gik0geck0

Wow, it's been 2 years since my last post, but I finally have good news to share about my G30-770! Last comment is here back on page 19. TL;DR: twinscroll 1.06 with reputable manifold is better than single-scroll 0.83 with chinese manifold (shocker). Around 500rpm faster spool and +30hp everywhere (ish). Changes: Sinco T4 Twin-scroll manifold single 50mm turbosmart wastegate Twin-scroll 1.06 housing from ATP (still same G30-770 core) TI 525 fuel pump in a surge tank (good early indicator, we ran out of fuel!) Everything else in my original post is the same The blue line is where we ended; red is just a random run that hit 22psi. At the beginning of the day, O2 correction was up to 14% at the top end, which fairly directly indicated a power/efficiency increase compared to the old setup. At equal boost, its about +30hp/30ftlb (ish), but the most noticeable change is the 500rpm faster spool making it way more drivable in the mid-range, no longer feeling like a pig. Do notice, we settled in at lower average boost and flattened the torque curve for drivability, where on the old sheet we held boost and rode the torque wave. Along with not-quite smoothed boost, not having the old run saved and different correction factor (oops), it's a bit difficult to compare old/new dyno sheets but the real world feeling is drastic and can be observed on the dyno. I hope this is still a helpful conclusion for on-lookers. Conclusion: good parts are good, twin-scroll works, and I'm pretty happy about the response now, resolving my dyno sheet envy. While I'm sure there's still room for improvement, I'm happy enough to not want to make changes. I'm sure a G30-660 would respond better and be a better fit at this power level. Surely a rebuilt and high-comp motor would respond better (and could take more boost/rpm). Oxygenated E98 would also come on boost better (this was pump E60). Maybe an EFR would still do better. Single-gate for TS seems fine in my application, but maybe there's a subtle advantage to true dual-wg (i.e. scavenging). Is the smaller runner size compared to 6boost beneficial in the mid-range? Hard to quantify without spending a crap-load more money for diminishing returns, but at least the low-hanging fruit was successful.

Thanks for confirming my suspicions that something isn't right. I've pulled vaccum and pressure on the intake manifold and held it to check for leaks, so I'm confident the intake side is fine. I have verified that the WG fire ring is correctly seated and that the flange gasket appears to be holding, though I've always suspected how flat all the manifold flanges are. I stuck a smoke machine in the turbine housing, and at least at 0 pressure, it's sealed. The CXRacing flange is drilled for both T3 & T4, so that has me suspicious of that seal, but I'm not sure I'll know until I switch manifolds. Your comments about ATP housings make me consider switching to v-band & Garrett housing, but T4 twin-scroll is still alluring; I have yet to decide on manifold choice, but I've been thinking T4 TS because it'd give me incremental confirmation of the single bad part; if it's better, then the ATP housing is fine and it was either poor manifold design or leaky flange at higher pressure. Here's a link to ATP's listing of the T4 G30 housing: https://www.atpturbo.com/mm5/merchant.mvc?Screen=PROD&Store_Code=tp&Product_Code=GRT-TBO-M30&Category_Code=Garrett-Turbo-GSeries-G30-770

Yeah, I did a basic test of VCT at idle, and have it configured to be ON from 2000 - 5500, though I forgot to do an ON/OFF comparison on the dyno, so it's possible that's still a factor. I'll also share how this looks in Autocross, where the lag is far exacerbated -- in my data-log, I was only seeing ~14psi peak and 5900 RPM in 2nd (barely into the meaty part; also possible I should just run a smaller turbo for this application; looking at you G25-660). Gear ratios are pretty close to stock R34 GTT 5speed, which is fairly long for autox as well -- lots of factors that are not ideal, ever a work in progress.

Hi all, been a long time lurker of this thread, ultimately leading me to a G30-770 w/ 0.83 T4 flange. Just wanted to share the results I've gotten so far; though compared to the last dyno chart shared by Lithium, I feel like there's something off or inefficient about my setup. Now that ATP has a T4 twin-scroll housing available, that might be my next move to try to fix the laze (not soon) and reduce the number of cheap parts on my build. Also, sorry about the low-res image. Important parts: Altitude! 1519m/4984ft RB25 neo (stock longblock & cams) G30-770 0.83 single-scroll T4, normally at 20psi (the run at 22 was a quick one to verify there's still headroom) Haltech Platinum Pro E70 ish ethanol CXRacing exhaust manifold (unsure whether an inefficient manifold would cause this much laziness) OtakuGarage intake manifold 3" exhaust with cat