GP Owner's Manual

Chassis Models

The chassis models cover the available combinations of suspension and diffusor.  See the suspension and aerodynamics sections for details.

Suspension

The grid-gp  is a typical open wheel car suspension with  normal adjustments.  Consult existing guides for information on setting up suspensions.

There is now only one suspension design, so all suspension setups should now be compatible with each other.

Engine

Common Specifications

If the engine is run above the maximum safe oil temperature or above the design rev limit the lifetime of the engine will be shortened.

The hamburg is the primary baseline engine and is the recommended choice when in doubt.  There are also three alternative base engines that may be chosen directly, or blended together to create a custom engine.  The hamburg itself is simply a blend of 50% cleveland (torque basis) and 50% milan (power basis).

Primary Engine

Alternative Engines

Example Custom Engine

An example custom engine with the recipe: 50% milan (power), 40% osaka (ramp), 10% cleveland (torque): 

Driveline

All of the available driveline options include a 5 or 6 speed semi-automatic gearbox.

NOTE: for GMWC season 2007C we will be running only the helotek.

quadtrac 

All wheel drive with adjustable torque split. For GPs this is a training driveline since at GP power levels the extra acceleration grip (using all 4 tires) available is significant.  

clk

Semi-AWD. All wheel drive with fixed torque split to 100% rear. However, upon rear wheel slip, depending on diff settings, the front wheels will take some torque. This has much of the benefit of the quadtrac but toned down to be reasonably competitive with the geartek.  Of particular setup  importance is the differential lock setting.  The higher the setting, the more torque sharing will happen, and hence more of the 'clk' effect.  However, often with more torque sharing comes more front tire abuse.  With high lock settings front tires temperatures will be harder to control and front tire life can be significantly reduced.

geartek 

Rear wheel drive. Even though not the default, this is the recommended driveline for experienced drivers. However, traction control is also recommended with this driveline.

helotek

Rear wheel drive.  This is a lighter, faster shifting driveline, but does so sacrificing a gear.  Helotek has only five speeds while all the others have six. With the right engine and gearing this may be the fastest driveline.

Tires

There are now three available tire options, but for GMWC season 2007C we will be using only Option B.

Aerodynamics

Wings

Wings are aerodynamic devices that provide downforce, but at the expense of drag.  Higher wing settings provide more grip, but reduce top speed and acceleration at speed.

Diffuser

The diffuser is an aerodynamic device built into the rear underside of the car.  It provides low drag downforce that is adjusted using ride height.  The optimum rake, or difference in ride heights (front vs. rear) is near zero (actually about 3mm).  However, since the rear of the car typically has higher downforce due to both the diffuser itself and the large rear wing, the rear suspension tends to compress more than the front.  Therefore, to achieve optimum rake (near zero) on the track, garage rear ride height settings will have to be greater than front ride height settings.

There are two aero packages, one with a wide angle diffuser and one with a narrow diffuser.  The wide diffuser is more forgiving to drive when the car oversteers a lot, while the narrow one is a bit more realistic.

The diffuser  provides more downforce with lower ride height.  However, the lower the ride height, the less available suspension travel and the higher the likelihood of bottoming out.

Suspension Compression Difference (rear compression - front compression)

With the default setup at Jacksonville (large oval to get stable ride height readings), including spring rates, ride heights, and wing settings.

So what does this mean?  The simple answer is to set the rear ride height to be approximately 1.0 cm larger than the front ride height.  To optimize for very fast sweepers, maybe a tick more.   To optimize for slow to  moderate speed corners, maybe as low as 0.5 cm larger in the rear.

Pits