Technosquare's Monster Naturally Aspirated Toyota 4AG - Part 3
The first issue to address was the lubrication system. As the 4AG has an iffy lubrication system, mostly due to very fragile oil pump gear rotors that become marginal above 8000 rpm, a dry sump system is essential for engine longevity. The 4AG also pushes the demand on the oil system to high levels. It has a marginal amount of bearing area for high rpm operation and any air entrapment in the system or fluctuation of oil pressure can cause failure at high RPM.
The Barnes dry sump pump has two scavenge and one pressure stage. The pump is belt driven from the crank. The TRD oil pan is very thick and greatly strengthens the block.
The low profile of the dry sump pan is shown here. The braided black hose is the external coolant bypass hose that max effort 4AG's need to prevent overheating.
To assure a steady supply of air free oil, Technosquare relied on a Barnes 3 stage dry sump system with a modular pump with two scavenge and one pressure stages. The two scavenge stages suck windage from a TRD Formula Atlantic pan. The pan is an important element in improving the engines structure. Since the 4AG's lightweight block is not well suited for stressful high RPM and high power use, it is reinforced by the beefy pan. The pan was designed to be a structural part as the engine is a stressed member when it is installed into a Formula Atlantic race car chassis.
The bypass hose takes hot coolant from the back of the head to improve coolant flow in the head. This helps keep #4 cylinder from running too hot.
The pan was built to greatly reinforce the wimpy 4AG block for this use and Technosquare used it to help keep the 4AG block from flexing. A TRD thick and strong Formula Atlantic valve cover was also used for this reason as the valve cover is also designed to strengthen the engine assembly in a Formula car chassis. These reinforcing parts should greatly increase the bearing and crank life as these were always marginal in the racing versions of the 4AG due to block flex at high rpm.
Oil pumped from the pan is cooled by a large Greddy oil cooler and de-aerated in a large Peterson tank. Peterson tanks are great because they are two- piece so they can easily be disassembled and thoroughly cleaned in case of an engine failure.
The coolant bypass hose goes to the discharge of the water pump then to the radiator. You can also see the beefy strong casting of the TRD Formula Atlantic oil pan.
The induction is handled using a TWM intake manifold with huge 50mm TWM individual throttle bodies sporting short 40mm velocity stacks. A TWM fuel rail feeds 285cc Denso injectors. A vintage TRD FIA N-1 4-1 header handles exhaust duties. We feel that there is a lot more power to be found in a modern header design with larger stepped primaries and a merged collector.
The TRD Formula Atlantic valve cover is very thick and strong which helps reinforce the weak 4AG block. This helps improve bearing and crank life.
The Autronic ECU, CDI box and Wide band controller mount on the firewall inside the car.
The CDI runs in individual coil mode and fires these coils from a Honda CBR Motorcycle one per cylinder.
Engine control is managed by an Autronic stand alone ECU and CDI system. The CDI fires Denso Iridium sparkplugs with an individual coil ignition system using Honda CBR coils acting directly on the plugs. Power transfer is handled by a twin disc OS GIkken clutch and lightweight flywheel.
An OS Gikken twin disc clutch and steel flywheel couple the engine to the transmission.
The TRD FIA N1 4-1 header is more of a vintage racing piece. A modern header would probably be good for more power.
The lower line is the old 1600cc engine. The upper is the result of adding the stroker crank.
In initial dyno testing the monster 4AG belted out 183 whp @ 8750 RPM with 122 lb/ft of torque at 6250 rpm on Technosquare's notoriously conservative Superflow dyno. This would probably equate to around 200 whp on a Dynojet or 230+ at the crank. This is in line with the most developed 4AG's ever built during the engines racing heyday in the Formula Atlantic era but with a wider powerband and more torque that the increased stroke gives.
We feel that there is potentially a lot more power to be found with development of this engine if Technosquare's customer wants to find some budget to do so. A custom modern designed header should help considerably. Also the cylinder head was put together using well worn vintage TRD parts, especially the valves which were worn thin with a narrow margin and sunk deep into the valve seats. Newer modern valves and a correct valve job should free more power as well. WPC treatment could also help. We think that there is another 10-20 hp to be found here.
We will continue to follow Technosquare's development of this engine in the future.