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Commonly called Magic boxes, these devices are spliced into the wiring between the sensors and the ECM. The circuitry in the device takes the signal and distorts it in a manner to trick the ECU into providing more fuel and/or timing to create better performance. The advantages of this systems is their relative low cost ($500 and up), ease of installation by the DIYer and effectiveness on mildly modified vehicles.
At some point however, we all realize that horsepower is addictive. The intercept boxes work well to a certain point and then are no longer able to compensate for extreme modifications. This limitation varies with the application. Another problem is locating the proper locations for splicing the boxes can be difficult and time-consuming. Improper splicing can lead to no effect or damage to the engine.
Adjustable fuel pressure regulators have been around for years and can have good effects on mildly modified vehicles. Usually the fuel pressure on an EFI system is set at a certain level and varies directly with a change in manifold pressure. Most factory vehicles are unable to compensate or even detect changes in fuel pressure and it therefore important to know that the fuel pressure level expected by the computer is the actual level delivered at the fuel injectors.
Usually AFPRs are adjusted to raise the base fuel pressure on mildly modified vehicles. This leads to more fuel being delivered during each injection cycle. The negative effect of this is that at some point this increased pressure is too much for the injector’s mechanism to open or close correctly, causing faulty operation. Too much fuel won’t usually cause damage, but a lean condition will destroy an engine. This is something to think about when driving a vehicle that has an intake, big throttle body, headers and exhaust and no tuning. This engine will have a lot more oxygen to burn, but no upgrade to fuel it.
A rising rate fuel pressure regulator or FMU is commonly used on hybrid turbocharged and aftermarket supercharger kits. These devices are designed to increase the fuel pressure an ever-increasing amount proportioned to manifold pressure. There are many Honda Turbo Conversions and Nissan 350z supercharger kits running with this as their main fuel upgrade. Be wary of the capability of this device. Once you exceed the ability of your injectors to deliver fuel under incredible pressure, you can not accurately tune the engine. Stay under 6psi at all costs !!!
Flash or Chip Reprogrammingis a process of modifying the factory installed fuel and timing maps directly. Chip burning has been around for years and only differs from flash in that the ECM must be removed from the vehicle to have a chip removed and a socket installed in its place. The actual programming is the same.
Most OBD-II vehicles (1996 and newer) have the capability to be flash reprogrammed, but for obvious reasons, only a few platforms have been embraced by the industry to be modified.
The important thing to look for in a chip or flash reprogram is to tune for your particular vehicle and modifications. Ordering a program over the internet practically guarantees you will be leaving some horsepower on the table. Custom tuning means everything is extracted and there are no surprises.
Chip and Flash tuning can compensate for new injectors, new MAP or MAF sensors, remove MAF or almost anything else used to modify an engine. Proper tuning can also remove throttle tip-in and that annoying bogging that the factory put in for emissions and warranty concerns.
Stand-Alone Engine Management is the newest thing in the automotive world, but it is not necessarily the best thing in all applications. Considering the time and money the OEMs spent developing the stock maps and ECU, one must consider their specific goals and application before undertaking this route.
Is your vehicle going to be driven on the street or is it a race car?
Is your vehicle pollution exempt, meaning built before 1975 or so?
Have you heavily modified the vehicle or are you just at the bolt-on stage?
If you answer yes to these questions then you might want to look at re-flashing your computer rather than going to a full stand-alone system. Also consider a fuel computer such as an S-AFC for simple changes such as a different MAF and/or injectors. The cost-benefit should always be considered, but so should the negative aspects of lying to the ECM by intercepting various sensors to trick the ECM. At some point, it is better that the ECM is aware of all of the modifications operating on the engine.
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