i sold my strobes, but buy my rig 
supa-special discount for j00!
umbrella are generally no good for an outdoor car shot. it’s always best to just do bare-flash, as when using an umbrella it’ll require more battery power to get the needed amount of light bouncing back. only time i ever used an umbrella was for interior shots, and even then, only on my Alienbee B800, which ran off constant power.
the problems with the shot is
a) white balance
b) only using one strobe, so should of had the flash more direct, OR had it on the side of the car, and used the street lamp to light the front/rear.
c) the shutter speed was too fast to capture enough light, giving not very pretty shadow’s, which mask the details of the car.
my suggestion is that you should always have a minimum of two flashes. if you’re on a budget, use what i used to use and buy the vivitar 285HV’s through amazon.com, about $70 USD + shipping each. you’ll also need some wireless remotes/receivers, but they can be had for under $20 shipped via ebay. Lightstands i’d suggest BHPhotovideo.com, and you’ll have a setup that will work under any condition. Look online and you can find some DIY’s on converting the wireless transmitters/receivers to run off AA’s instead of CR2’s, as well as doing a antenna mod to the transmitter, which increases the range/reliability of the receivers by 10 fold.
an example of the set up:
i always used my stronger flash (430ex) to light the sides of the car, as I could shoot it at a large light angle, and I always had that pointed generally around the middle of the door, with my other flash pointed at the rear
example:
outcome:
if you guys have any questions or want critique, feel free to PM me. I’m not a pro by any means, but I’d like to think that I had accomplished what I had set out to do while I was still in the photo game before school started. Have a look at my flickr, and if you want to know how I set up any shots, or have any questions, just lmk!