u/Crazyced22

There is not much info on the subject, which was surprising to me after it happened on my setup that I consider quite common.

So I figured I’d share my experience with what’s called boost creep. A mechanical phenomenon when the wastegate is unable to bypass enough exhaust gasses in order to control boost to the desired level.

1st my car, I’ve had it for a decade but due to how projects sometime (d)evolve, only recently drove it for the 1st time since purchase.

It’s an S13 240sx with an S14 notch top SR20DET swap. Powerplant wise it has: K&N filter, full intake piping, stock MAF, Greddy intercooler, yellow 500c injectors, HKS GT2530 turbo, HKS tubular manifold, 3” catless turbo back, AEM fuel pump, unknown custom tune.

Doing my initial test drive, I noticed that power would increase exponentially as the RPM went up during full throttle. Looking at my boost gauge I saw up to 20psi.

Given that I’m running a stock WGA directly to a boost source, I was expecting to run spring pressure, so no more then 10. I blamed the unknown divorced pipe turbine outlet and got myself a bellmouth style one.

To my dismay it didn’t change anything. So I did the ultimate test, I not only unhooked the WGA, but also wired up the wastegate flapper wide open.

The 1st image is a Virtual Dyno datalog of that run, where you can see boost and AFR. Pay no mind to the dyno numbers, seems like the tach source is not translated properly and reading wrong.

I was miffed. Now way I would have thought possible to hold up to 20psi with the flapper held wide open but here I was.

AFR were still somewhat ok, surprisingly. But definitely higher boost then I’m willing to risk on a 30yo motor.

Only thing left to do, some DYI porting. Something I’ve enjoyed trying my hands at, including TGV deletes in my old WRXs.

I started by opening up the wastegate hole as much as I could, making sure I kept a good amount of mating surface for the flapper to seal against.

I then turned my attention to the inlet side. I mostly worked on the roof (where the hole is) by streamlining a more direct path and creating a smooth radius into the hole as opposed to a sharp angle.

Also flattened other casting marks and smoothed everything while I was there.

I was finally able to test out the mod. Result? Holding a solid 8 all the way through with the stock WGA on spring pressure.

I got myself a Grimspeed MBC that I will use to bring up the boost. Probably to around 13-15 since I don’t know what the tune was for. But keeping an eye on AFRs.

My 1st gaming PC was the Dell XPS (with the Blue fascia, OG Pentium 4 and ATi 9800 Pro) that I bought with my savings as a teen in '03 (god that was a large chunk, still got the bill). Ever since then I took an interest in building my own and thanks to forums I learned how to. First build was a Thermaltake Armor LCS (liquid cooling), with Intel core2duo and ATi 2900XT. Then in 2013 I built my 2nd tower, with an Intel i5 and Radeon 7970, everything shoved in a Thermaltake Urban S71 with a 240 AIO of the same brand. That case included 2 200mm fans and was very quiet, but the internal layout now felt a bit dated. 5 year or so later I swaped the boad to AMD with a B450 and 2700x along with a RX480. Fast forward another 5 years and swapped to a 5600x and 6650XT in 2023.

Which brings me to last december, where I finally decided to upgrade my almost 20yo trusty samsung LCD for a 1440p AOC. My goal was to play Cyberpunk (late to the party) with good graphics. Unfortunately the 6650XT wasn't cutting it, so in january I decided to finally jump ship to green and got an Asus TUF 5070 Ti. (the 16gb vram fomo was real). Along with the 5600x it gave me ok performance and figure I would tough out whatever's going on in the market. But recently my local store had an Asus TUF mobo, CPU and ram combo sale. Visiting the store I also saw SSD were quite discounted (but still crazy) and notices they had an Asus TUF case. Gears started spinning and I decided why not do a uniform Asus build, the case was almost exactly what I was looking for, except I liked the Fractal Epoch XL front fascia more.

So I pulled the trigger and so far I'm very pleased, easiest and most satisfying build I did so far. In my last case I used both molex and sata power cables, it was a mess back there. In this one I needed neither! No optical drive, no stacks of 2.5in. CPU, GPU and MoBo were the only power cables needed. So much cleaner! Top of the chassi was also removable for an easy AIO install. And overall this case is just better though out for cable management and quit sturdy too. Really stoked with the results! Intergrated RGB and full fan speed management in ways we could only dream of 20 years ago and not having any front drives or rack makes for much better and open look and flow.

Anyways, here are the final specs:

-AMD 9800X3D

-T-Group Vulcan DDR5-6000 CL30

-Asus TUF B850 Plus wifi

-Asus TUF LC III 360 LCD

-Asus TUF 5070 Ti OC

-Asus TUF GT 302 case

-WD Black SN850X 2TB * 2

-Corsair RM1000x