discopotato03

Correct the T04R and T04Z use the same wheels so the turbine and compressor housings interchange . Actually from memory HKS had the turbine blades slightly cropped in their spec Garrett cartridges but that's not of any real consequence . Other than that the only difference overall would possibly be the turbine housing if its a HKS special . The complete HKS T04Z uses different housings and would be the pick given a choice . A .

I think if you really wanted to run a GT2860 family BB turbo the go would be to find a second hand "GT2530" designed for an RB engine and run that . If not enough you can run a GT2871R in its turbine housing because they use the same turbine wheel . Something to think about is the fact that HKS GT2530s seem to work well on RB20's so you'd think an RB25 could use something with a bit more airflow . I'm just looking at the maps for the GT2860RS and the GT2871R 48T , the RS hit the wall airflow wise at about 36 pounds and the 2871 48T at about 39 pounds by mass of air . JC put together the original RS turbo for an 1800cc four and while they also work well on 2L fours I think the airflow from them is a bit lacking for a 2.5L six . An RB25 isn't exactly lacking at low revs so it doesn't need boost for torque at 2000 revs . From memory std RB25 turbos have a compressor that's around 68-70mm OD so I wouldn't want to be going smaller than that . Possibly what the original poster needs to think about is what turbo would give OE like power delivery and have a bit more squirt without any loss of response or torque - anywhere . I can see where people think the lowest possible boost threshold would be good but instant torque at low revs can actually be tiresome to live with because you end up getting boost when you don't want it and it always feels on/off with little in between . Dale do you have the link to your hi flow thread ? A .

Actually the original form of the GT2860RS was with the 0.86 A/R turbine housing . Many at Garrett in the US reckoned that if it didn't have the larger ratio turbine housing it wasn't a real DP turbo . They also said that HKS was silly not to have had a 0.86 A/R turbine housing available for the GT2530 . Anyhow like most things in the GT25/GT28 families the hard bit is finding a T3 flanged turbine housing to make them bolt onto RB exhaust manifolds . HKS have them in 0.64 A/R and Garrett don't do any T3 flanged housings for them at all . A .

No time ATM but . GT2530 = 446179-5021 CHRA , from memory GT2860RS = 446179-5066 . The real original spec DP turbo uses a 0.86 A/R T25/28 flanged GT28 turbine housing . I reckon the 48 and 52T GT2871Rs are better sized unless you want a std replacement in the form of a Garrett GT BB turbo . Yeah Dale an OP6 housing on your Hi Flow looks like a good idea .... A .

It may pay to do some searches on Geoff's "R14" which was a USDM S14 240SX converted to basically most of a GTRs drive train . I seem to remember him trying a few TS turbo combinations on his RB26 in that case , was a while back though . A .

I know that if you use the GT2871R 48T cartridge to hi flow an R33's RB25 turbo you can keep the std compressor housing because when machined out for the larger compressor wheel you have just enough wall thickness left to mount the std inlet duct . With the 52T one I don't know . Didn't Lithium do this Hi Flow mod before the GT30 turbo went in ? HKS rates their 2530 and 2535 at 320 and 340 PS , I reckon you could look at a 2871R 48T as a 2535 with a more modern compressor wheel . You'd think 300 to 340 Hp out of a Neo spec RB25 would be smooth torquey and reliable , and not bank breaking . Lag ? Whats lag ? A .

Again my opinion only but depending on what you're looking for a 0.63 A/R turbine housing is workable on a GT3076R , HKS had 0.61 and 0.73 A/R turbine housings (sadly non gated and T25/28 flange) available and I don't remember anyone saying they surged - provided they had the 3037"S" port shrouded compressor housing on them . I'll quote from my HKS spec sheet and you be the judge . Std 3037 48T - 420 PS Std 3037 52T - 440 PS Std 3037 56T - 450 PS 3037S ... 52T - 450 PS 3037S ... 56T - 480 PS Everything I've read seems to suggest that the std compressor housings are aimed at four cylinder apps - generally larger cylinders that sixes and a flat plane crank meaning 180 degrees between power strokes . Quite often HKS have port shrouded housings for sixes and specifically the Pro S turbos for RBs all have them . I personally think the 76.2mm GT37 compressors work better with the full sized GT30 turbine and its the port shrouded comp housing that lets them get away with spinning the turbine/compressor group up earlier with smaller A/R turbine housings . AFAIK the most responsive GT3076R combination using Garrett marketed bits would be the 52 trim compressor version with the 0.63 A/R GT30 turbine housing option . ATM you can buy this combination of bits and even get the port shrouded comp housing for it just like the 56T version . Every one's different but for me getting some boost and extra torque at sane revs is ultimately more important than a sheet of paper saying 300 RWKW . The system is out to get you on public roads and the situation is getting better for the authorities every day . I think of it like this , when you drive your turbo car up long hills at 100/110 on expressways in its highest gear do you actually get any boost and can you sail up these hills effortlessly without changing down ? If the answer is no then IMO its not a very street friendly setup . Like someone said the smallest T housing will ultimately limit the top end but in a road car that's not as important as broad spread of torque where its needed most . My opinions only cheers A .

I believe in the World Rally Car class they reduce the latter part of the exhaust to keep the gas speed up as it cools which helps make more mid range torque . With WRC they are limited by turbo air restrictors so they have to make as much torque as possible over a limited rev range . They're changing up at five and a bit thousand revs because the restrictors won't allow enough airflow for them to make usefull power any higher . Between ALs and the restrictors they do make good torque but its very hard on the engines . A .

PSI just to add to the mix apparently Garrett sells a hybrid GT35R being the 68mm GT35 turbine but with the compressor end of the GT3076R - 76.2mm GT37 comp in 56 trim . It may pay to run that combination past Geoff because being an Australian XT6 Typhoon option they may not know about them in the US . In the end I guess it comes down to how much crank power you're aiming for and what sort of power delivery you want it to have . Cheers A .

Actually I had not opened that link but Jason Cavaganah knows what he's talking about and I gladly defer to him . I don't know if he's still working at Garrett North America or some other part of the Honeywell group . A .

Much talked about and difficult thing to make everyone happy . 260 to 300 is also a wide range with an RB25 because some turbos will just make a potential 260 with no hope of seeing 300 . This 260 and up area is getting towards the upper ranges of what a mechanically std 25 wants to flow and any non turbo breathing mods like porting and cams makes the ask easier . Realistically you probably need to go for a ride in a few sensibly modified cars to see what a responsive 260 Kw feels like because obviously a so called responsive 300+ isn't going to feel the same . Your call but I'd be aiming for a performance result rather than a number if response is an issue - and it is . One thing you see all the time is people fitting big turbos and being bitterly disappointed because the lack of response or turbine lag if you like kills the fun for them . If you don't have any example you like to go by I suggest you start a little conservatively with turbos because they tend to achieve good results over a wider part of the engines rev range you live in . Maybe the question people should be asking themselves with turbo sizing is when do I want the boost and torque to start and go from there . If money isn't an issue you could start looking at HKS units like the GTRS or the GT2835 Pro S because these are responsive things in their respective power ranges even on mechanically standard engines . The compressor housings are both port shrouded (the nearest Garrett equivalents aren't) so their conservatively sized turbine housings allow for response without compressor surge . The HKS turbine housings bolt up and with the GTRS so do std or aftermarket RB25 dump pipes . I have spoken to GCG about getting Garrett T3 flanged GT30 IW turbine housings machined to take the cropped GT30 turbine in some GT3071R/GT2835 cartridges but that's still up in the air . Also the full turbine sized Garrett GT3071R comes with a large boss T04E compressor housing but its not port shrouded . There is a possibility that results were not fantastic when using the Garrett GT3071R and the smallest available (0.63 A/R) turbine housing and some of this may have been because of compressor surge or being right on the edge of it . HKS uses the exact same comp wheel as Garrett does but their custom made (hint) housing does have it . Once you start into the GT3076R range your not going to get instant turbo response because of the size of the turbine and compressor . Using the mid or 52 trim compressor size and again the 0.63 A/R turbine housing is probably as good as one of these turbos is going to get "response wise" but I don't think that combination has been tried yet . I don't know much about the Trust spec Mitsubishi turbos other than it sounds like they did special compressor and turbine housings for Mitsy cartridges much like HKS does with Garrett cartridges . Some people feel that Mitsy makes more responsive turbos for their size than Garrett and occasionally put it down to development gained from lots of small/medium OE turbo production ie Evos and Subarus . Off the top of my head the only Garrett GT BB OE apps I can think of are some S15s and the XR6s . Anyway see if you can go for a spin in a few other cars and you be the judge . A .

Well its your calls but from my experience doing exhausts in sections starting at the front isn't a bad idea . I don't see any reasons other than packaging that you couldn't start out in the 3.5 to 4 inch from the turbo to the cat and progress from there . Also other than the transition in tube size I never found any losses from being big up the front and not so much in the middle and rear sections . I think this is a good way to go because you can develop an exhaust around how much power/gas flow you need vs the sound level you can live with / get away with . In my experience all the muffling gear is in the second half or rear third of the system so this should be where if there has to be flow limitations they should be . The exhaust gas pressure and temperature ie always highest in an exhaust directly behind the turbo so this is where easy power can be gained or lost . If you have any significant pressure (referenced against atmospheric pressure) here then the gas out of the turbo won't pass as easily as it could do if there wasn't . Take it to the grave , exhaust temperature drops very quickly after the turbo and when it does its density decreases and all else being equal it will slow down or lose momentum so to speak . So in my opinion make it BIG up the front and experiment with slightly smaller tubing along the way to keep the gas speed from falling too quickly . Also being big at the front tends to increase turbo whistling and whooshing noises if that's your thing . My opinions only , cheers A .

Out of interest do we mean T67 as in the Mitsubishi based Trust turbo or a Garrett thing built around the T04R/Z compressor and the T350 (AKA Stage "5") turbine ? By the sounds of things its a Mitsy if the turbine housing size is measured in cm . Cheers A .

Yes I think a lot of development is going on behind the scenes with turbos for smallish "high speed" - for a diesel - oilers . Actually a lot has changed with what Garrett has produced in the last 40 years , take a look at the old crude early 70s era T3 and even older 60s era T04B compressors and turbines . Then compare them to late 80s early 90s GT ones . Most people don't get to see the huge range of OE turbos , really the aftermarket GT BBs are a very small part of what Garrett produces . At times motor sport development drives turbo and turbo engine development , since the mid late 80s turbos were banned from F1 and many of the road racing classes eg Grp A . The major manufacturers have fast disappeared from rallying and IMO WRC is just a bunch of kit cars on dirt . If we ever see production based racing backed by the major manufacturers and forced induction allowed things may change . ATM the manufacturers are very interested in reducing engine capacity chasing better consumption figures , forced induction is one way to get around the loss of torque from less cubes . Interesting times , A .

Ah actually I mean the mounting hole centers . You can put a twin entry T3 flanged turbine housing on the DR30 skyline type FJ20 ET manifold provided the waste gate is on the housing itself . The S12 Gazelle FJ20ET manifold is not pulse divided so no not really . RB20DET same deal as the DR30 FJ manifold . A .

My personal opinion is that a large volume directly behind the turbine housing is the way to go . I think the separate waste pipe would be a PITA to make and you're chaining yourself to the size that it is meaning if its not large enough the wastegating system won't work properly . Also don't forget that these integral wastegate flat valves don't turn the full 90 degrees anyway so its not like the gasses out of the gates hole are going to fire directly out towards a divorced systems tube/pipe . The bell mouth is much easier to make and provided there is some physical barrier separating the turbines and wastegates flow paths I think its good enough in most cases . I don't think I've ever seen an OE performance turbo engine that used anything but a variation of the bell mouth and many/most are cast outlet pipes . I think in the bang for buck stakes bell is way to go and my reasoning is that a large volume is just as willing to handle gasses from the turbine or the gates bypass hole . Why limit the bypasses flow potential with a small pipe ? A .

I think you'll find that one is a divided T3 flanged housing . If those hole centers measure 86mm on the long side and 44.5mm on the short side this is what it should be . A .

Um its been a while since I looked at the back of a GT30 IW housing but from memory the section the flat valve vents into is in its own well so to speak so it probably doesn't need a divider welded to the turbine housing outlet flange . I guess if you had a flange with the inbuilt divider section you could form a mandrel bend around the profile of the flange and its bolt holes , ALWAYS make sure you make indents in the tube with enough room to get a ring spanner around the bolts or nuts BEFORE the final welding . Saves lots of swearing later . I'd be trying to make the first section of the dump off the flange in tube large enough to not have to add the teardrop shape behind the wastegate valve . I prefer the tube to be as large as can be fit within the space around the dump pipe as this is where the exhaust will be hottest (ex the turbo) and it needs enough volume for the thermal expansion to take place without a pressure rise . As the gas cools and increases in density (contracts if you like) you can afford to gradually step down the tube size to maintain reasonable gas speed - if it slows or stops you can at times have reversion issues . Not really sure about the inlet other than considering that there may not be much point in the tube being larger in diameter than the MAF housing assuming you use one . Z32s from memory are 80mm so maybe that size down to the turbo but then an increase in size to suit the 100mm/4" inlet boss if its a GT3076R . It may pay to feed the throttle closed recirc tube in close to the turbo to try and avoid MAF reversion dramas . I guess if it goes in behind where you step up to 100mm the extra volume may dampen the rush of air from the recirc valve . Something else to consider is the air filter packaging as I hear its virtually impossible to plumb into an R33s std air-box . I have not got this far myself with a Skyline so others who've been there would know from experience . Cheers A .

People I've spoken to here don't seem to notice any difference with using the HKS Pro S or Garretts own GT30 IW turbine housings . I know the HKS one looks the part with is scollap'd out vent path but the thing is that the gasses have to do a 90 deg turn to exit an IW turbine housing so that's probably more of an issue that the casting beyond the gates flat valve . Personally I'm not really sold on divorced dump pipes and as long as there is some kind of barrier to direct gasses out the waste gate hole away from the turbines outlet I reckon alls Ok . Don't people here call the "open" style dump bell mouthed ? Anyhow more about the HKS Pro s turbos vs the Garrett marketed GT3071Rs and the real GT3076R . One common factor with the HKS housing'd Garrett turbos is that they ALL have a port shrouded compressor housing when intended for a single RB six application - including the GT2530KAI and the GTRS . Garrett as a rule don't do this and I reckon only the fact that they make the port shrouded compressor housing for the GT3037/GT3076R that the Garrett marketed ones have the shrouded comp housing at all . In virtually every case where HKS had to have a custom port shrouded housing made the equivalent Garrett marketed turbo hasn't got it . As for turbine housings the other day I asked Michael at GCG if its possible to Have Garrett's GT30 IW T housings machined to take the cropped turbine and he's not sure . Also they now keep the 52T version of the real GT3076R in stock because they got lots of inquiries after I bought mine . Another interesting one is that they now have a backwards hybrid of the GT3076Rs 76.2mm compressor wheel teamed with the GT3582Rs turbine wheel . I suppose you'd call it a ball bearing GT3576R and they said its OE on late Typhoon Foulcans . Guys I can't say how the 52T GT3037/GT3076R will go on an R33 RB25DET , the theory is that it has a slightly better map and should be slightly more responsive that the 56 comp trim version . The cropped GT3071R or HKSs GT2835 Pro S often use the same cartridge - wheels - so any smarts is really in HKSs housings . In my mind the progression of Garrett based GT Ball Bearing turbos for RB25s is GTRS (GT2871R 52T) / GT2835 Pro S / GT3037 GT3076R 52T / 56T / GT3582R . A little later on if the need arises I'm going to look at ways to make a GT3582R in 52 comp trim but really the HKS developed Garrett "GT3240R" is probably easier if available . Its just a cropped GT35 turbine with a 54 rather than 56T version of the 82mm GT40 compressor wheel . Cheers A .

Your final call but yes I think a T04Z is overkill for 500 Hp , particularly on a T3 sized footprint . Arguably HKS do the more responsive T04Z because they use more appropriate housings for performance petrol engines . I would have leaned more towards a GT3582R for 500 crank Hp and even then I don't think it'd rip your head off much under 4000 , particularly with the 1.06 A/R turbine housing . I think the hard association to make is how much real world usable performance suits you vs this hard Hp number you have . Your call , I think the Z turbo is too big for what you're trying to do . A .

Yes I'd have thought a GT3582R/GT3540R (same) would have been better on a reasonably std and std capacity RB26 , particularly if the manifold has a T3 flange . Cheers A .

A feller I know recently was playing with an RB26 in a VL , it had a 6Boost manifold with a 44mm TiAL and a GT3582R with the 1.06 AR turbine housing + questionable 3" exhaust . He felt he made significant gains by having a 3.5" exhaust all the way through , just about everything I've seen indicates that the exhaust needs to be BIG right behind the turbo and if I was you I'd strongly consider having a 3.5" if not larger dump pipe . That feller mentioned above also found that the 44mm waste gate wasn't coping and boost crept upwards , had a different fitting welded on for a 50mm Turbosmart gate and that solved the creep problem . From memory he had a 100 CEL cat fitted , don't remember which brand . For the record does the turbo and manifold use a T3 or the larger T4 sized mounting flange ? A .

Maybe time to kick back with an ale - in the cold room ... It might be more relevant to stick to the now and what people have now and where they want to go with whatever car . Basically no large volume production car was ever designed to be an effective drag strip rocket . Most honest people say that hard core drag cars are terrible things to do absolutely anything else with . Making them survive the leap to light speed and hurtle in a straight line makes for a limited use vehicle . People who go back to the 60s and 70s tell me that the Prince Motor Company intended their Skyline marque to be an open road GT tourer type thing and they ended up in road race type classes . I think Rex was the ongoing evolution of a small FrWD bread and butter run about for the masses , much like the Mitsy thought on paper the Evos look to be a bit more serious . Everyone who's owned either Classic STi (GC8) or Evos 6's reckons they can be hard to live with on a daily basis . Ride rough and nothing significant under 4 grand with STi ram raider . Small fuel tanks short gearing and on it goes . Probably go real well when you drive them flat bat but no sane person does this for very long . Now with the humble R33 GTS25T manual , these are getting on a bit but I reckon they still have their charms provided you don't go silly with the mods and make them a cop to live with . I reckon an RB25 is much nicer thing than any EJ engine and Kw for Kw I reckon it has better power delivery . If it isn't enough stick an RB30 short underneath it and do the usual things with its top end . Ultimately AWD seems to be the ticket to getting a car off the line quickly but the lack of it didn't stop those whatzit brothers getting increadible numbers with VL Commodes some year back . Yes they were tubbed but no sign of a front or middle diff and I didn't hear of four claw ant eater getting the same numbers . I think people end up being Nissan or Subaru punters and the best way I can put it is they are different . Possibly for suburban use the non STi GC8 would be a good means of getting around but for general use including long open road hops I'd rather take the GTS25T . GC8's are lighter but also smaller and don't know what you do for a boot . Any AWD is a major PITA to work on and the live front end ties you up in knots geometry wise because you have to compromise for drive shaft angularity issues . GTRs I reckon are underpowered off boost and being very front heavy lose that nimbleness that agile cars generally have . It really is a big ask to be lightweight and have good weight balance front to back . For anyone that hasn't driven AWD cars believe me when I say that AWD creates almost as many problems as it solves and DOES NOT overcome the need for good front suspension and steering geometry . It may be good for getting the best proactive effort for driving in a straight line but the extra weight has to be made to change direction in corners and its critical to get each front wheel turning at the right speeds to not be a plowing on understeering cop . I think if you accept the fact that you and your car can be beaten and sleep at night life becomes much easier . The burning question is do you want to be a slave to your cars or have a life . A .

The whatzit brothers have been doing REALLY fast run times with drag VLs for 10 or more years , yes they are tubb'd and not road cars . The focus here is they are Rear Wheel Drive . Personally I think you are pushing it up hill with a pointy stick trying to drag with 2 x 235 width tyres , IMO to get anywhere you need as much rubber as you can get under the back of it . Also don't lose sight of the fact that you probably use your car for other purposes than drag racing . The trouble with rex is gearboxes and aluminium engine cases . Out of time , cheers A .

Yes an interesting , I take Vizard to be David Vizard and I like his experience (thousands of hours flow bench testing) based ideas on most engine design things . You may find it interesting to dust off Corky Bells Maximum Boost , it has a chapter on inlet manifold design . From memory he reckons the radius of entry into the runners should be equal to the diameter of the runner . Also according to him there should be three times the diameter of the runner clear as in no other runners bell mouth within this "3d" area . As for the shape of PMs plenum . As soon as I saw it I thought that's along the lines of a Nissan FJ20 plenum only with six runners instead of four . With the DR30 Skyline type FJ20 inlet manifold the throttlebody also "aims" if you like the airstream along a curved back wall of the plenum rather that straight across the six inlet holes . I think the fact that you are getting individual pressure drops as each cylinders inlet valves open means the challenge is to be able to feed each one adequately and as equally as possible . I also reckon that there is something to be gained by using two three cylinder plenums obviously with their own throttlebody , this is common on V6 engines but possibly hard to package on an inline 6 . The I6 firing (and induction) order 153624 means that as it goes through its 6 cycles their is alternate drawing through each group (front 3/back 3) so maybe something to be gained . If you look at the Z32 VG30 four cam engine you can see that Nissan went to a bit of trouble to keep the runners reasonably long and the two plenums of reasonable volume . Yeah I reckon two plenums and two throttlebodies gets you to halfway between what a single vs the RB26s six throttles achieve throttle response and cylinder filling wise . One thing I have noticed missing on all these plenums is a staged twin throttle plate arrangement where the primary one opens to a point and then the second one , often larger , goes from closed to full open over say the second half of the accelerator pedals travel . That may be the way to give good low speed (car and engine) driveability and still be able to open a large passage to try to keep up high rev volumetric efficiency . I guess the hard bit is always going to be getting good breathing characteristics in a non supercharged state and with turbo engines typically lower CR and relatively soft cam profiles . I think the go is to have very low restriction yet with runners long enough to give some ram effect into the cylinders at low revs . The transition to the runners and the runners themselves is probably more important that the plenum volume but it and the throttle/s obviously need to be able to feed as well as possible in a pre boosted state . Possibly this is why Simon Gisgus (sp ?) of Nispro used to say that the best way was to build the best NA engine possible and turbocharge that . Corky adds that the turbocharger just goes on to add more air when its spinning fast enough . Food for thought ? Cheers A .