Stock turbo wastegate vs upgraded

[dannyroz]

Ok so my brother has a WRX with a upgraded ECU which makes it have the same spec as the STi 2.0 ver and he leaks off boost after 5.5k to redline. I mentioned that he might want an upgraded wastegate to hold the boost longer but he responded...

"What good would that do me? How much power is lost when you leak boost that high and is there any gain when you keep full boost at that rpm?" And I felt dumb cus i dont know...anyone have idea?

[CMonakar]

What makes you think the wastegate is the problem?

Typically when boost drops off at high rpm it is because you're exceeding the flow capacity of the turbo compressor. A motor is basically an air/fuel reactor. The more air/fuel it processes over a unit of time the more power that is made. At high rpm a motor takes in and pushes out more air molecules than it does at low rpm. Accordingly, at high rpm the turbo must push more air into the motor than at low rpm to maintain the same boost level.

So while the WRX turbo may be able to maintain a boost level of say 12 psi from idle to redline it may not be able to hit 14psi at redline even though it can do it at low rpm.

If boost INCREASES at high rpm the wastegate may be too small, in which case a larger wastegate is necessary.

[dannyroz]

I never said the wastegate was the problem, i was just wondering if there would be any difference that I would substantially notice

[coombsie66]

Surely if you preloaded the wastegate slightly more, or got a stiffer spring then it would hold higer boost?
Im no expert on turbos i have to admit.

[goose93]

i don't believe the Subaru uses an external gate, but even if it does that is not your problem. Tell him to look into a good electronic boost controller. This will allow him much better control over the performance of the turbo.

[Garretts_turbo]

yeah, forking over some cash for an electronic booct controller is probably the best bet.

[StanAE86]

Most OEM set-ups will use an internal wastegate...in which case, to get higher boost, you have to leak pressure off the wastegate so that it doesn't see the "true" pressure and will not open as soon (boost controllers).

Normally, you'd only upgrade the wastegate for flow purposes, so that you can flow more exhaust and don't cause a boost spike. That's where the wastegate can't bypass enough exhaust to maintain the set boost levels, allow more than the set pressure. Example: you trick the motor out so that it flows much better than before, and your boost level is set at 10psi...if the wastegate can't keep up with the exhaust flow, you'll get boost creeping over 10psi, and if you're unlucky, it could spike to like 18psi and blow the motor. So the bigger gate is for flow.

If your bro's car is leaking boost off, it could very easily be the BOV cracking open...

The short and simplified answer to your brother: lost boost is lost power...it makes a difference. Whether it's enough you want to fix it...depends on how much your brother wants those few extra ponies....

Good luck.

[edwardbauer]

Just upgraded mine works great t25 turbo with modified proformance wastegate 21 psi plus