Fuel pressure was controlled by this return-style SX billet regulator (PN 15404). Also shown is the MSD billet crank-trigger distributor (PN 84697). Fuel pressure was controlled by this return-style SX billet regulator (PN 15404). Also sho BSFC And Proper Injector SizingThis can get tricky. Fuel injectors are rated by how many pounds of fuel they'd flow wide open in one hour at a given pressure, typically around 43.5 psi. Yet, horsepower output, fuel pressure, the engine's Brake Specific Fuel Consumption (BSFC = pounds of fuel consumed per horsepower per hour), and the injector's duty cycle, all determine proper injector size. Since we know DM worked very efficiently with its Demon carb running in the low-to-mid .400 BSFC area, we wanted to test the EFI in the same range. We figured BSFC would be around .400 and we'd need a minimum injector duty cycle of .85, which means that at max power, the injector will be open 85% of the time. Keep in mind that fuel flow through the injector is affected by fuel pressure, as pressure goes up, volume goes up and as pressure goes down, volume goes down. We ran most of our tests at 50 psi so the actual amount of fuel flowing through the injectors was higher than its rated figure. You can plug your own figures into this equation to estimate injector size needed for your application. It's safer to estimate a .500 BSFC, not the .400 we used, unless you know your engine can run that efficiently. We used the following formula to estimate injector size for Danger Mouse. The F.A.S.T ECU can work with any electronic distributor, but you get the most accurate trigger signal and fuel/spark control from a crank-trigger like this MSD PN 8600. The F.A.S.T ECU can work with any electronic distributor, but you get the most accurate tr Injector size = (HP x BSFC) / (Number of Injectors x Duty Cycle)Ex: 480hp engine w/ 8 injectorsBSFC = .400480 x .400 = 1928 x 0.85 = 6.4192 / 6.4 = 30 lb/hr The math says that with 8 injectors operating at 85% and .400 BSFC, Danger Mouse would need a 30 lb/hr injector. We also tried larger 36 lb/hr injectors at both 43 and 50 psi (Test 23), which made the a little more peak hp, but averages fell off and low-end torque dropped enough to be noticed on the street. Keep in mind that horsepower estimates in all these calculations are at the flywheel, not the rear wheels. A less efficient engine, (i.e. higher BSFC figure), will need more fuel pressure and bigger injectors. It's necessary to properly "phase" the rotor when running a crank trigger. Dyno-Steve shines a timing light though a hole in a modified distributor cap with the engine running to check the rotor phasing. The big power DM made this month is also thanks to a special big guy. Harv St. Mary from Harv's Performance came out on his own time to help us tune it to peak perfection. We owe him big thanks. It's necessary to properly "phase" the rotor when running a crank trigger. Dyno-Steve shin One of the other really trick features of aftermarket EFI is the ability to "data-log" your performance. This means the computer records the info from a run and plays it back on the laptop so you can diagnose a problem or compare figures from previous runs for fine-tuning. One of the other really trick features of aftermarket EFI is the ability to "data-log" you Although the math told us that 30-lb/hr injectors were right on, we wanted to try bigger injectors for more power. And just like installing a too-big carb, the large injectors made a little more peak power, but hurt the bottom end. Although the math told us that 30-lb/hr injectors were right on, we wanted to try bigger i SOURCES Accufab 1516 E. Francis St. Ontario CA 91761 909-930-1751 www.accufabracing.com Harv's Performance 12221 Rivera Rd. Whittier CA 90606 COMP Cams MSD Ignition El Paso TX 9-15/-857-5200 msdignition.com Demon Carburetion Dahlonega Ge 7-06/-864-8544 barrygrant.com Russell Performance Products 225 Fentress Blvd. Daytona Beach FL 32114 904-253-8980 www.russellperformance.com Edelbrock Dept. 5.0 2700 California St. Torrance CA 90503 310-781-2222 www.edelbrock.com SX Performance 7700 Gravois St. Louis MO 63123 Fel-Pro 26555 Northwestern Hwy. Southfield MI 48033 Summit Racing Equipment P.O. Box 909 Akron OH 44309 FUEL, AIR, SPARK, TECHNOLOGY (F.A.S.T.) 151 Industrial Dr., Dept. SC Ashland, MS 38603 Westech Performance Group 11098 Venture Dr., Unit C Mira Loma CA 91752 9-09/-685-4767 www.westechperformance.com « | 1 | 2 | 3 | View Full Article By Mike Petralia Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!