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.
This is how the computer comes...
This is how the computer comes in the mail when you order the MegaSquirt kit. Tim Moore assembled the kit, and he reports it required between six and eight hours to complete...
If 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.
...including the separate...
...including the separate relay box system. MegaSquirt claims the relay board can be located under the hood but that the computer should reside in the cockpit where it can be protected from moisture and dirt.
Since a couple of the TPI tubes had been mangled, we also decided to spice up the intake with a set of SLP runners and a new set of fuel injectors. Since we were purchasing new injectors, we decided to go with larger 38-pound-per-hour (lb/hr) injectors that would allow us to make more horsepower with this same MegaSquirt system. The new injectors were the most expensive single component of our swap at $420, but there are less expensive alternatives. For example, Olds Quad 4 injectors are capable of significant fuel flow and are boneyard cheap. Spend $10 apiece to clean them and you have a performance injector for a ton less cash. The MSD 38-lb/hr injectors will easily support 540 hp at an 85-percent duty cycle with a brake specific fuel consumption (BSFC) of 0.48. Factory 305 TPI manifolds came with 19-lb/hr injectors (the 350 engines used 22-lb/hr units) that are only good for around 270 hp at the same efficiency level.
We loaded up our trusty small-block Chevy and headed for Westech Performance where we bolted the 355 up to the dyno and, after some mild difficulties, created a carbureted baseline for the engine. That's when the fun stopped. After bolting on the TPI manifold, the engine struggled but never ran correctly despite our efforts. We discovered we really weren't ready to test the system because we hadn't spent enough time reading the MegaTune instructions. Eventually we also realized we had not loaded the base fuel map into the new chip we installed (see the "Installer Errors" sidebar--it's high comedy). Eventually we ran out of time and packed up our small-block and headed back to the barn.
Later, we regrouped and headed to Ken Duttweiler's facility for another shot at the dyno. This time, the engine fired right up and ran pleasantly, responding to tuning changes for a short time before an errant ignition ground caused us some grief. Once that was repaired, the MegaSquirt system responded instantly to tuning changes and within a few minutes we had tuned the entire wide-open-throttle power fuel map, making an impressive 450 lb-ft of torque with the almost-stock TPI manifold and SLP runners. We also quickly tuned the idle air-fuel and a portion of the part-throttle map before calling it a day.
Despite some initial skepticism, it's clear that this MegaSquirt system works extremely well, becoming easy to work with once we learned how to navigate through MegaTune. There's a bunch of detailed material that isn't in this short story due to space constraints, so it's worth going up on MegaSquirt's Web site to dial yourself into all the details involved with this program. The biggest thing we learned from this project was that the system works as advertised, but that the overall project required a little greater investment than we anticipated. If you already have a complete EFI manifold with injectors, this will dramatically reduce the overall cost. We would suggest doing a cost estimate first before diving in if you're planning on spending less than $1,000 to complete a system. It's also important to note that we did not include the cost of building a high-pressure fuel delivery system.
Overall, we feel our MegaSquirt effort was successful, it worked as advertised, it is the least expensive system on the market, and it's a great way to immerse yourself in the world of EFI. The system has its limitations, as you might expect, but it will make power and do the job for a whole bunch less money, especially if you're good at shopping for parts. If you look at the MegaSquirt system as a great entry-level EFI system that will teach you all kinds of things about EFI, then you've got the right idea.