Lithium

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

Just had a squiz at tune and logs over brekky but don't have a lot of time for yarning. Still mostly head scratching but things I felt compelled to mention: It's been ages since I've tuned a pump gas RB25 but I'm pretty sure the timing looks a bit soft, not necessarily crazy soft but enough that if my memory serves correctly - RB25s I've tuned (and others I've seen tunes for) would lose noticeable power if your timing map was applied to them. Not saying as a criticism, but an observation. The tuner could have either been competing with knock, or generally "not confident in the setup", but one way or another that alone could explain some of the lower power at the top end. There clearly is stuff going on, I'm not pointing at timing as possibly being the problem - just added that to the discussion. Also, you aren't logging turbine speed... do you have a sensor or was there just one used for tuning? And what gear were you accelerating in with those logs? It didn't look THAT bad lag wise, and looking at the datalog from the dyno - most dyno operators I know of let the engine accelerate at 500-600rpm/s for a dyno sweep but your tuner has run it WOT from 2000rpm to 6000rpm in ~4 seconds, or almost 1000rpm/s. When you consider the "action zone" for boost threshold is 2500-4000, yours is given about 1.5s to build target boost when most RB25 dyno plots you'd be comparing with may well be given closer to 3 seconds. A good part of double the time to hit target boost in that rev range makes a difference, and may account for a bit of the less spool... if it's driving quite nicely then maybe the "lag" could be a red herring, though I could be overestimating this difference. I personally do most of my tuning in the 5xxrpm/s range so that's what I use to build expectations of spool. You could try giving it beans from low rpm in 3rd or even 4th gear to get a solid picture of the actual boost threshold.

Here we go, this car "upgraded" from Precision Gen2 7675s to Xona Rotor 10569S (the previous generation 72mm compressors) using a reverse rotation turbo for one side and here is the video for how they found that: This car has just upgraded to the new XR7169S (also mirrored) which goes from being 105lb/min with a 99mm exducer to >120lb/min with a 92mm exducer, and so far have proven to be MUCH more potent than what this R8 was running at the time of the clip but no cost to spool. Out of interest that car is supposedly the quickest 60-130mph "street car" in the world according to Dragy results from when it had the old 72mm Xonas:

I would say it's a case of when, not if the echo (Xona term for that kind of thing) versions come out of the new ones

Oops I meant to link them: XRE7169S Ball Bearing Turbocharger – Forced Performance Similar area to the equivalent Precision

Instead of starting a new topic I'm going to revive this zombie. Forced Performance/Xona Rotor have started releasing turbos based off their latest range of compressor wheels, the "XRE" range and so far they are looking like the ducks nuts. As people who've been around a while would know, I've generally liked what FP do and been pretty excited about their UHF turbines but haven't pushed the idea *that* hard in the RB world as there have been theories and murmerings I've heard which have had me not 100% confident of how well they'd work on this platform. At face value everything sounds perfect, the turbines are low inertia, have very low back pressure, and their compressors had decent flow for their size... but unfortunately there is more to the picture. This isn't gospel persay, just me extrapolating and theorising - though it's not all completely unfounded and I'm just painting a picture of why the previous generation may not really reflect on what we should expect with the new ones. The HTZ compressors used on the Xonas ALSO like higher pressure ratios to do their flow, and the UHF turbine wheels seem to like to operate at higher rpm to generate shaft torque. This essentially ended up meaning the Xonas only really suited RB/2J engines when using larger exducers (94mm+) but those exducers kept the rpm down on the 69S turbine that on paper also suited best, meaning they potentially struggled to drive the larger compressor as well as you'd hope. Instead of high EMAP, there was the risk of more lag than you'd hope and actually "running out of turbine" in terms of not actually having enough shaft torque to drive the compressor fast enough to make the numbers. This could potentially end up with people undersizing and overspeeding their compressors on larger engines to try and make the numbers they were looking for - and essentially "look" like they were getting away with it because the crazy not-restrictive UHF turbine stiiilll didn't get up generating massive back pressure. Not ideal, but this is how some went forward. Bring on the new releases (so far), the XRE6869S and the XRE7169S - running a 88mm and a 92mm exducer respectively, both in that mid 80-mid 90mm exducer range that seemed to compliment the 69S turbine very very well, but *also* pumping a crapload of air for their size. A lot of the magic I expect to start showing up when people use these will probably be attributed to the new compressor aero but I think the MUCH better match between compressor and turbine behaviour will make the gains way way better than expected, and start actually showing the magic the UHF turbines should have already had the potential for - just hadn't got the right pump for the job. The XRE6869S: This is a 68mm inducer compressor capable of 105lb/min of airflow max, paired up with a low inertia turbine. Picture something capable of 1000hp @ hubs on E85 with good spool and lower inertia than most things capable of this kind of power. The Xona 68mm turbos have already been known to be better underfoot and lower EMAP than their key opposition, but the old 68mm/94mm 95lb/min compressor was maybe not quite up to the task of a complete takeover in that "68mm turbo for street use" zone. The new 68/88 105lb/min jobby on the other hand, should be very interesting. Unsurprisingly they've been proven to outspool and significantly outflow the old XR9569S which were already beasts. The XRE7169S: This is something that could be VERY interesting to see on an RB. I know of these replacing PTE7275s (and in one case even twin 7675s) and matching or improving their power but MASSIVELY improving power delivery. They are already proven to be absolute monsters for their size, talking 1100-1200hp @ hubs on ethanol and beyond that on methanol on full send - but without the "Big frame" power delivery of most things capable of these power levels. The nuts thing with these is you can literally get both turbos on what is essentially a GT3582R style frame, T3 flanged etc. There will be a slight cost to compressor flow with the old GT3582R style compressor cover footprint but not THAT much. There have been posts in this forum where people have antagonised about whether to go with a 6870 vs 7275 or jumping from a EFR9180 to a 9280 vs jumping to another brand and losing a tonne of response - when talking about drifting into that 1000hp+ mark but still being a bit shy of turning the car into something that behaves completely like a drag car. These guys may make that compromise much less so much of one.

Nah I was more checking whether E85 or petrol, which makes a big difference. Ok Mainline hub, that shouldn't be THAT low reading. I would have expected this to be sufficient for what you're trying to do Yeah this seems the wisest at this point, if you are able to get more data to scrutinize then that MAY build a better picture. At this point I don't think I'll add too much until some data is available to try and build a better picture of what might be going on unless you have any other specific questions? In terms of turbo match you shouldn't be far off with what you have imho, an EFR7163 (with a bigger hotside) would be a nicer match probably, and some more modern things like Garrett G-series may be a better balance for a bigger engine but at this stage while the turbo match may not be OPTIMAL... I suspect there is something not performing as well as it should be in the setup. <250kw @ hubs on 98 isn't right.

You are FAR from the first person to overlook this. I've been in this club, though learned from it some time ago Very loose plotting of a generic "2.5 single turbo" on pump gas against an EFR7064, adding in compressor efficiency (and taking a random guess for the off the map one) and then adjusting the turbine expansion stuff to suit and it definitely paints a picture of excessive EMAP partly aggrevated by running off the comp map: https://www.borgwarner.com/go/CRTINK While still being unsure whether to treat this if it's an ethanol or pump gas / 98RON setup - did the tuner mention knock being an issue?

Well shoot. Thanks! My walls of text may get a bit less painful now

Haha the numbering thing is making things a lot easier to follow - I miss the days when it was easy to just quote selective bits of a post to make context easier to follow. 1) Ok interesting, I'm used to seeing stock plenum setups fall over earlier. Not going to question it if its stock, though you can run aftermarket plenums with stock throttle body fine. I wasn't saying it NEEDED to happen, there is definitely a sacrifice down low if you go a FFP and I'm at this stage definitely not saying its a thing you need here - just breaking down all the bits of what is going on as often there isn't "just one thing" if you're not getting the power curve you were expecting. 2) MAP is absolute pressure, so strictly speaking yes - 18psi + ambient pressure, so 32-33psi area absolute or ~18psi boost/gauge pressure to redline is what you're looking for. 3) Be interesting to know whatever further data you can get from logs but it DOES sound like you guys have been pretty thorough with boost leak testing 4) I would expect better spool than what is coming across on that dyno plot, from memory we saw around 300rwkw on a hub dyno with the .83 IWG on stock exhaust manifold, freddy FFP, BP98 RB25 on a Dynapack hub dyno. What fuel are you running, and is it a Mainline rolling road you're being tuned on? If so, that probably translates to about 260-270rwkw, and we WERE initially stuck at around 260kw when we had wastegate control problems (flapper being blown open). 5) I probably asked a redundant question here, sorry... I missed the point where you said there was no significant pressure drop across the TB. If that is the case at max rpm then this is very unlikely an area to be worrying about. In regards to the bonus round questions, we initially tried to be clever and fit a two port actuator with lower base pressure to the EFR and that didn't seem to be "enough" - I guess in hindsight the fact that we were still using a 3port solenoid and the fact it was clearly mostly back pressure causing the issue this was not the way. The problem was solved in that situation by just going to a much stiffer spring/actuator. In terms of what I'd have suggested, can you confirm the fuel and dyno (rolling road?) that you're using? And this is for 280-300kw with nice driveability?

Sorry, got no notification of the mention and just happened to stroll in for a nosy around while having lunch - will be brief (for me :D) because I don't have heaps of time right now but reading through all the comments, I'll address things I haven't noticed specifically mentioned yet: 1) This won't in itself cause enough of a problem to "be the problem" but it's worth mentioning that I'm *pretty sure* that the 3076 dyno plot in the comparison will not be running a factory plenum. I think people forget or don't even realise how much of a different the typical GReddy-esque plenum makes on power delivery and the resulting power-per-psi you can make. Stock plenum falls over much earlier in my experience. 2) Can we confirm that it is DEFINITELY holding a full 18psi to redline? There is mention of WGDC increasing to maintain it, but how often I see comments that something is tuned for xpsi and the curve actually drops off towards the end. I've had experience with an EFR7064 and they work decent enough on an RB25, not the "best" at all these days but you should definitely be able to get a better result than this. The one I was involved with ran a .83a/r open T3 IWG setup and took a lot of pissing around to stop the flapper blowing open, which depending on what the boost curve is doing could cover some of the WGDC going to the moon. The EMAP may not even be THAT bad, just the BW actuator setup doesn't necessarily play nice. Even dropping a couple of psi as the rpm increase could really put a damper on the curve. 3) In terms of using "it's not at max rpm" to confirm its not got a boost leak or anything like that, not necessarily a rock solid method with a 7064 which is more of a "I want high pressure ratios" turbo. At a PR ~2.2-2.3 (for 18psi at sealevel) we're looking at 120,000rpm *MAX* if you're staying within the happy-enough working area of the compressor. I treat anything <60% compressor efficiency as a point where the efficiency of everything starts becoming noticeably worse, EMAP starts ramping up more aggressively etc. If you were at 130,000rpm for sake of argument, and assuming you're in a pretty happy place because 153,000rpm is meant to be the "speed limit" then unfortunately it's a trap a lot of people have fallen into with EFRs. This combo SHOULDN'T be off the map there, at least that badly, so if you are 120,000+rpm then I'd not rule out pressure testing the boost system. Probably still wouldn't hurt if it hasn't been done. 4) In terms of your turbine wheel observation @Kinkstaah - it's a trap. The Borg wheel aero make them not comparable size vs size with Garrett ones, the EFR7064 turbine wheel flows a fair bit worse than a GT30 imho/experience. Also spools better, though. Which brings me to another observation, the dyno plot looks laggier than the T3 .83 EFR7064 a mate has on his RB25 which could be a hint. Maybe. 5) I'm not assuming your tuner (or anyone else) is useless - their investigation and frankness actually is pretty encouraging but I always feel obliged to mention *ANY* thought I have as its always worth ruling everything out. Are you 100% sure the e-throttle is physically at max WOT? This doesn't look outrageously unlike a part throttle "turbo" dyno pull, both in shape of the curve and also the data you're reporting back. Plenty of people who aren't the dumbest have missed things like this (like me) and it can be worth ruling stuff like this out when there are no other clear smoking guns. I gotta scuttle off now, but those are some "obvious" things that jumped into my head that I haven't seen mention of.

Yeah makes sense to a degree, like you have a "strong" 3.2litre engine anyway. As soon as it starts getting any boost the displacement advantage gets compounded and you start picking up speed (and with that, rpm) quicker than the poor beggers with 2.6s and even 2.8s. As soon as you get it up and cooking its going to be insane, but its only going to be useful in races you're allow to get up on launch control or at least involve very illegal speeds on the road but you were already there with the 76mm.

I was reading through the post and the comments and was basically going to say something along these lines - feels like you answered your own question really I haven't had direct experience with the exact kind of setup you are talking about here, but my observations and involvement with things of this level basically surmounts to - once you are talking about 80mm+ turbos on "small" engines the lag etc all becomes a bit academic. You are going to NEED launch/rolling start antilag, you're going to need to rev the hell out of it and a fast shifting trans with shift cuts are ideal if you want to keep progress happening well. At this point if you want more power and you have an option, the only thing to think hard about is "Do I have the trans, fuel system, and engine spec to ensure I can use the upper end of this turbo?". If you don't, then probably a waste of time... the extra lag without being able to get the treats is pointless. If you can use pretty much all it has to give, may as well.

So I have very little experience with restrictors so like always, just sharing my thoughts. The only car I have tuned with a restrictor was years ago, and had a standard Mitsi TD05 in it and the owner was on a tight budget so the approach I took with tuning the whole thing was "to finish first you must first finish" and kept the boost curve "within" where the turbo seemed to be working safe... enough. So before I get into the strategy I'd consider doing with such a thing ( @Full-Race Geoff / @GTSBoy / @discopotato03/ usualy suspects - I am not 100% confident on this stuff so welcoming input or corrections here) is the way I understand things a compressor map is a CORRECTED airflow chart. It assumes ambient temperature and pressure at the compressor inlet is "standard" near sea level, mild day kind of stuff. As you get closer to the max flow of an orifice the down stream pressure drops, which means the "actual" air density upstream of the compressor is miles off standard and I think that if I'm right there then it's very important to not overlook the effects of this, especially if you aren't logging turbine speed etc. If you are running say 5psi BELOW ambient pressure at the compressor inlet then the air density will be much lower than what the compressor map states and the *actual* airmass moved will not be what you see on the compressor map. You may need to exist at a point >50lb/min "corrected" flow in order to achieve ~36lb/min *actual* mass flow. I'd think of it that a compressor map really is a volumetric flow map that as an afterthought is converted to mass flow assuming that your turbo is feeding on sealevel air pressure at ~20c or thereabouts. I'm not saying that going for 50-60lb/min turbo will fix this issue as the more "actual" mass flow you try and move the higher the depression after the restrictor and the whole situation will just keep getting worse, but I think it's very important to bare this in mind if you are turbo matching as well - imho if you want to map a turbo that is going to be able to achieve near 36lb/min *actual* mass flow then you should probably size it for more like 50lb/min or more if you CAN if you want to run it without overspeeding the hell out of it. Regardless of how you go about sizing it, if you are able to measure the depression after the restrictor - or wheel speed, then you can at least make smart decisions about how to do your boost curve. I would target the boost curve to stay comfortably under where it's going to start spiralling out of control as realistically when the "depression" starts really kicking into effect what will happen is the harder you push the turbo the worse the depression will get, the EASIER (weird, right?) it may become to spin the turbine faster and the sooner you're likely to explode a turbo. If the engine etc are strong enough I would 100% send it as hard and safely as possible through the middle, you get the added advantage there that mechnical loss is less at lower rpm so more power for the same mass flow. *HARD* on the engine, but if you have a narrow power curve then that's the way. I'd definitely bleed it back at the higher rpm "in anticipation" of the pre-compressor depression ramping up. If you had a way of getting a gauge on that I'd be tempted to decide what you think is acceptable and tuning it to not exceed that. Just my 2c.

I like all this. The thing that killed my ability to resist responding was the mention of modded S58s 💦 God they're good.