discopotato03

The Garrett numbers I posted are based on what the compressor sections can do airflow wise , and a formula of what quantity (by mass) of air and the power potential that quantity has . Not all RB25's are created equal , with mods some flow more gas in/out far more easily than others . Because a turbocharger has a set capacity doesn't mean an engine can run it to its limits . A .

For the broken record these are NOT GT28 based turbos even though HKS's handle implies they are . They have cropped GT30 turbines and in todays language are called GT3071R's . GT28 turbines have 9 blades where GT30's have 10 . A know a little late now but GTRS's would've probably been a better spec turbo . The cropped GT30 turbine does not like being in GT28 turbine housings and this is what they get in CA/SR/RB26 T25 IW flanged forms . The GTRS's use a GT28 turbine in a matching GT28 turbine housing . Your call but I'd be trying the std cams first because I don't think twin 2835's are going to be super responsive on 2.6 liters . A .

You want to read that whole thread from NASIOC not just the original post . This type of industry direction is hardly new , I can understant the employees pain but the world has moved along lots since the 1960's . Much of the manufacturing industry in the western world has migrated to places where labour is cheap and rights of workers few - we'll let you breathe but not on the companies time . To be blunt a lot of it has to do with the masses want to buy cheap and replace often . To buy a good quality spanner or socket costs good money but if you don't lose or abuse them you have them for life . Not quite the same with a drill bit but a good one may do 50 holes where a garbage one may do 5 . Tis a sad fact of like that retail price bears no resemblance to manufacturing cost . Its all about supply and demand and what the market will bear price wise . No friends in business and family history means jack sh#t . You don't win wars with bullets anymore , you do it with cheap manufacturing industry . I guess the only saving grace is that with luck we'll run out of countries with 3rd world working conditions - but theres a few to go yet . A .

As promised the GT2535's cartridge number is 446179-19 . Garrett actually make two 69mm OD compressor wheels in the T3 family . Part No 446279-0001 69mm x 51.65 56 trim 6.2mm tip height . Normally its bore size is 6.25mm but can be made smaller to suit the GT25BB center sections turbine shaft . Part No 466279-0002 is 69mm 46 trim . Both are 6/12 bladed . Personally I think its easier these days to use the GT2871R cartridges because they are readily available . The 56 compressor trim version is known to be a bit lazy/laggy so I'd say its wise to avoid them if response means anything to you . My HKS list is not complete and shows a couple of cartridges not identified - 446179-17 and -20 . Pretty sure they would be the GT2510 and GT2540 . A .

Just breifly , work to do , the HKS "GT2535" has a 69 x 51.6mm 56 trim compressor wheel . Judging by the barb sizes the compressor housing is probably the same as a "GT2530" , T04B 0.60 A/R . Note these housings can be the truck or Nissan style . My lists show the power ratings of the 2530/2535/2540 as 320/340/350 PS , PS is supposed to be very close to HP figures . The GT2871R's use a 71.1mm compressor in 48/52/56 trims , the GTRS has the 52T one . Gotta scram , cheers A . I'll give the cartridge number later .

The turbobygarrett site shows two of them the difference being turbine trim . 84T version - turbo no 700382- 3 cartridge no 700177-3 . 90T version - turbo no 700382-20 cartridge no 700177-4 . In that form they have a machined out , bastardised , GT28 turbine housing and a std snout 0.50 A/R T04E compressor housing . My gut feeling is that one of those cartridges in a suitably machined GT30 IW turbine housing may fill the gap between the GTRS (GT2871R 52T) and the GT3076R . HKS had such a thing and called it GT2835 Pro S , if Garrett housings can be used then very likely a cheaper alternative . The main issue is getting whoever casts and machines those Garrett GT30 IW housings to take less out of the center for the slightly smaller , cropped , GT30 turbine wheel . The std or full sized GT30 UHP turbine is approx 59.9 by 54.9mm and the cropped ones around 56.6 by either 51.8 or 53.6 for 84 and 90 trim versions of this turbine . My HKS specs quotes GT2835's rated at 410 PS in normal form or 420 in GT Pro S form . By normal I mean in a HKS supplied T25 flanged GT30 turbine housing in 0.61 or 0.73 A/R . From memory they don't have port shrouded compressor housings . My spec sheet quotes the GT2835 Pro S (T3 flanged RB20/25 bolt on) as having a 0.68 A/R turbine housing and the port shrouded compressor housing , power rating is 420 PS or roughly 420 Hp/315 Kw . Note the smallest Garrett GT30 IW turbine housing is 0.63 A/R vs 0.68 for the HKS one . The point of all this is to spin the turbine and compressor a little faster for the available exhaust energy than the 60 x 55mm full sized GT30 turbine can . A .

The names of these things ties everyone up in knots What I ment was the cropped GT3071R AKA GT2835 cartridge in the Garrett GT30 0.63 A/R IW housing . I'm pretty sure the one you are refering to is the std or 60mm GT30 turbine version of the GT3071R cartridge - 700177-5023 . Cheers A .

The GT"2540" only used a 0.64 A/R turbine housing in "T3" footprint because thats all HKS had made , stupidly didn't do a 0.86 A/R one as well . Garrett do both sizes but only in T25 sized mount flange . I wouldn't bother recreating the 2540 because it was never a good thing IMO , you really have to wonder when you pull a small comp cover off a turbo and find a 76mm T04E wheel ... The GT2871R 52T used in the GTRS units is definitely a step in the right direction . The GT"2835" , or as they are now known GT3071R , move up to the GT30 turbine family and in this cropped turbine form tend to work best in a GT30 based turbine housing . Hopefully one day Garrett will have their GT30 IW turbine housings machined to suit these 56.6mm cropped GT30 turbines and we will have affordable turbos along the lines of HKS's GT2835 Pro S ones . Who knows , maybe they can be machined to take a sleeve and the sleeve machined to take the 56.6mm turbine . Throw in a comp housing altered to take the surge slot and holes and suddenly you have a cheaper competitor to HKS's GT2835 Pro S . Don't quote me but maybe a 0.63 GT30 IW housing on a 56T cropped GT3071R cartridge with a surge modified T04B truck cover may make a nice sort of bolt on for a sensible street R33 RB25 . A .

I don't see any reason why the 56 compressor trim version of this GT3037/GT3076R would do it any easier than the 52 trim one . From memory , airflow wise , the 52T is good for around 49 pounds (by mass) of air and the 56T ~ 54 pounds . The rule of thumb is 11 Hp per 10 pounds of air though I work off 10 (hp) not to be on the hot bleeding edges of the comp maps . So in theory 490 and 540 Hp potential (367 and 405 Kw) based on compressor airflow maps . If you input the bleeding edge numbers you get 539 and 572 (404 and 429 Kw) potential Hp's worth of air . A .

Hint , many SR20 OE water cooled turbos use the same size banjos and bolts as the Garrett BB turbos in the GT2554R to GT3582R range . Sometimes import wreckers will sell them to you for not a lot of money . All you really need the steel water lines for is to get far enough away from the turbos heat for rubber hose to survive reliably . High pressure (EFI) fuel hose makes good rubber water line material . The Nissan banjos/bolts are compact and look factory because they are . Just make sure the water supply line runs uphill to the turbo and the outlet one uphill to wherever it connects to the system . Cheers A .

More facts . HKS don't make turbochargers , they get Garrett to do that . Some time back HKS had Garrett make up turbine/compressor ball bearing cartridge combinations and had the exclusive rights to sell them . If Garrett happened to have suitable housings HKS used them , if not HKS had unique ones made to suit the application and the Garrett supplied cartridge . Garretts turbo/cartridge numbering system has changed over the years and a good example is this GT25xx thing - ie GT2530 . Back when these turbos were new all the GT25 and GT28 series turbines were called GT25 , this is where the "GT2530" got its name though technically they are a GT2860R . The only unique thing about the 446179-21 cartridge is the compressor wheel which is 60.1mm OD 63 trim . Garrett sell a couple of cartridges with very similarly sized compressor wheels only in 62 trim . The one from the GT2860RS has the greatest tip height AFAIK and probably performs very similar to the HKS spec Garrett GT2530 . Different applications with the GT2530 means different housings , what suits in TT form an RB26 wouldn't suit an RB20/25 . The single GT2530 for RB apps tends to get a generic Garrett T04B 0.60 A/R compressor housing , they make it a simpler bolt on by machining off the truck housings snout and bolt on an adapter to suit the OE rubber inlet hose . The GT2860RS usually comes with the same housing in unmodified form . HKS had their own integral wastegate turbine housings made in T25 and T3 flange . The T25 style one has the Garrett style dump pipe flange where the T3 flanged ones were designed to suit the RB20/25's std dump pipe flange , again to make them a bolt on unit . The HKS GT2540 is literally a GT2530 but with a 76mm T04E 46 trim compressor . You could call it a "GT2876R" but I reckon that would confuse people with the POS Garrett call a GT2876R . Neither is really a sparkling turbo but the T04E compressor is along more modern lines than the S or TB41 , don't remember which , the Garrett GT2876R has . HKS replaced the GT2540 with the GTRS which is a GT2871R 52T in HKS housings , actually the compressor housing of the GTRS in a HKS special port shrouded one in RB20/25 form or Garrett ones in SR/CA/RB26 apps . Cheers A .

You are talking about a factory 3 Liter engine there and a 0.82 A/R GT30 turbine housing is not big by 3L standards . Rather than me guessing where did in come on boost with the 2JZ . May have been a case for the larger 1.06 A/R GT30 IW housing . A .

I forgot to add that when a turbo manufacturer makes a range of compressor wheel trims often the mid sized one is the best match for the turbine wheel , larger and smaller trims can be used to tune the maximum airflow either side of the middle one depending on whats needed . The production engineers at Garrett in the US I used to be able to speak to always liked the mid or 52T GT3037 , possibly the overall response was what they liked and power/airflow was more than adequate . Really there's only about 3-4 pounds odd airflow difference between the 52 and 56 trim GT37 so maybe 30-40 maximum Hp potential . I try to remember that not every RB25DET out there has had breathing improvements eg better porting/valve sizes/cams/manifolds so the limitations may not actually be caused by the turbocharger itself . People have said that the OE exhaust manifold becomes a limitation at ~ 300 Kw and the std porting and cams probably needs the boost to be reasonably high to get to 300 Kw . Many will probably disagree but I reckon sizing turbos to work within the gas flow parameters of the head and manifolds makes sense , having a turbo with the capacity to go beyond these flow limits I think means you can't use a lot of the big turbos potential so why bother . Often the larger turbos don't boost till higher up the rev range and then the flow limitations are reached befor the capacity of the turbocharger is . IMO to have a wide power range the turbo needs to have just a bit more flow capacity than the engine does on boost . If you take turbos to the bleeding edge airflow wise they blow pretty hot which is not what you want at the rev ceiling . It also makes sense to try to aim to have the engines torque peak correspond with the middle of the island of highest (coolest) pumping efficiency - coolest charge temp and highest volumetric efficiency should make for highest torque numbers if tuned properly . A .

Really a GT3776 is a long way from a GT3076R//GT3037 52T . From the compressors point of view those use a 0.54 A/R GT40 compressor housing where the BB one uses a 0.60 A/R T04E housing . Near as I can find the 52T GT3076R/GT3037's compressor map is similar to the 56T version but moves everything about 3-4 pounds to the left of the map . The center island is about 78% and is wider that the 56T's one . Not rare anymore , Bretts decided to keep a small stock of these 52T cartridges and their port shrouded compressor housings at GCG . A .

The GT25 and GT28 BB turbo story . The GT25 based turbos use a 53mm 11 bladed turbine in 62 trim . The GT28 based turbos use a 53.8mm 9 bladed turbine in 62 or 76 trim . The GT25 BB turbos mentioned in this instance can have 54.3mm or 60.1mm diameter compressor wheels , basically GT2554R or GT2560R . The former has a 0.80 A/R T25 compressor housing where the latter uses a 0.60 A/R Nissan style T04 compressor housing . From memory the GT2554R is a bolt on for CA18DET's and the GT2560R original equipment on some SR20DET's . The part number 466541-4 (GT2560R) was mentioned above , that is the JDM S15 manual trans version of that turbo . The 466541-1 and -4 only differ in that the -4 gets the Ni Resist turbine housing and Inconel turbine , higher temp capable materials than the -1 version . -4 also gets that deflector vane in the back of the turbine housing as well . As I said the GT28 based dryers get 53.8mm turbines , the GT2854R has the 9 bladed 62T turbine while the Disco turbos get the 76 trim one . There are a few variations in the GT2860R family with the DP turbo being the highest performance variant . I know people want to argue the point in SR20 circles but these were intended to have the larger of the two sizes , 0.86 A/R , turbine housings on them though some prefer the 0.64 A/R one . There is also a HKS GT2860R variant for SR/CA known as the GTSS , not the same as the RB26 GTSS . It has the GT28 76T turbine and the cold side from the GT2560R . There is also a Garrett variant that looks very similar spec wise to the DP turbo , its compressor wheel has exducer tips not quite as high as the DP's and has a different cartridge no . If buying new I'd strongly consider the GT2554R or GT2854R , responsive things on 1800 turbo 16v engines and I think they pretty much bolt up . Recently I've been speaking to people in the US turbocharging MX5's (Mazda BP18 engines) and they quite like the GT2554R's . Some use GT2560R's and while they make more top end they come on later as well . The GT2854R is interesting in that it gets the GT28 62T 9 bladed turbine so makes a little more top end than a GT2554R . The GT2854R isn't normally imported into Australia because it costs a bit more and isn't much larger internally . The cost issue is mainly due to them having the hi temp capable turbine and housing material , the good manual S15 turbine housing with that vane in the back . If you want one they can be brought in , just not usually on the shelf here . Personally I look at the GT2854R as a scaled down DP turbo , higher flowing and more efficient turbine than the GT2554R so possible to push a bit more timing in and gain overall . I've never had CA18DET's and I'm not sure if the Disco or GT2860RS turbo would be a little big for street/drift use . Just so you know these have the GT28 76T turbine and a high tip height 60.1 mm 62T compressor wheel normally in a truck style T04B comp housing . I've had SR20DET people say they didn't like the 0.86 turbine housing DP turbo combination claiming it was too "laggy" . I have one I used years ago on an FJ20 and really liked it , a bit lazy until you learn to throw in extra light load/low boost advance which makes them really come alive . Go to turbobygarrett and look at the GT25 and GT28 turbo specs before you make your decision . Cheers A . PS , the turbo in that pic is not from an RB30ET . The compressor inducer is too small and the housing is too I reckon . At home I have a VL's compressor and housing kicking about and they don't look like that . Even if it was it would be a laggy dinosaur on a CA18DET . The Early low CR FJ20's and all RB30 turbos got a 0.63 A/R turbine housing , lazy on the FJ and possibly not big enough for a 3L engine . Both engines were rated at ~ 150 kw with 6-7 pounds of boost so you don't want these dinosaurs . They wont bolt to a CA/SR and wouldn't be nice if they did . Drink the slab yourself , cheers A .

Strictly from an actuators point of view the larger the diameter of the can/diaphragm/spring the better . Note how external wastegates are generally not small in this area . Also as mentioned the external has no swing valve arm to multiply force against the actuator . A lot depends on boost and exhaust manifold pressures , if the exhaust (turbine inlet) pressure rises markedly faster than boost pressure then the pressure/area force eventually overcomes the waste gate actuator and forces it to open . Its trying very hard to tell you that the system is not running in regulation . Just another indicator that high boost pressure does not guarantee reliable high horsepower . A .

I believe Ferrea and one of the American mobs do as well . My S2 33 has them , they were fitted by Harris Engine services in Sydney . They go in on the existing seats and are a cost effective fix with some performance gain as well . Cheers A .

I think this issue is going to be one of those things based on what pressure the engine runs . If its higher than std then obviously something has to be done for the turbocharger . As Dirtman said restrictors are a far simpler means of restricting oil flow to the turbo but always remember that restrictors are flow related not pressure . Anything in the system crud wise will damage engines and turbos so really everything has to be as clean as possible . I'm not really sure about the 0.8mm restrictor getting blocked up , if you had crunchy bits that big in the oil then you've got real problems downstream of the pump and filter (main oil filter) . An oil strainer in the turbo oil line may not be a bad idea but you want to inspect them often , lack of oil kills turbos real quick . If you really want to keep an eye on this theres no reason why you couldn't have an electric sender type oil pressure gauge in the oil line and experiment with restrictors . At least with the sensor there you can differentiate between engine oil pressure and turbo oil line pressure . As a point of interest some businesses are turbocharging Quad bikes and their engines are more bike like than car engines - roller crankshaft bearings . They survive very happily on "low" oil pressure - something like 10-15 psi but don't quote me . Bush bearing turbos like a bit more than that so turbo'd bike engines seem to do better with ball bearing turbos because that bearing system doesn't need the extra flow and pressure that bush bearing turbos and slipper crank bearing engines do . One thing I do know is that excess oil flow in ball bearing turbos adds extra drag for the balls so its something to avoid if you want good turbine response . A .

A complete Garrett GT3071R IW or GT3076R IW , the real ones , don't match anything on an RB25det except the mount flange stud pattern . Most of what you have to change is a change for the better so I don't really understand why people try to resist this . The water banjo fittings are smaller - no drama . Oil fitting is different and most get/make a suitable braided oil line . The dump is different - part of the power up improvement process so all good . Air , outlet needs a bend or elbow and inlet a new pipe . I think the go is to plan ahead and have everything ready for the changeover . HKS do make it easy with say their complete Pro S kits , it costs good money and I think people may be beginning to understand where it goes . In some ways I'm a bit surprised that no one makes an air inlet pipe to suit this GT3076R RB25DET conversion . I've not been there yet but I don't reckon mine will have 100mm/4" pipe . The Z32 AFM many use is 80mm from memory and you don't really need 100mm at the compressor housing anyway . The GT37 compressor inducers are ~ 53-57mm depending on trim and the housings boss is only 4" to package the ported shroud , plain boss T04E housings are 2.75" or around 70mm . Probably if anything the smaller volume would cause less dramas for the MAF sensor . I remember people saying the air returned from the throttle closed recirc valve can cause dramas MAF wise so it probably needs to be closer to the turbo than the AFM and maybe even aimed back towards the compressor housings inlet . A .

Grey Ghost the 707160-9 is made by Garrett for HKS , all HKS do is get them from Garrett without the Garrett wastegate actuator and supply their own higher rated ones . 707160-9 , Garrett turbo for a Garrett price . Why better than std units ? More modern wheels and a lower friction longer lasting bearing system . http://www.turbobygarrett.com/turbobygarre...9R_707160_9.htm A .

All I can say is the guts of it is that the ones John West reject are not the best match of compressor to turbine . The logic is that the "7 bladed" compressor wheel is not a GT (Garrett Technology) era design like the GT30 turbine is . IMO best like technology match is GT turbine + GT compressor wheel . Garrett do actually make a larger frame BB turbo based on T series technology using a "7" blade compressor , it uses an old 76mm 60-1 compressor and a T04 P trim turbine . Old but effective match from the same era/family . You can take the simplistic approach and ask yourself what HKS did - quite some years ago . The original GT3037 turbos all used GT37 compressor wheels , if the 7 bladed thing suited their purposes they'd have used them as well or instead . They didn't . Back in the days when the GT30 turbine + GT37 compressor in the BB center section was HKSs intellectual property Garrett needed to market an alternative and the 7 bladed compressors were the result . I imagine they needed the larger 0.70 A/R T04S compressor housing to stop them surging . After the specified time Garrett was able to market the GT3037 56T themselves only they call them GT3076R . For reasons best known to themselves they only pushed the 56T version but as we now know the 52T version is available if you're prepared to chase it . These are GT37 compressor wheel versions I mean here . Also note that , or so I'm told , BB GT30 turbos are not OE on anything so all were aimed at the aftermarket . All have Inconel turbines and Ni Resist turbine housings and I can't see a manufacturer paying extra for them in a Diesel application . Anyway don't believe any supplier that says they can't get the real GT3076R - 700382-12 . They may not be able to get them at a favourable price but they are available through Garrett here or OS . If they feed you a line check with the local Garrett franchise in Sydney at Chipping Norton then ask why the dealer can't identify a telephone book . Cheers A .

A few thoughts based on what the RB26 people tell me . I understand that the "steel" turbine generally used to flick the ceramic one is the GT28 62T 9 bladed one . Not as fragile as the std ones but nevertheless a slightly larger higher flow capable wheel . The thing to remember when doing this is that with less resistance to exhaust flow the turbines response gets a little lazier and you don't have the lower oil shear drag advantages of annular contact ball bearings to compensate . The simple truth is that ball bearing cartridges are more responsive with the same wheel combination but the wheels need to be sensibly sized too . Durability wise ball bearings win hands down , hardened balls running on hardened races with small point contact areas . Given a choice I would not put bush bearing turbos on an RB26 , if you damage them the sheer work involved in R&R makes them uneconomic in the long run . These 707160-9 AKA GTSS turbos I reckon are the ones to use and its good knowing that someone at HKS spent time and money dialing in a specific turbo to be powerful and responsive in a specific car/engine application . They are not a Garrett generic maybe . Smart cookies developed this combination . It's unfortunate Garrett doesn't appear to want to sell the cartridge used in the 707160-9 turbo because an economic upgrade may have been to have the std turbos housings machined to suit this BB cartridge . Anyway it looks expensive initially but for a "sorted" turbo that you can buy at a Garrett price I think they are hard to beet , short of losing oil pressure or something foreign smashing the wheels these should live a long and healthy life . Response cautious people like them and I don't think I've heard anyone say they didn't work better everywhere that the std turbos while being more responsive everywhere as well . Extra functionality and durability - bargain I reckon . Cheers A .

Grrrrrr , lost a long post because the final preview post cross connected with an incomming PM and the web page had expired ... Short version , yes thats pretty much the story with the GT3037/S/Pro S . All Pro S GT3037's have the full sized 60mm GT30 turbine , the cropped version is in their spec "GT2835/Pro S/R" versions . My turbo is literally a GT3037S with a Garrett GT30 IW turbine housing in 0.82 A/R . The main differences are that mine has the 52T GT37 compressor and its matching port shrouded compressor housing and a Garrett made turbine housing . It looks just like any other real GT3076R with a Garrett IW turbine housing except its compressors inducer is ~ 55mm instead of 57mm . It also looks like a GT3037 Pro S with a Garrett turbine housing and without the funnel mouthed insert in the compressor housing . Ok its missing the HKS tag as well ... Bought through GCG but I'm sure Garrett at Chipping Norton can do the same thing . The theory is it should work pretty well on an RB25 though I don't think I'll be the first to try it . Evench . A .

The facts - you do with them as you wish . Garrett turbo families are known primarily by their turbine family ie GT28/GT30/GT35/GT40/GT42 etc . A given turbo should say eg GT30 , then a compressor wheel diameter , eg 76mm , and if BB have an "R" tacked on the end meaning rolling element or ball bearing . There are turbine families with numbers like GT30/GT32/GT35/GT37/GT40/GT42 etc etc . Then there are compressor wheel families you can call GT30/GT35/GT37/GT40/ etc etc . These GT turbine and compressor numbers do not mean the same number for the same turbo , for example I doubt you'd see a 60mm GT30 turbine and a 60mm GT30 compressor used together . A lot of confusion still exists because the HKS and Garrett numbering systems changed over the years . Originally HKS , mostly , used the above mentioned turbine family and compressor family to describe their units . This is where the handle GT3037 comes from . Same deal with GT3040 and GT3240 though this last one is GT32 dimensionally as it actually has a cropped GT35 turbine . The whole "GT25" in the early days was a screw up because there are GT25 turbines and GT28 turbines , for whatever reasons HKS called them all GT25 as in GT2510/GT2530/GT2535/GT2540 . The fact is that the GT2510 has a GT25 turbine and the other three have GT28 turbines - I don't know why I just know what they have . The MAJOR screw up was HKS having Garrett make what they called the GT2835 series , It was probably something to do with them wanting a turbo sized in between the GT25xx series and the GT30xx series . The "GT2835" series does NOT use a GT28 turbine it has a cropped GT30 turbine which is why I mentioned somewhere that it should have been called a GT3035 , fact they have a GT30 turbine with a GT35 compressor - sounds like the marketing team had another win over the engineers ... Down the track you had an unofficial system which I think started in the US and went round the globe with the Internet explosion . They started the GT30R/GT35R turbo system but its a trap because you don't have a clue as to what compressor hangs off that GT30 or GT35 turbine and they aren't all the same . Then for some strange reason they wanted to measure the size of the external holes on a complete turbo and start naming them on these sizes . Based on this wild cat system if someone said to you I've got this GT5557 turbo and its just what you need what would you do ? The numbers sound big for a GT3037 but that is roughly what a 3037 has - 55mm turbine outlet and 57mm compressor inlet . The system is flawed because either side wheel can have variations in trim size and that alters the inlet and outlet sizes and you don't have any idea what the actual wheels are family wise . Could be a big wheel in a small trim or a small wheel in a big trim , cant see without removing the housings can you ? And now you have The current Garrett system where they tell you the turbine series followed by the compressor wheels major diameter ie GT3076R which means GT30 turbine + 76mm compressor + R meaning ball bearing . It is also flawed because telling us the compressor wheel major diameter doesn't tell us what generation compressor wheel is used . You can have a GT3076R with the proper 6/12 bladed GT37 compressor or you can have the 7/14 bladed wheel like in the pics above . The reason I wont call it a REAL GT3076R is because it doesn't have the same GT37 series compressor wheel like the GT3037 turbo does . So where do you go from here ? I end up going by the complete turbochargers and or cartridges Garrett part numbers because I know what they've used or can look them up if I don't . If anything the cartridge number , sometimes listed as CHRA or Center Housing Rotating Assembly , is the most important number because it will differentiate which wheels AND trims each one has by number . All the GT30 ball bearing turbine based turbos have a cartridge number starting with 700177 , followed by a dash number ie 5007 . That dash number tells you which turbine variation because theres three of those and which compressor is used . In this case its a 60mm 84 trim GT30 turbine and a 56 trim GT37 compressor wheel . So , if you want what I call a REAL GT3076R turbo it must have a GT37 compressor wheel like HKS's spec GT3037 units do so the cartridge number must be 700177-5005 or -5006 or -5007 . The 5/6/7 means compressor wheel trim size 48/52/56 . With the GT25 and GT28 series ball bearing turbos the cartridge numbers start with 446179 and end in a dash xxxx number ie the GT2530 , really a GT2860R in current Garrett speak, is 446179-5021 . Lastly to the hybrids like slapping someones OE housings on a Garrett cartridge . If this has been done you can forget all about thing working as the turbo manufacturer intended because the housings are usually nothing like the turbo manufacturers ones are internally . The manufacturers turbine and compressor wheel maps mean zip as well . From what I've seen it's logical to reuse OE housings on someone else's cartridge provided the two wheels major diameters are sort of similar to what the original ones were . For example people here have used their RB25's Hitachi housings on GT2871R cartridges and got quite reasonable conservative results . Granted the GT28 turbine is a bit larger than the Hitachi's ceramic one but not nearly as much as a full sized GT30 turbine . You have to think in terms of cross sectional areas when looking at wheel diameters because a mm here or there doesn't look like a lot but do the Pi R squared thing and it grows real quick . The turbines themselves , the GT28 is 9 bladed 76 trim where the larger GT30 is 10 bladed in a bigish 84 trim . The diameters are ~ 54x47 and 60x55mm . For the 250 odd Kw I'd have used the same cartridge as a HKS GTRS (GT2871R 52T) and you'd have a choice of whatever compressor housing/adapter ring that those Garrett cartridges can take . HKS used a T04B format comp housing though theirs was port shrouded . If that was not enough for you then maybe a cropped GT3071R (inaptly called GT2835 in HKS speak) . Or just buy the GTRS and bolt it on with you home brewed plumbing . I'm sorry but I just can't see the point in using a nearly 500 Hp capable cartridge to make 330 odd Hp . Yes it may bolt up , no it can't reach anything like its true potential . For whoever it was , the GT37 wheels ARE the ones that work better with the GT30 turbines . GT turbine + GT compressor = happy GT combination - if sized properly . IMO odd sized or non GT compressors were used in Garrett marketed turbos back in the days when HKS had the monopoly on wheel combinations they paid the R & D on . I believe its their intellectual property and they have exclusive rights to it for about six years after which Garrett can sell the cartridge , and housings if they made them , to anyone . Many of these HKS GT BB turbos have been around for a lot longer than six years which is why if you have the part numbers and they are still in production you can order them ex Garrett Japan . Its the reason why you can buy GTSS or GTRS turbos or "the real" GT3076R turbos from Garrett at a Garrett price . You won't get the HKS housing if it was a unique enough one that only HKS produced it . In the case of the RB26 GTSS you're buying the whole shooting match bar the actuator . So these are the facts as I see them . For most power asks there will be something suitable out there , the questions always be what are you prepared to pay to get the best matching combination . Sometimes its straightforward and sometimes its not and often the best bits are low volume expensive ones . Everyone wants to save a buck but sometimes the compromises made to achieve that hurts some performance aspect . Such is life , cheers A .

From everything I hear its difficult to make the "real" GT3071R (cartridge ID is 700177-5023) work over a wide range , the cropped versions seem to work ok in a proper GT30 based turbine housing which Garrett don't make for this sized turbine . HKS do and they found it necessary to use their own brewed port shrouded compressor housing and called it GT2835 Pro S which is expensive . I think the 76.2mm GT37 compressors are a better speed match for the 60mm GT30 turbine than the 71.1mm GT35 series compressor wheels . I really wish HKS had called the "GT2835" series GT3035 because thats what they are - GT30 turbine (cropped or no is irrelevant) + GT35 series compressor wheel . I managed to get GCG in Sydney to order me a GT3076R (AKA GT3037) in 52 compressor trim because I want a little better response than the normal 56T GT3076R and the top end doesn't matter to me in a street R33GTS - adequate , not installed yet . A little birdie tells me that a few others got on the bandwagon with this particulat turbo and they will probably get them running before I do . The rarest of the GT3076R/GT3037 group is the 48 compressor trim version which HKS rate at 420 PS , they rate their GT2835 Pro S and GT2835R variants (both using the 71.1mm 56T compressor) at the same 420 PS . My gut feeling is that the 76.2mm GT37 compressors are a better speed match for the GT30 turbine and I'd rather run a small trim GT3037 than a big trim GT3071R (AKA GT2835) . Amongst other things eventually I'll try to get Michael to chase up availability of the 48T GT3037 because I have a feeling it would do the job on a lot of roadies . Cheers A .