12/4/2023 0 Comments Compound sequential turboOne is that the 60mm wastegate from the #1 turbo may not allow enough exhaust flow around the #1 turbo resulting in excessive back pressure or over boosting. After discussing this design with a friend, there are two areas that I think may cause issues. As this is a different design to what anyone else has done, its possible that it may require some tweaking to work correctly. This will hopefully be achievable with around 35psi boost. I use E85 and my goal is 1000whp through the TH400 gearbox which is around 1300hp. These turbos are good for 700hp each on gas when run around 30-35psi boost, making for a potential of 1400hp from both turbos on gas or 1500+ hp when using E85. My setup will use two Turbonetics 60mm wastegates, the Supra OEM reed/air intake control valve (50mm) and two MasterPower race series R6164 (61mm) turbos. I am planning on changing my single turbo 2JZ-GTE Supra to this setup over the next winter season and I will update my website with the results from this setup then. The curved section will be removed to make it straight through. This is the 2JZ-GTE intake air control valve I will be using. My design uses a 3.5" down pipe between the #1 and #2 turbo, a 4.0" down pipe for the #2 turbo and the 60mm wastegates have 3.0" pipes to maximize the flow. Here's a drawing I did to show how my sequential setup will be implemented in practice on my 2JZ-GTE Supra engine. My design uses a proper high flowing manifold to the first turbo, eliminating the ugly and often poor flowing log manifold seen in many sequential designs. This could either be done using a Hobbs switch set to the same pressure as both wastegates are or by an aftermarket ECU controlling the flow of boost pressure to the air intake valve's actuator. There is also one combined reed/air intake valve (with an attached actuator) required that needs be opened when the second turbos boost catches up to the first turbos boost pressure. This can be done via two boost controllers or via one boost controller and one aftermarket ECU. These wastegates need to be controlled separately as the two turbos will require different duty cycles on the wastegate to maintain the same boost level. There are two wastegates, one used for each turbo and they are set to exactly the same boost level. This setup is super simple and only requires 3 devices to be controlled, which is simpler then any other sequential turbo setup I've seen. This means that instead of having a big dip in the torque curve when the second turbo comes on-line, there should be little to no dip in the torque, resulting in a torque curve more like a large single turbo. By spooling the second turbo with the gas exiting from the first turbo, the second turbo will spool much quicker then if it was just receiving some exhaust gas diverted from the first turbo, as most other sequential turbo systems do. Also both turbos are exactly the same size, so you don't get any issues with different size turbos fighting each other in the sequential setup and having the large one potentially overpowering the smaller one. This means you get all the advantages of a compound turbo setup for spooling the turbos, but with none of the disadvantages of the compound setup such as the boost being too high for a gas engine. This sequential setup is basically a compound turbo setup on the exhaust side (but with identical size turbos) and a sequential setup on the intake side. They say a picture is worth a thousand words, so here's a diagram of how it works. Therefore I decided to design my own sequential turbo system. Having looked at every compound, sequential, and twin turbo setup that I could find on the internet, there wasn't one of them that I was happy to install in my own car due to various fitment, cost and complexity reasons. A lower stall will allow me to have a converter that holds more power and has less converter slippage, which results in more power to the rear wheels. I've been thinking of doing a sequential turbo setup for a while now as a means of getting more boost at lower rpm, so that I can run a lower stall in my TH400 converter.
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