There are several ways to go about creating a budget electronic fuel injection (EFI) system. The problem always comes down to how much you're willing to spend. Generally, the least expensive aftermarket ECM and wiring harness combinations start at around $1,000 and go up from there. Recently, we ran across what has to be the least expensive way to get into a truly programmable EFI system. Called the MegaSquirt, it's available through two East Coast hot rodders, Bruce Bowling and Al Grippo, who decided to offer an inexpensive EFI package that anyone could build.
Condensed to its essence, the MegaSquirt system is a truly build-it-yourself EFI computer. Bowling and Grippo will sell you the entire electronics package for roughly $225, and you solder it all together. Once you've assembled it, you can also build a bench-tester to ensure your box works, then you can install it on virtually any engine from a single-cylinder weed-wacker to a 12-cylinder Formula 1 engine. The MegaSquirt system we experimented with commands only the fuel system, leaving the ignition to be controlled however you wish. That's a very simplified overview. Because the whole MegaSquirt story is more complex, we've had to edit this story down to the major bullet points in order to make it fit. That means we're only going to show you the highlights of this kit. But we will get into how it worked for us, our dyno-testing, and how you can get started on a similar system.
The KitIf you're old enough to remember the Heathkit build-'em-yourself radios that came in the mail as a pile of electronic parts, that's exactly how the MegaSquirt system arrives at your door. There are a couple of aluminum boxes along with a stack of circuit boards, relays, drivers, diodes, capacitors, and all other sorts of tiny electronic pieces. We're not that good with electronics, so we convinced our pal Tim Moore to sit down and solder in all those tiny connections, which he accomplished in roughly eight hours by following the instructions!
The computer is designed to operate in either an alpha-N or speed density mode. The alpha-N mode is intended for engines with very large camshafts that make using a manifold absolute pressure (MAP) sensor difficult. The speed density mode is far more popular, and it uses the MAP sensor to help establish engine load along with a throttle position sensor (TPS). The MegaSquirt system also employs the popular and inexpensive GM-based sensors such as the TPS and manifold air temperature (MAT) sensors, except for the MAP sensor, which is a dedicated sensor built into the MegaSquirt box.
Assembling the computer will also expose you to all the nuances of EFI and is an outstanding opportunity to learn how these systems function. The MegaSquirt system requires a separate computer like a laptop to tune the system once it is operational. This may seem like a much larger added expense, but the laptop is only necessary when first configuring the system. Once your tuning is complete, the laptop is not necessary for daily operation. We all know someone who owns a laptop that can be borrowed for the tuning process to reduce expenses.
Once Tim completed the assembly of the MegaSquirt, he opted to build the stimulator box that allowed him to bench-test the MegaSquirt to ensure that it worked. Tim also then downloaded the free software from the MegaSquirt Web site that would allow us to configure the computer for the engine we would be testing. In keeping with the budget approach of this system, we decided to test the MegaSquirt on a basic small-block Chevy. Rather than invest in an expensive aftermarket fuel injection manifold, we dug up a used TPI manifold from an '87 Camaro that Tim purchased for $200 at a local swap meet.