The Cosworth Subaru Plenums/Intake Manifolds/Inlet Plenums started shipping last week finally. Depending on who you talk to, it seems intake manifolds go by different names. The British like to say “inlet” whereas we Americans tend to say “intake”. A “plenum” is defined as “a space in which a gas, usually air, is contained at a pressure greater than atmospheric pressure” and a “manifold” is defined as “a chamber having several outlets through which a liquid or gas is distributed or gathered” so it’s really both in our case. Whatever you call it, the Cosworth Subaru intake/inlet plenum/manifold is here finally. Check out Tyler’s blog post at the Cosworth USA site here.
The only test information released to the public (it takes us a while…) shows a +15bhp gain from 4k-6.5krpm at low boost (1880mbar/.88bar gauge/12.76psig) with a stock EJ257B engine and a GT35R turbo. There is absolutely zero loss in horsepower from 2-4k rpm. Other test information has not been released for public consumption yet, but I can tell you with more boost + more RPM = even bigger gains. Add a set of Cosworth S2D cams (Ian and I just completed testing them on the engine dyno so they’re coming very soon) and the gains will be pretty damn incredible. Chances are tuners will be posting dyno sheets before we will so look out on the web for some kick ass plenum results soon.
Here’s one on the Red Dragon (RD is in limbo waiting for it’s big baller Cosworth long block). The plenum is designed to work with front mount intercooler systems. I think it could be rigged to work with a wrong mount, oh sorry I meant top mount, but Cosworth is not supporting any top mount installations. I’m sure somebody will figure it out. In all serious though, top mount ICs are ok for moderate power at moderate vehicle speeds (that scoop only works so well).
Here’s one on a 2006 STi with a “rotated mount” GT30. Yes, the Subaru guys seem to have their own names for everything (e.g. bellmouth, uppipe, ALK, etc.).
Yes they really do exist. We aren’t stroking anybody like we did on the Nissan plenums for a year. BTW, the Nissan plenums are now shipping also.