Lithium

Again be interested in hearing your thoughts, be the first person I know who has gone from a G-series to an EFR or vice versa. I hardly follow Racepace as they seem to hold back info, sometimes showing a dyno plot but not sharing spec - or vice versa, and thats the main interesting stuff . For some reason they never posted the dyno plot for an RB28/VCam/G35-900 setup they did so I'm not assuming they'll share the G30 one either.

The absolute worst case scenario is you can cash in on the advantages of having a compact turbo with vband stuff and swap without needing to change anything else if it is a problem. Shouldn't be though

To be fair I'd be surprised if the G30 would have been any spicier from low rpm than the 8374, and I guess it all takes time - but good tuning/boost control should ensure that you don't have too much being dumped at the tyres at once. I think with RWD cars use for corners people get a bit too carried away with trying to make turbos run all the boost they can from low rpm just because they can, nothing wrong with keeping the good response but holding it back from making more than is driveable in the lower revs. Like I just say that for discussions sake, I'm not expecting the G35 to be a nugget - but I do suspect it's going to be noticeably less snappy with all else being equal. Be cool if I'm wrong though, or at the very least its at the level where it works nicely for what you're doing Looking forward to results as data is way more fun than speculation haha

Will be interesting to see how it goes, look forward to results - shame the EFRs are so bulky/tricky to swap in that case but it is a thing, as you say you're likely taking a performance hit to make it more serviceable buuuuuut realistically with VCam and 2.8litre when you're keeping it on steam (and you have a sequential now?) I doubt it's going to be an issue. A 2JZ I play with has a G35 900 on and from what I've seen so it behaves quite a bit like EFR9180s that I've also been around on 3litre 6s spool/response wise, obviously not quite the same level of flow (But on the other hand, definitely more potential than the 8374) but you're not trying to make that power so the response is the main thing. EFR9180s are pretty proven on static cam RB28 track cars, so with VCam I'm sure it'll be fine. Would have been interesting to see a G30 900 with a bigger housing on it if you were aiming for low 400kw, but the G35 feels like a safer bet

That depends on how hori the ECU or tuning is. Depending on the car I usually use both timing retard and fuel cut to manage the launch control as I tend to get quite OCD with the control range of the launch setup, and also try and ensure it ACTUALLY does what you need from a launch control - such as spool the turbo. A lot of 90s/2000s launch control (and to be fair you still hear this used) did "100% cut" which basically meant all injection events were stopped until the engine speed fell under the target threshold, which is a bit self defeating as when those injection events stop so does the fuel which provides the energy you are meant to be using to spool the turbo. With a decent ECU the "fuel cut" doesn't cut every injection cycle, it just cuts a % of the injection events based off the rules set - so even during a full engine cycle where the is limiting happening there will often be at least 1 fuel injection event, so the retarded timing will be applied to that event. The reason for doing both is the retarded timing both means the engine makes less torque meaning you need to cut less injection events to not overshoot the target rpm, which means more fuel going through the exhaust, and also with the retarded timing less of the fuel's energy has been used driving the piston and is instead available for helping the spoolyboi. So yeah, that's the point of retarded timing if it's fuel cut - at least with a decent ECU

Motive DVD share a lot of good info, and try their best to interpret and explain data well but there are plenty of times out there where the same data can look different depending on what you know and what you are looking for. Truth of the matter is here.... This. There is no "RBs like big rears". RBs don't have a clue what is attached to their exhaust side, from the turbo's perspective its the dynamic of how fast the compressor needs to spin to pump the required air, intake manifold pressure required to achieve that and how efficient the compressor is at that point, and well the turbine/housing combo works at that point. Sometimes you need to go a bigger a/r to achieve what you're doing, whether it be that the whole setup works best there or sometimes just if you are pushing the turbo to the absolute limits and don't want to upgrade the rotating mass so going to a bigger a/r is a bandaid which is what imho has happened in a few situations that are used as evidence that "RBs like a big rear". I'm pretty confident that with everything else being equal that an EFR8474 with 1.05 hotside would be all around equal or better running at 520kw than the RB28 with the EFR8374 and 1.45a/r hotside in the example above. If the compressor is being more efficient to move a given airmass than a different compressor on the same turbine without making the turbine work any harder to the work then the wastegate will end up not having to close as much to keep driving an out-of-it's-depth compressor to do something to the edge of it's limits. It can take a pretty significant turbine wheel/housing upgrade to match the effects of boost control creating an exhaust leak that is required to hold back the compressor from pumping more air than is needed when comparing with something that probably effectively has the gate shut to achieve what it's doing. To throw a bit of data into it, here's a 1.05 EFR8474 on a big cam 3litre being revved to 8000rpm on ethanol. The car made over 600kw (/800hp) on this run, around 87lb/min of airflow which is WAY past what an EFR8374 can support - so while 39psi EMAP is getting up there a bit in this case (which is why it was stopped here).... the thing would be barely working up a sweat at 520kw on an RB28.

This isn't to beat a dead horse or have a go or anything, just basically adding a +1 to the other comments about internal wastegates on "big turbo" RBs and add some further reason to it so it doesn't feel like you've just hit a trigger point that people are going to hate on because it's trendy to. For what it's worth, I've not yet seen a situation where someone has gone that way initially and not ended up regretting it, and potentially changing at significant expense. The stuff you see in regards to the design itself is perfectly right, aerodynamically the Borg Warner internal wastegate setup is very nice - no issues with boost creep and they also don't appear to negatively impact turbine efficiency. If you can keep the gate closed when it needs to be then you won't have issues with performance, and when target boost is achieved the wastegate path allows the drive pressure to be managed nicely. Borg Warner are not being misleading about this at all, in my opinion. The issue however is the actual control of the gate flapper itself. The significance of exhaust pressure on boost control is often massively underestimated, when you see wg spring pressures that really effectively is making a big assumption about what exhaust manifold pressure will be doing at that point and how whatever drive pressure management being used actually responds. Flapper style wastegates seem only too keen to crack open a little bit under any amount of pressure which can immediately start reducing the effectiveness of the turbine, and it only gets worse as exhaust pressure increases. A stiffer wastegate actuator can HELP, and often the solution seems to be using a stiff enough spring to be able to achieve the "high boost" target pretty much by itself - and then additional electronic boost control input to maintain the target boost. Basically the result OFTEN (but not always) seems to end up being pretty poor flexibility in terms of boost control, and often a lot of messing around to get what would often be seen as the bare minimum with an external wastegate setup. I would argue that if there was a good electronic wastegate actuator option (so it can keep the gate properly shut until it's meant to be open) that was compatible with the EFR IWG range then a lot of the criticism would be completely negated, buuuut a .92 IWG housing is still probably on the smaller side for a RB30 unless you're going with an 80-series turbine wheel. That's at least my limited experience and opinion on the situation, there could be other things I've not seen or considered.

So this is kinda relevant to this conversation, someone else have mentioned non-Garrett options so I feel like its not MILES from being appropriate to mention anyway as this suits the turbo matching concept and also possibly offers a housing option if you go genuine Garrett G35 900 core. A mate with a GT-R which was running twin -5s on an RB26 with Kelford 272s had one of the turbos fail recently and it was going to be annoyingly hard work to replace when he already was aspiring to put an RB28 in it and go single turbo at some point, probably the likes of an EFR8474 when the budget allows but he was not ready to take it off the road. Some big yarns were had about what would be the most rewarding way to get it running now but also not result in too much back tracking in the future. The target was be at least as good as the -5s, fairly typical low mount twin setup with just over 500whp on 98 and full boost in the late 4000rpm range. After much discussion around things like G30s, going straight to EFRs etc the budget right now wasn't suiting so partly to get it going sooner but also just to try something different he went with a Pulsar G35-900 copy with a .85a/r divided T4 housing. Hoping it will be going in a couple of months or so with the divided housing, I can report on how that goes but I do realise people view the Pulsars as not at all a comparison with Garretts and the T4 hotside isn't even an option from Garrett, but I mention it partly because Pulsar *do* do a .85a/r T4 divided hotside which in theory should suit a G35, genuine or copy. The Pulsar will at least be on there to get it running until an EFR/RB28 build can be sourced and delivered - though if the Pulsar performs too good it may stay in there longer haha.

Oh wow! Sorry, a bit sleep deprived today and I had started rewriting some of my original post and got sidetracked and managed to turn it from being hard to read into complete nonsense. The intention was to delete everything but the last sentence because I decided I was going too off topic, but seeing as I screwed up... the two points that paragraph was meant to convey and got garbled: 1) I know people pushing 10+ yo BMWs with mostly stock hardware hard enough to run 130+mph traps without issue 2) When our Skylines were that kind of age we thought nothing of replacing the equivalent kind of stuff to keep them happy, and make them go quicker. Ignition stuff, oil control, fuel bits, boost leaks. All par for course when playing with "special" cars - BMWs just have more sensors and flash more lights than the Skylines did when something isn't working, but helps you know something is up instead of eventually running a bearing, blowing a turbo or generally having a subpar performing setup and tends to not be a biggy if you deal with the things that need to be dealt with properly. Anyway, sorry - I had MEANT to make it a far more concise and less off topic post but fumbled it.

So far I've not seen any reports from people I'd call "neutral" buuuuut I'm obviously open to finding out if they are something I should be more apprehensive about sticking up for. I have nothing to gain personally, not a dealer or anything - like yourself just like trying to give people "what I know" to try and help them be best equipped to make the right calls... the whole "are you ok with buying a copycat" is a different ethical decision best made by the buyer.

Lol funny, I was thinking when reading through this I thought about a couple of mates BMWs when reading the "funny how a 9 year old Euro car is considered old" when I've got mates pushing late 2000s (over 12 years old ) BMWs with stock almost everything harder than we'd typically not even think anything of having to replace a heap of stuff on our Skylines to be able to achieve when they were the same age. I've got a BMW around that age and it is still farrrrr from a horrid car, best thing I've owned in every way aside from fuel consumption haha. It's 1.5l/100k worse than my old Honda Jazz in equivalent driving conditions, but otherwise that too.

Are there any good examples of this in terms of media we can see? I've seen a couple of "just happen to be Garrett dealers/sponsored by Garrett dealer" people make these claims but so far have been involved in a pretty solid amount of Pulsar turbo based builds without seeing this issue. The only issues I have seen have been regarding needing to make sure things are done up properly, ie - not assuming vbands are done up, or turbo speed sensor plug screwed in properly etc. Have heard of 3rd party folks who are doing mix-and-match sells of Pulsars selling them with the wrong housing, ie GT35 turbine housing with GT30 turbine but that's not a build quality thing and could just as easily happen with the same people selling legit Garrett bits.

Yeah for sure, I figured seeing as you were on that track I might throw this in just in case you hadn't seen it - be nice if it all wraps up as being this kind of thing. Fingers crossed for you either way as it seems like a kient of an issue.

Just throwing this in here in case... fwiw, never run into issues with one of these kits though apparently some people have with G4x setups, but G4x aren't the most well behaved of ECUs at times regardless of what is trying to talk to them

Truth be told I've got all the parts but not everything is sorted yet, it's Christmas project stuff so I can't give a full review at this stage BUT I've got the MHD dongle and everything inc. XHP license purchased. I'm impressed with the trans even with the stock tune so pretty excited to see what it's like with the XHP tweaks, from what I've seen it'll be pretty key to making it "work" as well as it can well combined with the "Stage 2" (groan) level of mods and tune it'll have if I take it out for a sneaky 1/4 mile run. Is your E90 the N54 or N55 version?

Been a long while since I've owned something that seems at all related to Skylines, but my latest car kinda has aspects which feel make it related to my old R33 GTS25t - is an F20 BMW M135i: He runs the 3litre single turbo N55 engine, if you are a BMW propeller head it's the later model version of this engine with the larger electronic wastegated turbo (which brings it up to par with the old twin turbo N54 engines in terms of stock turbo flow potential) and suchforth. In stock form these guys are meant to develop 450nm of torque from 1300rpm, and a conservatively rated 240kw peak power. Mods for now are a Wagnar tuning dump pipe, Masata hard piping and CTS intake and retuned stock ECU (and not pops and bangs 🤮) which while don't make a huge amount of power, when combined with the complete lack of lag (turbo is pretty similar in spec to an EFR6758, which is a tad mental when combined with a high compression 3litre spinny cam 6cylinder and twin scroll :D) and the ZF8 8-speed gearbox real world wise it's a significantly quicker car than my old GT30R equipped R33. Aside from the nice handling, all the nice modern car comfort things its also pretty sweet being able to get sub 7l/100k fuel consumption on road trips where the roads are hilly and windy etc when combined with being pretty sporty. I'm somewhat surprised these things aren't more popular!

That's a fantastic result mate, nice work and cheers for sharing. The Gen2 3582 has often been well underestimated in terms of it's ability (and effective size), but that's probably gonna be on kill haha. What are you hoping to see with the G35 vs this?

All good, I used to overexplain everything - now I'll just assume people know or will ask if they are interested EMAP is the exhaust manifold pressure, basically. When trying to make an engine efficient one of the best things to do is make a good pressure ratio across it, or in other words - make the exhaust pressure as low as possible compared to the intake (/ boost) pressure. The reason for this is that fluids (in this context, gas...) want to even out pressure. If you have higher exhaust manifold pressure than intake manifold pressure it actually starts becoming harder work for the engine to keep drawing air in and pushing exhaust out. "1:1" is basically what naturally aspirated cars run at, and for all intents and purposes the engine is "not restricted" due the turbo and instead is operating more like it just has super dense air with minimal cost. When you start going to the bad side of that 1:1 ratio the exhaust from the last combustion cycle starts getting significantly less reluctant to get pushed out of the engine and instead kind of hangs out and reduces the amount of left over space in the cylinder for the next bunch of new fresh air. This directly affects volumetric efficiency, exacerbated by the fact that the left over exhaust gas is also hot and going to generally make things less nice and less efficient in the cylinder. The reason that your wastegate duty cycle needs to start going up is that it's not JUST boost that affects the wastegate, exhaust manifold back pressure also works against the wastegate valve - so when it starts getting higher than the boost pressure you start seeing that you have to increase wastegate duty to offset the effect of that as well. Basically, OVERLY simplified (it's not quite this simple) if exhaust back pressure never exceeds boost pressure then you'll typically see a fairly flat wgdc to get a flat boost curve. So if you're needing 25% duty to hold 20psi of boost from 4000rpm to 8000rpm then the turbo is probably operating in a fairly happy place. If you are running 25% duty from 4000-5500 to hold 20psi for boost, but then from 5500 to 8000rpm it creeps up to 35% while you aren't actually seeing any more boost then there is "something" making it need to do that, and often it will be the increasing exhaust back pressure trying to force the wastegate open from the exhaust side. If it's pushing the gate open that effectively, it's ALSO going to be working against the engine during it's exhaust cycle - so effectively the mechanical efficiency of the engine starts taking a bit of a hit, as with volumetric efficiency due to more exhaust gas hanging around in the cylinders. Hope that kinda makes sense.

Strictly speaking it can't, or shouldn't be. The assumption is that most sensible people keep things within parameters, we expect tuners to not keep advancing timing past the point knock starts happening even if there are gains to be had because you obviously start making things degrade a LOT faster. We let engines warm up properly before thrashing them. We run appropriate oil and change it before it loses it's usefulness. We don't overspeed turbos. You also massively overstate the fragility of EFRs. It is farrrrr from a case of "pass the max compressor speed limit and they explode" like some people try to paint the situation as being. The thing I *do* strongly agree with what you said, and have been sorta expecting to get clarified at some point - the actual power goals and therefore the match required is a pretty critical thing that needs to enter this convo before it really gets too much further. I threw the EFR8474 down there as the OP mentioned response and it is kinda a "cake and eat it too" option when discussing something like an RB28 for happy street use. It'll be a nice super responsive turbo on an RB28 if you "only" want 400kw, but will also go past 600kw @ hubs on E85 while still being well safe from running the risk of grenading if you wanted to go there. The response and flow is good enough that if you want anywhere from 400-600kw then it will do so without any excessive lag or strain, so you're unlikely to end up with regrets going for one. If you aren't building a roll-race or drag car then it'd be pretty hard to make a case for another turbo unless it's a fitment or budget concern driving the decision making - but that is still making some assumptions on what OP wants. Be nice to have clarification.

Lol I actually am here nor there about you tbh, if anything my understanding is you have a huge issue with me for some reason and that'd be the main reason I'd be less cordial with you. That aside I'm not sure why you're taking it personally when I simply responded to you after you quoted me - I *always* try my best to keep in mind what OP is looking for even if it doesn't align with my personal tastes, so my response would have been more or less the same regardless of who said it. And I'd also not have had a cry if someone said the exact same thing to me as it seems perfectly reasonable.

Just to remind you the key requirement of the thread: I am building a Street Car (Not a Race car) and will be using mostly RON98 But will be E85 compatible. I want Response more than Top End.

It's not really that simple, and again it's making a comparison of things that don't exist. Often with aero there is a compromise, where you get more flow from a given size you sometimes need more speed before it starts working well - a smaller wheel that flows more can end up being less responsive. Defining aero as only being good if it makes more power for a size is a very drag racing view of the world, aero which starts pumping effectively quickly for a given size is also a thing. The Precisions are fairly lazy for their wheel sizes as well, before you even bring Ti-AL into it. The Ti clearly helps transient a huge amount and is part of the package, but it's not the only thing that is making the combination work. Either way, the reality is that a 8474 smashes a 6266 in response and beats it in flow as well - so no need to speculate on what a thing that doesn't exist goes like because there is something that already exists that offers it all.

This is all accurate, but kinda leaves out a critical part - unless you are racing in a class that has a wheel size limitation then the "given comparable compressor wheel sizes" thing is a completely pointless comparison, other than fitting class rules there's not tangible benefit to it. Power vs response EFRs shit all over Precision turbos, and that's what actually counts in real life.

On the topic of EMAP, while it's kinda anecdotal evidence to a degree - the boost curve if you're purely gate controlled, or the wastegate duty curve to maintain a fixed boost level using electronic boost control can totally paint a bit of a picture of what EMAP is doing. If your WGDC is pretty flat to achieve flat boost then it's typically fairly good sign EMAP is pretty kosher, if you start needing more WGDC (like 25% at 4500 then 30+ at 6500) then it's a safe bet that you're walking to the dark side of 1:1 EMAP/boost

GENERALLY speaking, if you are just looking for more midrange with the same peak power then you're unlikely to actually end up pushing the turbo any harder. Mechanical efficiency (how much power you make vs air/fuel consumption) drops as rpm increases, so it's theoretically possible to make more power at earlier rpm with the same air flow. Basically the turbo will be working *less* to make a bit more torque in the middle than it would be to make your peak power at the top end. G30 660 keeps close to it's peak flow capacity to boost levels well beyond what you'll run on an RB25 on P98, so if you aren't aiming for a higher peak number then I feel fairly confident that your turbo won't be the limitation for filling out the torque curve past boost threshold - it will be how hard you are willing to lean on the engine with that fuel. I don't see any benefit going to the G30 770, its the same hotside. It sounds like you've fallen on a pretty good "goldilocks zone" of what works for you... I wouldn't change unless you had a strong reason to.