discopotato03

I don't suppose anyone is intending to use the HKS cast manifold/ext gate and a real GT3071R ? I'd like to know more from the feller who had the real GT3071R 0.63 A/R on the RB20 as well . A broken record I know but the cast manifold and ext gate + the TS GT32 turbine housing is going to be as affordable as it gets and give good all round results on a GT3071R/GT3076R . When you team a pair of big trim wheels ie 84T/56T low end is not the combinations strong point , it seems obvious that Garrett have leaned towards big trim wheels so that small and medium frame turbos can give acceptable gas flow (both sides) on reasonably big engines . This keeps the turbo compact in relation to the engines physical size . Another thing you find snipets of if you dig deep enough is that the real GT3071R is basically a productionised version of the competition oriented TR30R . These use a 60mm version of the NS111 turbine in 76 or 73 trim , NS111 series are 9 bladed rather than the GT30 UHP's 10 and almost certainly use a different inducer tip width and turbine housing nozzle form . The smaller 53.85mm version of this turbine in 76 trim is most of what makes the better versions of the GT28 BB series like Garretts GT2860RS and GT2530 work as well as they do . The turbine trim size alone makes a huge difference to spooling a turbine , if the choices were small trim big A/R or big trim small A/R the former almost always gives a better average result . Edit : A/R meaning turbine housing size . I know most are tired of hearing it because of cost reasons but twin scrolling is the only way to have med-large A/R housings that work up high and not suffer down low with large trim turbines . The Cheaper way to achieve it is with reasonably large wheels and more medium sized wheel trims ie 78/52T rather than 84/56T . Now Garrett for some idiotic reason don't seem to be in any hurry to offer their GT30 and 35 UHP turbines in say 78 trim or market the 71/76/82mm GT compressors in the 50-52 trim size range . If and when they do you'll start to see spool differences in the GT30/35R turbo ranges just like there has been in large frame GT BB turbos like some GT3782R's/the GT4088R and the T51R . I suppose you could include the T04Z even though it has a very large trim compressor (63T) , the saving grace is its dinosaur T04 turbine in 76 trim . Until things change the workable options are all expensive - more cubic inches/twin scrolling/custom compressor options . I'm guessing turbo wise things will change but who knows when and how - that will depend on how much pressure the market puts on Garrett or if their oposition makes more effective turbos and starts to steal their market . Cheers A .

Hi Simon , I don't suppose that turbine housing has 0.78 A/R on it by any chance ? It looked to me like a housing that I believe GCG Had made to get around the shortage of RB25 and BB VG30 turbine housings . As for the Garrett cartridge there could be some issues there . The Garrett ID tag mentions GT2835R and its the one HKS uses in their GT2835R turbo . Garrett and HKS put a different spin on the "R" designation . In Garrettspeak they tack the R on the turbo models name ie GT3071"R" to show it has a rolling element or ball bearing cartridge . HKS use an R on the end of some turbos they market ie GT2540R and GT2835R , from what I can tell it means the highest potential power producing version of a turbo series - biggest trim wheels and possibly housing A/R's . Mayby R for race edition ? I wouldn't write the cropped GT30 turbine off as crap , it works reasonably well as long as the compressor option is sane and the housing families and A/R's are suitable . One thing significant with that cartridge - 700177-5004 is that its cropped or ~ 56.5mm GT30 turbine happens to be in 90 trim . Usually turbo manufacturers make turbines in large trims when they want low restriction and not necessarily a large A/R turbine housing . Because the exducer diametre at ~ 53.6 is large in relation to the major diametre restriction to flow through the blades will be low - as will its ability to "spool up" at low engine revs and load . Its a trade off biased towards high end performance (high flow with low restriction or turbine inlet pressure) . On a track car with close spaced gear ratios and a 4-8 power range it would be the way to go . Another way of looking at is if for instance Cubes RB30 was limited to using a GT2835 turbo the largest available turbine trim (90) and A/R turbine housing (1.12) would be virtually essential to not have it choke on its own exhaust gas . In that instance the turbo is a little small for the engine so supersizing it would be the only way to make it acceptable . Where the wheels fall off is when you have an RB20 or 25 that generates less exhaust gas flow , large trim turbines don't always react positively to smaller A/R turbine housings used to pull down the turbos boost threshold . Obviously it has to help but if you have to go very small to get some boost at round town speeds it all falls apart at high revs and loads . Sorry to sound negative but there are other issues - namely available T3 flanged turbine housings in the GT30 family . HKS's GT Pro S housings may not work given that they are already very thin on the wall seperating the turbines outlet and the wastegates vent path , it would be expensive to reprofile a HKS housing and have it crack . Garrett don't make T3 flanged GT30 housings for either the 84 or 90T cropped GT30 turbine - never have . So for a purpose designed housing for the cropped 90 trim your stuck with HKS housings and I've only ever seen them in T28 flanged GT30 housing form . All that really leaves you with is an aftermarket housing which I think your one has or a bored out Nissan/Hitachi housing . Your call there . If it was me using a GT2835 type turbo I'd prefer to stick with the 84 trim cropped turbine because there are good housings like the HKS GT Pro available for it and it would be aimed more at being broad range than mid to top end performance . Before I finish there may be a bit of confusion between cartridge and turbo assembly part numbers . 700382-xxxx are BB GT30 complete unit part numbers . 700177-xxxx are BB GT30 series cartridge numbers . To use the above example 700177-5004 (cropped 90T GT30 turbine with 71.1mm 56T GT35 compressor) , this is the cartridge number . My list of HKS bits shows that -5004 cartridge was used in three versions of the GT2835 , being 700382-5004 -5020 and -5021 . The differences would have been housing type and size because those three all use the same cartridge and wheels . Again your call but I think you need to talk to people who've used that 90 turbine trim before fitting it and not being able to exchange it . I wouldn't think Brett would have a problem exchanging it if you you asked him but you need to have an idea what you want from a turbo and what different versions are likely to do . If you can find someone with a HKS GT2835 Pro S on an R33 that would give you a bit of an idea what to expect from one . You don't have to necessarily buy the HKS turbo because with the Pro S turbine housing you can make one up with the cropped turbine 84 trim cartridge and comp cover . If you are sure you really want what I call the real or 60mm turbine version GT3071R then only the 700177-5023 will do . I cannot tell you exactly what power chartacteristics it will give on a reasonably std RB25 because I've not tried that combination . I bashed out a bit yesterday afternoon in Mafia's 300 Kw thread so possiobly worth a read . Out of fingers cheers A .

Hi Cubes , I assume your still using hydraulic buckets and if thats the case they are probably heavier than the RB26's solids so maybe have more innertia for the valve springs to control ? May need higher than 26 rates to achieve the same control . Just briefly back to those 71mm 56 trim GT35 compressor wheels , the HKS spec GT2835 Pros S is said to hit the wall at ~ 300Kw in 0.87 A/R turbine form on a std ex manifold RB25 . If you check you'll see it uses that GT35 71mm 56T compressor , just like the real GT3071R does . I went back and had another look at the compressor maps for the above mentioned compressor and a non Garrett map of the 76.2mm GT37 52 trim one . The 71mm 56T hits the 50 lbs/min wall at ~ 3.2 PR or 2.2 bar positive (32 PSIG) . The 76.2mm 52T does about the same at a lower pressure - 2.3 PR or 1.3 bar or 19 PSIG . My map of the 71mm wheel shows the wheel speed as ~ 128000 rpm and the speed line is just about doing a vertical power dive . The 76.2mm map does not show speed line numbers . Had to say with non genuine maps but if its accurate its easy to see that the larger wheel in a smaller trim is doing the same job at lower shaft/wheel speeds . My thinking is that they both use the same GT30 UHP turbine but the different compressors pump air differently for a given shaft speed . The smaller wheel is demanding lots of rpm and high pressure to move the air while the larger mid trim one is doing it at a less frantic pace . The critical difference overall is how we size the turbine housing to achieve the most usable result . IMO if you want to use the real GT3071R in single scroll form and need it to be responsive then its going have to have a small (for a GT30) turbine housing , then I'd reckon you could forget about 50 lbs air and 30 odd lbs of boost because the turbine inlet pressure would choke it for sure . Its the legacy of having large trim sizes on the compressor and turbine and very much shows how altering the large trim turbines performance with A/R size is not the same as having a smaller trim turbine . My gut feeling is that the 52T GT3076R/GT3037 would be a better suited to pulling 300 odd Kw from an RB25 if you could get a suitably sized GT30 turbine housing . HKS do GT30 housings in 0.73 A/R but unfortunately they're T28 flanged so no good . Out of time now more tomorrow , cheers A .

From what I've seen the XTR tag is an extra GCG put on them . The Garrett ID tag should still be on the other side of the bearing housing . I don't go with the KB numbers , I think they are some form of complete turbo assembly number and there isn't one for the real GT3071R because they market them as a cartridge to which the user options housing kits . GTS-T T/Hsg . Does this mean your using an original RB25 Nissan Hitachi turbine housing ? If it does then you can forget Garretts maps because they test their turbos with their own native turbine housings . My opinion only , THE only housings that work properly with Garretts GT turbines are the native family turbine housings . HKS housings mostly work a little better than Garretts the exception being the bored out GT28 housings for the cropped GT30 turbine . Before I go Garrett have hinted that they are going to release to the public their TR30R competition turbos and in I think four variations of compressor and turbine . Most importantly these TR30R's use the NS111 family of turbine (like the GT2860RS does) but in 60mm instead of 54mm . I knew there was an NS111 60mm 76T turbine but the maps also show a 73T version as well . From memory the compressors are 60 and 76mm and you can read about them if you became a "Garrett Gearhead" member through their turbobygarrett website . If they decide to sell them with more production oriented turbine housings there's a good chance they may help get around the low end response issues of the 60mm 84T GT30 UHP turbine . Should be available in the new year - maybe . Cheers A .

The real GT3071R (700177-5023) can easily go beyond 270 Kw / 360 Hp , if you go all out with them theres no reason why you couldn't screw 400 Hp / 300 Kw out one and that not the absolute limit either . Read the compressor map and look at the turbine maps as well . Out of time cheers A .

Actually there are five versions of the Garrett GT3071R/GT2835 group . Just bashed this out the other day at the Silvia site but not everyone goes there . This group of turbos is based on the GT30 turbine and Garretts 71.1mm GT35 compressor family . HKS sold all of the cropped versions and Garrett two of the cropped and the only uncropped version . 1) Cropped 84T turbine with 71mm 48T compressor 700177-1 2) Cropped 84T turbine with 71mm 52T compressor 700177-2 3) Cropped 84T turbine with 71mm 56T compressor 700177-3 4) Cropped 90T turbine with 71mm 56T compressor 700177-4 5) Uncropped 84T turbine with 71mm 56T comp 700177-23 My opinion only but the only time I'd go anywhere near a cropped turbine GT30 based turbo is if I particularly wanted a GT2835 Pro S . The cropped turbine is not a bad thing but there is a very limited range of turbine housings that work properly with it . The T28 flanged GT28 IW housings are a bodge with this turbine so avoid at ALL cost . The flange size is wrong for a single turbo Skyline anyway so no reason to go there . Garrett most certainly do make T3 flanged integral wastegate GT30 turbine housings and the "real GT3071R" uses the matching uncropped GT30 turbine so they bolt together as a set . I wouldn't write off the 0.63 A/R turbine housing as too small particularly on this GT3071R cartridge . To get high power (260-300) from the 71mm compressor your going to have to spin it a bit faster than the 76.2mm compressor in the GT3076R so the .63 is probably not as restrictive as you think . The shaft power required to drive the 71mm comp won't be quite as much as the 76.2mm one needs so it should spin up a little sooner and have slightly better transient response . I would think it would "windmill" a little faster than a GT3076R so you should get a bit more part throttle torque at lowish engine speeds . Cubes can give you the details of this theory . I always thought that if I was going to bolt an IW Garrett GT BB turbo to my R33 it would probably be the real GT3071R with the REAL GT30 IW turbine housing in 0.63 A/R . I did try for a while to locate A HKS GT3037 Pro S turbine housing in 0.68 because that I think its as good as it gets for a responsive GT3071R or GT3076R single scroll turbo thats not a hybrid one off cartridge combination . As for the .63 , if Mafia can get 300 Kw from a 0.63 GT3076R which has a 500+ Hp caple compressor you should be able to get close with a 440 Hp capable one . Remember the real GT3071R should have 700177-23 or - 5023 on its ID tag . To be doubly sure the turbine diametres are ~ 60mm x 55mm , if the turbine outlet or exducer diametre measures either 51.9mm or 53.6mm its not the real one . Cheers A .

Some very valid points of view here IMHO . Nismoids experience shows how going for that bit more often makes unacceptable compromises overall , and yes the semi trailing arm IRS would make it - interesting . First thing is budget because that dictates how good you can get the most critical areas to be . You also have to ask yourself if your means and goals will allow you to remove /strip/rebuild the engine itself before you bolt on externals . If you don't intend to remove the bottom end then lets hope for your sake that its in very good condition . The path to making more power in most engines is to get more air and fuel in and then to vent the increased volume of exhaust gas . There is a cheap and a propper way to go about it , cheap being to raise the pressures and temperatures and propper to remove the restrictions in the system - and waste a bit more heat . Most production heads just don't cut it when it comes to large power increases so getting it sorted will make the power lifting game much easier and more reliable later . Critical areas are exhaust porting and valves , the exhaust ports need improving and since you can buy slightly larger valves that go in on slightly modified std seats why not . Tomei Poncams are supposed to fall in and you may get away with re shimed std springs if they are in good condition . This sorts the head out and it can go back on if the bottom end is not being opened . If I was spending money on an RB25 short for fast road I'd look seriously at factory RB26 bits like the crank/rods/pistons . These would be the best std Nissan bits and probably the most price friendly as well . Assuming that all std RB26 pistons are dimensionally the same the later/last evolutions would be worth considering to get the later technology . I'll assume they all have that oil cooling passage under the crown and run ~ 8.5:1 CR . If you seek the means to remove the engines breathing and venting restrictions generally temperatures and pressures drop so it gives more affordable components the ability to survive reasonably hard use . I can just about hear people say yeah cops mate but the cost and effort of fitting forged pistons is considerable . Forged pistons are good in two areas , firstly they are mechanically stronger so stand up to the innertial loads better . Secondly they'll generally cop a bit more detonation abuse before they fail . The thing is if your not going to rev beyond what RB26 pistons can reliably stand no problem here . If you tune the thing properly so it doesn't detonated it should cope fairly well . For externals there's lots of choices . The std exhaust manifold seems to be able to cope with 300Kw worth of exhaust flow so thats a reasonable base option . Next up is probably the single low mount HKS cast manifold , it offers external wastegate (can blank it off) , its internal "bends" are a bit less abrupt than the std one and it angles the front of the turbo outwards slightly so the compressor cover is further away from the casting . After that there is a large range of fabbed manifolds but they are expensive and some have cracking issues , for 300Kw the above options are more cost effective and I believe long term reliable . Turbos ? A real GT3071R could probably get there with the medium sized turbine housing in single scroll form . A GT3076R/GT3037 would easily get you there . IMO the HKS manifold/ext gate with the twin scroll GT32 housing on a GT3071R or GT3076R would be very impressive . Your bux your call .

Just to fill the gaps in . If you read my last post carefully you'll see mention of T28 flanges and T28 (actually GT28) housings . They are not always one and the same thing . Its confusing because people want to call a turbine housing by its flange size when they should call them by their intended turbine family . Some examples are , HKS made a lot of T28 flanged GT30 turbine housings so that people could mount GT3037's on engines with T28 flanged exhaust manifolds . There's absolutely nothing T28/GT28 about those turbochargers - except the mounting flange . Another is the T3 flanged GT25 (nowdays known as GT28) turbine housings found on HKS's GT2530/GT2540/GT-RS turbos which are designed to be a bolt on for the T3 flanged exhaust manifolds on RB20 and RB25DET's . Again there's absolutely nothing T3 about those turbos - except the mounting flange . You see people try to do things on the cheap like buy a 2nd hand T28 flanged GT3037 and use an adapter to bolt it on a T3 flanged manifold . It never works as well as the properly designed for the job part . Garrett and HKS are both guilty of using T28 flanged GT28 family IW turbine housings as a cheap convienent way to get 2835/3071 turbos - with their cropped turbines - onto engines like CA18DET's and SR20DET's . All they do is bore their existing GT28 turbine housings out further inside to take the foreign modified GT30 family turbine . The propper solution would have been to develop and manufacture a housing like the T3 flanged GT Pro S one but with a T28 flange and the Nissan style dump pipe flange . They took the easy way out because making one off specialised turbine housings is very expensive particularly when they are cast in Ni Resist or some other high Nickel content iron alloy to withstand petrol fired EGT's . For all sorts of reasons any really serious SR20 will have a T3 flanged exhaust manifold and T3 flanged turbine housing designed for the desired turbine family ie GT30 . Nissan designed the SR20 for fairly compact engine bay apps and thats also why the turbocharger system is compact itself . In its (arguably) highest state of factory tune (GTiR) it still had a T28 but it was a large series T28 and had a better flowing exhaust manifold than the S13/14/15 or U13 Bluebird . Back to RB's and R32/33's the way to go is either Garretts GT30 turbine housing in IW or external form or the similar equals from HKS . If you short change the conversion by using some cheaper bastardised turbine housing then you risk the success of the whole thing . Cheers A .

Cubes not 100% but pretty sure the Pro S GT3037's had a unique port shrouded compressor cover in 0.50 A/R though not sure if it was based around Garretts T04B or T04E comp covers - probably the "E" type . A good chance that was to help clear the exhaust manifold and pull up a bit more bottom end . Actually the 3037 and 2835 Pro S turbos appear to have almost the same housings . You have to be a bit careful with the IW turbine housings because even though they look like the same castings they were machined on different turbine centres . By this I mean the larger GT30 (60 x 55mm) turbine would have broken into the Pro S housing wastegate flow path had they not offset the cartridge in the casting . I think the port shrouded 0.60 A/R T04E comp cover similar to the one on the GT3076R comes std on HKS's GT3037S . With GT Pro turbine housings I've never seen or heard of any with T28 flanges on them , the ones HKS used for IW GT2835's for SR20's appeared to use T28 flanged GT28 housings - the dreaded GT28 housing bored out for the cropped GT30 turbine scenario . The Garrett version according to ATP speak is called GT3071R WG or waste gated . I wouldn't bother with any T28 housing version of those turbos - low turbine efficiency and lag city . Cropped or std GT30 turbines only seem to work properly in a GT30 based housing , so if your using a 2835 that means the matching HKS Pro S housing . For a GT3037/GT3076R the propper Garrett GT30 IW or EXT gate housings are now availabe or similar things through HKS . Only HKS make dedicated T28 flanged GT30 turbine housings . Cheers A .

Thats a lot of turbo even for an RB30 , I think somewhere between a GT3582R and a GT4088R would make more sense on a number plated car .

Long story short , the turbine or exhaust housing housing is the hard part to get when you want to hang a GT28BB based turbo off an RB20/25 . Garrett originally intended GT28 turbos to use the T28 flange and don't make a GT28 exhaust housing with the T3 flange that you need . When HKS decided to use Garrett cartridges (centre section and wheels) they had to have model specific exhaust housings made so that the turbo could bolt up to the std manifold and dump pipe . The one they use on their RB20/25 specific GT2530 and GT-RS etc is probably the one to use if you can find one from a dead HKS turbo . The alternatives are the ones sold by GCG and one of the turbo mobs in I think Victoria though they are possibly more aimed at RB25's - larger A/R ratio may not be so hot on a 2L six . At least one person here has had a Nissan/Hitachi exhaust housing reprofiled to suit a GT28BB based turbo so that may suit your means . Personally I think the HKS housing would be the best way to go but thats your call . Cheers A .

The HKS GT3037 Pro S mounting flange is open T3 and will bolt to your std exhaust manifold . If you bought it as a kit it will bolt up properly and they give you everything . Cheers A .

Mafia only you can know what sort of money your prepared to spend , the RB30 short being 20% larger will show up in the overall torque output for that reason . The thing is how much of this can you get to the tarmac before the rears go up in smoke ? Your call but I'd be looking at an RB26 head and inlet system to plonk on the RB30 block with possibly std rods and good std pistons if possible . You wouldn't need to fix the 25 VCT issue and the solid bucket valve train has lots of advantages if your chasing real power . Exhaust stud pattern different though not too difficult to change . Fair std RB30's can be freshened up reasonably cheaply so if you used up a few who cares ? Could even have a spare standying by . Food for thought , cheers A .

Mafia engine size is irrelevant , lower exhaust manifold pressure is a benefit to any engine under load because it allows them to scavenge that much more effectively . Power out the crankshaft is what you get after all the parasitic losses are taken into account and that includes pumping losses . Cubes divided manifolds and housings that work properly are much less A/R sensative than single ones so you get the large hot side benefits without the negatives of the same sized SS system . Yes the wastegate issue again , next time we want the housing and integral gate divided . If I remember I'll take pics of the divided housing with its divided integral wastegate paths that I have . Such a pity that its a T4 flange one of GT40 frame size and in 1.17 A/R - even if it is profiled for a GT35 turbine . Its compressor is the same GT37 56T wheel as a GT3076R ... One of the American mobs , possibily Precision Turbo is , doing a hybrid turbo made up from A Garrett GT3582R but with a different compressor which may be a Holset . Its 7/14 bladed and claimed by Burscher Racing to have a lower boost threshold than the std 3582R . You can read the thread about it over at EvolutionM.net in the Engine/Turbo/ Drivetrain section . I believe they call it the HTA35R . One thing I've not gotten to the bottom of is a slight difference in the designations on the GT3076R and GT3037S compressor covers . One has KTT1 on it and the other BSK1 , not at home so can't check which has which . It would be interesting to check the two housings to see if there's any diffuser differences . Cheers A .

Go Lithium . Yep the Garrett GT turbine housings are always going to be a better match for their GT series turbines , the volute and nozzle section are designed to work with those UHP family turbines where the American spec Ford style T3 ones are not . This shows up as you found with higher turbine inlet pressure and larger flat valves don't often do much good . Just on those IW type actuators or "cans" . They are not really designed to be adjustable other than to get some pre load on the valve to initially hold it shut . If the shaft is made length adjustable and you keep making it shorter what happens is that you are eating into your diaphragms limited travel , meaning while the spring load may climb a bit the diaphragm bottoms out earlier and the valve now can't open as far as it may need to . I noticed that you had an external gate on the T3 housing and some places in the US do this for some reason . Probably the chief disadvantage of IW is that the exhaust gas has to make a sharp 90 deg turn out through the side of the turbine housing and another to go south out the dump pipe . Provided the exhaust gas velocity is not too high its quite a reasonable way of doing the job . When gas velocity gets really high it doesn't want to know about changing direction any more than it has to so the IW can lose its ability to regulate mass flow through the turbine , pressure in the housing climbs and boost creeps upwards . You get a bit more say in waste gate valve size with externals though as we know that introduces other issues , as Lithium found the larger valve or hole anyway doesn't always fix the problem . I've seen so many people use non native turbine housings particularly IW ones and strike creep problems . Another nasty that can happen is the larger flat valve having more area for the hightened exhaust manifold pressure (turbine inlet pressure) to act on is forced open more easily so the punter uses higher and higher spring loads to hold the valve stut . Naturally turbine inlet pressure goes ballistic and the engine is in danger of killing its pistons or at best not making the desired power levels . This is why I've been harping here for years about the evils of high turbine inlet pressure , and getting the turbine/compressor match right , and that if you don't get the turbine/housing combination right it won't work as well as it should . Here we go again they'll say , a PROPERLY designed twin scroll system gives more of the same mainly because it allows even lower turbine inlet pressure , it allows the use of larger turbine housing A/R without the turbine lag penalty , allows us to run the compressor to its limit without turbine inlet pressure restricting the hot side while it does . Now depending on how fast you spin it the real GT3071R's 71mm 56T compressor maxes out at around 440 Hp's worth of air . If you could have the turbine response and have enough low restriction exhaust flow to get there the result should be pretty good I think on an RB25 . For the 3L people , fingers crossed , there could be a twin scroll T3 flanged GT35 turbine housing in 1.06 A/R next year . If Garrett are smart they may cast enough material into the blank to be able to profile it to suit the GT30 turbine as well which could be very interesting on a GT3076R . Anyhow good results and thanks for posting your journey , cheers A .

Frame size . Garretts BB turbos in the GT2554R to GT3582R are said to use the GT25 sized or small frame centre section . The large frame GT BB centre section from memory starts at the OEM GT3576R through the GT3782R's (two different comps) the GT3788R (all these use the diesel spec HP series turbines) to the GT4088R , the GT42R's etc . I think they are a BB mod to the GT bush bearing centre which also uses the four ears to bolt the turbine housing to . The large frame turbos (both ball and bush bearing) have a compressor backplate bolted to the comp end where the small frame BB's use a large circlip and a range of adapter rings to suit the chosen compressor housing family ie T3/T04B/T04E and T04S . The compressor end face of the small frame bearing housing is machined to accept 60/71/76 and 82mm OD compressors where in the large frame variety this is machined into a removable compressor backplate . When you look at a small frame BB cs (centre section) its shorter and smaller in diametre than a T3/small shaft T4 or the Nissan Hitachi BB cartridge ie RB20/25/VG30 . The large frame version as a larger shaft diametre and a larger/longer bearing pack and housing . A few people have hinted to me that the large frame ball and bush bearing shaft is same/similar but not 100% sure . I do have a bush GT3576 to gut eventually but need to heat the turbine housing to get it off . One day ... Cheers A .

I think you'll find the situation works like this . Most production cars in good condition run with a reasonable amount of reserve capacity in their cooling systems which allows them to be driven normally in a wide range of temperatures without rupturing themselves . One of the by products of making power is making heat so with more power you get more heat . In a turbocharged production car I think they intend you to give it the odd squirt rather than be on boost and using the extra torque/power for extended periods of time . For this sort of use an R33 in tip top condition is probably marginal and once you open up the exhaust and make greater than factory output (more heat than std) its going to need help . I assume all RB25DETs have the water/oil heat exchanger and for hard use this will go against you . Firstly the system is trying to maintain reasonable oil temp with its coolant so not as effective as an external oil cooler and secondly its dumping extra heat back into the coolant which your trying to control with a std cooling system . I think the best examples to look at would be the highest factory spec GTR's to see how Nissan went about beating the heat issues with a more powerful and higher state of tune engine . I'm not suggesting you buy an N1 or NUR spec cooling system but you can look at affordable alternatives say for example a JJ radiator and a decent air cooled external oil cooler . Something else you could possibly look at for track days is the cooler Nismo thermostat not because it regulates lower than the std one but because it would be fully opened at the sort of temperatures you are likely to run on a track . I think it would also help on the cooldown laps if the system was getting full flow for a bit longer mainly to help pull down oil temp . Good fliuds would be a must and I know several who use and swear by the Castrol synthetic 10W60 probably because it would stand up to the higher temperatures and still have reasonable oil pressure . Your call but I'd do the radiator first , oil cooler second and see how it went . My affordable fuel pump fix was a good second hand R33 GTR pump which is a direct replacement for the std one . Those air deflector plates seem to help too . Handling the heat should be the number 1 priority because you won't get reliabilty untill you do - in other words I'd be spending money in this area first . Before I go what is this JJ "header tank" and what computer are you running ie std ? Cheers A .

The way I read it the GT4294R/02R use the same inconnel GT42 turbine but with either the 94 or 102mm GT compressor . The BB T51R's cartridge wise are basically the same deal but with a 76T T51 turbine and some minor comp trim trip changes on either the KAI or the SPL . I have not looked but the T51R's may also use the slightly different mounting system for the turbine housing like a T04Z does , basically the crab plates and bearing housing register instead of the four "ears" and bolts like most of Garretts large frame BB and plain bearing turbo cartridges . Thats just a simple method of making the T series turbine housings fit the large frame T type turbine equipt turbos . It would be interesting to know if Billet can supply turbos using Garrett GT BB compressors and turbines in combinations not offered or only expensively through HKS . Also are they going to do large frame type centre sections as well ?

To do properly the larger single costs significantly more than parallel twins - up to the power limit of integrally gated twins that is . There are several ways to approach the AFM issues , a single can meter air before or after the twin turbos or you could sell your PFC for an RB26 one though fitting that involves a fair bit of wiring and the two AFM's . My opinion only but I don't think any single scroll T3 flanged turbo on an RB26 is a good thing . These engines were designed to have free flowing gas paths on the inlet and exhaust sides and they got their power from a lot of flow without a lot of pressure (restriction increases pressure) . I don't think its any coincidence that when HKS had their single turbo cast manifold made for the RB26 it was split pulsed and T4 flanged for good reasons . There are limits to how much gas flow you can get through a T3 sized flange before the restriction forces a pressure rise . The T4 flange is significantly larger and if in split pulsed form this is not a problem with a divided turbine housing . How that system works is a lot more flow for a lot less restriction and more ideal gas pulses from the turbines and engines points of view . Anyhow many here don't see this as any advantage once they work out what its all going to cost . Parallel twins are effectively split pulsed because each turbine nozzle only communicates with either front or rear three cylinders like a split pulsed twin scroll system does . With the latter system your up for manifold gate/s and turbo where with the former you only need direct fit turbos and they generally have their own integral waste gates . Your money your call .

You would have to check this (not at home to look at my R33) but don't 33's have an elbow bolted to the compressor covers outlet ? Not certain but reasonably sure that the RB20's ceramic BB turbos housing has a three bolt outlet but the holes are on a slightly smaller PCD than the RB25/VG30 BB turbos housings . If you can find one the RB25 elbow possibly bolts to the VG30 comp covers outlet . Hope this helps , cheers A .

I reckon a Neo RB25 could possibly get away with a real GT3071R and one of Garretts GT30 IW T3 flanged turbine housings . That way you get the exact same compressor wheel as a HKS GT2835 Pro S and the non cropped GT30 turbine . I think the Neo's variable cam timing could pull the bottom end up a bit better than the R33 version and thats probably why Nissan used the larger OP6 type turbine housing on R34 GTt's . Also with Garretts turbine housings the available A/R ratios are 0.63 0.82 and 1.06 , the 2835 Pro S's are 0.68 and 0.87 . For a GT3076R I would always use one of the the above mentioned Garrett GT30 IW housings , a good chance you could buy such a turbo complete and know the housing is designed to suit the turbine . Once you move away from OEM turbine housings its generaly best to use one designed for the turbocharger , if you can get one that bolts to the std manifold the rest is pretty straightforward . Cheers A .

Hi Mafia , one thing I've never gotten around to proving is the worth of putting "soft spots" along an exhaust system to beat that low frequency vibration or drone . The story I get is that everything has a set or natrural frequency point where it will ring like a bloody bell and transmit vibration into everything around it . It seems to me that large exhaust systemys are quite rigid and capable of acting like a great long engine steady - transmitting lots of vibration to our speaker box like cabin area . David Vizard used to say that exhaust systems should be hung not mounted to isolate unwanted noise . I tend to think that if soft spots like those stainless mesh covered concertina things are placed along the exhaust in a few places the tailpipe loses much of its rigidity and can have its vibratioin isolated by well thought out flexible hanging mounts . I remember on occasions being in Goulburn where they have an Olden dealership and Commodes backed up on ramps , they seem to have quite a few soft points down the back and I doubt its to do with stopping the pipes cracking when the engine moves about . By any chance would the drone occur at low revs in high gears and mysteriously correspond to 60/80/100 km/h ? Any how I'm interested in what other peoples thoughts are , cheers A .

IMO the std Hitachi turbine housings are fine for what they were intended to do , the fact that there are three sizes available for the same turbine/cartridge is a bonus . What you need to understand with turbine housings and area radius ratios (A/R ratios) is that they are sized to to achieve a gas velocity range to suit a certain sized turbine and engine . Nissan used the same basic ceramic BB turbine for RB20/25 and the single BB turbo VG30 . So with 2L 2.5L and 3L engines exhausting through them the turbine housings had to grow so as to not choke the larger ones . Also IMO its a catch 22 trying to make lots of power with the ceramic BB turbos mainly because that ceramic turbine is quite small . When you go up a turbine housing size with them yes the restriction is reduced but then so is the gas velocity to spin them up in the engine speed ranges most road cars are normally used in . In simple terms using say an RB25 turbine housing on an other wise std RB20 turbo means the engine has to rev higher to achive the necessary gas velocity to spin the turbo up or spool if you like . An interesting thing is that once you go to turbos like for example a GT2530 for an RB25 the compressor wheel is actually slightly smaller than the std Hitachi's but the turbine and its flow range is actually higher . You make more power by letting the engine excite the turbo but with less restriction on the exhaust side , people have for some reason this love affair with big compressors but its critical to get the turbine and its housing right to suit the engine and the compressor . Your call but if you just want to have a bit more exhaust flow I'd go up a size in Hitachi turbine housings . The advantages are you know it will fit and keep the turbo in its std position (don't need to alter water/oil/air/exhaust fittings) . Also the housings material spec will be some sort of high nickel content iron alloy so should not crack like some aftermarket housings made of lower temp resistant iron . If you shop around you should be able to find a complete 2nd hand turbo or just the housing for a lot less than 700 bucks , I was lucky and via someone elses swap got a complete VG30 turbo with the OP6 housing for I suppose equal to 300 . All things considered if you want some half serious grunt you are probably better off trying to find a used RB specific HKS GT2530 or at least its turbine housing . Once you have that any GT28 based turbo will bolt to your manifold and std/aftermarket dump pipe . Cheers A .

GeeTR 500cc pots are ~ 1.5 times the size of 333cc pots so more power per cylinder and a greater slug of gas going into the turbine housing each time . Most production engines use plenum type single throttle inlet manifolds and the fours induction events don't overlap as much as the sixes . On the exhaust side you only have two cylinders venting into each side of the divided twin scroll manifold and housing every two crank revolutions . Its the phasing of the fours flat plane crank pins 180 degrees apart vs the sixes 120 degrees apart that makes a difference manifolds wise . A thing to note as well is that some parts of an FJ20ET make it in a higher state of tune than an RB20DET , the cams are a bit hotter at 256 deg by ~ 8. something mm lift and their ports are reasonably big by production engine standards . In std trim the FJ's smallish T3 turbo uses a larger turbine than an RB20 and the early ones had a 0.63 A/R turbine housing which would be nearly as big internally as the VG30DET's ball bearing type turbine housing . Also I mentioned the FJ's large bores (which can fit large valves) so are an advantage . Most of todays current 2L fours are used in east west apps ie CA18 and SR20 so the blocks have to be short along the crank centre line , this forces smaller bores and longer strokes which is fine for shopping trolley cars but not the best for all out power . From memory RB20's have 78mm bores so valve size and valve lift is probably limited . A few manufacturers made larger capacity fours such as BMW's I think E30 M3 (LHD only) with good bore/stroke and rod/stroke ratios and I reckon they would have been very strong in turbo form . Porsche had a 3L I4 but it may have been N/A and 2 valves per cylinder in std form . Nissan does do a KA24DE but it's 89 x 96 bore/stroke make it not a real high crank speed thing . Twin scroll systems on those are supposed to be capable of making VERY strong torque without many revs - perfect for fast road and why people out here don't do them up is beyond me . Perfect for the S13/14 and they fall in with the right manifolds because thats what US spec S13/14's get std . Another 2c spent , cheers A .

To replace a GT2530 with a GT2860RS centre section (cartridge) you will need to re use the GT2530's turbine housing . Garrett don't make a T3 flanged GT28 turbine housing which you will need on a single turbo RB25DET exhaust manifold . The GT2530 (RB25 spec) turbine housing should go straight on a GT2860RS cartrige because they both use the same turbine . As for the tune I guess you could try it innitially with a little less boost to see if it wants to ping or run lean on full load . Cheers A .