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Mazda 13B-MSP Renesis Engine Review

13B-MSP Renesis Engine

The 13B-MSP Renesis engine is an entirely different and the most advanced Mazda’s rotary engine which was used in the Mazda RX-8 from 2003 to the 2011 year. It was designed with the target to retain the performance of the turbocharged 13B-REW but at the same time to improve fuel efficiency and reduce emissions. The name Renesis is a combination of Rotary Engine (RE) and Genesis. The abbreviation MSP is Multi Side Ports which make the engine different from its Mazda’s rotary predecessors.

Instead of the 13B-REW, the 13B-MSP is a naturally aspirated (NA) engine. It kept two-rotor layout with a capacity of 1308 cc (79.81 cu in), the same rotor radius and length. Each chamber volume is 654 cc. The biggest improvement is the 13B-MSP has two exhaust ports per rotor in a side housing instead of one peripheral exhaust port for each chamber on the Mazda RX-7’s engines. That reduces gas flow resistance (almost the double the exhaust port area than of the 13B-REW), eliminates intake/exhaust overlap, and increases thermal efficiency, power, and fuel efficiency. Now the unburned gases are not carried in the next combustion cycle. The result is more stable and efficient combustion. The 13B-MSP engine was offered in standard and high-output versions. The standard versions have two intake ports per chamber, and high-output - three intake ports per chamber (primary, secondary and auxiliary). The cross-sectional area for the intake ports is an almost 30% larger compared to the 13B-REW engine. The engine equipped with lighter parts to reduce rotational mass: rotors are lighter by 14%, flywheel - by 20%. That gave a high throttle responds, more power, and allows the engine to rev up to 8200 rpm.

All 13B-MSP engines got Sequential Dynamic Intake System (S-DAIS) for controlling the secondary and auxiliary ports, and the variable intake valve. The primary intake is used at low rpm only. The secondary port starts operations at 3750 rpm after the shutter valve would open. The high-output engines have the auxiliary port which would open at about 6250 rpm. The variable intake valve is used to lengthen the intake manifold and for increased mid-range torque. It would open at around 5750 rpm (at 7250 rpm for high-output engines). Variable fresh air duct (FAD) is one more intake system which you can find in the high-output versions of 13B-MSP. It opens a special valve at around 5500 rpm to shorten the air intake manifold. Together with the variable intake valve, they increase power and torque at high engine speeds.

The engine has fuel injection operated with the injection pressure of 392 kPa. The primary intake port injectors have 12-hole. The secondary and auxiliary ports got 4-hole injectors. Mazda also developed and applied Jet Air-Fuel Mixing System for intake air. The 13B-MSP engine also has two iridium-tipped spark plugs per rotor chamber, due to a large combustion cycle. The leading and trailing spark plugs had different lengths.

Mazda's engineers made a huge step forward in the development of the rotary engines. The Renesis engines is an actual embodiment of all former advantages (compact size, lightweight, high performance) combined with lower fuel consumption and emissions. Mazda's 13B-MSP Renesis manages to have an output of 250 hp, which is really close to its twin-turbocharged predecessor - the 13B-REW. The Renesis won International Engine of the Year and Best New Engine awards 2003, and it was on the Ward's 10 Best Engines list for 2004 and 2005.

Engine Specs

Manufacturer
Mazda
Production years
2003-2011
Cylinder block material
Aluminum
Cylinder head material
-
Fuel type
Gasoline
Fuel system
Fuel injection
Configuration
Rotary engine
Number of cylinders
Two rotors
Valves per cylinder
-
Valvetrain layout
-
Bore, mm
-
Stroke, mm
-
Displacement, cc
1308 (79.81 cu in)
Type of internal combustion engine
Wankel engine, naturally aspirated
Compression Ratio
10.0:1
Power, hp
192-250 (141-184kW)
Torque, lb ft
156-163 (211-222 Nm)
Engine weight
247 lb (112 kg)
Firing order
-
Engine oil weight
5w30 or 10w40 Semi-Synthetic oil
Engine oil capacity, liter
3.3/3.5 (0.2 litres - oil filter)
Oil change interval, mile
12,000 (20,000 km)/12 months
Applications
Mazda RX-8

Mazda 13B-MSP Engine Problems and Reliability

Very fast wear of the main bearings of the eccentric shaft. Apparently, because it rotates three times faster than the rotors. The second problem is uneven heating of the rotor housing. The upper part (here are the intake flow and compression strokes) are colder than the lower (combustion stroke and exhaust gases flow). However, the engine will be deformed at an uprated supercharged power of more than 500 hp.

The engine is susceptible to the type of oil. The practice has shown that synthetic oils, even special ones, form a lot of carbon residue during the combustion process. It accumulates on apexes and reduces compression. Mineral oil is combusted almost wholly. Service experts recommend changing oil every 3,000 miles (5,000 km). Oil nozzles in the stator can fail because of dirt entering the internal valves. Atmospheric air penetrates them through the air filter, and the late replacement of the air filter leads to this problem.

Problems with the cold start of the engine, especially in the winter, are due to the loss of compression. That often happens due to the wear of apexes and the appearance of carbon residue on electrodes of spark plugs due to poor-quality gasoline. Always use the premium fuel and change spark plugs every 10,000 miles (15,000 km). An average mileage before a complete rebuild of the 13B-MSP is less than 100,000 miles.

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