CPT Fuel Systems & Engine Performance Flashcards
6 cards from real CPT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CPT Fuel Systems & Engine Performance flashcards as text
A performance technician is calibrating a standalone ECU and needs to set the base fuel table. What three inputs are most critical to establishing a correct base fuel map?
Answer: Injector flow rate, engine displacement, and target AFR at each load/RPM cell
Injector flow rate, displacement, and target AFR are the foundation for calculating how much fuel each cell of the map should command.
When performing a fuel system flow test on a high-performance build, a technician measures 420 lbs/hr of fuel pump capacity. The engine produces 600 hp on E85. Is this pump sufficient?
Answer: No — E85 requires approximately 30-35% more fuel than gasoline, putting demand beyond the pump's safe capacity
E85's lower energy density requires ~30-35% more fuel volume than gasoline for the same power output, meaning 600 hp on E85 can exceed a pump rated near that level on gasoline.
What symptom would a CPT technician observe if a fuel pressure regulator's vacuum port diaphragm ruptures internally?
Answer: Raw fuel pulled into the intake manifold via the vacuum line, causing a rich condition and rough idle
A ruptured FPR diaphragm allows liquid fuel to pass through the vacuum port into the intake manifold, causing an uncontrolled rich condition.
Which condition would cause port fuel injectors to deposit excessive carbon on the injector tips over time, degrading their spray pattern?
Answer: Extended use of low-detergent fuel combined with heat soak cycles during hot shutdowns
Heat soak after shutdown bakes fuel residue on injector tips, and low-detergent fuel lacks the additives to keep injector tips clean.
A CPT technician is diagnosing a stumble during tip-in throttle transients on a carbureted race engine. Which carburetor circuit is primarily responsible for tip-in fuel delivery?
Answer: The accelerator pump circuit
The accelerator pump squirts a shot of fuel during rapid throttle opening to prevent the lean stumble caused by the sudden increase in airflow.
On a returnless fuel system, what component takes over the function of the traditional remote fuel pressure regulator?
Answer: A pressure regulator integrated inside the in-tank fuel module, controlled by the ECU via fuel pump driver module
Returnless systems integrate the pressure regulator into the fuel module inside the tank, with the ECU controlling fuel pump speed to maintain target rail pressure.