+15 STI VF48. A little increase boosts a long way
Hey!.... Welcome to #modmonday! This week will feature my 15+ STi turbo that is installed on my 05 STi. When my old turbo began to fail this was my decision and has been running strong since.
When looking at replacement turbos they are many options.. older used turbos, brand new from Subaru, eBay and aftermarket. Weighing my options I decided upon a very lightly used 15 STI turbo given it was very new and the price was right.
There were many forum posts and dyno charts showing that there are a few differences between the 15+ VF48 and these peaked my interest. A slightly enlarged hot side gives you a bit more top end power and it shows on dyno charts. Given the car spends most of it's time on the auto-x course this is no issue. The difference between the factory Vf39 is quite noticeable as the spool time is a bit delayed but it is worth the wait.
With this upgrade like many others you will need to tune for this even if you were tuned for a another VF turbo. A quick run and datalog showed that my old tune wasn't up to snuff and the numbers let me know.
There are no fitment issues with this as it looks quite similar to it's fellow VF brethren. Looks can be deceiving as next to a vf39 it will look very similar but the hot side is just a tab bit larger. One benefit noted from this change is a delayed spool for less ringland issues. Is this a 100% fix for ringlands? No, but I believe it helps by lower the chance of a high boost low rpm detonation that can easily crack a ringland.
I would recommend this turbo to anyone looking for a bit more power without heading to the aftermarket. Oem fitment means it is easy to adapt to the factory location and without additional upgrades.
-Questions, comments, thoughts? Leave them below!