Thanx walaber. I played your game. Good Job. But i can't reach high speeds like yours. How much torque do you apply to the wheels in your game? And i couldn't understand that "torque curve + gearbox" Can you explain it clearly?
2. How do I set the friction values?

A typical engine doesnt always exert the same amount of torque. At each RPM due to the characteristics of an engine like squish the bore, ignition timing, exhaust length and back pressure etc, the power changes. A torque curve can be represented as a graph of power vs rpm. So thats the engine. In real life though, there are forces working against the output of the engine such as aero drag and friction between tyre and road(rolling resistance) not to mention power loss through the driveline. aero drag and and rolling resistance increase as the speed increases. A car will only accelerate when the engines output is greater than the opposing forces. A very basic formula would be: Torque = Engine Power + Aero Drag + Rolling Resistance. The last two are negative values. After that you get into weight transfer both longitudinally and latitudinally which influences how much traction you have.

Because of my English I couldnt understand clearly especially technical things... But i got the main idea. (At least i guess so ) Thank u 2.
Now I'm thinking about using gearbox system. Just tell me whether it works. For example when the gear is 1, I will aplly an increasing torque (for example 500 to 1000) after a while the gear will be 2 and i will apply again an increasing torque starting with 500...and blah blah...
Or something like that!? Maybe I just thougth some bullshit What do u think about that? Thanx again...