Body - Weight Reduction
Fiberglass and Carbon Fiber Fenders – Not Much Lighter Than Steel
Fiberglass fenders became a staple of the compact car scene. But their value in weight reduction is minimal.
Steel fenders are made of very thin metal and weigh just over 5 pounds each. Weight savings with fiberglass
or carbon fiber would be less than 5 pounds for both fenders.
Carbon Fiber Hood
Carbon fiber hoods are the other cliché in the compact car scene. The Geo Storm hood is not particularly heavy,
a little over 20 pounds. A carbon fiber hood that is rigid enough to hold its shape for real world use is going
to be substantially thicker than the steel hood. A carbon fiber hood might save 10 pounds.
Fiberglass Rocker Panels – A Bad Idea
The rocker panel of a unibody car is part of the vehicle structure, and forms the outside half of the box beam
that runs from the base of the A pillar, beneath the doors, to the base of the C pillar. This is the frame cage
that is the skeleton of the car. It is a very, very bad idea to remove that structure from the vehicle. The
spot welds holding the rocker panels to the floor pan are responsible for all of the rigidity in the floor of
the vehicle. Without that structure, the unibody will fold and crumble like tin foil. These panels can not,
under any circumstances, be replaced with fiberglass, because it simply is not strong enough to act as part of
a unibody frame. Even if the panels were structural carbon fiber (4+ layers of 6K fabric with a 1/8 inch panel
thickness), no one short of an aerospace contractor could bond the composite to steel with enough strength to
make it safe.
Carbon Fiber Doors
Doors are quite heavy (though much of that weight is due to the glass window). Fiberglass or carbon fiber doors
would save a bit of weight. However, the complexity of making a door, out of composite material, pushes the
price of such an item into some serious money. Chances are that only a shop like Restored.Jp, in Japan, could
produce such an item. If they could be convinced to make doors for the Geo Storm (Gemini Coupe), the price
would likely be over $3,000 + shipping from their location in Sakaiminato, Japan.
Carbon Fiber Bumper Beams
The bumper reinforcement beams behind the front and rear polyurethane bumper covers are made of 3/32 inch thick
stamped steel, and account for 40+ pounds of weight at the extreme forward and rear ends of the vehicle. Looking
at the vehicles built in the last 5-15 years, many of them use injection molded plastic bumper beams. Replacing
the steel beams with structural carbon fiber would reduce the weight by more than half, and still retain adequate
crash safety structure.
JDM Bumper Mounting Brackets
In the Japanese market, the Gemini Coupe was available with the USDM Geo Storm appearance front and rear
bumpers, through the Yanase distribution network. One major difference between the USDM and JDM siblings is
that the Japanese market cars do not have the heavy bumper beams behind the polyurethane bumper covers.
Instead, they have light weight mounting brackets made of thin gauge sheet metal. These are worth about 20
pounds of weight reduction at each end of the car.
However, ignoring the complete and total lack of crash safety, using the JDM bumper mounting brackets renders
the expensive, and increasingly difficult to find, plastic bumper skins disposable. The light weight brackets
provide no structure or bump absorption. Even the mildest 5 MPH bump from another vehicle will crumple the
polyurethane bumper cover like paper, ripping it to shreds, and rendering it un-repairable.
Smaller Racing Battery
For a daily driven, all season use automobile, to be used as reliable transportation, in sub-zero-temperatures,
the best choice is the largest, heaviest, most durable, sealed battery that will fit into the engine
compartment. (Sealed because lead-acid batteries vent corrosive gasses and leak corrosive liquids that will
quickly eat the battery tray, engine mount, frame rail channel, and front fender skirt).
From the standpoint of performance, the goal is to find the smallest, lightest battery that will provide adequate
voltage to run the vehicle engine while it is on the track. Whether for summer season use, or racing specific
use, a smaller, light weight battery, is a quick and easy way to drop 30+ pounds of weight from the right front
corner of the vehicle. Powersports or motorcycle batteries with automotive battery post kits are common for
racing use. Recognizable brands include Odyssey, Hawker, Deka, Big Crank, etc.
First note: Braille brand batteries have identical dimensions and specifications as Deka, with a Pulsed Cranking
Amps rating that has no scientific meaning. But Deka batteries are significantly lower priced.
Second note: In the event that the vehicle has a voltage drain, or the battery is allowed to go dead due to
leaving something switched on, be prepared to throw away and replace powersports or motorcycle batteries (and
even larger sealed or gel-cel batteries), because they can not usually be recovered and usually will not hold
a charge after they have been completely drained.
Battery Relocation – A Bad Idea
Battery relocation was a really big deal in the mid-90’s. The idea was to take the weight of the battery out
of the engine compartment, and move it back to the trunk, to help with weight distribution. The problem is
that this adds 20+ pounds of heavy gauge primary wires, sealed battery case, and mounting bracket. And moving
a 40+ pound weight from in front of the front axle, to behind the rear axle, has negligible benefit, compared
to simply reducing the battery weight within the engine compartment, and not adding the extra weight of the
electrical cables, battery box, and mounting bracket.
Air Conditioner Delete
Four cylinder engines are not really strong enough to power a car and an air conditioner compressor. Drive
along at a steady speed, turn on the air conditioner, and it is like opening up a parachute. But at least the
air conditioner has an electric clutch, and when not turned on, the pulley freewheels, with only the friction
of the belt and drag of the bearing. For racing or performance, the car is better off without the 30+ pounds
of weight of the air conditioning compressor (on the engine), condenser and fan (in front of the radiator),
evaporator (under the dash), and all the piping.
It may take some careful looking to find an air conditioner delete duct to replace the evaporator assembly under
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