Quote:
Originally Posted by redpoint5
Also, why haven't gasoline engines been DI from the beginning, with no spark plug?
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...because
Diesel engines rely upon the 'self-ignition' point of fuel to run so no ignition-system is needed; and, they produce LOT's of torque but only at slow speeds (typically <3-4,000 rpm).
...
Gasoline engines require a spark-ignition system (coil, distributor, wiring, plugs) to ignite the air-fuel mixture at a
precise(*) timing so that they can achieve much higher engine speeds (6-7,000 rpm) and thus higher power (but not torque) than Diesel engines.
...even the "new" HCCI engines (diesel-like operation using gasoline) will use BOTH Compression Ignition (CI) (at light loads) and Spark Ignition (SI) (at high loads) operation...Direct Injection (DI) with gasoline is "trickier" than with diesel, because of gasolines' lower self-combustion temperature.
...why SI before DI? It was easier to get electricity to occur quickly than it was to get mechanical injectors to squirt quickly.
(
*) = gasoline engine power is very sensitive to changes in ignition timing.