By now, you've read a lot about Isuzu's latest achievement: the RZ4E engine.

The new engine from Isuzu, which can be found under the hood of the D-MAX pick-up and the mu-X SUV, is truly interesting. It's tiny by the standards of the class but has the performance to not only keep pace with the competition, but lead. 

How did Isuzu do perform this feat of automotive engineering and what makes this RZ4E the undeniable pound-for-pound champion of diesel engines? 

The answers, it seems, aren't too hard to find.

Why the Isuzu 1.9L RZ4E is the pound-for-pound champ of diesels

Sophisticated in every way

There was a time when most of us needed a desktop computer to get a job done; devices that were big, heavy, and not mobile. Today's smartphone can do more, achieving the feat with sophisticated technology and design, and they can all fit in our pockets. The RZ4E follows that same idea of innovation. 

As early as the 2000's, Isuzu was already pursuing technology that would make their engines more powerful, more efficient, more environmentally-friendly, and more compact. To do so, they designed an engine that was just 1.9-liters in displacement surpassed the performance of the 2.5L 4JK1 engine.

Isuzu’s extensive history and expertise in the design and production of diesel engines was focused upon the development of the RZ4E engine.

Utilizing Isuzu’s original analytical technology, Isuzu engineers redesigned the combustion chamber to achieve the most efficient mixture of the air and fuel as well as creating the optimum swirl to maximize engine performance while reducing fuel consumption and exhaust emissions.

The RZ4E engines have “graphite coated” pistons, which dramatically reduce piston wear during cold engine starting. The piston pins (gudgeon pins) are coated with Diamond Like Carbon (DLC), which is a man-made anti-friction material, designed to be effective under high temperatures and high pressure.

All these features and more, coupled with a 6-speed transmission that assists in improving fuel efficiency and lowering CO2 emissions, makes the RZ4E one of the most sophisticated turbo diesels in the market.

Why the Isuzu 1.9L RZ4E is the pound-for-pound champ of diesels

Light makes right 

One key difference of the RZ4E engine is its weight, or lack of it.

Even with its many features and sophisticated technologies, the RZ4E is much lighter than the larger Isuzu 4JK1 engine by 62 kilos.

Let's put that in perspective. You know those 5-gallon jugs of water we commonly have at home? If you've lifted one, you'll know that each one is heavy: about 20 kilograms. So, Isuzu was able to reduce the weight equivalent of three 5-gallon jugs full of water. We don't even have to look further than the weight of the average Filipino male: which is just at 61.3 kilograms according to the National Nutrition Survey. 

Less weight means better performance and better overall fuel efficiency.

Why the Isuzu 1.9L RZ4E is the pound-for-pound champ of diesels

Smoother and quieter

Diesels of the past have been known for being much louder than their gasoline counterparts. They were also known for their vibrations, and contrary to the popular song, not the good kind. But Isuzu is changing all those perceptions with the RZ4E. 

Being the specialists of diesel engines, Isuzu used all of their decades of experience, as well as new technologies put forth by their research and development departments for the RZ4E. Being a smaller and lighter engine -and featuring advances in diesel engine design and development- Isuzu was able to make the RZ4E run smoother and quieter than larger engines like the 4JK1.

A resin cylinder head camshaft cover and high-stiffness cast iron cylinder block results in reduced noise, vibration, and improvements in structural damping of the cylinder block. The RZ4E cylinder block is manufactured from cast iron and utilizes the “Long Skirt” design. These two features result in a light, rigid and stiffer cylinder block. The customer benefit is reduced noise, vibration, and harshness. A lighter cylinder block means an increase in payload and an increase in performance.

Why the Isuzu 1.9L RZ4E is the pound-for-pound champ of diesels

Stronger and more durable

A key aspect about the RZ4E is that it's engineered to have increased engine life, increased performance, and a lower the cost of ownership.

The components are made stronger -therefore more durable- than before. Conventional connecting rods and their adjoining end caps are separately forged and machined. The RZ4E however has Fracture-Split connecting rods and are manufactured quite differently. The connecting rod is forged as a single piece of metal. Next, using specialized equipment, the cap is then literally “snapped” from the rod. This process results in an uneven fracture surface on the rod and cap parts. This uneven surface allows for a more precise, durable cap-to-rod fit versus the conventionally manufactured connecting rods. The Fracture Split method improves engine reliability and decreases power loss because the accuracy of the inside diameter of the big end is improved due to the improvement in the positioning accuracy between the cap and the rod.

Variable Geometry Turbocharged System (VGS) works to precisely and efficiently control the turbocharger system, based upon intake air volume. The VGS overcomes the lack of turbocharger performance associated with low engine rpm, when there is very little exhaust flow from the engine. The turbocharger’s turbine is made from a high temperature resistant material for longer life. The turbocharger’s central body is water cooled for reliability, longer component life, and low cost of ownership

Easy Serviceability

The Hydraulic Valve Lash Adjuster maintains the correct valve lash clearance without the need of adjustment. These also improves the performance and reduces service costs. A Single Engine Accessory Drive-belt eliminates the need for multiple drive-belts for components such as the alternator and air-conditioning compressor. The auto-tensioner maintains the correct drive-belt tension to ensure correct operation and minimizes drive belt wear for increased component service life.

The Cartridge-type Oil Filter is an ecological feature. Instead of discarding a metal canister with fixed paper element “spin-on” type oil filter when changing the engine oil filter, the RZ4E oil filter is a paper cartridge type. When replacing the RZ4E oil filter only the paper element is replaced.

As for emissions, the RZ4E has Blue Power technology, making it conform to cleaner Euro-4 emissions standards.

Why the Isuzu 1.9L RZ4E is the pound-for-pound champ of diesels

Do just as much, with less

The key thing about the RZ4E is its performance and efficiency. It is normal to think that such a small engine will be unable to produce the power and torque required by the D-MAX and mu-X, but thanks to Isuzu's advanced engineering, that is not the case.

When compared to the 2.5-liter 4JK1-TC which produces 136 PS and 320 Newton-meters of torque, the smaller 1.9-liter RZ4E produces more power at 150 PS and 350 Newton-meters of torque. 

Perhaps the best part about the RZ4E is its fuel efficiency. Previously, the 4JK1-TC was the most efficient engine in certain variants of the D-MAX and mu-X, but the RZ4E takes that same fuel economy several steps further.

Why the Isuzu 1.9L RZ4E is the pound-for-pound champ of diesels

During a fuel economy test conducted by Isuzu Philippines Corporation to conform to Department of Energy (DOE) standards and verified by the Automobile Association Philippines (AAP), the new RZ4E-equipped mu-X models proved to be a force for fuel economy runs. The Isuzu mu-X RZ4E 6-speed manual did much better, able to achieve 37.27 kilometers to a liter, a 14.3% improvement over the manual gearbox variant of the 2.5L 4JK1 model. The Isuzu mu-X RZ4E LS-A 6-speed automatic variant was able to deliver even better fuel economy of 35.8 kilometers per liter, a 48% improvement over the previous 2.5-liter 4JK1 5-speed automatic variant.  

This sophisticated 1.9-liter RZ4E is truly a revolution for turbodiesel engines. Isuzu gave it the performance of much larger engines through technology. They made it smoother, quieter, and lighter. They even gave it outstanding fuel economy and far better eco-friendliness to match. Like a pound-for-pound champ, Isuzu built the RZ4E to punch way above its weight class.