Are you experiencing an unusual drone in your Pontiac G8 Gt, especially at highway speeds or around 1800-2000 RPM? You might be encountering Active Fuel Management (AFM), a system designed to improve fuel economy. Let’s delve into what AFM is, how it affects your G8 GT, and what happens when you disable it.
Understanding Active Fuel Management (AFM) in the Pontiac G8 GT
Active Fuel Management, also known as cylinder deactivation, is a technology implemented by GM to enhance fuel efficiency in vehicles equipped with V8 engines, including the Pontiac G8 GT with the L76 engine. The system is designed to seamlessly switch off four of the eight cylinders under light load conditions, such as cruising on the highway. By effectively reducing the engine’s displacement, AFM minimizes fuel consumption when full power isn’t necessary.
Does My 2008 Pontiac G8 GT Have AFM?
Yes, if you own a 2008 Pontiac G8 GT with the L76 engine, your vehicle is equipped with Active Fuel Management. It’s important to note that AFM is specific to the G8 GT models with the V8 engine and is not present in the V6 sedan or the GXP model, which features the LS3 engine. To confirm if AFM is active, you can utilize the engineering mode in your G8 GT. By accessing this mode through the steering wheel controls and navigating to the “active fuel management” display, you can monitor when the system is engaged. “Half Active” indicates AFM is operating and four cylinders are deactivated, while “Full Active” signifies all eight cylinders are in use, typically when more power is demanded.
The Impact of Disabling AFM: Drone and MPG
Many Pontiac G8 GT owners consider disabling AFM, often due to concerns about exhaust drone. The transition between V8 and V4 modes can sometimes create undesirable sounds, particularly with aftermarket exhaust systems. Disabling AFM can eliminate this drone, providing a more consistent and potentially more enjoyable driving experience, especially for enthusiasts who prefer the constant rumble of a V8.
However, disabling AFM does come with a trade-off: fuel economy. As mentioned in owner experiences, you can expect to lose approximately 2-3 MPG on the highway by deactivating AFM. While the exact figures can vary based on driving habits and conditions, it’s realistic to anticipate that your highway fuel economy might not exceed 22 MPG with AFM turned off.
Methods to Disable AFM on Your Pontiac G8 GT
If you decide to disable AFM in your Pontiac G8 GT, several methods are available:
- Tuning Devices: Using a device like a Cortex tuner allows you to directly disable AFM through custom programming. This is a popular method for those seeking more control over their vehicle’s performance parameters.
- Manual Mode: Simply shifting your G8 GT into manual shift mode will also deactivate AFM. This is a quick and easy way to disable AFM for a particular drive, giving you immediate control.
- Engineering Mode (for Testing): While engineering mode doesn’t permanently disable AFM, it’s useful for observing AFM activity and confirming if it’s the source of your drone concerns.
Conclusion: Is Disabling AFM Right for You?
Disabling AFM in your Pontiac G8 GT is a straightforward process with clear benefits and drawbacks. If exhaust drone is a significant annoyance, particularly after installing aftermarket axle-back exhausts, disabling AFM can provide a noticeable improvement in driving pleasure. However, be prepared for a reduction in fuel economy. Consider your priorities – whether it’s maximizing fuel efficiency or achieving a more consistent V8 driving experience – to decide if disabling AFM is the right choice for your Pontiac G8 GT.
