shav wrote:crazyricochet wrote:Agree with Manaz's comments, it's all been done many times before.
The VF52 is the best bang for buck upgrade if you can get a cheap 2nd hand one, or if you spend around $1000 get a new Kinugawa 18g, or if you can afford to spend $2200 get a new ball bearing AVO 380/450 etc whatever tickles your fancy.
The more expensive options will be able to take you a bit further in terms of power but on a stock engine I'm slightly more comfortable with the OEM option. P.S Get the wastegate on the VF52 ported BEFORE you install it and find out it boost creeps to 22.5psi
I'm happy with the VF52 for now and leaving it like that until the engine decides to cark it. *touch wood*
Thanks James. I have never heard of the boost creep thing you mentioned if the wastegate was ported. What is that about?
Ok, I'm no expert on the topic some of this info may be not all technically correct but you get the idea. This is from me doing some research from google and talking with my tuner.
Boost creep is a condition of rising boost levels past what the predetermined level has been set at. Boost creep is caused by a fully opened Wastegate not being able to flow enough exhaust to bypass the housing via the Wastegate itself.
Say you meet your target boost - 18psi, the extra exhaust gas that's coming from your engine should be flowing out the wastegate as it opens because you're at desired boost level. But instead it keeps flowing past the exhaust turbine and not out the wastegate even when it's fully open, this generates more boost than required and suddenly you have no control over how much boost you make as the wastegate isn't taking enough gas flow away from the exhaust turbine.
Now on a stock car it's usually fine and not an issue but once you start adding intake and exhaust mods and turning the boost up and flowing more air it is really really common with these VF52s, some will do it worse than others but generally ALL will.
Numerous threads are found about boost creep with VF52s in google
http://legacygt.com/forums/showthread.p ... 00488.html
http://forums.nasioc.com/forums/showthr ... ?t=2021754
You fix it by "porting" the wastegate, this usually means using a grinder to increase the size of the flapper hole slightly and smooth out the internal area of the exhaust housing to allow the exhaust gas to flow towards the wastegate when it opens.
http://www.wrxforums.com/forums/11-suba ... ing-2.html
A stock VF52 has hard edges inside which seem to restrict flow. Porting it is basically the only cheap reliable answer any decent workshop should be able to do it if you can supply them with the turbo, although you can also use an external wastegate but that would cost significantly more.
Had mine fixed from a dude with an STI from facebook for $100. He'd done quite a few and didn't remove much material, mainly just smoothed out the internal areas and before I was boosting to 22.5psi, then after it was ported was dead level at 14psi and with a retune it's happily peaking at 18psi nice and controlled like.
I just wish I knew about it before I put it on, taking the turbo off again sucks balls but I wasn't aware of boost creep at all until I had the tune done.