The law of diminishing returns means that at a certain point, the dollar spent becomes exponentially more compared to the weight lost. Take the amount you spend ($) and divide it by the weight (kg or lbs). This will give you a good idea of how best to address weight reduction. Here is the definitive forum thread on the subject.
This guide focuses on parts that bolt right in and out and is ranked in increasing order of cost/kg lost. FT86 forum user Anthony has brought this approach to near conclusion by stripping an incredible 181kg out of his car. While this might work for him, the car that we will be developing is designed for maximum driving pleasure on normal roads.
This means that the car still needs to be usable for a daily commute, with some basic comforts thrown in. The list below is by no means exhaustive (two links to the bottom that are more comprehensive), and decisions were made looking at the money spent relative to the weight lost.
The system I use to calculate the price to benefit of weight loss in a car is based on the following criteria:
1) Free - Usually free (eg. spare tyre removal).
2) Cheap - Simple bolt in parts (eg. lightweight battery).
3) Expensive - Complex part replacement or removal (eg. carbon roof)
For category 2 and 3, you can make a better decision if you list the parts and the relative performance and or weight loss. If you are trying to shave seconds off a lap-time, the cost goes up exponentially, so consider value (price to performance) if it is a road car.
The list below is by no means exhaustive (two links to the bottom that are more comprehensive), and decisions were made looking at the money spent relative to the weight lost.
Starting Weight: 1250kg
Note: all weight figures represent net weight loss : (original weight minus new weight)
Free Weight Loss:
19.0 kg - Front Passenger Seat
14.5 kg - Spare Tire & Tools
3.0 kg - Manuals and Carpet
2.0 kg - Window Washer + Fluid
1.9 kg - Head Unit
1.1 kg - 1xRear Seatbelt Delete
0.9 kg - Sunshades
0.8 kg - Sound Generator Delete
Cheap Weight Loss:
11.8 kg - Shorai Lithium Battery
8.8 kg AP Essex Front Brake Kit
6.0 kg - Recaro SR6 Driver Seat
3.8 kg - TRD Flywheel
3.1 kg - JDL UEL Headers
2.7 kg - HKS Spec L Carbon Tip
2.2 kg - Beatrush Front Bumper Brace
1.6 kg - Momo Mod 78 330mm Steering Wheel
Total Weight Loss: 83.2kg
The expensive weight loss will lie in the carbon roof, lexan rear window, carbon hood and trunk, and carbon doors which will net another 57.5kg of weight reduction. However, given the high cost of these items and safety compromises, I have elected to stop the weight reduction at 7% (1167kg) from the original weight (1250kg).
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General weight reduction:
Race weight reduction:
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“Simplify and add lightness. "