hi all , my cars been rebuilt to sti spec "2002wrx" and its nearly run in and soon going to be mapped . i have a brand new ihi vf34 turbo fitted and was wondering what boost they make on average ?? cheers all

 

they make whatever its mapped to, lol

vf34 is sti spec, similar to my vf35 which is mapped to 1.5 bar (21 psi)

 

As above 1.4-1.5 bar

 

As above 1.4-1.5bar,VF34 is only turbo which has been only found/used on V7 Spec C Type RA and difference between the VF35 and VF34 is VF34 using slightly bigger exhaust housing(P18) and VF35 using P15,and VF34 is ball bearing turbo,when VF35 is still sleeve/thrust bearing turbo


Jura

 

Get it ported to prevent boost creep, speak to Harvey on here.

 

With boost creep usually suffer VF35 not VF34


Jura

 

I thought both units suffered along with the Vf43.

 

Both the VF34 and VF35 with the smaller housing can suffer boost creep. It may be more prominent on the VF35 but my conclusion may be influenced by seeing many more VF35 than VF34. One of the problems is that not all of these turbos suffer boost creep so until you have the turbo fitted and start mapping you do not know you have an issue. The turbo fitted to one car may have no boost creep but suffer badly on the next car with a different spec. It will depend on how efficient the exhaust side is and the ability of the intake side to keep up. Then the WG orifice can become a constriction and boost pressure creeps beyond the value set in the map.
Porting the wastegate orifice is easy but obviously has to be done with the turbo off and exhaust section removed.
Contrary to Scoobynet and other popular myth, porting the WG per se does not increase power output.

 

You could argue that boost creep itself increases power output ..... just before the engine kacks itself!

I had a problem with the wastegate actuator not being man enough to withstand exhaust pressure and had to upgrade to a turbo dynamics 1bar jobby to hold peak..... but apparently thats pretty rare, especially with the extra back pressure of a 2.5" exhaust.

 

All the new turbos I sell always have a 1 bar/14 psi actuator.

 

it seems to be one thing after another !!! now im worried about boost creep !! knowing my luck i bloody get it !!

 

From what i gather the vf39 suffered boost creep and the vf43 was the modified unit designed to prevent it.

 

Can someone clarify boost creep, what exactly happens and what are the symptoms? (vf34 owner)

 

From above.
It will depend on how efficient the exhaust side is and the ability of the intake side to keep up. Then the WG orifice can become a constriction and boost pressure creeps beyond the value set in the map.

The turbo boost is controlled by a penny valve opening and closing or being partially open. When the turbo produces more exhaust gas than can escape through the exhaust section and turbine with the penny valve fully open then the boost backs up or builds, hopefully, slowly. This is boost creep and the remedy is to open the diameter of the penny flap/valve orifice slightly. More gas can escape from the increased diameter and boost can be held at the mapped figure by the wastegate control.

 

Harvey, whats your take on the porting? My mapper was of the opinion that it was only worth doing if it proved to be a problem when running! My argument was that if its potentially going to be a problem why not port it anyway while the turbos off just in case? Save having to pull the tubby off again!

If the porting isnt needed does it have any adverse effects?

 

If I was fitting a turbo that I thought might cause boost creep I would port it before I fitted it if I was responsible for it simply because it avoids the additional expense of removing it and replacing it at a later stage. Not everybody has the luxury of fitting a turbo and then deciding it needs porting.
Porting a turbo will neither add power nor detract from the power produced but it can make it possible to control boost that was previously out of control. Unfortunately it is not possible to predict exactly which cars will need a proted wastegate orifice.

 

hmm wish the bloke who fitted mine suggested it before it was fitted , i would of defo had it ported