The Mazda SKyActiv is the brand name Mazda gave for their series of technologies developed under the same name. It employs vast improvements in fuel efficiency and engine output. Apart from that, new engines, transmissions, chassis, and bodies appeared in the 2011 model years.
One of the engines that possess the SkyActiv technology is the Mazda SkyActiv 2.5 G engine. Let us look at some of the characteristics of this engine.
What are Mazda 2.5 SkyActiv-G Engines?
Mazda 2.5 SkyActiv engines replaced the older L5-VE engine. This engine initially shed light on Mazda KE CX-5 and the GJ Mazda 6 in 2012. The Mazda 2.5 SkyActiv engine has the same technologies presented in the Mazda 2.0 SkyActiv. However, the Mazda 2.5 SkyActiv has a larger displacement.
In addition to that, the SkyActiv engine technology, to which the Mazda 2.5 SkyActiv belongs, is created to have far more efficient and provide more power output. Mazda SkyActiv engines are direct injection engines that achieved the highest gasoline compression ratio of 14.0.
For other markets such as the United States, the compression ratio was lowered to 13.0 to accommodate the operation on standard fuel. However, that also reduces the torque and fuel economy of the engine by three to five percent.
Other than that, SkyActiv has a lot of improvements in its development.
Among the most recognized is the significant engine efficiency improvement. This was achieved due to the high compression combustion, resulting in a 15 percent increase in torque and fuel efficiency.
It makes the SkyActiv engine your go-to choice for everyday driving with its increased torque in low to medium engine speeds.
Moreover, the Mazda 2.5 SkyActiv engine features an all-aluminum lineup construction with chain-driven dual overhead camshafts design equipped with VVT and direct ignition.
Engine Specifications and Design:
- Production Run: 2013- Present
- Cylinder Head Material: Aluminum
- Cylinder Block Material: Aluminum
- Configuration: Inline 4
- Bore: 89.0 mm
- Stroke: 100.0 mm
- Valvetrain: DOHC four valves per cylinder
- Displacement: 2.5 L (2488 cc)
- Compression Ratio: 14.0 and 13.0 for Canada, USA, and Australia
- Weight: 260 lbs.
- Maximum HP: 189 HP at 5,800 RPM
- Maximum Torque: 189 lb-ft at 3,250 RPM
Let’s take a closer look inside the engine!
The Mazda 2.5 SkyActiv G engine replaced the L5-VE engine. However, like the L5-VE engine, the new kid in Mazda has the same aluminum cylinder block with steel-molybdenum alloy bores. Further, this engine has a big four-cylinder balancer unit.
The engine block has a bigger bore size as well as a longer piston stroke to accommodate a larger displacement capacity of 2.5 L.
Mazda made the engine more powerful but lighter in comparison to its predecessor. The internals such as the forged connecting rods, steel crankshaft, and aluminum pistons are also strengthened.
The Mazda 2.5 SkyActiv engine has lesser friction in its bottom end by at least thirty percent.
The Mazda 2.5 Skyactiv engine’s cylinder head is almost the same as the two-liter version. Aluminum-silicon dual-overhead camshafts, rocker arms that featured needle roller followers and, four valves per cylinder – two for both intake and exhaust.
In addition to that, the Mazda 2.5 SkyActiv engine has a variable valve timing system called Dual Sequential Valve Timing. This technology allows the engine to provide much efficient fuel consumption depending on different driving conditions. Apart from that, the fuel system used was also upgraded.
The Mazda 2.5 SkyActiv engine uses a direct injection system that injects the fuel directly into the combustion chamber. That is done through a high-pressure fuel pump and injector nozzles with six holes for better fuel mixture and air.
Moreover, the Mazda 2.5 engine has distinctive features attached to it. These include a long, sporty 4.2.1 header or exhaust manifold. This system is designed to prevent the hyper recirculation of hot exhaust gases and gas parking inside the combustion chamber. However, this does not result in the environment.
The exhaustive distance between the catalytic converter and the engine lowers the temperature of exhaust gases that are not hot enough to fast the catalytic converter in the early seconds of operation.
In cold operation situations, the Mazda 2.5 SkyActiv G engine increases the temperature of the exhaust gases through ignition timing delays. With that, the hot gases warm up the catalytic converter faster.
Cooled Exhaust Gas Recirculation
The Mazda 2.5 SkyActiv G engine is an excellent engine for anyone who wants to save gas. But it’s not all about saving money.
The company has gone above and beyond to maintain the engine efficiency at high loads by using a cooling system that can be seen rarely on gas-powered passenger cars like theirs – cooled EGR (Exhaust Gas Recirculation) module.
Among other things that keep internal temperatures low when operating under heavy workloads, so you don’t enrich your fuel supply with excess heat buildup inside the vehicle due to its operation within normal ranges outside those boundaries.
Without this, the engine cannot offer the same fuel economy.
Idle Stop and Restart System
The Mazda 2.5 SkyActiv G engine has an idle stop and restarts system. Mazda’s imposition of the said technology used combustion as a part of the idle-stop system in collaboration with the electric-powered starter motor.
The system is smart enough to identify which cylinder was in the correct position and injects and ignites fuel into the cylinder. In this way, it lessens the wear on the starter motor.
High Compression Ratio and its effect on the Mazda 2.5 SkyActiv Engine
As Mazda claimed, their 2.5 SkyActiv engine achieved the highest gasoline compression ratio of 14.0. But how does this affect the performance of the engine?
Well, it involves risk, the same risk when you gamble in the casino. However, this risk allowed the engine to be more thermally efficient by nine percent. But, this improvement also decreases the torque production capabilities of an engine – due to knocking.
Knocking is not normal in combustion because the air-fuel mixture ignites prematurely due to high pressure and temperature exposure, creating a high-frequency noise. With the increase in compression ratio, the chances of knocking also increase.
Thermally efficient engines are substantial in this era because their mechanism inside the engine reduces the total amount of hot exhaust gas remaining inside the combustion chamber.
The Naturally-aspirated engine produces 187 HP at 6,000 RPM and 186 lb-ft of torque at 4,000 RPM.
Mazda 2.5 SkyActiv G Turbo
Mazda also released a turbocharged version. This turbocharged version produces 250 HP at 5,000 RPM and 320 lb-ft at 2,500 RPM on 93 octane gasoline, and 227 HP at 5,000 RPM and 310 lb-ft at 2,000 RPM on 87 octane, operating with a 10.5 compression ratio.
Mazda designed a different set of passages and butterfly valves acting on low RPMs to pass exhaust gases through smaller holes, spooling the turbo faster and minimizing turbo lag.
To add, the engine has a different exhaust manifold than the naturally aspirated, 4-3-1 headers, improving the exhaust scavenging and a cooled exhaust gas recirculation system. Both are designed to lower down combustion chamber temperatures and allow a greater boost with better fuel mileage.
Applications of Mazda 2.5 SkyActiv G Engine:
- 2013 – Present Mazda Atenza/Mazda 6
- 2013 – Present Mazda CX-5
- 2014 – Present Mazda Axela/ Mazda 3
- 2016 – Present Mazda CX-4
- 2016 – PresentMazda CX-9
- 2018 – Present Mazda CX-8
- 2019 – Present Mazda CX-30
Problems Surrounding the Mazda 2.5 SkyActiv G engine:
The Mazda 2.5 SkyActiv engine is still a young engine and does not yet have a long production history. But in this short period, there were some issues that the owners encountered.
Yes, it is mentioned as a reliable engine, but there are things and shortcomings that the engine sometimes faces.
Some of those issues include:
1. Power Loss and Excessive Fuel Consumption
This issue stems from the use of low-quality fuel. When you use low-quality fuel for this engine, the injectors become clogged and cannot deliver the right amount of power needed to operate.
Hence, resulting a more fuel consumption to compensate for the power shortage.
2. Rustling sound at low engine speed
The rustling sound that you hear in the engine is due to the timing chain – an overly extended one. This has an easy fix; you can inspect the engine and replace the drive chain if required.
3. Oil Pressure Alarm
Sometimes, there are circumstances where oil levels dip and cause the alarm. Maybe due to leakage or any peripheral reasons. You can add lubricant to the engine if this happens.
However, if the problem does not disappear, you have to turn off the engine and bring the car to service to know the cause of the problem.
Even at its young age, the Mazda 2.5 SkyActiv G engine continues to impress automotive enthusiasts through its fuel and thermal efficiency. It fits the profile of an excellent city driving engine; along with its high fuel economy, it does not have devastating issues that you have to deal with.
It delivers the right amount of power and torque where you want it to be. The powerband range and torque are also at par with its abilities, making it a comfortable drive, even lasting for more than thousands of miles.
You just need to take care of this engine by regularly changing the engine oil every 3,000 to 5,000 miles to ensure proper lubrication and cooling of the power unit, especially in the city where it is far more congested than other driving spots.