The Mazda RX-8’S Rotary Fails to Be As Good as the RX-7’S

Old is gold, they say. The newer, the better, they say too. Which of them is correct? This question often pops up in our mind. Well, in the context of Mazda's RX 8 and RX-7's rotary, it is definitely the previous generation that holds the trump card.

And that is precisely the reason behind big-power rotary tuners picking older engines from the older RX-7 rather than the newer RX-8 successor. In spite of the far cooler appearance of the chassis, the RX-8 engine is not up to the mark.

Presenting before you is a detailed study of what features makes the predecessor excel as compared to its newer version of RX-8. Compare the luxury cars on the parameters of their traits and features. Know if they are green and environmentally-friendly enough to be on the roads.

Although both Mazda RX-8 and RX-7 are par excellence in augmenting  your driving experience, there are differences in speed, comfort and performance that make the two rotor engines unique from each other. There are quite a few engines compatible with the rx8 now. Let's see if it's worth the investment though.

Weight Considerations

The weight of the engine is an important factor to consider to gauge the car efficiency. The performance of vehicles is impacted by the weight of the engine to a large extent. The RX-7 rotor engine  weighs around 1100kg in both automatic and manual transmission models, while Mazda RX8 rotary engine has a weight of about 1370kg in manual transmission and 1380 kg in automatic transmission. From the point of curbing weight to optimize performance, RX 7 rotor engine stands out when compared to the RX8 motor.

Poor Build

The engine housing of RX- is not so strong and wear- resistant as the RX-7 stout and sturdy rotary engine housing. The RX-8 housing is of lower quality and has shown signs of warping and erosion after being used for a certain period of time. The RX-7 is at a vantage point as it offers the facility of its rotor housing being reused on an engine rebuild.

Poor Exhaust Breathing

The bigger opening engines are better to provide a clear exhaust path as the rotary turners are always boring out the openings in earlier rotary engines launched by Mazda.

The earlier versions of the rotary engine like RX-7 have a clear and easy exhaust route in the rotor housing. The RX-8 motor, the successor, although more stylized and compact in its look, has the exhaust exit within the plate. It is a self choking path, that requires some of the exhaust gas to turn to exit the engine. This paves a more difficult exhaust path in RX-8 than in the predecessor, RX-7 rotor engine.

Apex Seals Are Not Up to The Mark

With poor build quality of engine rotor housing and a difficult exhaust route, there is more tendency of the engine being worn down due to continuous use. There is therefore a need for good effective seals to keep the engine clean and keep the rotating lobe of the engine isolated.

The rotary engine requires good seals to prevent warping, that tends to affect the rotary engine, caused due to the relative heating of one part of the engine after combustion and the other half trying to expel the exhaust and intake air. But study reveals the poor quality of apex seals in RX-8 rotary engines, which is thinner than those used in the veteran form of RX-7 rotor engine model.  They pose reliability problems even though the lighter weight of the skinnier apex seals helps the engine to function effectively at higher RPM.

Transmission

Driving featured with automatic transmission is something adored by most drivers, while some still admire manual transmission for a better experience. There is a difference between the two engines on the grounds of Mazda RX-7 and RX-8 rotor engines. RX-7 rotary engines  allows 4 and 5 -speed manual transmission and 3 and 4-speed automatic transmission. RX-8 rotor engine comes in 5 and 6- speed manual transmission and 4 and 6- speed manual transmission.

Engine Power and Capacity

Mazda RX-8 and RX-7 are excellent with regards to engine power and capacity. The RX-7 is available in 1.1 L to 1.3 L capacities, which make the cars set the roads ablaze with their speed and power for generations. The RX-7 has a twin turbo 13b rotary, the turbos being sequential to reduce the turbo lag. The engine has a valveless design and no reciprocating parts, making it sturdy and almost resistant to any sort of destruction.

Now, the Renesis engine if RX8 with turbos removed and a higher compression ratio. With reduced cylinder pressure, the torque was reduced and was not enough to sport competitions.

Boost

The Mazda RX7 rotary engine is a twin turbo with the sequential arrangement of the turbo, which can rev up to ridiculously high rpms. All you need is a boost and fuel it up, for it to gain high power apart from intake air temperature management. Thus RX7 is renowned for making power easy. This is one prime factor that had skyrocketed the demands of the Mazda RX7 rotary engine, making it an iconic engine to be featured in the 90's films. We have come a long way though if we compare it to the 2004 Mazda rx7.

Now, RX8 with the turbo removed, it is relatively difficult to boost. There was a need for more upgraded and customized fuel, exhaust and the intake system. This makes the car even heavier.

The Top Reasons for the Failure of the RX8

The main point of failure is that the RX8 rotor housing warps easily due to poor quality of the build and cause compression loss. The apex seal gas pressure is lost, which further mars the rotor housing.  The RX8 does not allow an easier boost and air intake as well.

The exhaust route being more complicated creates a back pressure, which also is a disadvantage when compared to its predecessor RX 7. Thus, it comes as no surprise when the rotary turners choose Mazda RX7 rotary engine over the RX8 rotary engine, when they prefer to give more leverage to the old generation than the present.

Final Verdict

The RX-7 has more wins than RX-8 collectively to make it stand out when it comes to a comparison of the two rotary engines in motorsports.  The RX-7 is a legendary rotary engine, which is strong when you want to drive with forced induction. While RX8 comes with an impressive chassis, the tainted engine mars the looks. The question still lingers in the minds as to why Mazda would be producing a new generation engine that is inferior to its predecessor.