I will be adding content to this thread about my current twin charge project that I am working on I will step back in time and first talk about my orignal cam build that happened roughly 2 years ago and bring you to to update with the current projects that I have going on so stay tuned
Some Background about TwinCharing
The theory behind this kind of system is to use a small positive displacement (roots style) supercharger. Supercharger performance efficiency is typically its highest at lower engine and supercharger rpms (for example from idle to 4000 rpms). Above 4000 rpms the supercharger’s performance and efficiency starts to drop, the horsepower required to drive it starts to rise exponentially, and the air temperature coming out of the supercharger starts to rise dramatically limiting performance.
On the other hand, using a generously sized turbocharger will allow us to feed the engine efficiently with cooler air (than that from an overworked supercharger) and maintain high rpm performance. The problem with using a larger turbocharger is that a generously sized turbocharger typically doesn’t spool before 3000 to 4000 rpms giving us a limited power band and thus providing no performance boost at lower rpms.
The idea of twin charging is to use both a supercharger and a turbocharger to have each one do what it does best, have the supercharger boost the motor for low end torque, and as it runs out of steam, the turbocharger comes online to carry us through to redline.
There are three aspects to these types of systems that make them prohibitive to most tuners:
1.Cost and complexity: Having a complete supercharger system as well as a complete turbocharger system on the same time is a lot of money to spend and a lot of parts to deal with and diagnose in case something goes wrong.
The bypass valve used to bypass the supercharger (and yet hold in all the air pressure coming from the turbocharger) as well as being able to control this valve electrically or mechanically requires a custom made one off valve that isn’t quite available off the shelf.
2.Since we are using two different types of chargers with two different efficiency maps, it can get very complicated to figure out how to tune the motor (especially with much simpler fuel injection systems that were used at the time) because the air density can vary dramatically at the same rpm point and pressure level depending on which charger is feeding air to the motor and at what proportion. This is also where the HKS turbo kit for the 4agze was at its weakest, namely at smoothing the transition point fueling between the supercharger to turbocharger switchover.
3.However, what is interesting to me, is that even with the advent of more efficient superchargers (such as the 4th generation Eaton chargers with coated rotors, higher tolerances, and lower friction drives capable of extending their working rpm range from 12000 rpms up to 16000 rpms), and with the availability of faster spooling turbochargers such as dual ball bearing turbochargers, or VTN (variable turbine nozzle) turbochargers that some people still attempt to turn twin-charger theory into practice.
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