| TOYOTA MARINES SPORTS | |
Toyota power has been used in the air, land, and sea. Officially on land based vehicles of all sorts, unofficially in the air and water…until now. The old K engines have powered boats of all types in Asia, the M engines have powered speed boats all over the world. Now officially Toyota has produced a marine engine and boat !
The heart of Toyota Marine Sports' boats is its VT300i 4.0-liter, V8 engine with 300 horsepower and 310 ft. lbs. of torque. The VT300i engine is a marine version of the 1UZFE VVTi engine used to power several Lexus automobiles. With hundreds of thousands of Lexus vehicles on the road, the engine has proven to be a standard of reliability and long life. Additionally, each marine engine is individually tested twice before it leaves the factory.
This engine (and the automotive version similarly featured in the Lexus LS 400, GS 400 and SC 400) is fitted with twin double overhead camshafts and Variable Valve Timing with Intelligence (VVTi) for improved pulling power over a wide RPM range. What this proven power unit means for the boat driver is rapid throttle response with no RPM fall-off when towing.
The VT300i has its own version of "fly-by-wire" when it comes to throttle response. The Electronic Control Unit (ECU) controls intake throttle valve position using a potentiometer and electrical motor. The boat throttle cable connects to the potentiometer, and any movement of throttle varies an electrical signal sent to the ECU. The ECU, in turn, controls a DC electric motor connected to the throttle valve assembly. The throttle valve moves through a zero degree (idle) to 84 degree (full-throttle) angle. In fail-safe mode, the throttle angle is automatically set at 24 degrees for limited engine operation.
The ECU continuously adjusts the intake valve timing. Timing is changed hydraulically using two VVTi controller units consisting of an outer gear, an inner gear, a helical splined hydraulic piston and electronic/hydraulic circuits for directing oil to one or the other side of the piston.
The outer gear is driven by the engine timing belt, and inner gears are connected to the intake camshaft. A moveable piston, with helical cut splines, is located between these gears and is pushed in or out by hydraulic pressure directionally controlled by the ECU. As the piston moves in or out, the helical splines continuously reposition the inner gear to outer gear position relationship thus changing intake camshaft timing.
The VT300i is a 90-degree bank, 32-valve V8 gasoline engine featuring state-of-the-art engine management and operating systems. It features an onboard computer with built-in malfunction diagnostics, electronically controlled distributorless ignition, continuous variable valve timing for maximum performance and intake air assisted, sequential fuel injection.
For reliability, there is no distributor assembly, and each spark plug has an individual ignition coil and igniter controlled by the ECU. The ECU electronically monitors crankshaft RPM, camshaft angle, throttle valve position and other critical engine information in determining the optimum spark advance curve. For long life (approximately 1,500 engine hours), the spark plug center tips are constructed of iridium and the outer electrodes are made of platinum. Twin engine block-mounted knock sensors detect engine knocking with the ECU adjusting ignition timing and RPM to protect the engine from damage. A highly reliable powerplant, even the serpentine drive belt is rated with a 100,000-mile life.
Even the intake air induction is acoustically controlled for improved performance. The (ACIS) or Acoustic Controlled Induction System increases the power output at all RPMs. The intake manifold has a built-in adjustable bulkhead (door) that divides the intake manifold into long and short tube lengths. Using an intake air control valve, this bulkhead is opened or closed depending on engine RPM and throttle valve position. Long-intake runners are used below 4,900 RPM with short runner lengths being used above.
The VT300i features Toyota's Air-Assisted, Sequential Multi-Port Fuel Injection (SFI) using Four Hole Injectors. A combination hot wire-type air flow meter/temperature sensor (located in the air intake system) measures intake air volume and temperature for precisely controlled fuel injection timing. To improve fuel economy, idle mode and to reduce emissions, a small amount of intake air is directed to each fuel injector based on the position of the throttle valve. The system's target is to optimize combustion at all loads and RPM conditions. Maximum performance is assured with the Pentroof combustion chamber with the sparkplug located in the center between valves.
Vapor lock protection is provided by using two separate electric fuel pumps. A continuous flow primary fuel pump recirculates fuel from and back to the boat fuel tank. A secondary fuel pump provides fuel to the injector rails from the pressurized output of the primary pump. Excess injector rail fuel is returned to the fuel tank by the primary pump, improving fuel economy. Protection from water in the fuel tank comes from an in-line replaceable water separator.
Although the engine is protected from the elements by the hull, additional corrosion protection is afforded by an epoxy-based anti-corrosion primer coat with an acrylic top coat. A recent addition is an optional self-contained, freshwater cooling system. The engine's 85 amp alternator keeps the batteries charged, allowing virtually unlimited accessory use throughout the day without draining cranking power. The starter motor is located on the upper part of the assembly in order to protect it from moisture for improved durability and longer life.