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| Here’s a better look at the MSD 90-mm throttle body. Cast from aluminum, the throttle body incorporates a parabolic bore shape. MSD points out that the parabolic bore allows for excellent drivability characteristics during part throttle. Typical billet straight bore throttles don’t have this cut. The result is difficulty in modulating the throttle. MSD uses OEM style bearings, seals, and shaft design to achieve a very robust design that can stand the temperature swings seen by street applications. The bottom line here is, you don’t have to worry about throttle sticking issues. | |
How does the injector work? Kinsler explains the basics: “An EFI injector is an electronically controlled solenoid that controls fuel flow through and orifice. When the solenoid is activated, the orifice is exposed, allowing fuel to flow. EFI injectors are available in various flow capacities. The injectors are electronically pulsed, typically measured in milliseconds (thousandths of a second) to control the amount of fuel delivered to the engine. The percentage of time that the injector is pulsed is called the duty cycle. When properly sized for a specific application, the injector will operate at 80-90% of the duty cycle. Injectors that are too large will not accurately deliver small amounts of fuel for good idle quality. Injectors that are too small may cause severe engine damage because of lean mixtures at large throttle openings and/or high engine RPM.” So what injector goes where? MSD offers a simple computer program to determine the right injector for the application. Similarly, Kinsler, ACCEL and FAST can properly size the injectors to the application. Call them for more info. |
Sandwiched between the fuel rail and the intake manifold is an electronic fuel injector. MSD offers four competition injectors – two saturated circuit types and two peak and hold types. Flow rates range from 38 lb/hr to 96 lb/hr (dependent upon type). The static flow rates (pound per hour) are approximate with fuel pressure set at 43.5 psi (3-bar) and fuel specific gravity at 0.788. The flow rate tolerance between individual injectors of the same static flow is 1.5% -3%. Additionally, MSD has recently released a new “Jammer” fuel injector (saturated circuit driver) with a static flow rate of 60 lb/hr. They point out this is the most linear injector available. It features exceptionally precise fuel control, with excellent idle and driveability characteristics. Jammers work with either saturated or peak & hold ECUs, and are compatible with Bosch square connectors.By the beginning of the nineties there were more than a dozen companies manufacturing EFI systems. Most were reputable with solid engineering and testing behind their products. Road race and Indy cars were the first to jump on the EFI bandwagon, followed by the street machine crowd (which, because of their nature mandated more elaborate EFI systems). Even though fuel induction systems for most drag race applications were simple enough not to mandate electronics, they soon began to creep into (of all places) Stock Eliminator. As MSD relates, it is no secret that electronically fuel-injected Firebird Stockers were soon tearing up the drag strips and the record books (more insight on this later). And that's not the end of it. A sort of "trickle up effect" began. More and more racers in quicker Eliminators were and are taking notice (for example, Super Stock cars and the occasional Comp Eliminator racecar). But MSD points out that the first big “users” happened to be the folks in various Fastest Street Car classes. Those racers quickly recognized that EFI could be mixed with other power adders to their (considerable) advantage. And the reason EFI is making inroads is pretty simple: It allows virtually complete control of the air fuel ratio from idle to wide open throttle. It also allows for more precise tuning when nitrous or a turbocharger or two are tossed in. The result is improved drivability and superior performance even when weather and track conditions prove ugly.
So what types of electronic fuel-injection packages work best for drag racing? FAST notes that two EFI arrangements are generally suited to drag race applications: Bank-to-bank engine management systems and sequential fuel injection systems. A bank-to-bank system is currently the enthusiast's choice for an easy and affordable EFI installation. This type of system fires half the engine's injectors each 180 degrees of crankshaft rotation, offers improved fuel delivery and performance and is ideal for converting from carburetion to TBI or EFI. It can accommodate a 1-stage nitrous oxide system or an electric fan option and is fully upgradeable to sequential operation.
On the other hand, FAST notes that sequential fuel injection systems are state-of-the-art in that they allow the engine tuner to take precise control of the operating parameters of an EFI engine. As a true Speed/Density system, this design allows for maximum performer tuning by firing each injector individually and optimizing the fuel delivery. It can be equipped with a Wide Band O2 Sensor, individual fuel/timing options for each cylinder and a two stage nitrous control. And if you give those tuning capabilities some thought, it's easy to see how an EFI system can increase power and increase reliability at the very same moment.
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| Electronically fuel injected engine combinations can have some sensors racers are familiar with (for example, a crank trigger), but others aren’t quite so recognizable. Common sensors you’ll encounter include the following: The coolant temperature is one of the primary inputs for EFI management systems. This means a sensor is often located within the water jacket somewhere (for example, in the cylinder head). Another is an intake air temperature sensor. That piece is installed in either the air cleaner assembly or intake. It tells the computer the temperature of the air entering the engine. This information assists the ECU as it works out an optimum air-to-fuel ratio for the engine. The oxygen content of the exhaust gases can also be used to calculate the fuel mixture. When a “heated oxygen sensor” is used, that means sensor uses an internal heat supply to remain at a constant 1,300°F or so for less variance in producing important signals. This is also a benefit in that the sensor doesn't have to warm up and is active even when the engine is first started. The manifold absolute pressure sensor is found inside the intake manifold. It responds to changes in manifold pressures and relays the information to the ECU in the form of a voltage signal ranging from about 1 volt to 5 volts. Several different versions are available for normal aspirated and engines with blowers. Finally, you’ll almost always find a throttle position sensor. Essentially, it tells the ECU how much the throttle blades are open. | |
The Buck Stops Here...
The various ECUs or "black boxes" now available for racing range from basic models at $900-$1,300 with programmers and software costing $300 to $500 to extremely complex systems that sense everything you can possibly think of at $2,500 to $7,500. A lap top computer adds anywhere from $500 to $2,500 to the tab and additional programming tools (software) for some systems can increase the total by as much as $3,500 (although many of the drag race friendly packages include the price of the software with the system). Add to all this the cost of nozzles at $40 to $80 each for common types, wiring harnesses that range from $80 for a simple street accessory version to $650 for a good quality race harness to $2,000+ for a super quality F1 type harness. Fuel rails cost anywhere from $50 for a very basic model to more than $400 for the best stainless steel versions. Factor in the price of a manifold, fuel pump, fuel filter, pressure regulator valve and other hardware and the costs range from a complete system for high performance street use at about $2,000 to a serious on-track system at $6,500 to the most sophisticated at $9,500 to $15,000+ including engineering time.
So where will this lead us? Fuel injection (of any sort) can improve ultimate performance, improve consistency against atmospheric conditions, and improve reliability. Often those improvements are gained in massive bunches, too. And if used in the correct applications, can actually save you money. Fuel injection is here to stay (more next issue).
Sources -- Fuel Injection |
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| ACCEL 216 688-8300 accel-dfi.com |
BIGSTUFF3 248 887-7072 248 887-0344 bigstuff3.com |
| FAST 3400 Democrat Road Memphis, TN 38118 PH: 877-334-8355 Website: http://www.fuelairspark.com |
Kinsler Fuel Injection Inc. 1834 Thunderbird Troy, MI 48084 PH# 248-362-1145 Website: http://www.kinsler.com |
| MSD Fuel Injection Autotronic Controls Corporation 1350 Pullman Drive, Dock #14 El Paso, TX 79936 PH: 915-857-5200 Website: http://www.msdfuelinjection.com |
Wilson Manifolds Inc. 4700 N.E. 11 Ave. Ft. Lauderdale, FL 33334 PH: 954-771-6216 Website: www.wilsonmanifolds.com |