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505CI Twin-Turbo Pontiac Engine - Twin-Turbo Tail Twister
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Here's where things go off... Here's where things go off the charts-literally. We poured in some C16 racing fuel, upped the boost from 13.4 to 17.7 psi, and quickly pegged the needle, so to speak, on the dyno. The reason the left side of the torque graph is flat is because it is up against the upper limit of the dyno's measuring ability. Peak power also occurred about 1,000 rpm lower than with pump gas-mostly because of greater boost coming in earlier. Because of the different burn rate with the C16, the fuel and timing tables needed some tweaking, but they were saved and can be loaded any time Hutchens is feeling bored. | BOTTOM END | | Block Description: | IA II | | Deck Height: | 10.220-in | | Crank: | Butler Performance forged, 4.250-in stroke with 3.00-in mains | | Preparation: | Balanced by Wheeler | | Balancer: | ATI | | Rods: | Scat 4340-forged steel, 6.700-in | | Bearings: | Sealed Power | | Pistons: | Ross forged, 49cc dish | | Piston-to-Deck Height: | 0 | | Piston Pins: | Ferrea (big-block Chevy style) full floating | | Rings: | Total Seal, file-to-fit | | Fasteners: | ARP | | OILING SYSTEM | | Windage Tray: | Milodon | | Oil Pan: | Milodon | | Oil Pump: | Melling high-volume | | HEADS | | Casting: | Edelbrock Performer, ported | | Combustion Chamber Volume: | 90 ccsMaximum Flow at 28 Inches of Water | | Intake: | 304 cfm at 0.600-in lift | | Exhaust: | 232 cfm at 0.600-in lift | | Compression Ratio: | 7.96:1 | | Valves: | Edelbrock SS, 2.11/1.66-in | | Angles Used in Valve Job: | 30, 45, 75-deg | | Rocker Arms: | Comp Cams aluminum roller, 1.5:1 | | Pushrods: | Smith Brothers restrictor-type, 0.040, 3/8-in | | CAM | | Brand: | Comp Cams custom hyd. roller | | Duration at 0.050: | 258/248-deg | | Lift: | 0.541/0.541-in | | Centerline: | 111-deg | | Lobe Separation Angle: | 115-deg | | Installed Position: | Straight up | | Lifters Brand: | Comp Cams roller | | Valvesprings: | Edelbrock | | Seat Pressure: | 140 pound | | Open Pressure: | 360 pound | | Timing Chain: | Cloyes Tru-roller |  The Volumetric Efficiency...  The Volumetric Efficiency table models the amount of airflow through the engine. The higher the number, the greater the volumetric efficiency (cylinder fill) the engine is experiencing at that load and rpm.  The Base Spark table takes...  The Base Spark table takes over the function of both the initial and mechanical advance in the distributor. Besides starting with known safe numbers for the engine, it's a good practice to run a few degrees less timing than optimal until the fuel maps are dialed in. Then timing can be added until peak power is reached or detonation is encountered.  In closed-loop mode, the FAST...  In closed-loop mode, the FAST ECU is constantly monitoring and adjusting the A/F ratio to match the Target A/F Ratio table. That's a good thing. The positive and negative correction limit tables allow the tuner to set the range of authority for the oxygen sensor (how much it can take out or add).
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