Hi guys,

Got a problem that seems to be wastegate creep, its a v6 sti with OEM vf28 turbo and a Forge 1.2bar VF24 actuator ( assume, i have the reciept for the actuator but havent actually checked ). With the boost controller turned off i get around 13 psi by about 4krpm in 4th gear, which will then gradually continue to rise to around 16psi by 6krpm. It feels really lazy coming on boost and the creeping is really noticable when driving. Car has Full H+S manifolds, up and downpipes, and exhaust 3", APS FMIC. I could add more preload to the adjustable wastegate but dont want over 1.2bar and not confident this creeping issue would be resolved.

Now, i would like to install a lower pressure wategate/spring, maybe a 8-10psi spring and use the boost controller to get me to 17-18psi, this will give me more confidence in identifying if there is something else wrong as i am reluctant to continue increasing RPM whilst the boost isnt holding stable.

I would like to know if the VF24 and VF28 turbo actuators are exactly the same, or if this may be the reason for my actuator creep?
Where can i get a replacement OEM actuator for the VF28 if i cant use the Forge VF24 item with correct spring?

Thanks guys.

 

The VF28 is not generally prone to creep.
Don't make the job hard on yourself. Do NOT tighten the actuator. Slacken it of a little. If you have access to a mini vac pump you want it cracking about .8 bar or marginally less. At that point your boost controller, if it is any good should be able to hold 1.25 bar, around 18psi which is a very sensible boost level.
What boost controller are you using? Does it have a single setting or can you map in a tapering boost level?
If there is going to be any overboost and you have a boost guage just lift your foot off the throttle and turn the boost controller down or take a little more pre tension off the actuator.
Generally in 4th gear expect the VF28 to have 1 bar of boost, starting from 1500 rpm at around 3,000 rpm on a level road.

 

Boost controller is a Profec B spec 2.

I will turn it back on and see if i can get it to steady out and improve spool up, but i still dont think it should be creeping running just off wastegate.

 

sorry to seem like im hijacking a bit

What does a boost controller do and how does it work

and what is creep?

 

and sorry again ive only had my scoob 12 weeks and i didnt know squat then!!! im still none the wiser.

 

Boost creep is when the level of boost creeps up beyond the set or intended level. This can happen for a number of reasons. Perhaps the wastegate port is too small a diameter or the wastegate actuator is too tight or the electronic boost controller is not properly controlling the wastegate actuator.
Funnily enough a boost controller controls boost and there are mechanical boost controllers and electronic boost controllers. An electronic boost controller controls boost by controlling the action of the wastegate actuator. The EBC is set to a particular boost pressure and by adjusting wastegate duty cycle it should be possible to maintain the pre determined boost level.
I hope this assists you but feel free to ask other questions.

 

Wastegate creep is where the wastegate starts to move off the seat before the predetermined boost pressure, set by the strength of the actuator spring, this will cause a lazy boost response.

 

So is it as simple as just buying a boost controller fitting it and lower boost for higher mpg and raising for more power or is there summit els I'd need to do

 

Not quite that simple, check out the manufacturers websites and take a look at the install instructions, this will give you a good idea of what is involved. Check out the Greddy Profec B, and Apexi AVCR boost controllers ( greddy being the simpler to understand )

You cannot lower boost below the wastegate spring pressure, and you must not raise boost higher than the vehicle is tuned for.

 

So are u saying then it's pointless fitting it to a standard car which is 13 psi isn't it? And I can't go lower or higher than 13 (if that's it standard)

 

13 psi will be with the factory boost control solenoid which you would be replacing, the actual wastegate spring pressure will be lower, probably 6-7psi ( someone will confirm ). You will be able to run between wastegate pressure and mapped pressure.

 

So I take it that solenoid thing is part of the new boost controller that u buy. So I can go between 6-13 psi? So wus I save much fuel dropping it to say 8 psi?

And can I do it on the fly say I'm going to work I want economy buy say I get bored and wanna go faster can I just push a button and go straight back to 13?

 

Thanks for all the help btw!

 

Yes, Yes and Yes, although im not sure on the actual boost figures for your car, if you post some more details im sure someone will be able to tell you your WG Pressure.

 

Awesome it's a classic turbo 2000 my2000 and If gonna save fuel I might get it done