Lithium

I'd verify how invested in exactly 9.5 he is if it turns out to be a massive amount more effort to go 9.5 vs 9.0 or 10.0. He may have just said that as a suggestion not realising it'll be a huge deal to go specifically there when half a point either side isn't so bad.

Interesting, I know folks who have taken these turbos with that housing over 600kw @ hubs before back pressure started becoming a thing - do you have an EMAP sensor? 4" should be heaps Epic setup regardless, 480kw even is no joke.

So long as there are no leaks etc it should be fine, 480kw @ hubs on 25psi should be a walk in the park for an 8474. Any reason it didn't get taken further?

Awesome outcome, thanks for the update. One thing that leaps out to me here, and I (and others) had been asking about this back at the time you were working through issues... it seemed like timing was held back on and your tuner said it was normal, yet here it's mentioned that the knock threshold has improved and suddenly it could be pushed further if the engine was stronger - which to me very much implies that knock was an issue where it wouldn't normally be so much of an issue. I don't know what testing was done for triggering issues but I can say first hand that just relying on your typical ECU trigger problem detection to pick up on the issues you can get with the stock CAS setup isn't the way. I know of plenty of people who have had a stock CAS and had issues that have not resulted in an error logged but have 100% got timing drift which adversely effects the knock threshold and even general driveability. Here's example of a car that had trigger issues (knocky and just not making the power it should) and they changed to an NZ Wiring kit, 0 mechanical OR tune changes at this point from when it was tuned with the dodgy triggering... so would have made more with further adjustments, this is just to show the effects of a stock CAS not playing nice. Doesn't look wildly unlike where yours woke up.... but either way, highlights the importance of a good trigger setup and why I always insist that at the very least someone gets an NZ Wiring kit if they're modding their RB at all and still have the stock CAS.

I feel like you just need to soul search about how much what compromise matters to you. Firstly, you're going to NEED ethanol for the kind of power you're talking about. Next, how much does the absolute power figure matter to you? There's a bit of a goldilocks type zone where you may not make 1000, or much over 1000hp but the car will be FAST and while not as punchy as the 9180, if you didn't think about or talk about the peak power figure then it's realistically (in my opinion) going to be a pretty epic all round road car. I'm kindof thinking the Precision 6870/Xona Rotor XRE6869S area, maybe even the Xona XRE7169S. They would both sacrifice some vs the 9180 but on the flipside they'll give you a reasonable step up in power while not quite fully committing to big turbo lag life. If you *really* want to walk past the 1000hp+ mark then realistically stop thinking too hard about the specifics of spool, its all going to be academic anyway. You have a sequential, you have a big engine, its not going to be dead in the water like the old 2.6s would be at low rpm and once it's on "its on". The 72mm+ turbo combo on a 3.2 stroker is a pretty known quantity in terms of how usable they are, check out Andrew Hawkins driving videos with his G45 1450 on his RB32 GTR, or That Racing Channel when they put their Precision 7685 on their R32 GTR. Ideally try and find someone with this kind of setup in real life as give or take - most 76mmish 1000+hp RB30 based builds are going to be "there or thereabouts". Dyno plots aren't going to paint the picture anymore really at this point.

That HKS turbo (or a G42 1450) would give a massive hit to response but definitely a heap more headroom too. I guess you just got to decide how much "heaps more power" or keeping some degree of down low punch matter though I think that's come up before. Realistically expect the ability to make 800+kw @ wheels but also 1000+rpm more lag too. @DVS JEZ Ran a G42 1200 on his RB30 (so size down turbo from what you are asking about on the size down engine) and that even made big numbers, but also paints a picture of how much later spool will be. Realistically probably not terrible for the power when you factor in the stroker, but if you're picturing something that drives like the 9180 then it's going to be pretty disappointing.

Look for results on Garrett G42-1450s, basically the same thing. What is your target power etc? Are you less worried about response now?

Interesting (but I suppose not massively surprising) the dyno plot doesn't put this car across as THAT much better down low than it was with the -5s, the old "transient response" beast back with a vengeance. I guess you'll have to take my (and every other person who has been in or driven it) word that the car is a completely different beast now, feels WAY more alive basically everywhere. Holds power better, "wakes up" faster under foot. It's generally a significantly faster and better car to drive, beyond what the plot shows. Anyway, only changes here are swapping from low mount -5s to a Pulsar G35 900, and from a stock Nissan RB26 intake manifold to a Hypertune single throttle jobby. On the dyno pull it doesn't really pick up noticeably harder until it's got about 10psi into it, then it gets from there up to target boost a good 500rpm earlier. Same boost, same fuel (98 pump gas), same dyno: Note: This is both 22psi. It's a stock RB26 aside from cams, the turbo was chosen for headroom - and there should be HEAPS in it with a built engine and ethanol flowing through it's veins.

So we had a bit of a session today and didn't have much chance to test it perfectly for the point of this thread but the theme seemed to be it can hit 1bar close enough to 4000rpm in 3rd gear, give or take a little and man it feels a lot perkier between 3000-4000 than the -5s.

I've only tuned one 4-port setup and I've essentially ended up finding it increasingly difficult to control nicely as I go further from gate pressure and haven't been tooooo certain that it's resolution alone that's causing the issues for me. It's an RB30 in a RWD R32 and owner went with a ~.4bar spring in a 66mm Precision wastegate and 4 port BCS, the aim to be able to get the turbo (75lb/min Borg Warner) to it's limit with it while also being able to hold back power in the earlier gears to make it usable. If I use "open loop" boost control boost follows a nice curve at high boost levels buuuut it will deviate from that curve easily in different atmospheric conditions. If I use closed loop to manage it the thing is pretty stable up to around 20psi, but anything past then and it starts getting a little erratic - any input from closed loop boost control is too aggressive and if I dial the PID back then its "not enough" either, I guess you could blame the tuner but this is far from the first car I've done PID with with using the same engine management (G4+ Link). I've put it down to being a perfect storm of soft spring, huge bypass area with the gate, the aforementioned resolution with the 4-port and also limitations with the closed loop tuneability on the Link which isnt NORMALLY a problem. What we're aiming at trying soon is as you mentioned, two 3-port gates. I'm going to try running one of them as a standard PWM with a fixed value for each boost target just to "bring up the base pressure", then use the other one as the target of the actual boost control logic and see if that helps things or makes them messier.

Ahh gotcha

I am really trying to resist responding to this, things are getting pretty offtopic but not sure if I'm missing something or maybe you've not had direct experience with centrifugal superchargers but ESPECIALLY a centrifugal charged RB25 on 15psi sounds like an absolute nightmare of a setup - not least because... have you heard an RB25 with an exhaust that would support well north of 200wkw and no turbo in there to "clean up" the sound? Not good. Never good. Also centrifugal chargers make peak boost at peak rpm, I don't know what magic one would need to do to make a centrifugal supercharged RB25 make 210kw by 4000rpm but the best I can imagine would be overspinning the heck of it at max rpm or some such thing to make a compromise that works. I love all kinds of forced induction and centrifugal blowers are heaps of fun, but best suited to things that you DON'T want heaps more torque down low and instead want the power to increase linearly with rpm. To pull things back on topic again, it's hard case that @34GeeTeeTee's result over a decade ago with an old Garrett GT30 based turbo with an FP HTA compressor wheel on it would stand up very well compared to popular options available today. 391rwkw on a Mainline roller dyno would be comfortably into the 400kw @ hubs range, and is making ~280rwkw by 4000rpm if I'm looking at that right. They have done multiple generations of compressor improvements and have all new turbines that are in a different league in terms of flow and inertia compared to the GT30 of the time, imagine a modern equivalent Xona based turbo like this on an RB25?

Tbf impressive numbers in stock location (even if clearly huge work has been done to replace EVERYTHING about the stock mount setup) but it "sounded" pretty damn laggy and when I tried to keep an eye on the tacho to get an impression of when it started lighting up I realised the tacho is not working 🤔 They said it's running 4.11 diffs, so assuming this was dyno'd in 5th gear this is the power curve vs rpm (in white) Not convinced this is better delivery than a 6870 like Hawkins asserted, even if it does look like there may be a bit of effort to deliver a softer boost curve it still is clearly quite laggy

Dammmnn, gutted This definitely has a lot of potential to explain some stuff though... on the "bright side".

Haha that's a pretty sweet way of fixing that issue, cool to see it's still trucking along! I thought I may have seen you around recently. Thursday night catch ups are still plodding along btw, if you're ever around