A stock car that operates with a stock EFI system works very well with it, no question about it. Car manufacturers spend millions in designing software to run the way that it's supposed to run. But when you begin to add aftermarket parts to the team, your parameters change. A header or higher flowing exhaust is ok, but once you get into turbocharging-things become somewhat more difficult for the stock ECU to handle. "None of the current manufacturers feature an ECU that can automatically correct itself at full throttle. This is what is known as closed loop" says Rob Smith of RPS. "Closed loop means that when your throttle and rpm are at a certain position, you get the right amount of fuel. That's great if you're at sea level, but what if you live in Denver? The air up there is thinner than it is at sea level so the car will run too rich because there's less air." This is where an aftermarket engine management system can come in handy.
Engine Management SystemsWhy should you use an aftermarket engine management system? Well, you should consider choosing one when you do modifications that are beyond the realm of what the stock computer can compensate for. It's different for every car. Take a twin-turbo RX-7 for example-it's known that the factory computer runs so lean that if you remove the catalytic converter, then the motor will most likely say a few parting words and depart the building. Why? Because the extra air flows through the motor with the catalytic converter removed, the stock computer says the engine will receive a certain amount of fuel at a particular rpm and boost. It's assuming that it has so much backpressure through that catalytic converter, and it's assuming that it has so much restriction through the intake. You add a free-flowing intake, remove the catalytic converter, and put on an exhaust-you're probably flowing 20 percent more air than what the computer is allotted and that particular computer doesn't have 20 percent adjustment.
Aftermarket systems can help to alleviate some of the problems associated with not having adjustment capablities. They allow for the complete customization of an engine's timing, air measurement, and fuel delivery. The best candidate for one of these things? Any car that comes non-turbo from the factory and then has a turbo put on should consider this option as a road to travel. Now, all of these systems essentially do the same thing, and that's controlling the fuel injector, timing control, and firing sparkplugs at the right time. They all use a crank angle sensor, a throttle position sensor, water/air temperature, and either a MAP sensor or airflow meter. Take a look at our guide to see which aftermarket units will suit your engine best. Keep in mind that the price listed includes only the unit itself and excludes any wire harness, installation, or tuning involved (unless otherwise stated).
Speed-ProSpeed Pro Sequential Fuel InjectionMain Features--shock resistant ECU with waterproof casing and connectors-C-Com PC software is capable of 32-bit memory-ECU circuitry is hardened to prevent high-energy ignition interference-True Speed/Density algorithm allows for higher resolution for injectors and improved idle control
Why the Pros Like It--user friendly-wide band O2 sensor that's self com pensating-data logging-consistency-affordable
Why You'll Like It--great technical support-availability-widely supported by top drag racers-easy to tune
You Might Not Like It Because--pricing on the unit and upgrade features can become costly
Average Price-$2,600 for Honda-specific sequential unit with harness (Westside MS exclusive)
SourceFederal Mogul Performance,Dept. SS09P.O. Box 1966Detroit, MI 48235800/325-8886www.federalmogul.com
Westside Motorsports, Dept. SS09436 Lincoln Blvd.Santa Monica, CA 90291310/664-6000www.wsracing.com