Sil15 – Creep… Goto Rebore…

Soooo after a few power run’s on the Dyno my tuner ran into a little snag…. My GT2835 / “GT3071 as some call it” is boost creeping…… Only minor, yet something I needed to get fixed. Especially if I plan on running another 1/4 mile again – foot flat to the floor on full boost! Yeah buddy!

Both the red and green lines are two different power runs. You can see the power doesn’t continue to flatten off, it continues to rise further and doesn’t stop….

Image of first Dyno run with Boost Creep
First Dyno run

At the time I had no idea what was causing it, surely it’s not creep right? At least that was what I was hoping for. So I checked the pre-load on the wastegate.

Because the bigger turbo I’m running has an internal waste-gate I figured, perhaps the pre-load was too tight? But unfortunately no, the pre-load could have actually done with a little extra load.

Image of wastegate actuator pre-load
Wastegate actuator pre-load

Ahah! I know! … I’ll see how far the gate open’s in case something is restricting it. So out come’s the air compressor! Again, everything looked okay. Gate opened fine…..

So I spoke to a mate whom I originally purchased the turbo off. He found it odd, because his S13 had no dramas. In fact, he specifically purchase this turbo originally because, word was these don’t creep. That said, there was probably a world of difference between his modded S13 and my nearly stock S15. I was also still running the stock manifold…. Time to Google!

So Google said I goto re-bore…. How the hell do I do that? Off to YouTube! I almost decided to send the Turbo away to be re-bored by someone. Instead, I figured why not give it a crack myself?

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