Take your pick. Whether you choose to let nature fill your engine's cylinders with 14.7 psi of absolute pressure or you cram a bit more in the hole with a blower, Weiand has you covered. For about as long as our hobby has existed, the company has been providing top-notch intake manifolds and superchargers to the salivating masses.
In the decades since their inception, aftermarket intakes and blowers have made tremendous progress thanks to a wave of technological innovations and cutting-edge CNC advancements. To learn more about the modern state of induction, we got together with Jay McFarland and Jim Dralle of Weiand. A multitude of factors determine which induction combination is best for a given application, so it seems rather wacky to skim aimlessly through a parts catalog and hope for the best. In addition to helping you maximize the potential of your top end, the boys at Weiand shared some fascinating info on what goes into designing high-performance intake manifolds and blowers.
Compression Ratio
Forced induction motors necessitate lowering the static compression ratio, and traditionally the tradeoff is a loss of low-rpm torque before the motor makes usable boost. However, since roots-style blowers offer such immediate off-idle torque, this is less of an issue than with other forms of forced induction. "When building a new engine specifically for use with a roots-style blower, we recommend a maximum static compression ratio [CR] of 7.5- to 8.0:1," says McFarland. "If you already have an engine you are retrofitting, you can use the formula below to determine your effective compression ratio [ECR]. If it is above 10.5- to 11.0:1, you should go with race fuel."
ECR= (Boost PSI/14.7+1)x CR
Manifold Selection
Considering all the different cylinder heads on the market, selecting the right intake manifold for your engine combination can be daunting. "With both cylinder heads and intake manifolds, the cross-sectional area of the ports or intake runners controls the velocity of the incoming charge, which is what most strongly affects cylinder filling at a given engine speed," says Dralle. "It's important to understand the engine speed where peak torque should occur and how broad the power curve should be for your application. Dual-plane designs typically provide a broader power curve, especially between 2,500 and 6,500 rpm, whereas single-plane designs should only be used where a narrower powerband is acceptable at engine speeds above 6,500 rpm. Furthermore, customers should feel free to use the information given by reputable manufacturers and also use their tech lines."