Lithium

Yeah it can have an effect on the engine in the relative scheme of things, the turbine housing and wheel are TINY and at that boost level the pressure and heat in there will go through the roof. That ends up with a much higher chance of reversion, and reversion raises the cylinder temperatures something crazy - high cylinder temps are what increase detonation and ultimately can speed up the wear and tear of the engine. I partly upgraded my turbo as I wanted to go a bit quicker but was already at 10-11psi on the stocker, as far as I am concerned running >250kw @ wheels on a big turbo on 1bar is FAR nicer on the engine than running just over 200rwkw on the stock turbo on the same boost level despite the higher power level. You would be surprised at how little extra force is put on the bottom end by running a decent matched turbo on 1bar with a good tune versus the stock turbo on similar boost, if not a bit less. Making more power on the 1bar with a decent turbo using the standard rev limit and good tune is the definition of having your cake and eating it too with an RB25DET, if you are looking for a bit more power out of your stock internals. Just my opinion, anyway.

You're right, boost isn't everything (I wouldn't say nothing by any stretch of the imagination) but I would be far more confident of running a T88 on the side of my stock engine at 1bar than a stock turbo. The T88 will have far lower turbine pressure and heat from an overworked compressor than a stock turbo and will not magically make stupid power just because a T88 is a big turbo, the big power numbers on low boost seen on some engines running T88s are partly as a result of the big cams and revs that the engine has been built to use to rev high enough to justify the bigger compressor.

Clipped the pain points of interest here - I think you may be a bit short of luck if you want a stock displacement RB25 powered a 1700kg+ car to have the possiblity of doing 12s and getting 6-7psi of boost by 2000-2300rpm, as you will need to make a fair bit of power to make those times possible in my opinion. For what its worth, if I load my .82a/r GT3076R up at 2000rpm it makes about 2psi. I am up around the 7psi mark by 3000rpm off the top of my head, so in terms of your comment you made about not wanting it "worse" under 3000rpm than with the stock turbo - it WILL be even with a .63a/r GT3076R unfortunately. That is really the only time I feel anything relating to compromise for having a bigger turbo, above 3000rpm its all joy and really below 3000rpm There are definitely things I'd have done differently now that I am where I am at with my build, one of the biggest things I (others may have different opinions and I am open minded on this one) regret doing or wish I had the option of doing when I was in your shoes is just going high mount turbo on a decent manifold etc - getting all the other bits sorted out so it was done once and done right. If I had a stock R33 *now* and wanted around 300kw @ wheels with the best possible power delivery/spool etc from an RB25DET I would personally be going for a proper twin scroll .78a/r GT3076R setup using a TS 6boost manifold. I don't know if it would be the best combination or not, but if I hadn't already spent the time and money I have and if I knew what I know now it IS what I would do to try and achieve what I was trying to achieve when I set out 3 years ago While I am pretty sure it still wouldn't make 7psi by 2300rpm on an RB25 I would like to think it'd happily give the spool people with the .63a/r GT3076R (probably better) without the violence but have not far dissimilar resistance to knock and "smooth" power delivery the .82a/r has. If you are going to go single scroll/internal gate/low mount I personally recommend the .82a/r housing. It IS a bit laggier, a bit dougher below 3000rpm but honestly the delivery is nice a smooth and predictable, the flow is really good, the power potential is there and the exhaust pressure etc are far more under control and as such likelyhood of knock, boost creep and other nasties is far reduced. I've had my .82a/r GT3076R on a stock RB25 running 1bar+ (expect 1bar by probably around 3700rpm with decent boost control setup on stock manifolds/cams etc) for a couple of years and I still love the turbo, just took the car for a thrash tonight and its awesome fun. Great on the track, too - though I'd call the power delivery more of a 4000rpm-7000rpm thing. That doesn't mean its incapable below 4000rpm, but from 4000rpm up is where its really cooking. To do the same thing I would rather a .78a/r GT3076R on a twinscroll manifold and I guess that is an admission there that I would welcome a little less lag - but I'd certainly not consider downgrading the turbo size if the option was given to me. I can't guarantee how such a setup would work, as I am unaware of anyone with a 6cylinder trying it but in my head it would be the dogs bollux. Hope this helps?

Which GT30? - Garrett GT3071R - The GCG "GT3076R" with the .70a/r EC-1 compressor cover - Garrett GT3076R with anti-surge compressor cover - Garrett GT3082R - some other combo? They're all reasonably different beasts!

A GT3582R is definitely better than a GT3082R on an RB25 (or most things), one of my mates went from GT3082R to GT3582R on his EVO and the drive was much of a muchness - just made quite a bit more power. GT3076R is a fair bit of an improvement to drive, but a twin scroll GT3582R would be the dogs bollux I reckon.... if they were around when I was doing my turbo choosing I would have put a fair bit of consideration to one of those as an option.

I tend to have Boost, RPM, Speed, Throttle.

I'll have to see if I can get a hold of one of my mates dyno plots - one has done 380awkw on a GTR and another 399rwkw on an R32 GTSt running an RB30DET. Both cars were limited to the power they made by things other than turbo, had hoped the GTR would get an ECU upgrade (its current one only allows mapping to 1.5bar) and tune for more boost but the car is for sale now. The highest I have personally sited was a local whose CLAIMED power is 450kw from a .82a/r but I think thats a dyno that is on the happy end of the dyno scale and as such I think the plot is pretty, the car felt more like what I'd call a 400kw @ wheels on your "typical dyno" car. It ran 10.6 on pump gas with full interior in an R33 GTS25t, trapping around the 130mph mark. Had a good power spread, was "all in" by 4300rpm and revved out strongly to ~8300rpm on a stock displacement RB25DET.

Gah this kind of thing is frustrating - it makes threads like this turn to crap and kills the usefulness of information from people willing to share. Its a FACT that .82a/r GT3582Rs can make 400kw @ wheels, even on pump gas. It won't happen all by itself, just having a .82a/r GT35R on a motor doesn't make it do 400kw... it just means its possible with the right setup. You don't appear to realise there is no such thing as a .86a/r GT35R (.86 is a Garrett T25/8 size), and are talking to people who are saying they HAVE made that power - then I think you need to realise that you aren't being very constructive so much as being an empty can.

Will see if I can get one off him

Surprised the VQ30DET turbo has not been mentioned here, quite a few have been sold mistakenly as VG30 turbos here and they aren't a bad unit from all I hear. I believe they are a decent sized BB core turbo.

Yeah I couldn't remember off hand which had offset side turbos or otherwise - I was more focussing on the complexity of whats involved with them. An interesting device which has emerged in the aftermarket is the "Spool Valve" which Forced Performance have released which they have made wild claims as to the potential of. It is a "device" which goes between an exhaust manifold for a single entry turbo and a twin entry turbo which shuts off one of the turbine scrolls until a set pressure level is reached - which apparently hugely improves spool with minimal cost to top end flow. I am a bit of a critic of it but I still prefer the idea of it to a sequential twin turbo setup, however I don't know what longevity would be like with it.

I'd say it would be much too laggy but I guess it depends on what you are using it for, and what power level you are after?

About those 8.4s.... 14 years later and people are still talking about it! HT's 7.57, people still talk about it.

I don't really blame Dirt or Eyre for claiming the record as there was nothing in concrete - though I remember back then picking on the guy who was tuning Eyres car when he did the "record" about the fact that its a made up record and that I was SURE that the Japs had done single digits with GTRs in the 90s, but had nothing to back it up. I was sure I'd seen such videos/mag articles at peoples places back in the 90s when I was really getting into Skylines before I had access to youtube and WMV files etc and as such only had vague bourbon adjusted memories of such things. I'm glad someone dug that up, I'm pretty sure there are various other Japanese 90s achievements which would still get people up and paying attention now. We need youtube clips to immortalise

Think about how you would mechanically do that... it sounds like you understand basically how a turbo works. Its a mechanical thing, for an ECU to "turn it off" it'd have to redirect exhaust/intake flow which regardless of how you look at it is going to be complicated and potentially wasteful as well. Its not going to change the fact that two different turbos feeding into the same engine are going to fight each other. All the turbos know is they are compressing air - all the engine does is breathe in the air from its source. I'm not sure the extent of your understanding of the whole system but think about it this way: If you have a hose attached to a pressure gauge and you blow into it, it shows you can blow a maximum of 2psi - and you get a mate with a big set of lungs to try the same trick... turns out he can blow 5psi! What if you get two straws and attach them to the same gauge and both blow into it? It won't read 5+psi, its more likely you'll have air trying to force itself back down your throat and you will let go of the hose before you burst stuff. With a car, the engine is the same as the gauge - it won't bleed off the extra, it will just take more pressure - changing its valve timing will just change how it uses the air you are forcing at it. As far as the turbos are concerned, they can't "back off" if it has more pressure than it can blow against - it will surge/stall as the pressure gets blown back down its throat. Not sure if that'll help? Sequential twin turbos tend to use a complicated bunch of valves etc to bypass airflow etc in such a way as to allow progress flow to the engine but they are invariably quite complicated to work with and are prone to misbehave and cause huge problems. With a turbo setup there is no beating a nicely matched turbo/engine combination with good tuning etc. If its too laggy, get a smaller turbo or a bigger engine

Thats pretty much correct, as on the pushing turbo side of things that is pretty much what RB26s have - except the two turbos are of course the same size. The trouble with having two different sized turbos is that they will pump air at quite different speeds and efficiencies, and the airflow will naturally try and follow the easiest path. When the smaller turbo starts spooling up better than the bigger one there is nothing (assuming you just bolt everything up with no funky valving etc to control where the turbos push their compressed air) from stopping the smaller one from forcing its air back through the bigger turbo which is not yet pushing as much boost through it. You could possibly run the risk of the first turbo actually fighting the bigger turbo, depending on how its done. Same goes the other way, when the smaller turbo can't force any more air and as such beyond its efficiency - the bigger turbo could potentially start forcing air down its throat the wrong way. I can imagine it getting all kinds of nasty...

OK sweet as, was unsure as to how much effort you wanted to put into it - as you can't mix and match the parts between the two turbos your only other option is to just use the .82a/r GT3082R for reasons others have already outlined. It won't exactly be gutless, and will make a reasonable amount of power. For what its worth EVERYONE I know who have had GT3082R have not stayed with them for long and moved on to a GT3582R and have been happier with them, the main thing I think which leans towards a better daily drive is at least its not a 1.06a/r housing like your GT35R.

Why don't you just change to a .82a/r GT3582R housing? They are a fair bit less laggy than a 1.06 and the 1.06a/r GT30 housing on a GT3082R has about the same amount of exhaust flow as a .82a/r GT35R but you have less matched wheels. ie, you'll probably have a nicer drive on a .82a/r GT35R than a 1.06a/r GT3082R.

OK its like banging my head against a brick wall here, so this is my last post in this thread. I'll try and spell it out as simply as possibly in easy to follow bullet points for you to follow so all the info is easy to access: - The guy wants: which a GT30R has been proven time and time again to do piece of piss- Dyno plot of GT30R vs GT35R maxed out on race gas overlayed: - Dyno plot shows GT30R destroying the GT35R in power delivery UNTIL it reaches ~500hp @ wheels (aka 373kw @ wheels) - Guy who posted the thread wants up to 400hp @ wheels, which is safely under the GT30Rs choke point I have said before on a full on race motor a GT35R will beat the GT30R, so you stepping up and pointing out that the GT35R flows more after 5800rpm (actually where the GT30R would hit choke at ~500hp - unsurprisingly for a turbo rated to that area) is not really overly amazing. So, aside from the fact that the GT30R (see easy to find dyno plot above) actually makes more power from 2500rpm up to 5800rpm with a max distance of 150hp, or 3300rpm of goodness as opposed to 500 or even 2000rpm .... he is also aiming for WAY under the power levels demonstrated there. Going by your logic so far he should use a GT47R, you should see how much more power under the curve on Mark Jacobsons car it makes than if it had a GT3582R both on 2.5bar or so running Methanol.

Sorry my bad, looked at it again - its "only" 150whp Look around the 5000rpm range at the valley between the GT35R line and the GT30R line.

Reasonable correct, the GT30R up to around 6k has more power - as much as 200whp more at points through the midrange (5-5500rpm), which I wouldn't call slightly more. Eventually the GT30R maxes out (410kw @ wheels.....) while the GT35R keeps going, which makes sense as its a much bigger turbo. So yes, when you run both turbos up to 2.2bar on race fuel the GT35R makes quite a bit more power - any idiot would know thats going to happen. I posted it as it'd be neutral honest input as to how far both can go when pushed hard, on an ideal and equal setup. The GT30R monsters the GT35R up past the midrange, the GT35R wins on top end (if you run high enough boost). If you run both of them on pump gas and 1-1.3bar the GT30R will basically dump on the GT35R for the first part f the rev range - then give nothing away up high which has been proven many a time. The only point the GT35R will start winning is when the GT30R starts maxing out, which the guy in this thread is not going to reach that point as he will be running under 20psi - as such a GT30R would be a much better choice. I can't make it any more obvious that that, so will leave it at that

Visually a GT2876R is not a small turbo, look pretty much like a GT3582R or a T04Z with a little turbine housing - but they are a piece of crap. Stick with the high flow.

I mentioned in an earlier message that Garrett sell GT3076Rs without the turbine housing, the one HKS put on it is spaced out and flanged to make bolting on easy. Thats one of the neat things with the HKS turbos - the most tangible advantage is they take the homework out of installation, you know you can buy it and bolt it up to most of the stock gear. In terms of the CHRA, the CHRA is the rotating assembly - the wheels, bearings etc etc are EXACTLY the same parts on the GT3076R as the GT3037. Hence the fact they are they same part number If you have a bearing failure in yours you can just order another "70177-5007" core from Garrett and bolt your housings onto it and you will be good to go. As I mentioned earlier, thats why I refer to them as one and the same things as they really are the same moving bits. No worries anyway, we're all wrong sometimes - I have been over this heaps/ages ago when I was researching what I wanted.

Mine has the "5" as well, as with all the GT30Rs I have seen. Check this thread: http://www.skylinesaustralia.com/forums/Gt...et-t222781.html. There is reference to that part number in my GT3076R upgrade thread I posted back when I was doing it as well when people were asking how to identify the proper Garrett GT3076R. ATPTurbo also can sell you a new compressor cover for your GT3076R if you damage it or what to bling one up http://www.atpturbo.com/Merchant2/merchant...tegory_Code=HSG <- look at the part numbers they refer to

This reminds me, Oz was flooded with some random GT3076R thing which GCG used to (or still do?) sell with a .70a/r EC-1 housing which didn't seem to make the power the real GT3076Rs do. My GT30R never pinged on the dyno, power would just stop climbing after a certain point.