Originally Posted by Irace86.2.0
Dude, this is really going over your head. I'm not talking about the existence of the bypass valve being bad; I know what it is there for and that it is good. Your talking about a separate thing. Pope and I were talking about replicating an electronic boost controller (EBC) on a supercharger system, so a supercharger could be controlled/tuned to do boost-by-gear, boost-by-rpm, multiple boost maps, etc.
For a turbo, this is easy. The EBC bleeds pressure off of the wastegate line, so the wastegate stays closed, which raises the boost beyond the wastegate spring--super simple and easy to control. To raise the boost level on a supercharger, a smaller pulley has to be installed. Obviously this can't be done continuously, so the only way to control boost the same way as the turbo in order to do boost-by-gear, etc is to install a small pulley, and then the tuner would have to use an EBC on the bypass valve pressure line to open the valve partly when someone is on-throttle to bleed off excess boost, so the driver can limit boost. This would mean the supercharger is being asked to work harder, but not produce more, so it is inherently inefficient in a way that generates heat and raises the parasitic load on the engine. The result would be a greater chance of heat soak for a given power output and less fuel economy and less power for a given amount of work. This is analogous to someone digging a hole at a fixed speed and someone throwing some of the dirt back in the hole, so the rate of the depth of the hole can be controlled, where a turbocharger just asks the digger to slow down or to speed up, which is much more efficient and easy.
The advantage the supercharger has over the turbo is that the turbo can't add any more boost down low if the turbo threshold hasn't been met, but the supercharger will add more boost down low with just a pulley change. A wastegate can add more boost to extend the power curve, but it can't make boost come on sooner like a supercharger can. In order to do that, a smaller turbo would be needed or other modifications would need to be done like restricting flow through the head, so pressures are higher/faster to spool the turbo faster or a ball bearing or twin scroll setup is utilized, but for the most part, people use turbo housing sizes to move the boost threshold up and down the rpm band, where a supercharger changes size in order to change the steepness of the power curve, which will result in progressively more boost at every rpm (typically), meaning more down low. While this is an advantage, a turbo will build boost so fast, that unless the turbo is large for the motor, the turbo will still out boost a supercharger.
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