Lithium

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.

I would never have bought or recommended an EFR9280 for this kind of power level (helped by the fact I've seen less impressive results from them), there is not much info on exactly how hard this one is being pushed, but I still feel like this result is worth knowing about if you hadn't already given GameOn aren't unheard of or anything. EFR9280 on a VVTi 2JZGTE making 1130hp @ hubs with respectable spool is a solid result no matter how you cut it https://fb.watch/gA5azNc8fg/

A screen shot of boost / rpm log showing where target boost is hit would probably be pretty meaningful, I've already posted dyno plots of these things pushing 800+hp to the hubs on a 3litre - the flow potential of them shouldn't really be in question at this stage, but how it comes on with an RB28 would be pretty good data to see. There is always talk about how good these come up between gears etc, but not that much data for people and I can fully see why people develop an attitude that the enthusiasm for these turbos are just fanboism, as opposed to earned respect for being that good.

Nice, actually really interested to see how the .85 divided setup goes - please post results when it's done The 9174 will be interesting as well but better suited to a 1.05a/r hotside.

Yeah. I wouldn't assume that the 6470 is kinda a smaller 6870, class legal turbos are designed with max flow for inducer size possible - which does not at all promise to maintain the response you'd expect from the size (not to say that it won't work out ok anyway, just can't promise). Fwiw most 67mm class turbos are pretty laggy but make mental power for their size, and I fully expect the 6470 will be crazy power for a 64mm - it wouldn't shock me at all if they behave like a turbo at least as big as a 6870.

Sorry taken me some time to respond, been super busy lately - but public holiday today so have a moment to yarn about turbos. So this will be on Racepace dyno, which is a roller dyno? Assuming the things which have been assumed so far, these are my suggestions: 1) If you're in a rush and trying to spend as little as possible, I've seen 500+kw result results on Oz based Mainline hub dynos for G30 900s but that's squeezing the lemon pretty hard, feels like the G35 900 copy (PSR 6262G) would have to be the go if you're going the Pulsar direction. I'd go the .83a/r hotside option, really not sure if or how much the 25DE Neo head will be a problem... pound for pound your results so far suggest that it'll be up for 500kw with that G-series turbine/compressor combo will do with more boost going through them but really depends on what magical fluid dynamic stuff which may be beyond me might happen when you start trying to push more gas through the smaller ports. I wouldn't bother with the divided housing change as that involves a bunch of reworking, and if you're trying to save time and not spend money to "do it right" then it's not worth investing in all new manifolds and fabrication - if you're going down that path then you should be doing : 2) The "right way" would be a 1.05a/r T4 divided EFR8474. It'd be glorious for a setup like this IF the head didn't become a limitation.

It wouldn't really be a valid test, my statements assume someone is running a native twin scroll housing. Any observations I (and pretty much anyone else here) offer relating to EFRs assume twin scroll housings. Any data for them and suggestions relating to them apply to the housings they come with. For it to be realistic it'd have to be a typical G35 setup and typical EFR setup, matched appropriately for the car they're going to be running on.

800-850 is a pretty big step up from where you are, imho you'd need to go up an exhaust housing size (or two) to support the extra power - especially on a 600cc larger donk. That's going to take a lot of steam out of the response, and while it's not going to be rubbish still... it imho will shift it outside of EFR league (well, further outside of). So I wasn't saying it's rubbish or not a valid option, just when we're talking about an EFR8474 then imho it's definitely a step backwards. That's because EVERYTHING is a step backwards, nothing against the G35.

This is on E85. I know I've said this before but I have more data to back it up now, I think the Borg Warner turbines have been given less credit than they are due in terms of how well they flow because of the previous generation(s) lacking a bit compared to their competition in terms of compressor flow, especially with how the compressor maps looked for some of the EFR range. The fact that Borg Warner have now released an EFR8370 is evidence of this, in my head. I had a 2.3litre Mitsi hillclimb beasty recently on the dyno with an S257SXE running the 1.15a/r divided hotside on the dyno recently which had EMAP logging and with 1.8bar of boost in it the thing it still hadn't reached 1:1 EMAP/IMAP at max rpm at 390awkw / 520whp. It would only be where it starts running out of compressor where the EMAP goes seriously south. I feel the typical EFR range usually ran into EMAP (and turbine failure) issues because of people trying to drag flow out of compressors which really weren't the best for their size.

Actually. Here's some data, this is from a 3litre 2JZ with a VVTi head running a 1.05a/r EFR8474. Looks like I've not posted this before. This is 830hp @ hubs at 25psi, 111,000rpm turbine speed, 39psi EMAP... so safe wheel speed but EMAP is getting up there, which is why I'd push for the 1.45a/r hotside:

Again the 9180 and 8474 will both get you to the 800hp @ hubs area. Going to Precision or Garrett will definitely be a step backwards in response, if you're wanting to go north of 850hp but not too much then the 9280 is OK with the 1.05 but I was partly addressing situations where you're more looking for a healthy 900+hp. In the Garrett range you'll be needing to look at a .95a/r G40 1150 btw, which will be laggy than the EFRs - but will do the power quite happily.

Unfortunately as per the compressor efficiency stuff I was rambling about above, extra cubes and headwork with a 9180 are a liability - not an advantage. The compressor doesn't really do it's best work until higher boost levels, boost levels that with a saucy 3.2 you need a lot more flow than the 9180 will provide. At the boost levels that a well flowing 3.2 will be happiest moving "900hp" levels of airflow are not where a 9180 is really doing it's best work. A 9280 would definitely let a 3.2 "hang on" better in the higher rpm, but they are a little lazier and the 1.05 hotside is a bit of a restriction - but it definitely makes a bit more sense. My general view on the EFR range is that if a 8474/9180 is too far short of someones target then it's time to consider going to something from Precision or Garrett.

Yeah, this is what I was getting at above. Realistically BOTH turbos will be on their upper end of capability at this power level, but if OP is happy with "getting over 800whp" then I actually am going to go against the grain and say I still think the 8474 is the better option. The trick with the "pre-black edition" Borg Warner turbos is the 8374 and 9180 compressors let the side down and made it seem like the turbines were more restrictive than they are. The turbine from the EFR8374 had heaps up it's sleeve but people would often see high EMAP because of the compressor going inefficient and the boost control setup effectively going into "send" conditions. Same goes for the EFR9180, they are better suited to higher boost/lower flow. This is somewhat speculative because I don't have direct experience with the combo, buuuut if I were a betting man I'd back an EFR8474 with a 1.45a/r hotside to be the "best" for if you're looking for a "being able to nudge over 800hp @ hub with epic response" on a build like this. I wouldn't aim for 850hp, but you may be able to get it as a hero tune type thing.. it'd definitely be getting more on the sendy side though. To put the compressor efficiency into perspective, I've plotted where the 64% compressor efficiency (ie, the point where it's still happy as but where things usually start getting sad quickly afterwards) for 20psi, 22psi, 24psi, 26psi, 28psi and 30psi on an EFR8474 on the EFR9180 compressor map. Basically, the EFR8474 is still operating in the happy zone where a 9180 is getting quite into "shut the wastegate and cook the intake air" territory.

Overall sounds like a lot of fun

I love this discussion, brings out some interesting and valid points. I've never argued hard against people chosing to stay twins at 350kw as really the single benefits aren't going head and shoulders away from twins YET. I still prefer them, but the argument is less one sided. Now in regards to the high power vs control thing, this is really what got my attention in this discussion - we at the best of times get hard ons for showing and bragging about epic power delivery but the reality is often what matters SO MUCH with racing is making the car driveable, and reliable. A good number of the turbo race cars I've tuned we've done a lot of work in managing the torque to keep the cars predictable, and it can seem like you're just leaving stuff on the table for no use - but honestly its amazing the difference you can make giving what people may grumble and call a "peaky" power delivery. No point making it hit like a train if you are going to be all over the show trying to keep the car on the road. An option you have with the likes of your 6466 that you don't with the twins is you can more or less tune the 6466 to do stuff that makes the twins good, but you can't do the other way around. As a hypothetical thing, if you look at the dyno plot for the twins - which you know you can control the car with nicely then identify the peak torque you make with them, then select a boost curve with the 6466 that never exceeds that torque.... but ramp the boost up to carry the torque to the far end of the dyno plot, instead of letting it plummet like the twins do then you potentially have some degree of having your cake and eating it too. Well maybe a 6466 is a bit more snappy/laggy transient wise than the EFRs/G-series that I've played with but you'll get the gist of the what I'm saying? I've done this kind of thing with numerous FWD/RWD/even 4WD race cars when creeping up in power levels where the owners have decided to try the suggestion as an "in between" while working up with a bigger setup and then ended up finding that it actually at least in those cases made the car easier to drive faster and is generally less hard on the car on the driver and been relatively happy leaving it there. It may seem counter intuitive when we work so hard on finding ways to improve torque, but really in a lot of cases the "how hard is it to get to the torque I'm looking for" is a lot more important than "how much torque can I make?" when you're trying to go fast.

What are your power goals? A mate has an RB30 with the 9180 and a 1.05 hotside, it's nice and responsive but the down side to the 9180 is that it does its best at higher boost levels (compressor wise) while a 3.2 with a decent head will find it easy to run off the map. The 3litre works very nicely but a 3.2 would arguably be pushing it, the bigger 1.45a/r exhaust housing being a bandaid which doesn't fix the actual cause. An EFR8474 compressor is actually more efficient in the 20psi range than the 9180, and the turbine wheel is surprisingly up to the task at that level. I'd consider going 1.45a/r if you have a big head and want to make the most if you consider the 8474 but if you are mainly looking for a super responsive solid power level the 1.05 is likely to work better than many may expect. Tl;Dr both are solid options - if you want significantly more than a 8474 can do then the EFR9280 is a more tangible improvement than the 9180 is, but the 9280 definitely comes at a cost in boost threshold. On a 3.2 with a 1.05 you won't see solid solid boost until in the 4000rpm range but they can support a fair bit of power... But you DO need the 1.45 hotside to make the most of a 9280 and they start becoming a pretty laggy setup, I feel like other brands offer better options for that territory.

That's pretty cool to read! Good on them for making improvements and not making a song and dance about it or offering it as an upgrade, instead just improving the existing thing.

Faster to take off and put on, slower to spool. Pick your preference - though I get the impression cost and spool not being a top priority came into this which makes sense.