This page is being created to put idea's together whilst planning a twin charger system..
BUT the question has to be asked... Why would you want one?
The main advantage I see, is a smaller capacity engine can be used in the pursuit of better economy and emissions. (Some countries having extra taxes on larger capacity cars) and have the power of a larger engine when needed. It'll pull like a larger engine due to the supercharger providing boost at lower rev's and being able to switch to a more efficient larger turbocharger for top end performance. The idea here is that most of your normal driving is done cruising along motorways or idling in traffic and you do not need a big block for this. The big flat torque curve is also unbeatable in a small capacity engine. In drag racing situations the supercharger could replace antilag or NOS to get the turbo spooling off the line and between gears and wont cost you every time you press the 'GO BABY GO' button.

There is fair argument that later day ball bearing turbo's are more responsive and efficient than they ever used to be and therefore 'turbo lag' is not much of a problem. This is very true and is the better option in most cases. Running a twincharger system on 10psi is also rather pointless. Either turbo or supercharger alone can do the job nicely. When seeking big power with larger turbo's (where lag is an issue) and low rpm use is required (hairpin corners, stop starts, off/on boost driving ie drift battles or balls out streeter) then the twincharger could be considered.

Challenges with the twincharger system:
* Designing a system with a smooth transition from one charger to the other.
* Controlling the Supercharger: (depending on system type). automatically disengaging the supercharger for best accelleration at higher rev's. Being able to switch back on under low rpm accelleration and staying switched on whilst changing gears, but switching off at idle and low load situations for efficiency.
*Bypass valve control. On a system that uses it... In a sequential charger system there's a need to have a way of bypassing air around the s/c at higher rev's for better flow and efficiency.
* Heat.. More boost and power means more heat created. therefore a need for better cooling requirements. More engine parts and piping means less engine bay space and more heat sink.
*Weight: Extra weight is undesirable in any performance oriented car. All the extra components in the twincharger can add up to a heavy engine.
*Cost: All those extra parts, fabrication, time, labour, design, tuning... is the extra cost worth it all?
*Tuning.. any high performance highly boosted engine needs accurate tuning for safe and reliable running, so it not wise to scrimp on your engine management system and tuning after building such an engine.

Non Intercooled Supercharger system in RWD layout
Notes: Probably the simplest setup in terms of parts and plumbing. The engine in this system will require low compression to handle the hot supercharger air (non intercooled) and s/c boost will be limited to how much resistance to detonation the engine has (all in the tuning and internal component strength).

Main parts required:
turbo
turbo exhaust manifold and dump pipe
turbo oil feed and drain
external wastegate and plumbing (if not running internal wastegate)
supercharger
supercharger mounts, pulleys, belt, tensioner
electromagnetic clutch for supercharger
supercharger controller (to switch on and off)
bypass valve (and bypass controller) or one-way valve
boost controller
plumbing everything together
intercooler and bov
programmable ecu
beefed up fuel system, bigger pump, injectors etc
stronger engine internals, stronger drivetrain, bigger brakes... how fast do you want to go?

Useful links:
Notes on the AW11 4agze supercharger
Fensport hks twincharged ae92
mr2supercharger.com website - twincharged AW11's
wikipedia twincharger info
'Twinchargers' website - 20v 4agtze ae86
autospeed ae92 HKS Twincharger article
4agzte datsun 1200
Autozine.org Lancia Delta S4 twincharger info
Shalco Motorsport Lanca Delta S4 twincharger info