GR engines are introduced as the designated replacement for the previous MZ V6, JZ inline-6, and the VZ V6. And the GR family is represented by its initial release, the 1GR engine. But we will not talk about 1GR machines; and we will talk about its analog version, the 6GR engine.
So, let us talk about the 6GR engine’s design, power, applications, issues, tuning potential, aftermarket support, reliability, and many more.
What are 6GR engines?
The Toyota 6GR engine or 6GR-FE is the 4.0 Liter version of the GR family series. It has the same displacement as the 1GR and features most of the updates covered by the 1GR as mentioned above. 6GRs are water-cooled naturally-aspirated engines and feature a dual variable valve timing system (VVT-i) on the intake and exhaust camshafts. To add to that, Toyota also improved the cylinder head, updated the cooling system, lighter pistons, and modified intake ports and cylinder sleeves.
Toyota 6GR engines are made as an analog version to the updated 2009 1GR-FE engine. Some updates on that engine include camshaft carriers, more compact pistons, added spacers in the cooling jackets, a simplified crankshaft, and advanced spark plugs are also used. Toyota also installed a collapsible oil filter and oil cooler, which are moved to a separate bracket under the engine. This engine is exclusively sold to the Chinese automotive market.
Engine Specifications and Design:
- Production Run: 2013 – Present
- Cylinder Head Material: Aluminum
- Cylinder Block Material: Aluminum
- Configuration: V6
- Bore: 94 mm
- Stroke: 95 mm
- Valvetrain: DOHC with four valves per cylinder
- Displacement: 4.0 L (3956 cc)
- Compression Ratio: 10.0
- Weight: 336 lbs.
- Max HP: 229 HP at 5,000 RPM
- Max Torque: 254 lb-ft at 4,400 RPM
Toyota 6GR engines are made for longitudinal mounting in rear-wheel drive and all-wheel drive pickup applications. The machine has a six-cylinder encapsulated in a huge Aluminum 60-degree at V arrangement block with cast-iron sleeves. 6GRs have a bore of 94 mm and a stroke of 95 mm, resulting in a four-liter displacement. The 6GR power output is rated at 229 HP at 5,000 RPM with 254 lb-ft of torque at 4,400 RPM.
Inside, the 6GR engine, like the 1GR, features a spiny type cylinder liner cast into the block made from cast iron. This uneven surface in the block promotes a better adhesion between the Aluminum cylinder block and the liners, which results in better heat dissipation and reduced heat deformation of the cylinder bores. So, when the cylinder walls are damaged, you must replace the overall cylinder block.
The 6GR engine has Aluminum-made pistons along with a taper squish combustion chamber design to improve the intake and fuel efficiency while simultaneously improving the engine’s performance and anti-knocking properties. It adopted a siamese-type intake port to prevent fuel from mixing by those walls due to the port wall’s reduced surface area; dual VVT-i like the 6GR has a higher compression ratio due to the optimized piston shape.
In addition to that, the 6GR engine is equipped with a high-temperature plastic insulator that drastically increases the rigidity and durability of the block. This kind of protection fills the space between the block materials and the outer portion of the cylinders, which are common to open deck engines. In addition to that, Toyota installed jacket spacers, as an added upgrade, to the water jackets, which draws the coolant above the cylinder bore and prevents the water flow in the middle and under the water jacket for a more uniform temperature distribution. This feature results in lower oil viscosity and reduces the friction between the cylinder bore walls and pistons. There are also two oil passages for each bank that sums into four to keep the combustion chamber temperatures at uniform levels and reduces cylinder hot-spotting.
Its crankshaft is made from forged steel with four journals and five balance weights optimally placed to reduce vibration and noise. 6GR uses high-strength forged steel connecting rods and bearing caps that are made from Aluminum; it also used nutless-type plastic region tightening bolts to reduce friction. The piston skirt is coated with resin, while the piston ring groove is covered with anodic oxide to enhance rust and wear resistance. Oil cooling jets are installed under the pistons to regulate the heat accumulated in the piston when running.
The 6GR cylinder heads are made from Aluminum with steel laminate-type head gaskets; double overhead cast-iron camshafts with four valves per cylinder. Toyota added a shim around the cylinder bores to increase the sealing surface for more improved durability. In addition, this engine also used roller rocker arms with built-in needle bearings to reduce the friction between the roller rocker arms and the camshafts.
Toyota 6GR engine is only available at a particular car application in 2013 Toyota Coaster which is exported for the Chinese market. There are no other known applications besides that, and maybe there are others whom they swapped their engines with 6GRs.
Engine Tuning, Upgrades, and Modifications
6GR engines are generally powerful engines, as evident in their displacement. Monster numbers for such engines are justifiable since their applications are meant for big guys like trucks and other SUVs. And like a typical engine, you can tune, upgrade, and modify your engine, especially this 6GR.
Toyota has its in-house line of performance kits, also known as the TRD or Toyota Racing Development. TRD is the ones who make supercharger kits or turbos for Toyota engines, though there are also aftermarkets, TRD is accredited, and other aftermarket parts for the GR engines. These aftermarkets are designed out of the Eaton M90.
So to add some finishing touches to your engine, as it is already powerful, you can install a supercharger kit for the 6GR. First, you need a lower compression ratio, and to achieve that goal, you need to buy forged pistons, Carillo connecting rods, and a thicker cylinder head gasket. You will also need a TRD intake system and a 3-1 design headers kit. Bolt and install these performance parts on the engine, and it can develop 320 HP and at least 380 lb-ft of torque; do some head porting and polishing, which can push the outputs up to 350 HP.
Problems Surrounding the 6GR Engine
6GR and 1GR engines are almost identical to each other and share most of the issues we will discuss here. These are common problems that may occur, and it is best if you could get prior knowledge regarding some issues that might arise on the 6GR engine. It is helpful to get some precautionary heads-up so that when you own or planning to, you already introduced yourself to some failure scenarios.
The first issue is the overheat occurrence. For the 1GR engines, there are reports that some 1GR engines suffered from blown head gaskets. For which we all know that head gaskets conceal the engine block and cylinder heads. So, if the head gaskets are faulty or already worn out, seals for the cylinders, oil, and coolant leaks might be some manifestation of this. Misfirings, coolant loss, and white smokes coming straight from the exhaust are some things that might indicate that you have blown gaskets. Original head gaskets can last around 250,000 miles.
The next weak point of the 6GR, but not only 6GRs but also other GR engines, is the water pump issue. This problem is like an introductory reference to the head gasket problem; the lack of coolant flow can, indeed, lead to overheating and may escalate to worse head gasket problems. The water pump is an essential part of the engine as they provide the adequate cooling process of the engine. With that being said, they are highly subjected to standard wear and tear with years of use and poor maintenance. If this issue occurred, you need to replace the water pump immediately if you see coolant stains or actual coolant leaks near the drain holes. The problem might appear close to 150,000 miles.
Another issue is the ignition coil. Premature ignition coil failures do happen, and fortunately, they don’t cover the majority numbers. But to tell you, this component is also a victim of ordinary wear and tear, which means that this is a standard maintenance item that needs replacement in due time; however, there are exceptions because some ignition coils last a lifetime. Some of the signs that you might notice if the ignition coil is faulty are the experience of rough idling, power loss, misfirings, and stuttered acceleration.
There is also a reported case of ticking noise, which is absolutely normal for the GR engines as it only emphasizes that the gasoline steam ventilation system is functional; that noise also accompanies the operation of the fuel injectors.
6GR engines are enormous, powerful, and efficient; they are also highly reliable and durable. We cannot deny that 6GR is made to last long with its strong internals, which is proportional to its power output and other reliability characteristics. Though others may consider this engine a bit underwhelming as a modern engine with such a large displacement, that outweighs the pros over the cons. It featured most of the presents by the 1GR engines. It has some minor issues and problems such as head gasket problems, weak water pumps, and thin cylinder walls that make it impossible to bore the block; and are not suitable for a work truck or a big SUV. However, this engine can last a lifetime with proper maintenance, high-quality engine oil, and fuel.
I hope that this simple discussion helped you understand the 6GR engine’s design, application, power, issues, problems, tuning potential, and overall impact on the community and the automotive industry.