Lithium

Yep, but who leaves their cars stock?? I think the more you mod them, the more that order changes....

OK, the reason I started defending single turbos is partly because of this point. In NZ Nissans are used by quite a lot of people very regularly for drifting, which is getting to be quite a big thing here. There are countless GTSts, Cefiros, Laurels and Silvias with RB20/25/30DETs running various setups and being thrashed on the track at least monthly (which is quite a bit) as well as being driven on the street, and some used for drag as well. This means that people have had to find combinations which are affortable to setup and maintain, and are able to function in different environments. The reason I mention single turbos, is there is only one twin turbo car used in the NZ drift scene - and drifting is obviously a sport you want good power and DEFINATELY want good response and midrange torque. The car running the twin turbos is a Cefiro with an Rb26DETT running the stock turbos, so its not that he decided to buy aftermarket twins. There is an RB25DET powered Nissan here running an XTR 3040 (afaik rated to happily over 500hp) and is on one of the top drifters car, and its blatently obvious that the guy has all the midrange power and torque that he needs with little compromise considering. I'm not 100% sure what would parallel this turbo in terms of twins, but I'm pretty sure it would cost quite a bit more to go down that path - and you obviously have twice as many things to break.

I understand that, but the comparison (aside from N1 turbos apparently) were between a plain bearing type turbo vs. twin ball bearing type. Shouldn't the comparison be between a single and twin turbo of similar technology? ie, twin GT2530s vs. a GT3040 or something like that?

Aren't the big singles that are being discussed here plain bearing, as opposed to the HKS GT-series and the N1 turbos which are all ball bearing, afaik? Wouldn't that mean that the drivability/torque delivery is more to do with turbo technology than being twin vs. single?

The main bit that caught my attention was between 90 and 110kph there is a "bump" which I didn't really see the same in the hub dyno plot, maybe its just me not being used to the different scale the plots are shown on :|

Are you talking about the rolling road dyno plot? That one for some reason seems to autoscale to the size of the window and comes out looking real crap - happens when I view it anyway. Try and maximize the window?! And yeah - the peak power drop isn't what bothers me... its known the rolling roads can read 10-15% less at times than a hub dyno, its the shape of the curve which caught my attention.

On a bit of a whim, I ran my car at a dyno day using a rolling road dyno (a Torque Performance one) to see how it went. All my other runs had been on a Dynapack hub dyno, but had been curious as to how the two would compare etc. The results were relatively interesting. The only things that have changed is that when the hub dyno run happened, it was peaking at 11.3psi and it was dropping boost quite badly in the high revs - the rolling road run was peaking at 10.5psi. During the first run on the rolling road, the rears lit up so I had to do another run with someone sitting in the boot to try and keep it stable - but the power curve looks quite different to the hub dyno curve. Could it have been been scuffing on the rollers? Tuning way out? Or just the way a different dyno reacts? Hub dyno run: And rolling road run is attached.

A leak somewhere? Maybe even on the hose to the boost gauge?

Basically, no - they are of a completely different configuration... it is highly unlikely you have them unless you have a custom plenum or at least some kind of custom fuel rail adapted to your factory plenum/inlet manifold.

Power levels mean a lot, its the actual amount of time you spend putting out the highest % of that power which makes you fast though. Having huge power and not being able to use more than 60% of it for 50% of your time on the strip is an absolute waste of time, but then having bugger all power and being able to put down 90% of it 100% of the time is not necessarily going to be that great either.

R33 GTS25t SpecII, Intake, Exhaust, 11psi and some tuning (sorry for the tiny pic)

There was a good percentage of a second difference in 1/4 mile times, basically the RX7 would get destroyed down the 1/4 and the trap speeds weren't listed. On the high speed bowl RX7s visibly reel in R34 GTRs, and while I can't remember the exact speeds - the RX7s had a measurably higher top speed over a measured distance.

I personally would go the Series 8 RX7, the compromise of cabin space and POTENTIAL reliability issues (not a problem with a good tuner and maintainence) not being enough to put me off. As a actual performance package the RX7 feels more balanced to me, light weight, good handling without the need for 4WD, an engine with the equivalent displacement of an RB26DETT (and just as much willingness to make power, not to mention happier pushing large turbos), obviously looks good, and after all that basically better peforming in many ways than anything short of a NurSpec R34 GT-R or NSX-R.... anyone who has watched Best Motoring videos from Japan would have seen the RX7s in stock form beating the non N1-type R34s on everything but 1/4 mile times - giving away the 1/4 mile times due to traction, not acceleration. I have driven a fair range of cars, and I'd say don't knock the Series 8 unless you have actually driven them - they are HEAPS of fun. I'm also not putting down the GT-Rs, as much as anything it comes down to personal choice....

Yeah, a RB20DET + TD06 running .65bar and making 300hp will not be as fast as a RB20DET + RB25 turbo running closer to 1bar and making 300hp....

Being that its a new record, not many - if any!

Actually the opposite, it takes a badly matched turbo to do that - at least one that is badly matched to the engine it is bolted on to. This is the reason you can just leave the same exhaust wheel on a turbo and bolt on bigger and bigger compressors to move more and more air into the engine. A very efficient turbo strictly speaking would be PERFECTLY matched to the engine, shoving just the right amount of air for the engine into it over a wide rpm range.

Entitled to opinions maybe, but have you heard of the phrase "If you don't have anything nice to say, don't say it"? There was nothing constructive about what you said. I know quite a number of people with EVOs that would probably make you cry if you went for a ride in driven hard.

Haha - while that is being mentioned, I have discovered that 10psi -> 11psi is the threshold where my car moves from being able to go into second (I dont flat shift) and get the rear wheels scuffing but still accelerate hard, and being able to go into second and start a fairly impressive second gear burnout

I'll have to check that out when it gets to NZ..

Thats pretty much what I aspire to getting, I haven't had the pleasure of experiencing one myself - but they sound good.

I run mine on about 10-11psi MAX and I am quite happy with the performance of the car at that boost level... if I want more power then I will probably just go for a larger turbo and sell on my still healthy R33 turbo, and know I can get that much more power reliably

To be honest, aside from the fact that I am in NZ and you are in Oz (currency, and that certain parts are more available, and others less on this side of the Tasman), I couldn't really say off the top of my head. I haven't looked at NA mods for a Skyline, being that mine is a 25T - and my previous mods were all for a 4cyl. Realistically the homework on pricing should really be up to you - it would be easier for you to find out the prices... you can pick the parts you like most etc, as that is a whole new discussion that could be had. Off the top of my head, I'd budget $10k and then go from there, you SHOULD be left with change.

Damn, I wrote a big response to Viscount but it seems my post has disappeared, or never actually saved properly!? Anyway, yeah - the compression, the exhaust, the intake and the exhaust manifold will be either incompatible or inappropriate for turbocharging. I'd recommend one or the other, a turbocharged RB25 that is in its peak between 4500-7500 is going to be a lot more extreme than the scope of this thread

The way things are at the moment, with both the RX8 and the 350Z - the manufacturers have given themselves room to improve and get feedback on what people want more. Unfortunately if they released the perfect package straight off, they wouldn't be future-proofing themselves... though it also means the customers (or journos??) get to have their 2c input into the design based on their reactions of the 1st generation of each.