The seventh generation Z06 is the most powerful production car from GM. The LT4 engine is to thank for that. It’s made with raw power combined with a higher level of efficiency than seen in other engines. The compact monster that is the LT4 is one of the most impressive engines ever made. Let’s take a deeper look inside the powerful LT4 engine.
|Bore/Stroke||4.06" x 3.62"|
|Pistons||Forged Aluminum w/Internal Ribs, Flat-Top Crown|
|Cylinder Heads||A356-T6 Rotocast Aluminum|
|Valves||54mm Solid Titanium/40.4mm Sodium Filled|
|Camshaft Type||Hydraulic Roller|
|Intake Valve Lift||0.492"|
|Exhaust Valve Lift||0.551"|
|Duration @ 0.050"||189|
|Camshaft Lobe Seperation Angle (LSA)||120|
|Fuel Delivery||Direct Injection|
|Engine Driven Fuel Pump||2,900psi|
|Oiling System||Dry Sump w/Oil-Spray Piston Cooling|
|Horsepower @ 6,400 RPM||650|
|Torque @ 3,600 RPM||650 lb-ft|
A Supercharged Compact Beast
The LT4 is built on the newest GM family platform that includes the LT1. It uses the same technologies GM introduced on the LT1. This includes direct injection, Active Fuel Management, and continuously variable valve timing.
Supercharging technologies are carried over from the LS9 engine. That includes the compact, high out supercharger/intercooler assembly, which allows for the ultra low hood profile. It’s hard to believe, but the LT4 is only one inch taller than the naturally aspirated LT1. Also, the LT4’s supercharger is about 20 pounds lighter than the LS9’s supercharger.
The new R1740 LT4 supercharger spins at 5,000 RPMs more than the LS9 — it can reach up to 20,150 RPM. As with the LS9’s supercharger, the R1740 has a pair of four lobe rotors with a 160 degree helix design. This broadens the effectiveness of the positive displacement blower and encourages more torque production at lower RPMs.
When compared to the LS9’s supercharger, the R1740’s rotors are shorter and smaller, which allows for the higher RPM capacity. Boost is achieved more efficiently than ever thanks to the more direct discharge port. This creates less turbulence, reduces heat, and speeds airflow going into the engine. The cooling system for the supercharger is more also efficient. It offers 10% more heat rejection compared to the LS9.
LT4 Versus LS9 Superchargers
|Name||R1740 TVS||R2300 TVS|
|Helix Angle Of Rotors||160º||160º|
|Application||C7 Z06||C6 ZR1|
The Nitty Gritty On Fueling, Combustion, and the Rotating Assembly
The LT4 engine is based on the Gen V GM engine that incorporates unique features. These features support its higher output and greater cylinder pressure as a forced induction engine.
The direct injection fuel system has a specific fuel pump and rail assembly with:
- 2,900 psi fuel pump (the LT1 is rated at 2,175 psi)
- Higher-flowing 25cc per second injectors
- Higher capacity fuel rails to accommodate the flow capacity of the pump and injectors
The cylinder head valve train assembly consists of:
- Large 65.47cc combustion chambers on the cylinder heads
- Lighweight 54mm solid titanium intake valve for exceptional heat resistance
- Sodium filled exhaust valves (same as the LT1)
- 10:1 compression ratio, perfect for the forced induction engine
- A longer exhaust duration camshaft to hold the valve open longer to handle greater airflow volume
- Stainless exhaust manifolds to withstand higher temperatures
- Unique rotating assembly to accommodate the pressures of the supercharger. It includes:
- A 1528MV forged crankshaft with tungsten balancing inserts, ground pin collars, and 1-6 rods intermediate pin drills
- A forged, lightweight aluminum dampner with anodized hub and iron inertia ring
- High strength powder metal steel connecting rods, made for reducing reciprocating mass and for quicker revving
- Forged pistons with a flat top crown
- Floating piston write pins
The oiling system is like the LT1's and uses a dual pressure control and a variable displacement vane pump. The dual pressure control allows for efficient operation at lower RPMs, and it’s coordinated with the Active Fuel Management system. The variable displacement ensures that the pump efficiently delivers oil flow as demanded. It also uses higher strength scavenge pump gears.
Dry sump oiling is standard on the engine. Oil spray piston cooling is also standard.
This engine, made at the new Performance Build Center at the Bowling Green plant, is a graceful banshee. Are you looking to add a little more performance to your engine? Check out our selection of GM Performance Parts here.