Description: Ginetta G40 Power-to-Weight & Championships
The following describes the standard, factory-spec G40 with 1.8 Ford Zetec, 17" wheels, Avon ZZR tyres, Quantum shocks, one Tillett seat and one Cobra seat.
The example calculations at the bottom show potential weight reductions and/or ballast if racing outside Ginetta-regulated championships.
Standard Weight
- Factory quoted weight: 840 kg
- Measured weight (dry, no fuel, factory spec): 915 kg
Power
- Factory quoted power: 135 BHP
- Power measured by Dyno Driven: 140 BHP (5k miles on the odometer)
Standard power to weight
- Including 85 kg driver: 140 BHP / tonne (1000 kg, 140 BHP)
- Excluding driver: 153 BHP / tonne (915 kg, 140 BHP)
Weight reduction / adjustment
To adjust power to weight, you could remove or change the following items and add ballast to adjust (see BHP calculator from launchtech.co.uk).
With the easy and medium-difficulty reductions you may get the dry weight down to about 875 kg (from an original GRDC / G40 Cup car, i.e. closer to Junior and GT5 weight).
Easy weight reduction (approx -17.5 kg, new power to weight excluding driver = 156 BHP / tonne):
- Passenger seat (Cobra) - 12 kg
- Passenger seat rail mountings, race harnesses and mounting points, inertia reel seatbelt - 5.5 kg
Medium-difficulty reduction (approx -13 kg additional, new power to weight excluding driver = 160 BHP / tonne)
- Air conditioning pump, belts, condenser and pipes - 3 kg (estimated - note this may also increase BHP slightly and removed a potential bearing failure point on the belts)
- Glass door windows and winding mechanisms could be removed and replaced with perspex and slider - estimated weight 10 KG
Expensive reduction (approx -20kg? additional):
- Lighter (carbon) doors are available (as used in Junior)
- Windscreen could be replaced with a perspex screen from a professional racing supplier
Other notes:
- Fuel load obviously affects weight. Fuel weighs approximately 0.77 kg / litre and the capacity of the fuel tank is approx. 38 litres. See Description: Ginetta G40 Fuel System for fuel consumption.
- The ballast plate mountings are in the floor at the passenger seat position.
Championship examples for 140 BHP engine
750 MC Roadsports Class D (145 BHP/tonne excl. driver)
- Class D limit = 145 BHP / tonne excluding driver, post 45-min race
- Remove passenger seat and belts = 915 - 17.5 kg = 897.5 kg
- Fuel weight post race from full at start = +7.5 kg (approx. 10 litres remaining)
- Result = 897.5 + 7.5 KG = 905 KG = 154.7 BHP/tonne
- Conclusion = Add ballast = 61 KG minimum = 966 kg = 144.9 BHP/tonne
750 MC Roadsports Class C (180 BHP/tonne excl. driver)
- Class C limit = 180 BHP / tonne excluding driver, post 45-min race
- Remove passenger seat and belts (easy reduction) = 915 - 17.5 kg = 897.5 kg
- Fuel weight post race from full at start = +7.5 KG (approx. 10 litres remaining)
- Result = 897.5 + 7.5 = 905 kg = 154.7 BHP/tonne
- Remove also aircon and side glass (medium reduction) = 897.5 - 13 kg = 884.5 kg
- Fuel weight post race from full at start = +7.5 KG (approx. 10 litres remaining)
- Result = 884.5 + 7.5 = 892 kg = 157 BHP/tonne
- Conclusion = With easy + medium reduction we're significantly down on power-to-weight for this class
MSV Trackday Championship / Trophy Class D (125 BHP/tonne incl. driver)
- Class D limit = 125 BHP / tonne including driver, post 45-min race
- Remove passenger seat and belts = 915 - 17.5 KG = 897.5 KG
- Fuel weight post race from full at start = +7.5 KG (approx. 10 litres remaining)
- Driver weight = 85 KG
- Calculation without ballast = 897.5 + 7.5 KG + 85 KG = 990 KG = 141.5 BHP / tonne
- Conclusion = Add ballast = 130 kg = 1120 kg = 125 BHP/tonne
MSV Trackday Championship / Trophy Class C (150 BHP/tonne incl. driver)
- Class C limit = 150 BHP / tonne including driver, post 45-min race
- Remove passenger seat and belts = 915 - 17.5 KG = 897.5 KG
- Fuel weight post race from full at start = +7.5 KG (approx. 10 litres remaining)
- Driver weight = 85 KG
- Result = 897.5 + 7.5 + 85 KG = 990 KG = 141.5 BHP / tonne
- Remove also aircon and side glass (medium reduction) = 897.5 - 13 kg = 884.5 kg
- Fuel weight post race from full at start = +7.5 KG (approx. 10 litres remaining)
- Driver weight = 85 KG
- Result = 884.5 + 7.5 + 85 kg = 977 kg = 143.5 BHP/tonne
- Conclusion = With easy + medium reduction we're close to optimum power-to-weight for this class.
- To be competitive, this needs a lap time of 56s at Brands Indy and 1:48 at Brands GP.
Ginetta GRDC 2020 (154 BHP/tonne excl. driver)
- For the GRDC championship in 2020, you'll need a minimum post-race weight of 910 kg excluding driver. The exact requirement varies each year, and it was higher in 2017-19.
- This weight is very close to the actual weight of the car as measured above, with no parts removed (i.e. factory spec). You could remove the passenger seat but you'd need to replace it with ballast.
Ginetta G40 Cup 2020 (164 BHP/tonne excl. driver)
- For the G40 Cup in 2020, you'll need a minimum post-race weight of 865 kg excluding driver and 980 Kg including driver.
- This is lighter than measured for my car, so some lightening from factory spec is required.
- I'm not sure how teams will get cars down to this weight. You can now remove the air conditioning for G40 Cup, but probably not the side glass, so the maximum I can think of is 915 - 17.5 - 3 = 894.5 kg. These are 20-minute races however, so we can remove e.g. 4.5 kg of fuel remaining (3 litres required for scrutineering), giving 890 kg (157 BHP/tonne). Also, these cars use the 15" wheel, which is 2 kg lighter than the 17", saving 8 kg, giving 882 kg (159 BHP/tonne).
- Conclusion = There's still 17 kg available to remove which I haven't found, and that should not include the side glass. It's now permissible to change the fuel tank within G40 Cup regulations, so that may be a further saving to deploy.