[No_Quarter]

Hey guys,

After using the search feature, I came up with no results. Anyways, I had some questions regarding the boost in the STi.

Anyways, I am an avid Mustang guy, and currently own a modded 06 Mustang GT. I am a member on numerous boards, and it was a known fact that the stock 4.6l V8 could handle about 10 psi or 450 hp before upgrades to the rotating assembly needed to be made. I know the stock boost in an '08 STi is 14.7, but how much can the stock EJ257 take before it explodes?

Not to mention, some members have claimed 17 psi with an aftermarket boost gauge. They claimed that the reason why was because of the driving modes that the STi comes with and that the 17 psi would be for a "competitive" like mode. I was wondering if any of you could chime in on this.

Lastly, does the stock turbo have a bottlenecking issue where it loses boost as the engine climbs in RPM's?

Thanks guys.

[GilMikalian]

In stage 2 form, i.e. downpipe and engine management, the boost target, according to our friends at Cobb are:

Boost Targets:

~18psi peak boost pressure tapering down to ~15.7psi
by the 7000 RPM redline, +/- 0.8psi. The ability for the vehicle to
achieve these targets will depend on the modifications performed to
the vehicle and the conditions of testing. If your vehicle is not
achieving or exceeding the boost targets, you may need to
mechanically adjust your boost control system, please refer to this
document “How Subaru’s Factory Boost Control System Works v1.X” for

instructions.

[renns]

I run 23 psi on the stock block and turbo, with meth.

Most people will say that 450-500 to the wheels is when you need to build the motor.

And yes, the stock turbo is pretty inefficient.