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An Interesting GTSB (Greg Transportation Safety Board) Report

An Interesting GTSB (Greg Transportation Safety Board) Report (Subject to revision) On August 29, 2024, at approximately 6:30PM (EDT), the engine in the #33 Porsche 914 suddenly stopped as it was slowly driving away from the town green of Falls Village, CT. Hearing a large noise (discernable by nearby onlookers), the driver immediately disengaged the drivetrain via the foot clutch and car coasted to the side of the street. Initial attempts to restart the engine were met with a starter that would not rotate; attempts to push the car while the transaxle was engaged were met with full resistance. It was quickly determined that the engine had locked up. After minimal roadside investigation, it was determined that the dry sump tank oil valve, which supplies oil to the engine oil pump, was in the closed position and it was obvious that the engine had been run without a supply of oil. As a result, the car was "flat bedded" back to Lime Rock Park and retained as a paddock display for...

On "Microsquirting" the Porsche 914

Bosch D-Jetronic The Bosch D-Jetronic system is pretty cool, especially when you consider it was designed in the 1960s. "Computer"-controlled electronic fuel injection with manifold pressure sensor, intake temperature sensor, crankshaft (well, distributor) angle sensor, and throttle position sensor/switch. It uses constant fuel pressure and flow, so only injection duration needs to be modified to control air/fuel mixture. It measures incoming airflow by monitoring the intake manifold pressure; engine speed, temperature, and other factors are monitored for the purpose of fine-tuning injection duration. Ignition is by a standard cam-driven distributor with an internal D-jet-specific pickup for the crank/cam angle position. This "speed-density" D-Jet system was used on many cars of the period, including Volvo, Jaguar, Volkswagen, and of course, the Porsche 914 (1.7L and 2L engines only; the 1.8L used L-Jetronic -- "L" for "luft" or "air...

On "Accusumps"

(This is another blog in a series of thoughts/ideas that I commonly see, created as a placeholder for future reference so I don't have to re-write it each time. I totally understand the limited audience and for such a post, but I invite feedback from those who have interest in this arcane subject...) -------------------------------------------------- This was posted in response to someone inquiring about PDM control, pressure sensors, switches, valves to manage an Accusump in his race car... You're making this wicked too complicated...and significantly failure-prone. An Accusump (AS) is a passive hydraulic/mechanical oil pressure accumulator (thus, "Accu"sump). Its purpose* is to provide oil flow when the pickup tube in your engine becomes unported due to side loads oil "slosh" or flow away from it. First, note that an AS is a "BandAid" for a design flaw in your road race engine. That design flaw is the unporting of the oil pickup. The ultimate res...

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