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

I'll have to get some logs when I do a little bit more work on an R34 GT-R I've been helping set up. Stock engine, 272deg cams, and a divided hotside Pulsar G35 900 with .85a/r T4 divided hotside and it drives fantastic - it's enough of an improvement over the old -5s that no data is really needed from our point of view to make a call on whether it's more responsive under foot to drive but boost threshold is always a handy metric. I'm far from saying that the G35 would be a good choice for the kind of thing you're looking into, more what I'm suggesting is "G-series" turbos seem to respond very well to divided hotsides and middling a/rs (obviously ensuring that it's not so small as to choke the given setup). If a static cam RB26 drives like this R34 does with a 80+lb/min turbo, then I can imagine a 60lb/min equivalent match on a VCT RB25 would be fantastic.

Nice spotting. Damn I wish I had more time to look over this tune now, that looks like a fk up. It's not unusualy for people to not be "not at WOT", or even for the APS to not be at a full 100%. With this throttle map if the driving was at like 95% (I've seen that plenty of times) then this would command 50% *actual* throttle. Not necessarily a thing that would have shown itself on the dyno (tuner was 99.8% APS so probably about 98% TPS which should be good enough) but very strange and would definitely affect things in the real world if it's not part of some other strategy.

Obviously a complete different kettle of fish, but the N55 thing I run around in these days is quicker than my old GT30R equipped R33 GTS25t and one of the marketing gimmicks they had about my car was it had 450nm from 1400rpm or something silly like that. Like in real world terms it comes across as slightly laggier than that, sortof. I can launch at 1400rpm and do a mid 12 so in terms of boost threshold its probably pretty on the money. Why would you do that!? It doesn't sound in the spirit of an RB26 to me, and per my previous comment - I clearly appreciate response! I think the absolute smallest turbo I'd entertain the thought of on an RB26 would be a twin scroll G30 660, I do prefer my EFRs but a 7163 would be a mismatch and a headache for the money and effort put into vs what you'd get from it. 7163 is magic for a small engine though.

I didn't mean it as a dig at all, I get and agree with all that - I was just pointing out the irony of me being excited about a low mount twin setup when I'm usually so against them ... have a well match single turbo The RB engine bay etc just doesn't lend itself well to it, and as you said yourself - an RB is no S58. May as well build it to it's strengths.

Haha cheers man ❤️ On the topic of the smaller frame things being looked into (kindof), as much as I love to criticise low mount twins on RBs.... on BMWs they aren't so bad, I have quite a thing for BMWs S58s (which are a 3litre twin turbo straight 6) so was pretty interested when I caught wind that there is a prototype bolton turbo setup based on the latest Xona tech and while this is preliminary stuff, the power and powerband of this looks pretty insane: 500whp before 4000rpm, 970whp up top and that's with engine protection kicking in due to fuel pressure dropping off - they're upgrading that and expecting about 1050whp. Absolute craziness from a bolt on low mount turbo setup on a 3litre engine, even if you factor in the US dyno thing these are wild numbers.

Yeah. In my general experience the more the engine is allowed to breathe the higher you can set it and hold torque. Upgraded intake manifold, aftermarket exhaust manifold/turbo that drops EMAP etc seem to let it carry. I've definitely had results which back up what @Dose Pipe Sutututu has found... late 6000rpm has been perfectly rational on some RB25 setups I've done. This particular car though, if I were tuning it from scratch I'd have "started" my VCT change over hunt in the mid 5000rpm range based off previous experience.

I haven't scrutinised the hell out of the tune yet, but my initial impressions are that I don't exactly have red flags about what he's done and said to you. Sure, there are things I can pick in there buuuuuuuuut nothing alarming so far and again, it seems like it was left safe and ok to drive while things get resolved so you don't burn money. Integrity and transparency are hard to find in a tuner, dude looks like he has both and left the car behaving a heap better than it was when it arrived. From the POV of someone who likes to think I'm not stupid and do an ok job, I've 100% taken a car off the dyno and later gone "ahh shxt I should have just done x to confirm y". We're all human, there are a lot of balls in play, and when something isn't going the way you expect it can throw you and you can't take all the time in the world to cover all bases when someone stressed about money has to pay for you to do it. It could age that made 100% the right call as well, and I'm a cowboy But yeah. I'm not just being diplomatic, if I raise questions suggesting mayyybe a couple of differences with the tuning approach may have left you a lot happier is not saying he's incompetent and I *could* be wrong as well. All I was saying is there a chance that even 3-4deg of timing through a lot of the map on the exact mechanical setup you have MAY have got it to a point that you'd have not raised an eyebrow at the result, and I'm not sure why that wasn't tried but not saying there was no good reason.

Sorry finishing lunch, can't spend much time - though for food for thought, the tanking VE I'm not 100% is thaaat bad. I threw your 220kpa VE line into excel, then calculated "Unitless flow rate"... basically VE x RPM and divided by a made up number to bring the final values into something that looks meaningful. Where VE is proportional to torque, this value would be proportional to power. Obviously mechanical losses etc come into it too, so power will roll over more than this shows but this is not close to showing power flat lining at 5000rpm. Now, short answer is timing doesn't affect VE - it's basically just saying how much air is moved by each cylinder in each complete engine cycle. But timing DOES affect how well the air moved (as a result of VE and boost) is used. You can increase torque without increasing VE if you aren't at optimal timing.

+1. I would love to know why more timing wasn't put into it, and it may clear a lot up but NOT a thing to do without the right gear At least for me, this also done when timing is "near" as if the timing is soft enough etc the picture you get may be misleading

Comparing a few points on the maps, it doesn't look like your timing map has been touched from the "catastrophic" version. I just ask questions for data, not accusing or judging anyone - just trying to get to the bottom of whats going on, but did the tuner bail without doing anything with timing when he saw the WGDC? My limited experience with "stock plenum" and modest size turbo RB25s is that they liked VCT do be disabled in the 5000rpm range, where your VE/torque rolls. Your timing is quite soft, and if he didn't touch it from the old tune because the WGDC was going high then I'm not saying it's a thing... but I'd not rule out the possibility that things would have changed a bit when you got closer to MBT area. Like there could potentially be 5deg more timing in areas of this map if it's not knock limited, that could make for a very different performing car. The spring COULD just prove to be too soft for 18psi, when we were tuning the EFR7064 setup before upgrading to a much tighter spring we hit the exact same kind of thing you're seeing in terms of WGDC and we just watched the actuator, and after 5000rpm it started pushing open. Obviously EMAP is getting up, I wouldn't push this turbo any harder than you are - but with the data I have so far I feel like soft timing, late VCT disengagement and a soft spring could absolutely explain a fair bit of what you're seeing. The boost control could also be refined a bit to as you say, make it faster on the road in terms of bringing the turbo on a bit quicker and also holding better - I can understand why this stuff wouldn't have been refined if there was cause to think there is an issue to be resolved somewhere, but there is a definite nagging thing for me that the timing is potentially soft enough that if it wasn't near MBT or knock limited then you may not be getting as accurate a picture of how well things are working as you might think. The EFR7064 and stock plenum combo is always going to roll over more than a bigger turbo/FFP setup (like most are these days) but if you guys pulled the plug because of the WGDC and that turns out to just be flapper blowing open a bit thing before checking how "on" the timing is, then I can't help but wonder if this thread would have existed if the timing was optimised at the current state or even at a slightly lower boost level before calling the party off. I am not saying that I've decided that's whats happening, but I'd be lying if I wasn't thinking that it is a possibilty - at least without having more data or info on why timing wasn't touched IF it wasn't touched. Definitely open to be called out for talking nonsense or pointing out where I may have missed something