Autoblog

Actually twin-scroll turbos and variable geometry turbos (e.g., variable area turbine nozzle) turbos work completely differently and do not exactly accomplish the same thing. For one, twin-scroll turbos do not accomplish much in comparison to non-twin scroll turbos top end, whereas VGTs accomplish a lot with its variable turbine a/r. The only thing VGT and twin-scroll turbos have in common is that they tend to perform better than conventional turbos low end, but even then there are some conventional turbos, such as the Garrett GT Ballistic Series, that outperform twin-scroll turbos.

Variable geometry turbos are designed to allow the effective aspect ratio (A/R Ratio) of the turbo to be altered as conditions change for better performance. For example, at lower rpms the a/r is less for a lower boost threshold, less lag, better response. At higher rpms the a/r ratio changes to a greater ratio so that the turbo doesn't choke at higher engine speeds, exhaust manifold pressures are decreased, and ultimately power output is increased as a result.

Twin scroll turbos work differently by requiring a divided exhaust manifold to separate the rotors or cylinders whose cycles interfere with one another to best utilize the engine's exhaust pulse energy. For example, on a four-cylinder engine with firing order 1-3-4-2, cylinder #1 is ending its expansion stroke and opening its exhaust valve while cylinder #2 still has its exhaust valve open (cylinder #2 is in its overlap period). In an undivided exhaust manifold, this pressure pulse from cylinder #1's exhaust blowdown event is much more likely to contaminate cylinder #2 with high pressure exhaust gas. Not only does this hurt cylinder #2's ability to breathe properly, but this pulse energy would have been better utilized in the turbine. The proper grouping for this engine is to keep complementary cylinders grouped together-- #1 and #4 are complementary; as are cylinders #2 and #3. Because of the better utilization of the exhaust pulse energy, the turbine's performance is improved and boost increases more quickly.

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Winding Road makes horrible predictions, an Rx-series car with a V8?? Mazda will allows put a rotary engine in an Rx-series car, because RX stands for Rotary Experimental, and there is too much pride, history, and tradition to abandon the rotary in an Rx-series car. If they wanted to make a sports car with a V8, they would create a new model name. In addition, Mazda currently doesn't make a V8, and I doubt they would make a brand new V8 for such a sports car. If anything, they would borrow from the Ford parts bin, but in general, all of it sounds very very unlikely. . .so unlikely I wonder why anyone would even mention it.

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They're magicial InvisiBrakes!

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Thats because it wouldn't be. Don't people who write this stuff know anything. RX = Rotary Experient.

If this "make believe" car were to come true, if powered by anything other than a Rotary wouldn't be a RX car.

Most likely if RWD would be a MX series. Maybe a large Miata MX-5 so say a MX-9 or a reborn RWD MX-6?

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Why would a rotary need water injection? Their main problem is low compression ratios, you don't need water injection at low compression ratios.

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That's what I was thinking Dustin. Mazda's naming scheme wouldn't allow that to be an RX- w/ a V-anything...anything w/ pistons for that matter.

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Many people argue that due to the specific way a rotary engine works, the displacement should essentially be doubled to be an accurate comparison to the displacement and power-production of a piston-driven engine.

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Here's your more complete answer:

"While a four-stroke piston engine makes one combustion stroke per cylinder for every two rotations of the crankshaft (that is, one half power stroke per crankshaft rotation per cylinder), each combustion chamber in the Wankel generates one combustion stroke per each driveshaft rotation, i.e. one power stroke per rotor orbital revolution and three power strokes per rotor rotation. Thus, power output of a Wankel engine is generally higher than that of a four-stroke piston engine of similar engine displacement in a similar state of tune and higher than that of a four-stroke piston engine of similar physical dimensions and weight. Wankel engines also generally have a much higher redline than a reciprocating engine of similar size since the strokes are completed with a rotary motion as opposed to a reciprocating engine which must use connecting rods and a crankshaft to convert reciprocating motion into rotary motion.

National agencies that tax automobiles according to displacement and regulatory bodies in automobile racing variously consider the Wankel engine to be equivalent to a four-stroke engine of 1.5 to 2 times the displacement; some racing regulatory agencies ban it altogether."

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thanks a lot! very informative. :)

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