CHALLENGE: WMD Squared had helped Caldwell Racing Technologies bring their 2.5L engine to life and was asked to help develop the 3.5L engine as well.
APPROACH: With all the knowledge gained from designing the 2.5L along-side Caldwell Racing Technologies, we jumped headfirst into modeling the 3.5L project. Due to the size difference between the 2.5L and 3.5L, not many of the parts were reusable. The new larger 3.5L presented its own set of challenges but it also gave us more room to work with. Matthew Caldwell saw this and improved this engine to have even more performance gains than prior to the design process. A major concern was keeping the weight of the whole package down, so after several prototypes were made, the design was revised to cut metal out of non-loadbearing sections of the motor. This material removal consisted of using advanced machining techniques to remove material in multiple locations and provide additional water channels to cool more areas on the motor. We also worked with Wiseco to develop pistons for the 3.5L motor as well. A new SVS setup was developed to be able to run either velocity stacks with custom reed cages or a carbon fiber plenum with a throttle body.
IMPACT: While the 2.5L aimed to fill a gap in the market from Mercury discontinuing their 2-stroke 2.5L motor, the 3.5L dives into a larger market that is dominated by big power and performance. In keeping with the spirit of the 2-stroke, the CRT 3.5L powerhead produces a better power-to-weight ratio than bigger 4-strokes in the same category.