Heh, I liked that line in Saving Private Ryan... I'm not an expert, but I would say around 100 pounds for it to start being significant... 200 or more until you notice
some good 0-60 improvements or faster lap times on a track. With 200 pounds or more off, if you have a good Zeal or other highly adjustable suspension set-up, you
could even start to compensate for the reduction in weight... With more than 200 pounds you could even start thinking about perfect weight distribution throughout
the car... But this is all fantasy... As per my earlier post, removing the A/C isn't the first way to go.
From an aerodynamics point of view, the 7hp or so that the A/C compressor uses is less than the power loss from the simple drag of your windows being down. So,
roll up your windows and you'll outweigh the A/C power "loss".
From Jay's post, here is the way to go with weight shaving on the 350Z:
What, you want superior lightness in your car and who cares about comfort, ok:
(This list goes from things that are easy to do and most people can do this - to complicated and only people tracking their car will do this.)
-Remove all your crap from the car first of all, this includes that owners manual too
-Go on a diet there tubby. Your weight gets factored into the equation
-Don't fill your gas tank up: 1/2 will get you to where you need to go
-Take out the spare tire and jack
-Remove all engine plastics
-Get lightweight pullies and a flywheel
-Look for lightweight wheels (Magnesium?) and brake components (Carbon/ceramic?)
-Make sure you have that CF hood, trunk, fenders, doors, and CF seats I was talking about
-Remove window washer tank and lines
-Remove all interior plastics and carpets
-Remove the headliner
-Remove stereo components
-Remove the exhaust and run open headers
-Remove AC and heater components
-Remove all sound deadening
-Remove power door locks and alarm
-Replace all windows with lexan (you may use NACA clear ducts to get air into the cabin)
-Remove side window motors and interior door components
-Remove windsheild wiper motors and wipers (front and rear)
-Replace the steering wheel to remove the airbag, remove passenger and any other airbags
-Remove front and rear bumper supports and door reinforcements (make sure you have a full cage)
-Remove the passenger seat completely