Subaru EJ255 VF52 Turbo Upgrade - Boost issues

Hey all,

I have recently swapped out stock TD04 turbo with a VF52 and Grimmspeed 3 port BCS (along with a new clutch kit + flywheel machined).

Now the car ran quite well with the TD04 and the tune I had developed for it, i had altered the fuel tables and boost map (waste gate duty cycle).

Fast forward to now, I have put the VF52 turbo on the car and it runs very average. I definitely made more power with the TD04 before!

This particular turbo was one I had purchased used, it appeared to be in good condition, minimal shaft play no major cracks (there is a hairline crack in the exhaust housing but from my knowledge its common and does not effect performance...but who knows).

Now when I try and build up some boost the car seems to make a strange turbo flutter noise, is this normal for the 3 port bcs? OR the VF52? The TD04 never made any noises like that before. Also it feels like it takes for ever to make any boost, i don't think its running correctly.

Does anybody have some advice on what I can do to start troubleshooting this issue? (what feels like for ever for spool up, lack of power compared to the td04 and that strange flutter noise i hear when the turbo is making boost)

It's hard to really make much of a conclusion from the very small log file you've supplied. From that small amount of data it looks like you're seeing 17 psi at around 3300 rpm which I wouldn't have considered terrible? What were you getting with the stock turbo? I've never found the EJ engines to be fantastic at spooling turbos.

I haven't personally used the VF52 but a quick search suggests it's a common option for the EJ20/EJ255 so I'd be surprised if compressor surge is what you're facing. this is normally a situation you strike with poorly sized turbos. You can however end up with an oscillating sound due to the operation and frequency of the boost solenoid. I'd disable the electronic control and see how the engine performs on minimum wastegae spring pressure - Is it smooth at this boost level? Another option I use to eliminate potential boost control issues is to use a manual bleed valve to test at your desired boost level. Compare this to what you're seeing with electronic control.

Thanks Andre for you insight. You are right, in the log file everything looks pretty good spool wise, but the car doesn't feel like it's performing.

With the stock the it built boost a few hundred rpm sooner then came in strong, this one doesn't have that same feeling and the lack of acceleration can be severely felt.

I have run the car with the WGDC zero'd out and it doesn't make the noise, so I am guessing it's how the new 3 boost controller works. Perhaps the noise is a non issue, but I wasn't sure and wanted to make sure I am not damaging my Engine or turbo. I will try and get a video of it.