Unless we're talking about the '68 Ranchero that your Uncle Hank lives out of, every car needs some sort of ECU (engine control unit) to tell each of its engine's moving parts what to do and how to get it done.
It starts with a series of sensors that sends information to the computer, where it's processed, stored, and converted into some sort of command that'll make the engine run the way it ought to. For example, input sensors like your engine's throttle position sensor tell the computer just how far you've laid into the gas pedal, delivering that information to the fuel injectors so they can accommodate all that air that just made its way in. Together, all of this results in the sort of performance you expect, the driveability your mother wants, and the reduced emissions earth-lovers say you need.
Whoever stuck the ECU into whatever it is that you drive cares about all sorts of important things, but you making any more power isn't one of them. Low emissions, smooth driveability, and the potential for crummy octane almost always undermine your engine's ability to satisfy whatever boy-racer tendencies you've got. As such, the things you care about, like how long the fuel injectors stay open, when redline occurs, or when exactly valve overlap happens, aren't easily changed. That's mostly because of the read-only memory (ROM) chip inside your ECU that allows it to do only what the engineers who drew up its software in the first place say it should. In other words, it's hands-off for you unless you've got the wherewithal, the money, or some of both.
Engine control systems have come a long way, especially in the past 20 years. Cars that relied on nothing more than mechanically driven cables, levers, and rods that only your grandpappy understands determined how much fuel should be dumped in and have been replaced by computers so sophisticated, they'll make gramps wish he'd taken that course at DeVry.
When we used them: '70s to early '90s
Carburetors are to fuel injectors what the abacus is to your iPad (What's an abacus?! I used a TI-82 in my day. -SD). Purely mechanical, they draw air and fuel into the intake manifold using a combination of prehistoric needles, jets, and floats that together are about as effective as Galileo's calculator. Still, pre-'90s tuners of the naturally aspirated persuasion looked to carburetors for their ability to draw in more air and fuel and, in some cases, atomize it better than early fuel injection systems could.
What: Rising-rate fuel pressure regulators
When we used them: Early '90s to mid-'00s
Early forced-induction setups knew better than to mix with carburetors, but introducing more fuel still had to happen were inspection holes in engine blocks to be avoided. Rising-rate regulators exponentially increase fuel pressure as boost pressure goes up. For example, push five pounds of boost out of your turbo and all of sudden fuel pressure's 20 psi higher. It worked, sort of...
What: Additional injector controllers
When we used them: Mid-'90s to mid-'00s
At some point, somebody realized that increasing fuel pressure alone wasn't all that effective. Higher-flowing, aftermarket fuel injectors were relatively unprecedented until the mid-'90s, which meant adding more of whatever injectors you already had was the answer. Here, one or two additional ones can be plumbed into the intake piping, much like a single-fogger nitrous system, and are controlled by a separate electronic device that determines when and for how long to open them.
What: Chips and reflashes
When we used them: Mid-'90s to present day
Chipped and reflashed ECUs are typically the simplest solutions. Generally reserved for OBD1 ECUs, third-party ROM chips are one-size-fits-all applications that've got to be soldered directly onto an ECU's circuit board. Reflashed ROM chips allow for the same sort of changes but can be made without having to yank the chip from the ECU and feature the sort of adjustability that more elaborate engine management systems offer. Some ECUs can only be reflashed a few times before they're toast, though, while others can be modified indefinitely.
What: Electronic piggyback controllers
When we used them: Mid-'90s to present day
Piggyback controllers, which gained popularity toward the turn of the millennium, intercept signals between an engine's sensors and its ECU, allowing changes to be made by means of PC-based software or a handheld controller. Here, larger fuel injectors that the factory ECU would normally throw a fit over can be put in place so long as the ECU's fooled into thinking none of this is going on.
What: Standalone systems
When we used them: Late '90s to present day
Nothing this side of a factory ECU is as comprehensive as a standalone engine management system and nothing allows for the same sort of adjustability. It's the only one of the bunch that can replace the original ECU and can control just about anything you throw at it, including factory ancillaries that've got nothing to do with you going any faster. A standalone system's difficulty lies in the system itself as well as the vehicle. Some are simple plug-and-play solutions, like AEM's Infinity for, say, Mitsubishi's Evo that connects right up to the factory plugs. Others are much more complex and can require custom wiring harnesses, sensor swaps, and more.
Blind to Boost
Native naturally aspirated engines are famous for not accommodating forced induction shenanigans. The trouble starts with some engines' MAP sensors that are typically calibrated to monitor vacuum-not boost-the results of which will trip a check engine light and toss you into limp mode faster than you can say I shoulda stayed all motor. The solution was as obvious as you think: Head to the local fish and aquarium supply and grab a handful of one-way check valves. Here, a cornucopia of foam-filled valves, vacuum hose, and plastic tees bleed positive pressure away from the MAP sensor before it knows any better.
In an age where YouTube videos show you how to do everything from filing taxes to milking a cow, that somebody would develop a do-it-yourself, standalone engine management system was bound to happen. But don't think you can just walk into Radio Shack, grab a circuit board and some resistors, and expect anything good to happen. You'll need somebody like MegaSquirt to tell you what you need, how to put it together, and, in most cases, sell it to you.
- No cheaper standalone alternative
- Offers many of the same features as more expensive systems
- Bragging rights (you just built your own ECU, for Pete's sake)
- Steep learning curve
- Lacks features of higher-end systems
What it takes to get/make your own:
Start by checking out the do-it-yourself systems on MegaSquirt's website. MegaSquirt's DIY kits include everything from the circuit board and enclosure to the resistors, drivers, and vehicle-specific plugs. Go this route and you're in for a whole lot of soldering and wiring, but it's the closest to building your own system you'll get.
Tuning Pro Q&A
SS: How are factory ECUs limited?
John Concialdi, AEM Electronics: In terms of tuning, they're not easily accessible. It's true that there are tuning programs that've cracked certain factory ECUs, but those are specific to a single brand. Standalone ECUs allow for an infinite combination of tuning aids, like boost control that's dependent on gear, rpm, or traction.
Doug MacMillan, Hondata: Once people start modifying their cars, it's useful to be able to monitor additional sensors and drive additional outputs, like boost-control solenoids. Factory ECUs aren't designed for this, which is why we add multi-channel input to S300 and K-Pro.
SS: What's made tunable systems more attainable for the average enthusiast?
JC: Aside from value, software now is easy to understand. We even offer a school for new customers taught by our development engineers. We want people who use our product to be in the winner's circle and not have to tinker with software all weekend.
DM: We're adding software and hardware to a computer that's already designed to operate a Honda engine very well. This helps keep the price down since we don't have to reinvent the wheel.
SS: How have advancements with engine management affected your ability to break records at the track?
Jeremy Lookofsky, championship-winning drag racer: It doesn't matter what level of motorsports you're involved in, having a reliable ECU is key. The current processors, speeds, endless channels that allow for different functions, and sensors that accurately read it all, play a big part in a record-breaking race program like ours.
Stephan Papadakis, championship-winning drag racer, drifter: The main contributor is its ability to control not just the engine but its ancillaries. Early systems only had basic fuel and spark control. We could make big power, but it took several more pieces of electronics to control boost, nitrous, launch rpm, and to data-log.
SS: How has tuning a competitive car today changed versus 20 years ago?
JL: Today, getting a car to run from scratch is 100 percent easier. Simple parameters can be filled in to create a base map, and some manufacturers even offer base maps for common setups. Fifteen years ago, we were all just guessing at these numbers.
SP: ECUs were simple in the 1990s, but there wasn't much information on how to use them. Today, there are pages and pages of parameters that can be adjusted, some of which can wreak havoc if they go unchecked. It takes an expert trained for a particular ECU to get it perfect, though.
Engine Management Buyer's Guide
AEM Infinity: A plug-and-play standalone system that replaces the factory ECU, AEM's Infinity allows for complete control for high-horsepower applications. And because it's integrated into the vehicle's existing CAN-bus system, factory instruments and ancillaries can all be retained and, in many cases, modified.
Cobb Accessport: Thanks to pre-loaded maps as well as the ability to upload customized settings, Cobb's Accessport gives users the ability to ditch the conservative settings of many factory ECUs for increased power. Cobb's ECU flashing solution also includes a high-resolution display that lets users monitor up to six parameters at a time.
Hondata FlashPro: Designed specifically for popular late-model Hondas and Acuras, FlashPro communicates with the ECU through the vehicle's OBD2 diagnostics port, allowing changes to be made on the fly to fuel and ignition tables, and features comprehensive data-logging capabilities.