Why am I getting poor gas mileage after installing a Brock’s exhaust?

Question: Why has my gas mileage dropped after installing your exhaust system? My bike is mainly used on the street, but I do frequent stoplight drag-style launches. The only modification is the Brock’s exhaust with the O2 plug installed.

Answer: Installing a Brock’s Performance exhaust system—especially when paired with a Power Commander and one of our maps—enhances your bike’s power, throttle response, and launch performance. But in doing so, you may also notice a drop in fuel economy. Here's why:

More Power = More Fuel Burned

Creating additional power requires burning more fuel. That’s just physics. Our maps are specifically designed to make your bike faster by optimizing air/fuel ratios (AFR) for performance, not fuel economy.

What Changed When You Removed the Stock O2 Sensor

• Your bike’s stock emissions system (including the O2 sensor) is calibrated to run extremely lean (AFR of 16:1 or higher) at idle and cruise speeds to meet emissions regulations.
• When the O2 sensor is removed and our map is installed, your bike now runs at a richer AFR (typically 12.8–13.6:1). This improves power across the board—from idle to peak—but naturally uses more fuel, especially under aggressive riding conditions like quick starts and high RPM use.

Mapping Options for Your Riding Style

We offer multiple map types depending on how you use your bike:

• Street Map: Tuned for better fuel mileage and smooth low-speed drivability.
• Pump Gas Track Map: Designed for consistent throttle response and drag strip launches. Requires more fuel at low throttle, so MPG will drop on the street.
• Track-Only Map: Built for race fuels and maximum power. Using this on the street will result in significantly lower fuel economy.

If you're concerned about gas mileage but still want performance, our Street Map is your best option. Visit our homepage, click the “Map Support” tab, and request the latest map for your bike.

Note: Modifying or removing emissions components (like the O2 sensor or PAIR system) may be illegal in your state, and it is strictly prohibited in California.

• Please refer to our Competition Use Only Policy for more details.
• Click here for PAIR System Instructions.