If you go back into your scanning software
Mine's under Edit, you will find a 'Size Object' or 'Re-size' or 'Re-size Object' or something along those lines. Click on it and you should find a series of boxes full of numbers relating to the length x breadth x height (in pixels) of the object.
Normally, you only have to change the first one and the others will auto-change to match the new dimension that you've entered.
I find 850 pixels is more than adequate.
Do it, because some of those cars are worth looking at!