Lithium
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Posts posted by Lithium
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On 08/10/2024 at 1:29 PM, Predator1 said:
Id be super keen to understand more about the GXR42-68 and GXR45-67.. Especially how it compares to the EFR9180.. Obviously I understand the spool and response wont be the same, but be keen to see how much of a hit it will take!
Also, the 4 seem to have a max tip speed of 109k..unless I misread something???
The GX-R turbos are mostly more about classes than outright response vs power, which is why there are 64, 67/68 and 73mm versions. They are an improvement over the existing inducer options at least flow wise but given they're G42 and G45 turbine options they will be a LOT laggier than the EFR9180.
109krpm isn't tip speed, thats rpm - the reason the rpm is lower than the likes of the 9180 is because the tips are further from the centre, meaning tip speed will probably be HIGHER than the EFR9180 at it's max suggested speed.If I had something like your car and the things you sound like you're into I'd probably be most interested with the Xona Rotor XRE7169S, it'll have a response hit on the EFR9180 but you won't get a more responsive turbo than it that's capable of >1000hp.
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15 hours ago, Komdotkom said:
What does everyone think about PSR vs Garrett? I've got a genuine G30-770 but would probably get away with a G35-900 because I've got a sequential.
Are the real ones worth more than double the price?
My opinion is they aren't worth double at all. Have used a good number of Pulsars with builds I've been involved with and tbh at least speaking for myself, Garrett aren't losing money they'd be getting if Pulsar didn't exist as for genuine Garrett money I'd probably be buying something other than Garrett.
We've used Pulsar 6262G (G35 900 equivalent) on an RB26 with a twin scroll hotside and it picked up 40wkw at the same boost over the old twin -5s and the improvement in transient response over the twins changed the car - this is before you factor in the amount of further headroom of the G35. Have also used one on a 2JZ drag car which has run 9.6 @ 141mph not even trying, from what we've seen so far it'll potentially go 8s when we turn it up
Crazy results for what is basically a NZ$1500ish turbo.
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On 23/06/2024 at 3:19 PM, BiZbAiRd said:
Not a lot of options with the G series when going to twin scroll. Garrett say not to worry about twin scroll?
I've never seen Garrett say not to worry about twin scroll - they have twin scroll options for all their G and GT series turbines from the 30 series up.
What kind of dyno are you expecting to be making 500whp on? So far it sounds more or less like you're doing a G30-770 kind of setup, and realistically an open housing will be good response etc -
A group of friends hired the local drag strip off season, cold weather and no prep means it was super slippery but still allowed for a fun day of 1/8th mile (no ambo meant we couldn't do side by side 1/4) roll racing and Dragy runs. The wee BMW didn't embarrass itself at all considering the 2WD group I was competing in had a couple of supercharged V8s (an LSA and a blown LS2), a 600kw M135i, a 500kw R32 GTS-t and some other spicy things - I actually ended up beating the blown LS2 & 600kw M135i heads up in roll races and faced the GTS-t in the final, losing by just over a carlength which is far more than I was counting on with a very mildly tinkered with M135i. For transparency sake this was EVERYTHING to do with being a fairly short distance on a shit track and having something without any lag and a brilliant gearbox, on a prepped track or a full 1/4 I'd have been destroyed.
I did do a single sneaky full (well actually turns out I hit the brakes 10 or so metres early) 1/4 mile Dragy run and hit 12.88 @ 109mph on the brakes which is precariously close to my PB in my old GT30R GTS25t that ran 12.6 @ 111mph on Hoosiers
Pretty damn stoked with that considering I had a single attempt, and despite seeming well suited to the conditions vs the higher power cars and the time slip not looking THAT bad I still was having to work hard to not just do a rolling burnout <100kph and doesn't really show it's best at all. I am pretty sure it would happily match the old R33 with a full run on a better surface
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On 29/04/2024 at 5:13 PM, Predator1 said:
Eyeing up the 9280, and wondered whether the OEM surge slots is the same as the T51R mod perhaps?
Has anyone done the T51R mod on their EFR, or even any other turbo?
Anyone do that locally in australia perhaps?
I've never had a T51R mod done on a turbo but can answer things to at least give you things to consider.
Firstly, I'm pretty sure "T51R mod" is not going to be a completely standard identical design. Different folks will make their own calls on how they want to make the sound, and different compressors and housings will give different amounts of space to work with as well - so the design and effect from company to company and turbo to turbo will be arbitrary.
In terms of "is it the same", no... it won't be, I'm pretty confident of that. Whether it will have a negative (or NOT negative for that matter) effect really would be foolish of any of us to speculate on without any data. Surge slots, or map width enchancement grooves basically bleed air from part way up the compressor out to the compressor inlet... effectively from the turbo's point of view it is an air leak that allows the turbo to be re-fed with the air that has been leaked. When done "right" it can allow air that the turbo can't pump into the engine efficiently to spill back into the intake as opposed to cause a surge condition.
Simply put, it has a direct effect on the efficiency of the compressor wheel. When you are getting up to the maximum capacity of the compressor wheel the design of the intake and compressor rely on every bit of area of the inducer etc to work as efficiently as possible, if you have something literally designed to cause a leak of turbulent air (to make the sound) back to the intake it's hard to imagine there won't be some cost to the higher end of the flow capacity but I wouldn't dare even try and guess if it were either major, or academic. Just bare in mind there will be an effect.
On the "upside", I'm assuming you are going to be running the 1.05a/r hotside you had on the EFR9180 as you mentioned you don't want to do any fabrication work, and the 1.45 hotside DOES need the dump pipe (and as such, possibly exhaust) shifted as it actually pushes the turbine outlet further from the CHRA... its a huge housing. I doubt you'll be able to safely push the 1.05a/r hotside on pump gas far enough for the 9280 compressor to actually start getting to the point you have to worry about sacrificing a bit of flow for sound.
As you know, I'm a big EFR fan where it suits - unlike some, I just go on merits and suitability for setups and there are a lot of cases they are unbeatable. In the case of where you're going though, I'm not convinced that line is the best thing for the job.
To do it right I'd either stay with what you have, as you're finding it's pretty hard to make the car more powerful than it is without sacrificing "something" - or do a "proper" upgrade to an all new beast that has the turbine flow to support what you are looking for, and arguably also has the T51R sound and vibe which I'm hardly going to throw stones at you for looking for... you'll remember that my turbo choice for my old R33 was absolutely influenced by the induction noise the GT3076Rs make haha.
Given the price of an EFR9280 and T51R mod, any work to get it installed and tuned to suit may turn out to give a result that makes you wonder if it was worth the effort - but if you're willing to spend that and not worried about massive gains, I'm pretty sure what you're proposing *will* give you some of that sound and probably stretch the power out a bit further in the rpm. I've so far not heard any unmodified EFR sound "whistly" like what I'm assuming you're looking for, though. -
12 hours ago, krysto_77 said:
t of topics on it
I found pistons with a CR 9.0 and 10.0 expensive IRP
what direction would be taken to achieve a ratio of 9.5 without having to plane the block by 2mm or to do it a minimum, but to be able to play with the thickness of the cylinder head gasketsthank you
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.
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4 minutes ago, Shyboy said:
Unfortunately not much info
was saying something about back pressure?? 4” exhaust
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.
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5 minutes ago, Shyboy said:
Not sure , this engine set up loves revving
The turbo hooked up to speed meter hope doesn’t over spin
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?
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6 hours ago, CowsWithGuns said:
Saga complete, coming back with a summary before bed
Installed the smallest kelford cams, replaced the turbo, added an NZ wiring trigger kit for good measure. No more problems, only good times.
Interesting bonus feedback from the tuner is the knock threshold has improved, and there is room for more power with more boost, but he advises against it due to the stock rods + reused bolts in my motor.
Cam centrelines at 125 and 114 per kelford's recommendations, no changes made on the dyno.
Car is fun as all hell, I'm traction limited in 1st and 2nd which is where most of my fun time is anyway. Major gains from 2000 rpm onwards, subjectively no change at 1500, significantly slower sub 1500. Probably due to the cams (?), but the improvement is violent at exactly 1500 so I think that's the currect VCT-on threshold and could be lowered. Regardless - car drive, car good, car fun
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.-
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9 hours ago, Predator1 said:
Obviously. Trying to figure out how much of a hit it will have on my response.
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.
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1 hour ago, Predator1 said:
I am still after response, but I want to see what kind of a hit it will take.. I want to take my car over to Japan soon.
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.
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19 hours ago, Predator1 said:
On the topic of the HKS GT III Turbo's....
What about GT75115_BB?
https://www.hks-power.co.jp/en/product/turbo/universal/index.html
Ive been having a look at this to replace my EFR9180 with. Theres a few cars that made 1250+hp with this on racegas:
https://www.hks-power.co.jp/product/turbo/universal/example.html
Anyone run this yet?? Especially on a 3.0 or 3.2 Perhaps?? Super interested..
Look for results on Garrett G42-1450s, basically the same thing.
What is your target power etc? Are you less worried about response now? -
On 15/02/2024 at 8:35 AM, Lithium said:
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.
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.-
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On 15/02/2024 at 8:35 AM, Lithium said:
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.
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.
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8 minutes ago, jdniss said:
I've heard several stories where 4-ports were ditched due to poor boost control resolution, both external gate and twin-port internal gate (including a number of tuners) - I bought one myself to replace a 3-port but never installed it.
Stephan Papadakis mentioned they use dual solenoids per wastegate on their Supra drift car as opposed to a single 4-port ~ around the 11min40 mark, should be timestamped: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.
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21 minutes ago, GTSBoy said:
Yeah, but Kinks has a 5.7L V8 in his R34.
Ahh gotcha
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On 16/02/2024 at 4:21 PM, GTSBoy said:
I think a blower on an RB25, running 15 psi of boost or thereabouts, should make double the stock power almost everywhere and be a riot to drive
On 16/02/2024 at 5:58 PM, GTSBoy said:Will give you more than the pathetic 130kW down low, more than the underwhelming 210kW at 4k
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?
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On 17/02/2024 at 11:50 PM, morboost said:
my other car is a Delorean
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
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On 11/02/2024 at 11:33 PM, CowsWithGuns said:
it's f**king siezed when you spin by hand
On 16/02/2024 at 5:40 PM, CowsWithGuns said:Perhaps the heinous noise I heard was the bearings flogged out due to getting sent to full boost on that unbalanced turbine dozens of times - if I want to engage my cynical side, this was already the condition of my 'never used' second hand turbo
Dammmnn, gutted
This definitely has a lot of potential to explain some stuff though... on the "bright side".
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15 hours ago, K-LESS said:
Small Updates, Idle motor broke so have converted to drive by wire.
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
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On 09/02/2024 at 4:06 PM, GTSBoy said:
What I actually want is an RB25 that comes on boost at 2000 rpm (or even better, if possible) so that there is some more torque than you get from the pre-boost threshold output, and is on max boost nice and early, say before 3000, and is happy to run out to 7500 or a bit more, making 500ish (engine) HP, ie, the upper 200s rwkW territory. I want better than stock characteristics at the bottom end and about double stock power at the top end.
I suspect that's why I still think about blowers.
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.
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10 minutes ago, jdniss said:
Is there supposed to be a "hole" in the E-Throttle target table from 6000~7000rpm below 100% TP?
Theoretically you wouldn't hit it under 100% WOT, but seems odd
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.
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55 minutes ago, joshuaho96 said:
Sure, but modern GDI turbo can get deep into the boost as early as 1800 rpm in the case of the pre-LCI S55B30
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.
58 minutes ago, joshuaho96 said:I still wish someone could just do all the work to put an EFR7163 twin scroll on an RB26
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.
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5 minutes ago, joshuaho96 said:
S58s are like what, 25 years of development ahead of the RB26? And the S55/S58 change up the turbo arrangement quite substantially from the N54 which requires both turbo dumps to do a pretty suboptimal turn.
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
6 minutes ago, joshuaho96 said:Seemingly the solution to the I6 twin turbo issue is to actually just...
... 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.
Pretty damn stoked with that considering I had a single attempt, and despite seeming well suited to the conditions vs the higher power cars and the time slip not looking THAT bad I still was having to work hard to not just do a rolling burnout <100kph and doesn't really show it's best at all. I am pretty sure it would happily match the old R33 with a full run on a better surface
This definitely has a lot of potential to explain some stuff though... on the "bright side".
Boost level and torque curve
in Engines & Forced Induction
Posted
There are a few variables here, some are relevant but not critical (IMHO) to help answer your question.
The two major things:
1) Ignoring anything to do with forced induction - all engines have their own natural torque curve, and it will ALWAYS roll over higher in the rpm. There is a fixed relationship between power and torque. When dealing with kw and nm, the relationship between them is roughly:
kw = (rpm * nm) / 9549
nm = (kw / rpm) * 9549
The peak torque of an engine (without boost) will typically climb until somewhere nearish the middle of it's operating rev range, give or take a bit - then start dropping again. The nearer the minimum and maximum rpm of the engine the steeper that drop off tends to be.
2) Boost simply increases the density of the air going into the engine, which inflates the torque at that point. The ramp up in the torque curve you see on a turbo engine is due to the boost rising, but it's essentially just multiplying the torque you'd see if it was naturally aspirated. The roll over you see at the end will typically be what would have always happened with the engine, whether it was naturally aspirated or turbocharged. If the torque never started dropping then power would climb infinitely.
The cool thing about this is you absolutely can tune the power delivery to suit the needs of the owner and/or the limitations of the car, and I regularly do this. With modern turbos we've got to the point where a setup that someone may run well over 20psi of boost with could actually reach target boost well under 4000rpm if the tuner/owner WANTED to - and a lot of people seem to do this when there is actually no realistic benefit, generally it just adds a massive amount of strain to the engine and drivetrain and often actually makes the car harder to drive.
As a general rule I tend to tune the boost curves for cars I tune to reach a "useful" torque level through the rev range and will often end up with a curve that ramps hard to a point, then creeps for the rest of the rev range - not to make the boost curve "soft" as such, but more to make sure its neither laggy nor pointlessly violent in it's delivery. There have been cars I've tuned to be almost like a centrifugal supercharger (or naturally-aspirated-ish) where they actually only hit like 8psi of boost before opening the gate, then ramp up the next 10psi over the rev range... if the car is "loose enough" to drive.
On the flip side I've tuned a car that had stock cams and the engine's natural torque curve fell over HARD in the higher rpm and resulted in a slightly awkward power curve to work with, in that case I actually started ramping up boost to boost torque in a way to offset the engines "NA" torque drop off... at peak rpm actually running a good 5psi+ more boost that what the "flat curve" would have defined. This gave the owner an extra 500rpm or so of useable rev range, and had a fairly solid impact on times he was running at motorsport events due to being able to hold gears a bit longer and also falling into a more useful part of the rev range in the following gears.
Here's an example of an RB in a GTSt I've done the "softened" boost curve to not pointlessly ramp straight to the max boost target early in the rpm, but still made sure it builds useful boost. If you went in the car you'd not guess at all that the boost curve was doing anything "weird", it feels like it spools immediately and accelerates relentlessly (traction dependent) and holds to max rpm. I don't know if you'd guess what the boost curve was doing by driving the car, or even looking at the dyno plot... but imho it suits the combination.