roush cars in stock and super stock

[Tim Kish]

There is a major difference between the Eaton roots supercharger and the turbos which have given forced induction in stock eliminator such a bad name. The roots supercharger is a positive displacement pump it can only pump so much air per revolution, that drive ratio is one of the factors which NHRA intends to control and is pretty easy to police. The turbos are a effectively a dual fan system where the amount of air displaced is a function of the impeller speed, impeller speed is easily manipulated with optimizations of the engine (cam profiles, exhaust restriction changes, etc) - there is alot of variability in how a specific turbo can perform given these variables. This allows a car factored based on the heavily conservative factory design to easily outperform that factory rating. The roots supercharged engines with regulation of the superchager displacement and drive ratio are only at best going to be able to flow so much air thus limiting the overall potential power output no different than a naturally aspirated engine. As with any new engine combination it will take time for the true performance potential to reach an appropriate factor but unlike the turbos where you can overspeed the compressor with tuning the is no "magic speed screw" on the roots blowers.