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" Engine Weights:
Mazda S4 13BT 171kg/376lbs (Brian long Book pg 84)
Mazda S4 13B 153kg/337lbs (Brian long Book pg 84)
S5 13BT full drivetrain 388kg/854lbs (3rd gen Yamaguchi book pg 110)
Full S6 drivetrain - including PPF 379kg/834lbs (3rd gen Yamaguchi book pg 110)

I cannot find official, reliable engine weights for the S5, S6 and Renesis engines, so I have calculated them using reasonable assumptions.

Mazda S5 13BT Drivetrain Minus Engine Estimated Weight Calculation:
388 (S5 drivetrain) - 171 (S4 13BT engine) = 217kg S5 turbo drivetrain (the this weight is likely slightly low seeing as there are some small known weight savings with the S5 vs S4 engine such as the rotors and flywheel)

13B-REW Engine Estimated Weight Calculation:
379 (S6 drivetrain weight) - 217 (estimated S5 turbo drivetrain minus engine) = 162kg/356lbs Maximum possible engine weight. (Estimated maximum given the fact that the transmission is likely nearly identical to the S5 and considering the added weight of the power plan frame it is likely the 13B-REW weighs less than the quoted figure. Also the S5 drivetrain weight minus engine was estimated in a manner that raises the estimated final engine weight)

Esimated Renesis Weight
80lbs lighter than the 3rd generation RX-7's 13B-REW. (Renesis Rotary Engine Design Technology: Technical Training Program, "Renesis Rotary Engine" Module 3. By Mazda - It's a Flash presentation designed for Mazda mechanics)
356 - 80 = 276lbs/125kg

Honda 2.0L S2000 Engine weight 158kg/348lbs (http://www.autoexpress.co.uk/?http:// ... e_news_story.php?id=37079)
Chevy LS1/LS6 497 lbs, 226 kg (http://www.corvetteactioncenter.com/specs/z06/ls1ls6.html)
Chevy (LT1) L98 600lbs, 272kg (http://www.angelfire.com/ar/dw42/engfyi.htm)
Mazda 20B 350kg, 770lbs (www.fc3spro.com) - This figure is repeated elsewhere and fc3spro.com is likely quoting these sources. I am not blaming fc3spro or the other's who quote this figure, but I have trouble believing this value because it does not make sense that the 3-rotor engine could weight more than two times a 13B-REW and more than a cast iron LT1. 3-rotor engines have a second cast iron intermediate housing that is much wider than those found in a 2-rotor, an extra rotor housing, rotor, longer eccentric shaft, wider manifolds. Hence the weight difference from a 13B-REW should be substantial, but more than two times is hard for me to swallow.

*Note: All engine weights are fully dressed wet weights. So for instance, the full S5 drivetrain would include ABS pump, power steering, air pump, air conditioning and alternator."