More Thoughts About The Rb/vg Gcg Hi Flow ...

[discopotato03]

I was at GCG today to pickup a special I had them do for my Subie dinosaur and enquired about their Hi Flow RB/VG BB turbo .

It seems they have not long ago changed to a slightly more modern compressor wheel and the limited feedback is that it works slightly better than the original I think "450" Hp one . The wheel is still 7/14 bladed but I didn't check it's number out and wouldn't let the cat out if I had .

I'm beginning to think that if people are reliably getting ~ 260 265 Kw out of these things then that should be enough for a road car , particularly if it bolts on .

I have a used VG30 OP6 turbo here but I need a little info from those that have used these things .

Firstly I had a vague notion that the VG30 BB turbo had a slightly smaller compressor housing than the R33 RB25 Hitachi's comp cover .

Secondly do any of the R34 GTt turbos have a larger comp cover again than the VG30 or RB25 Hitachi turbos ?

I'm just thinking that if I do end up having GCG build me a Hi Flow I'd like to have the highest capacity factory housings available to get the most potential from it .

Thoughts ? Cheers Adrian .

[hypergear]

Normally using a OP6 rear end with a stock R33 front housing with a GT2871R or similar spec CHRA would be good enough to get up to 260rwkws. Also you need to increase the factory air gap inside the comp cover.

There are also other options using .71 A/R AVO housings and GT3076CHRA (the 7pair fin comp wheeled CHRA you saw). which technically should make over 300rwkws on a RB25det.

As the 7 pair fin is made to throw more air but the additional fin also increase weight and becomes a slight flow restriction up top. wither its 6 or 7 pair you are unlikely to notice much difference.

[discopotato03]

No I didn't see a cartridge I saw a compressor wheel - bare .

The other thing is that if you sandwich a Garrett BB cartridge between Hitachi housings none of the OEM plumbing for water and oil fits , the cartridge is shorter too .

I am hoping someone has pics of R33 and R34 Hitachi's because I'm sure I remember one of the later versions having a larger comp cover .

Cheers A .

BTW yes it does matter the number of compressor blades , T series turbines usually prefer T series compressors and ditto for GT series wheels .

[R31Nismoid]

A 7 blade GT wheel is a restriction and hinderance to the older T04S wheels...

I wonder if Garrett would be interested to know they made something worse than what they had from 1970...

[KiwiRS4T]

I was at GCG today to pickup a special I had them do for my Subie dinosaur and enquired about their Hi Flow RB/VG BB turbo .

It seems they have not long ago changed to a slightly more modern compressor wheel and the limited feedback is that it works slightly better than the original I think "450" Hp one . The wheel is still 7/14 bladed but I didn't check it's number out and wouldn't let the cat out if I had .

I'm beginning to think that if people are reliably getting ~ 260 265 Kw out of these things then that should be enough for a road car , particularly if it bolts on .

I have a used VG30 OP6 turbo here but I need a little info from those that have used these things .

Firstly I had a vague notion that the VG30 BB turbo had a slightly smaller compressor housing than the R33 RB25 Hitachi's comp cover .

Secondly do any of the R34 GTt turbos have a larger comp cover again than the VG30 or RB25 Hitachi turbos ?

I'm just thinking that if I do end up having GCG build me a Hi Flow I'd like to have the highest capacity factory housings available to get the most potential from it .

Thoughts ? Cheers Adrian .

I've got an RB25 highflow from GCG. Their point of difference is that they can do them in a ball bearing version and all the original oil and water lines are retained so that the unit really does go straight back. They used to make the s1 and s2 Rb25 the same as the neo (GTT or VG) version but I understand that some people have asked for a different exhaust wheel set up to take advantage of the slightly larger housing on the GTT turbo. ( My understanding is that the compressor end is the same but the ex on the GTT is bigger - but I haven't seen them side by side). Mine was rated at 450hp presumably the GTT one can make a bit more. BTW very happy with the response and power.

[discopotato03]

Just for the record I got to remove and compare the compressor housings off a std Z32 VG30DET BB turbo and a late R33 25DET turbo and the housings look like virtually the same casting .

The differences are that the S2 RB25 one has no actuator pressure signal tap but it does have an anti reversion groove machined into it's snout .

For the sake of it I tried to fit the VG's housing on the RB's turbo but it won't go because the RB versions composite compressor wheel is slightly larger in diameter .

I'll have to check but I think the VG comp cover has 45V4 on it where the S2 RB one has 45V2 .

I also need to get the VG's OP6 turbine housing off its cartridge to have a look inside it as well . There may be something to be had by giving it a light extrude hone just to get the best gas flow through it - smooth surface and less depth of boundary layer for gas flow .

I also want to look at the size of the waste gates flat valve and the port it covers . I'd reckon if anything the exhaust gas flow is the limiter of most high flow turbos so if I can tart this housing up a little I might just get it a little closer to the 280+ Kw barrier and without much more than a bar of boost . Its would be nice , and a big ask , to get close to the 300 Kw limit the std exhaust manifold is said to do .

If memory serves me correct the integral compressor end back-plate on these Hitachi turbos is very close to that of a Garrett T3 or T4 , I have an old bastard highflow that had screwy things done to so if I can unearth that some of these questions may be answered .

In time , cheers A .

[SECURITY]

ive got one of the new version OP6 GCG hiflows on mine. i dont know much about it though. it wasn't a direct swap, the oil and water feed/drains had to be changed due to the new types of core. i havent really had the car tuned properly but it will be up and running really soon.

[simpletool]

Everyone showing off with their OP6 rears..... where is mine I ask ??? agghhhh.

[wolverine]

Disco, have you put much thought into a GT3071 with a 0.82 integral turbine housing. This would give you the hot side flow with no chance of choking the 450hp compressor. The cost might be higher for a new dump and intake mods but you get the result you are after with few if any compromises that nissan factory housings might cause.

[discopotato03]

I think if I was going to be serious with it I'd base it on a 2835 or 3037 Pro S turbine housing but the prices of those are not acceptable to me .

A .

[robots]

Offtopic. I was looking at my broken rb25 turbo today and how do you out a bush-bearing cartridge in there ? Bush bearing cartridges suppose to be bigger in diameter and longer than factory, right, no ? Could picture it in my mind. Spacers to make it fit to factory exhaust housing ?

[discopotato03]

The center section of these Hitachi turbos is larger in diameter and longer than a Garrett GT25BB based one .

The generic T3/small shaft T4 bearing housing can be made to fit easily enough if you like that sort of dated stuff , which is why there as so many plain bearing Hi flows around .

I don't think Garrett make their plain bearing GT cartridges with wheels smaller than say a GT3267 and the big frame GT BB ones start at GT3576R I think . Diesel turbines and too big for a Hitachi housing .

A .

[wolverine]

I think if I was going to be serious with it I'd base it on a 2835 or 3037 Pro S turbine housing but the prices of those are not acceptable to me .

A .

surely a 0.82 will outflow a nissan housing and you only have to look at nytsky's results to see there is plenty of untapped potential there.

i agree the HKS housings are a nice bit of kit (and pricey) but a garrett housing should be step up if you want lower exh manifold pressure compared to the nissan housings.

[SS8_Gohan]

not sure if it's much interest to you, but here's my boost curve for my OP6 high flow - keen to seen what a GCG one would look like... (this is a hypergear)

i fixed this howling/leaking noise i had around the FMIC, but unfortunately it didn't change the boost curve But she sounds great now and there's plenty of mumbo on tap.

and this is the pump fuel graph

the 2 lines are pre and post Z32 afm

thinking of maybe going a bigger rear housing to get a flat boost curve, and then get an adjustable exhaust side cam gear to make up for the loss of response. But unless they cancel each other out, i probably won't change.

[Dale FZ1]

surely a 0.82 will outflow a nissan housing

a garrett housing should be step up if you want lower exh manifold pressure compared to the nissan housings.

Adrian, having run with the 0.87 HKS Pro S option there is little to criticise about that turbo specification.

Face it, the high flow option while reasonable is not likely to be in the hunt for overall efficiency or a "best match" between housing and impeller. The OP6 will allow a greater mass flow than a stock RB25 housing, but neither are in the hunt compared to a combination cooked up by Garrett engineers. There is little to criticise about the GT30 0.82 A/R combination, and it is a great alternative to the HKS Pro S housing.

Unless you used a GCG high flow that allowed you to re-use the water + oil lines, there is an amount of plumbing work that would nullify any financial argument against using a proper GT30 combination.

Plenty said about skylinecouple's results with his GT3071 / 0.82 combination over time, and he's hit pretty much the output/response target you seem to want. It may not be the absolute duck's guts for efficiency (read single scroll and wastegate not as nice as a HKS), but it's available, effective, proven, cost efficient, and neatly installed.

[Sydneykid]

Unless you used a GCG high flow that allowed you to re-use the water + oil lines, there is an amount of plumbing work that would nullify any financial argument against using a proper GT30 combination.

I have never used a GCG ball bearing high flow that DOESN'T use the standard oil and water lines, RB20, RB25, and Neo, all of them are simple bolt ons. Having had a number of GCG ball bearing high flows, R32GTST, R33GTST, R34GTT and Stagea, they are without doubt the best value for money upgrade for a road car. Sure there are cheaper high flows around but I have yet to find one that doesn't come up short in either fitment, power, response and/or durability.

The problem I found with the GT30 use was not so much the turbo itself but the effect it had on the standard exhaust manifold. I cracked 3 in less than 12 months of use. All of them failed due to excessive heat in the log between #3 and the turbine flange. I also suspect that the extra weight of the GT30 was a contributor. With the GT30 in place I was able to extract 315 rwkw, but no matter how hard I tried I couldn't get the throttle response fast enough to satisfy my requirements. It always felt dull and slow to respond, plus it was very hard to drive briskly, it was either too slow or too fast. Launching it was a gamble, I'd get it right about 3 times out of 10, it was either bog down or wheelspin city. On the circuit it was very hard to drive, balancing the throttle was quite tricky because of the sudden ramp up in power where it doubled in 1,000 rpm.

I got so pissed off with it I took it off when the 3rd manifold cracked and replaced it with the GCG ball bearing high flow it had before, 265 rwkw, nice and responsive, get the launch right every tiime, easy to drive briskly, everyday. What I liked about it so much and why I have the same turbo on the R33GTST, even though it has a built engine, is that it had more power everywhere, from idles to redline than when it was standard. The advantage of the built erngine is that I can get my 266 rwkw at 1 bar, so it has even more response because of the low boost I can slip lots of ignition timing into it, safely and drive it everyday everywhere, anytime.. When we get more E85 outlets I'm sure I can get an extra 10% out of it for 280 rwkw which is about as much as I believe an everyday 2wd Skyline needs.

Cheers

Gary

[wolverine]

Which GT30 SK?

There are numerous variants over the years from GT3071, GT3076 (3037), GT3040 all with different configurations as you would well know that run the gamut from 56mm to 60mm turbines and compressors with 71mm to 82mm configurations with varying numbers of blades.

There is no question the GCG unit is a standout bolt-on option and would be the last person to suggest otherwise but Disco has long talked about going larger on the hot side and this is a great opportunity to do it with a 450hp turbo.

[Dale FZ1]

I’m not suggesting the GCG option isn’t a good one, rather that Disco has a viable option available to him. Yep, GCG’s version provides bolt-up capability – and that would have to be the reason to pony up with the extra dollars they want for their product. Whether they work better or have better durability than other remanufacturing efforts is probably a matter of conjecture and OT.

I agree that the bigger GT30 turbine combination is likely to give a different performance characteristic, but there is a degree of relativity from my experience. Vehicle usage – as always – should be the determining factor for what spec to run with IMO. Smaller impeller + tighter/smaller turbine scroll on a high flow should/will boost faster and plump out the torque curve down below 3000rpm, which is valuable for the street. Not into drags so I can’t comment about launching capability. I’ve not had any difficulties with the 0.87 Pro S spec for driveability or torque rise. It was completely linear, no surprises and definitely not a case of “nothing, nothing, smoke/sideways”. No doubling of hp in 1000rpm. Very predictable. And it allows the use of a fair whack of timing everywhere which is good for general response + overall power production.

Your experiences with cracking manifolds is interesting. What weight difference is there between (say) a GT3071 combo, and a GCG high flow? Where did the cracking occur, and was it in a consistent location? The OEM manifold definitely has hot spots at the runner junctions. I do think it’d be a long stretch to suggest that a particular turbo induced cracks when there is a general lack of complaints from other owners using similar setups. Cracking would appear to be indicative of some fairly extreme temp cycling – what use did you give them, and do you know what sort of use/abuse those castings had been through before hand?

I’m fairly sure Adrian has a lot of information at hand and will eventually choose what best suits him. The point I was making is that Wolverine’s comment about the GT30 being a viable, efficient alternative to a high-flow bears consideration.

Good discussion.

cheers

[discopotato03]

Thanks for the input all , I can fill in some of the gaps so you have an idea whats percolating under the copper top .

My dilemma is that I want it all where the reality is that there is always a degree of compromise and you need to bias that towards being good 90% of the time . Ecomomics come in to it too .

The problem is that the Garrett's need the most customisation and I don't have the facilities or abilities to make all the one off bits . The other thing with them is that they are generic turbochargers that don't necessarily suit a given application .

Yes I know in the past I've rabbited on about things that can be changed to tune these things a bit closer but you have to live with the results be they whatever . Also you have an orphan .

The HKS units - the Pro S ones - are supposed to be very good and at least were tested and tuned around single RB 6 apps . Expensive but they give you everything in the kit . BTW can anyone with access to Nengun and Greenline quote the current bite for the 2835 and 3037 versions .

Actually one here has offered me a quite reasonable deal for a second hand 3037 Pro S 0.68 but it wasn't off an RB and doesn't have all the doo dats to make it go bolt . It sounds good but there are no guarantees on the cartridges condition (seals/bearings) and you have to make up virtually all the rest of the kit .

The word is that this version is good for about 300+ Kw . The can of worms this opens is that this is a little too much for a street tyre shod RWD car (with 2.5L) and I think the lower end may be just a little lazy - particularly if you can't use all the potential power .

For a conservative like me the 2835 version is probably a better all round compromise for an ~ 270-280 Kw ask .

Enter the GCG Hi Flow in large turbine housing form .

I don't think anyone needs to be a rocket scientist to realise that these don't use the most modern wheels in existence but then again they were never intended to be a clean sheet approach .

Gary has got 266 from his Hi Flow and when you do the calculations a group buy Hi Flow starts tp make more exotic turbos look very expensive . New for new the HF one is not too far behind the 2835 but look at the dollars .

I wish I had money to burn and I'm not starving but money in the bank feels nice .

The bean counter inside me is bending the internal ear with HF HF HF and the cost is hard to ignore .

The right VG turbo I own and if it can be made a little bit smoother and better flowing with extrude honing then potentially 270+ is not unrealistic with a bar of boost .

I have to keep reminding myself that this is a street car that needs to be easy to drive and live with 235 width tyres and soon a JB organic 277 rated clutch .

Now to the extrude hone people and another OP6 housing if I can find one .

Cheers Adrian .

[zebra]

Disco - HKS2835 Pro S is $3017 delivered in any housing option

HKS3037 Pro S is $3538 Delivered in any housing

these are from nengun for the Turbo alone....looking at the kit prices now