The engines of the Dynamic Force range are powerful. The latest family of Toyota’s New Global Architecture (TNGA) strategy is a group petrol engine series developed under TNGA platform. This new generation, alongside similar vehicle types, was created to simplify production while still maintaining high levels of performance and fuel efficiency – making them perfect for traveling long distances on your own time.
And one of those engines is the Toyota A25A-FKS 2.5 D-4S engine.
What are Toyota A25A Engines?
Toyota’s new 2.5-liter engine, or the Toyota A25A-FKS engine, is the most technologically advanced engine the Toyota has ever developed in that period. The highest thermal efficiency test is rated at 40 percent, which is one of the finest outcomes for a conventional engine in the world.
Now that the A25A-FKS has pushed production and fuel economy to new heights, the 2AR has become a thing of the past. The engine is utilized in a variety of Toyota and Lexus vehicles, beginning in June 2017 with the four-cylinder A25A type installed in the XV70 series Camry.
The first engine in the new “Dynamic Force” series appeared in 2016 (2.5), the second in 2017 (3.5), and the third in 2018. (2.0). The complete family will include six inline and three V-engines by 2021.
The Toyota 25A-FKS (2.5 D-4S DVVT-iE) engine is the Dynamic Force’s base engine, with transverse, combined injection, and DVVT-iE. The Toyota A25A-FKS is an evolutionary progression of the 3-4 wave engines since its production.
Engine Specifications and Design:
- Production Run: 2016 – Present
- Cylinder Head Material: Aluminum
- Cylinder Block Material: Aluminum
- Configuration: Inline 4
- Bore: 87.5 mm
- Stroke: 103.4 mm
- Valvetrain: DOHC four valves per cylinder
- Displacement: 2.5 L (2487 cc)
- Compression Ratio: 13.0 and 14.0
- Weight: 290 lbs.
- Maximum HP: 205 HP at 5,7000 – 6,600 RPM
- Maximum Torque: 184 lb-ft at 3,600 – 4,800 RPM
Cylinder Block
The Toyota A25A-FKS engine features an open-deck aluminum alloy cylinder block with sleeves formed directly into the block material. The engine’s crankshaft longitudinal axis is displaced by 10 mm from the cylinder axes. There are eight typical counterweights on the crankshaft and one with toothed gear. The crankshaft gear powers the balancing unit, which is linked to the engine block at the bottom.
On top of that, the absence of water cooling on the front side of the #1 cylinder allowed the total length of the block to be reduced. Oil and antifreeze channels are combined for improved heat transmission, resulting in faster warm-up of the cold engine and cooling under heavy loads.
Between the cylinders, sloping coolant ducts have been drilled along with the spacer placed in the water jacket. Allowing more intensive coolant circulation at the top of the cylinder, which enhances heat dissipation and helps to distribute the thermal load more uniformly.
High-strength connecting rods and lightweight aluminum T-shape pistons with a unique resin coating were used in the engine. A DLC (Diamond-Like Carbon) coating is present on the top compression and oil rings. The piston’s “walls” are noticeably sloping, which should improve load distribution to the piston pin during the expansion stroke.
Further, just like the other engines, the Toyota A25A engine oil sprayed by two oil jets for each piston, cooling the pistons for a more optimal temperature range.
The oil system has also been improved. However, the main advancement is the second generation variable-pressure oil pump, which is controlled by ECM electronics.
Cylinder Head
The Toyota A252A-FKS engine has a 16-valve aluminum cylinder head with two chain-driven camshafts in separate casings on top. The cylinder head is covered with an alloy cover and has an oil supply system for lubricating the rockers.
Further, the intake port features a laser-clad valve seat, whilst the exhaust port has a standard pressed valve seat. The camshafts operate the valves through roller rocker arms, and the engine is also outfitted with hydraulic tappets to maintain constant zero valve clearance.
A low-friction single-row timing chain drives the intake and exhaust camshafts. Along with that, Toyota’s Dual Variable Valve Timing system is also used in the Toyota A25A-FKS. The intake camshaft is controlled by an electronic actuator (VVT-iE), while the exhaust camshaft is controlled by a typical hydraulic VVT actuator. Toyota added an extra cam on the exhaust camshaft for the high-pressure fuel pump.
Fuel Management
The Toyota A25A-FKS engine employs combined fuel injection, with direct injection in the combustion chambers and multipoint injection in the intake ports. As a result, earned the system an unofficial moniker ‘D-4S’.
Each direct injection high-pressure fuel nozzle has six holes and sprays gasoline at mid and high engine loads. There are ten holes in the low-pressure nozzles in the ports. Alongside, the multipoint fuel injection, in conjunction with direct injection, performs at low and mid-range speeds. The system’s fuel pressure ranges from 349 to 2,900 psi.
In addition, the engine is equipped with a basic fixed-geometry plastic intake manifold and an electronically controlled throttle body (ETCS-i). Since there is no air limiter in the intake manifold, Toyota equipped the engine with a vacuum pump driven by the exhaust camshaft to provide enough vacuum in the brake booster.
A stainless steel exhaust manifold with an integrated catalytic converter and Exhaust Gas Recirculation pipe is located on the exhaust side.
Emissions
Modern environmental regulations compelled significant changes in engine cooling systems. The Toyota 2.5 D-4S engine has a water pump powered by an electric motor, an electronically regulated thermostat, and shut-off valves. The redesigned technology aids in the faster warm-up and optimal cooling throughout all load ranges.
Applications of Toyota A25A-FKS Engine:
- 2017 – Present Camry
- 2018 – Present RAV4
- 2018 – Present Lexus ES 250/260
- 2018 – Present Avalon
- 2021 – Present Highlander/Crown Kluger
- 2021 – Present Lexus NX 250/260
Engine Potential, Modifications, and Upgrades
The powerful but note-worthy engine is capable of producing 205 HP at the factory. With an addition in tuning, this product might just turn into your dream when it comes to naturally aspirated engines. We expect 250+ horsepower with high octane fuel and plenty more surprises waiting for us during testing; who knows what could pop up next?
For all who loves to tune and build higher power production engine, there are options for you. 91 and 93 octane fuel is what we use now in our cars which means they are designed to run better on it. The peak power potential is lurking right under the surface, waiting patiently but inevitably getting released once you tap it.
Problems Surrounding Toyota A25A-FKS Engine:
The A25 engine’s history began in mid-2017, while the M20 engine’s history began around the end of 2018. So, based on prior history, it is necessary to wait a relatively long period for certain and statistically significant outcomes while simultaneously monitoring DF problems in other regions of the world.
However, the most common defect of the engine is its oversized pistons.
Another thing is a cooled EGR.
This system has relatively little documentation. The EPA conducted some benchmarking and has some nice cad drawings and layouts of how this system operates.
The engine emits exhaust gases, and without this mechanism, Toyota would fail new emissions testing. As a result, this system was employed. The way it works in the Camry is that it has a valved muffler, which causes backpressure in the exhaust, driving some gasses up this small tail and back into the engine.
This reduces the amount of gasoline used by the engine because it scans the air going into the engine twice, once at the MAF sensor and once at the engine block.
This system is quite simple to mitigate. Simply remove the cats or seal off the little tube by cutting it and welding it shut. Then, swap out the muffler for a non-valved muffler and install a cold air intake on the automobile.
This will allow you to get 100 percent outside air into the engine while also reducing back pressure and producing greater power. Some owners have seen a 10 to 20 horsepower increase just by doing this.
Recalls
Another issue is from the North American market: a total recall of A25 vehicles manufactured in the fourth quarter of 2019 owing to a “possible” problem in the cylinder block casting.
Summary
Toyota’s A25A-FKS engine is an engineering marvel with advances in fuel cell technology and car design. The engine has even more complex components than its predecessors, but it still feels manageable thanks to some fancy electronics.
We can see what those laser-clad seats look like up close, as well as how they were built for strength without weight gain – not bad, considering these will likely need replacement after a rebuild anyway.
If there is a first real hint at where Toyota might go wrong, it’s their casting cylinder sleeves. Some say that it doesn’t have enough juice left for a more power-demanding build. However, the engine is efficient, reliable, and excellent in city driving.