snoopster76

Can someone explain what overboost and boost creep are? What causes both? Thanks.

The Ace

Overboost is when your turbo achieves higher pressure than it's supposed to, due to mods or unknown factors, and starts spinning uncontrolably. When it's due to mods, you must supply the proper supplementing "fixes" in order to keep the turbo intact. When it happens for unknown reasons (in general), then you have problems with BOV, ports, turbo casing, primary/secondary spinwheel, pressure leak etc. All of these must be taken care of.

Boost creep happens only in FDs (i think). Its when both turbos are online, and a boost spike causes the primary to still spin at higher speeds than it should. This leads to higher pressure every time the secondary turbo comes online. This is also a bad thing...

snoopster76

so last night coming home in fourth gear WOT with the boostcontroller off, I boosted all they way up to 12 psi. In all other gears it was like 8-9 psi. Is this something to be alermed about.

PraxRX7

If you get an air/fuel meter then you can see for yourself if the 12psi of boost is bad on the engine

snoopster76

It's running two bars stoich and one bar rich when driving under any boost.

Scott 89t2

no that is boost spike... when the wastegate can't open fast enough.

creep is when the turbo wastegate is open all the way diverting air around the turbo but there is too much air flowing (from big exhaust, intake etc) so no more can fit through the waste gate so the rest goes through the turbo making it spin faster giving you more boost then what you should be running. like your 12 psi in 4th. that is creep. the only way to fix it is to port your wastegate to flow more air. or restrict the air going in or out (intake and exhaust) but nobody want's to do that...

fc3s.org

Scott is right, except for one thing. You can also get rid of boost creep on your series 4 motor with a series 5 turbo and manifold. The S5's had a much better wastegate and a larger manifold port with none of that twin-scroll crap

It also flows more air, therefore you get more boost out of it with less effort.

http://www.thepartstrader.com/single...0&adnum=197053

snoopster76

how do you port the wastegate? Would that lower the boost pressure than

TBoost

Scott is dead-on. A lot of people don't know what creep is. Good to hear someone with good knowledge of it.

In answer to the port causes lower boost pressure, no. The wastegate alone controls the boost pressure so if the wastegate spring is set to 7.5psi (considering no boost creep), then it will stay there no matter how big the port for the wastegate.

-M

The Ace

snoopster76

I have an idea, but I won't do anything without you experienced guys explaining procedures since you've been there and done it. So if you'd explain to me how to port the wastegate, I should have done it when I had the turbo off.

TBoost

Am I supposed to be an *** kisser?

Well, I stand by what is truth and fact.. so yea, I do kiss truth and fact's a$$.

-M