Quote:
Originally Posted by rotrex
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BEST Notes
1. Sequential injection will always get slightly better fuel economy and cleaner exhaust emissions. Also, according to page 152 of "How to Tune and Modify Engine Management Systems" (book by Jeff Hartman), sequential injection always gains power at peak torque and at peak horsepower.
2. With a highly atomized mix in the port, at intake valve opening, the lighter droplets of fuel will be partly blown back up the port [intake port reversion]. This is caused by the residual exhaust pressure [overlap period] still residing in the combustion chamber. Some of this reverted mixture will adhere to port walls and condense. This puddling fuel may find its way home, on the next intake cycle, but it will cause cycle-to-cycle air/fuel ratio variances.
3. At 8000 RPM the intake valve is opening and closing at 66 times a sec. and is only open for an average of 9 Mil/Sec.
4. "Fuel injected directly onto the intake valve yields a significantly better engine response"
5. Nozzle location should be as parallel to the airflow stream as possible
not be more than 45 degrees, although it can be less.
6. On the other hand, in theory, high-idle vacuum generated by mild stock engines permits placing the injector farther upstream without significant low-speed driveability degradation.
7. Moving the injector farther away from the valve allows more time for the air/fuel to atomize properly and remain in suspension when air velocity comes up at high rpm. This should improve peak power but-because of poor low-rpm velocity-at the expense of idle quality
8. On a 1,000hp engine, the injectors were originally located 7 inches back from the valves. Doubling this distance to 14 inches was worth 50 hp on top, a 5 percent gain-but "it wouldn't idle below 1,600 rpm.
9. A decent compromise for a hot-rod engine is to locate the nozzle about 1-2 inches upstream from the manifold flange to give atomization a chance, positioning the fuel rail at the best angle you can get away with and still package the harness and fuel rails