FS-ZE or KL-ZE Engines Which is Better?

In my search for a suitable engine for my Mazda MX3 I encountered this essential question, what should I power the car with? There are many different engines that would easily fit into the MX3, but I only retained two that could make it to the race track. The two different engines are very different in mechanism and output, though put out very comparable performance in an autocross event.

The two engines are:

• The J-Spec FS Series FS-ZE.
• The J-Spec KL Series KL-ZE.

The J-Spec FS Series FS-ZE:

This engine setup uses a 4 cylinder 16 valve 2.0L motor. It is only equipped in cars sold in the japanese domestic market. The FS-ZE and the whole FS series is based off the Mazda BP engine, it doesn't really have much similar features with the other F-Series engines. The FSZE series presents a serious problem for swapping, it doesn't share any parts (with some exceptions) with the stock 1.6L MX3 engine. This requires a lot of work, mainly rewiring the near 100 wires that connect the engine to the Engine Control Unit (ECU). Performance wise the FSZE is awesome because it combines a small 4 cylinder engine, into a turbocharger ready block. The engine is built so tough, that anyone can assume that the designers were expecting us to turbocharge it. This gives it a disadvantage in drag racing where "Turbo Lag" will make it accelerate slower than the KLZE. However, the turbocharger does allow it to gain a lot of power in an autocross event when revving high. The FSZE uses the VICS technology to give it an advantage over the traditional engine, the characteristics of this technology will be discussed later in this post. Swapping this engine is a major investment in time but there is only a very small number of these modified cars around (less than 100).

The J-Spec KL Series KL-ZE:

This engine setup uses a 6 cylinder 24 valve 2.5L motor. It is also only equipped in cars sold in the japanese domestic market. The KLZE follows the K-Series platform in almost all its features. A big majority of parts are interchangeable and swapping the engine is very simple. The swap with a 1.8L MX3 engine is very strait-forward, the ECU doesn't even have to be modified. The same transmission can be used, the main concern is that you cannot use the KLZE ignition distributor (without modification), you need the original 1.8L one. The KLZE will give better performance from a stop since it doesn't have any turbocharger. It will also dominate the FSZE stock as the KLZE produces 200 Horsepower (HP) compared to the FSZE which produces 170 HP. The KLZE uses the VRIS technology to give it an advantage over the traditional engine, the characteristics of this technology will be discussed later in this post. Overall, it is an easier swap but it is less unique than the FSZE.

Then Why Wouldn't You Just Turbochrge a KLZE to Get the Best Performance?

That's because the cylinder walls on the KLZE are very thin and wouldn't tolerate a high boost, and if they do it would significantly lower the life-span of the engine.

The F-Series VICS Technology:

This technology stands for Variable Initial Charge System (VICS). The system works by providing two air intake passages per cylinder. One passage is a thin and long, the other is short and fat. At lower RPMs the engine needs more pressure as little vacuum is produced by the engine, the thin and long tube serves that purpose. At higher RPMs the engine has plenty of vacuum but needs more air, thus the short and fat tube. The ECU determines when it is best to switch tubes. Typically this happens around 3500-3800 RPM.

The K-Series VRIS Technology:

This technology stands for Variable Resonance Induction System (VRIS). The computer determines the frequency at which the air resonates and opens the chamber tuned to that frequency. You will notice three plastic air chambers attached to the Intake Manifold and solenoids to engines equipped with VRIS. The VRIS objective is to lengthen the useable torque on the engine improving overall performance.

The Myth About Low-Milage Japanese Domestic Market (JDM) Engines:

There is no such law "requiring" engine replacement at a certain mileage. That is a urban myth propagated by importers and car owners who simply don't know or understand the situation in Japan. The high taxes (annually assessed), insurance premiums, gas costs, and especially the safety inspection/registration (occurs biennial) combine to keep turnover of vehicles high.

For example, the Safety inspection for your typical car (say Camry/Accord type) can typically cost $2,000....each time! New vehicles have a 3 year grace period before they are required to submit for the Safety Inspection. In other words, for a 10 year old car, you will have already paid over $8,000, in just Safety Inspection fees! Don't forget, gas over in Japan is also typically four times the cost of here in the U.S. Mileage is kept low on the vehicles as EVERYONE (unless your fabulously rich and patient) uses alternative transportation to get around. Most folks use the trains for local and medium distance traveling/commuting.

Source: TrustMyMechanic.com

To conclude, I don't believe there is any hands down winner for a competition engine. My advice is to go for the FSZE if you are willing to put the time to get it to work, you'll have a unique result and excellent performance. The KLZE is a much easier and cheaper swap but doesn't offer the best performance in an autocross event. The ideal would be to go for a Turbocharged KLZE but you have to be prepared to rebuild it often.

Keep reading for future posts!