The COMP Performance Group™ Techs often receive questions on how to increase fuel mileage in performance vehicles that are driven regularly. Most of the vehicles in question are street/strip applications that use flat tappet cams, carburetors and non lock-up transmissions. These older technologies may be the cause of the poor mileage problem.
The ability of today’s cars to run more efficiently can be directly attributed to electronic fuel injection, roller cams and overdrive transmissions with matched torque converters. However, there is no reason that a classic street/strip application can’t perform well at the track and still retain good fuel mileage for daily driving. In these older cars, it’s possible to increase fuel mileage and reduce friction by upgrading the following areas: valve train, drivetrain and fuel delivery. Changing just one of these will help, but the benefits are increased with every upgrade.
Many performance applications, especially older muscle cars and street machines produced before 1985, use flat tappet camshafts. Due to their design, flat tappet cams cause increased friction in the valve train that ultimately lowers fuel economy. COMP Cams developed retro-fit roller cams, lifters and roller rocker arms to eliminate this problem. Retro-fit roller setups reduce friction and drag while increasing valve train stability and providing for more power, thereby increasing fuel economy without sacrificing performance.
To further reduce valve train friction, a high quality oil developed specifically for muscle cars, such as COMP Cams Muscle Car & Street Rod Engine Oil, will improve surface mating of the rotating assembly, rod journals, piston rings, valve guides, cam, lifters and other engine components. The more you can reduce internal engine friction, the less horsepower will be robbed and the more efficient your engine will become.
Another area where fuel economy can be increased without adversely affecting performance is in the drivetrain. A TCI Automatic Overdrive Transmission will increase fuel mileage by decreasing engine RPM, which will also increase engine life. The gear ratios of overdrive transmissions are better spread out and more efficient, so in conjunction with the ring and pinion, it will lower your final drive ratio for jack rabbit starts. However, since it’s an overdrive, your top end RPM will not be affected, meaning you get faster starts off the line AND better fuel economy during highway cruising – the best of both worlds.
A lock-up torque converter will generally reduce RPM by around 400, which will usually increase fuel mileage over a standard non lockup torque converter by about 1-3 MPG. For example, if a stock torque converter setup runs at 2,600 RPM while driving 55 MPH, upgrading to a TCI overdrive converter will lower engine RPM to only 2,200 RPM at the same speed, thereby increasing fuel economy on the highway. Switching from a non lockup 3-speed transmission setup to a 4-speed lockup transmission with a properly matched torque converter will gain about a 5-7 MPG on the highway.
It’s common knowledge that fuel injection is more efficient than carburetion because it automatically mixes the most beneficial fuel and air combination for a particular engine’s needs. The switch to EFI used to be intimidating to many carb men, but with cutting-edge systems such as the FAST™ EZ-EFI, there is no reason not to make the switch. Some customers have reported up to a six MPG increase over their carburetors after installing an EZ-EFI elf-Tuning Electronic Fuel Injection System. While not everyone may experience quite that big of an increase, fuel mileage will usually improve when upgrading to EFI over a carburetor.
A properly configured fuel injection system doesn’t need to be tuned or tweaked the way carburetors do either. An advanced one such as the EZ-EFI will even correct itself for changes in altitude and weather, providing the best mileage possible no matter what the conditions are like, which is something a carburetor is simply not capable of.
If you have additional questions or need help selecting the right components for your application, the COMP Performance Group™ tech support services. You can connect with trained CPG technicians through a variety of methods: phone (1.800.999.0853), email (firstname.lastname@example.org), CPGNation support forums (www.cpgnation.com), Twitter (@CPGTech) and Facebook (facebook.com/COMPWins), or you can connect through each company’s webpage. COMP Cams, TCI and FAST™ all have extensive help sections, including Live Chat, which connects you to a real tech through a popup chat window.