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Electronic Fuel Injection Corvette Conversions - EFI Your Small-Block!
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It is important for the control... It is important for the control unit to know the load being placed upon the engine at all times. The manifold air pressure (MAP) sensor provides this information. Essentially, this sensor reads manifold vacuum, with lower vacuum equating to higher load. Hooking up the MAP sensor is as simple as running a vacuum line from the manifold or a point below the throttle plates on the throttle body to the MAP sensor, and then plugging in the harness connection marked MAP. | TORQUE | | RPM | EFI | CARB | | 3,000 | 352 | 339 | | 3,200 | 343 | 336 | | 3,400 | 340 | 339 | | 3,600 | 346 | 347 | | 3,800 | 354 | 356 | | 4,000 | 357 | 360 | | 4,200 | 367 | 362 | | 4,400 | 377 | 375 | | 4,600 | 379 | 382 | | 4,800 | 382 | 388 | | 5,000 | 388 | 390 | | 5,200 | 386 | 390 | | 5,400 | 389 | 390 | | 5,600 | 386 | 387 | | 5,800 | 380 | 381 | | 6,000 | 371 | 369 | | 6,200 | 363 | 362 | | 6,400 | 344 | 347 |  In an EFI system, the ignition...  In an EFI system, the ignition advance function is handled totally electronically, so the advance functions of the distributor must be rendered inoperative. We used a MSD distributor, which is readily locked-out-meaning the timing is mechanically fixed. Most distributors can be modified to eliminate the advance functions.  Virtually any OEM distributor...  Virtually any OEM distributor can be used with the FAST XFI fuel-injection control unit, as well as the popular aftermarket units such as our MSD unit. A conventional distributor will allow batch-fire of the injectors. A sequential system follows the firing order with the injector pulse on a cylinder-by-cylinder basis. To time a sequential system, a cam-position signal is required so that the control unit has a reference of which cylinder is firing. A dual-sync distributor is needed for this cam reference signal. MSD and Mallory (among others) manufacture distributors with this feature, while FAST is tooling up for a full line of dual-sync distributors. We ran a simple batch-fired system on this small-block Chevy, using a locked-out conventional distributor combined with a MSD ignition system. Batch fire worked well, and testing showed very little appreciable advantage to sequential. though with the dual-sync distributor, a sequential system can be easily accommodated if desired. The MSD points signal is wired to the XFI controller to provide the rpm signal.  A valuable feature for any...  A valuable feature for any aftermarket EFI system is the ability to run in closed loop, which means the mixture (air/fuel ratio) is monitored continuously, and the processor makes continuous minor adjustments to the injectors to keep the ratio in the targeted zone. A wide-band Lambda sensor creates a signal that corresponds to the air/fuel ratio at any instant, and the XFI control unit follows with near-instant adjustments. EFI can also be run in Alpha-Numeric mode, which means open-loop, where the fuel delivery at the injector is strictly controlled by preprogrammed fuel maps. Street or street/strip performance cars really benefit from closed-loop capabilities.
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