Quote:
Originally Posted by jippii ensio
Having a large WG in small housing and vice versa makes sense. however, already the stock configuration having twin turbos, is equal to having twin scrolls, one scroll in each turbo. Twin scroll is very important, but is there any additional need to enhance it from what it is already?
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Dear jippii ensio! You point it out well. To be more specific regarding the sizes:
ft_th1 = size of factory turbo turbine housing nr.1
ft_th2 = size of factory turbo turbine housing nr.2 (=ft_th1)
ft_wg1 = size of factory turbo wastgate nr.1
ft_wg2 = size of factory turbo wastgate nr.2 (=ft_wg1)
nt_th1 = size of new turbo turbine house nr.1
nt_th2 = size of new turbo turbine house nr.1
nt_wg1 = size of new turbo wastgate nr.1
nt_wg2 = size of new turbo wastgate nr.2
ft_th1 = ft_th2 < nt_th1 < nt_th2
nt_wg1 > nt_wg2 >= ft_wg1=ft_wg2
The smaller turbine housed (nt_th1) turbo will spool up sooner than the larger one (nt_th2). The larger turbine house (nt_2) can delivery more air and exhaust gas on high RPM/Load than smaller turbine house (nt_th2). To compensate the difference, the smaller turbine house has larger wastgate (nt_wg1 > nt_wg2) and the larger turbine house has smaller wastgate. In the smaller turbine house on high load some exhaust gas, which cannot flow through the turbine wheel can flow through via the larger wastgate (as the exhaust pressure opens a little bit the larger wastgate).
The problem with the factory turbos is the bottleneck of the exhaust manifold and the relative small turbine house. Depend on application, you can have great results with factory or factory upgraded turbos with the small turbine house and restrictive manifolds, but instead of upgrading them I choose a new PATH based on these ideas and give them a try.
Laszlo