discopotato03

Ok , so how much more do I want . I wanted to know the details in case there was anything people can work to their advantage . If I was going to do an RB25 head again I would go with a Neo one because of its smaller chambers and non hydraulic buckets . Really anything that potentially has better quench and resists detonation is worth having , Nissan must have had good reason to make these changes and it looks like emissions/consumption reasons to me . A .

Hi all , I've seen the question asked often about chamber and piston volume differences in R33 and R34 RB25DET engines . From reading about engines in the late 90s I know there was a push for LEV or low emission cars and ULEV for ultra low emissions approaching the 00s or naughties . Mechanically I think it involved differences in power steering pumps and belt drives and possibly lower drag alternators . Often VCT and valve timing changed and engine management was set up differently particularly for cold starting . By that stage most engines already had cooling systems with bi level thermostats and big bypasses to help them warm up quickly . I just ran a couple of searches to try and find out more about specific chamber and piston volumes in the R34 Neo RB25DET but couldn't find anything conclusive ie pics and exact measurements . Wiki reckons the chambers are different , smaller , and Nissan compensated with RB26 spec connecting rods which sounds odd . To have a piston further down the bore at top dead center doesn't sound like a positive to me , dunno . I did find a thread at an American site where a fella tried using an RB26 crank in a 25 block with 25 pistons and not surprisingly the pistons ran proud of the blocks deck . Should have seen that one comming . The thing is this fella eventually mentions a difference in chamber volume from 33 to 34 as being 63cc and 51.5cc . It would be really good if someones whos been inside a stock standard RB25 Neo can tell us what they actually have in the chambers/in the piston crowns/if the rods are different length wise . Assuming the chambers are smaller ie 51.5cc it starts to make the cheap RB30 conversion look good and may even get the static CR up around 9.5 instead of the 8.2 or whatever you get with an R33 head on an NA RB30 short block . Anyone know the real story ? A .

Yes but the thing is how are they different , maybe need to look at aftermarket direct replacement pistons to see if the dish volume changed . A . Actually this R33/R34 DET business needs its own thread .

I'd be looking through aftermarket piston catalogs to find out what the dish volume is like compared to an R33 RB25DETs and if they are same or very similar go for it . If all your R33s sensors interchange in the R34 block I don't see negatives , the positives are younger and potentially fresher pistons/rings/bearings depending on mileage . As was suggested a cheap RB30 with fresh rings bearings and a hone could be cheaper again , just need some welding on the heads face and its off anyway . Done carefully it may not cost much more than a "runner" RB25 . A .

I wish someone would prove conclusively that Neo chambers were smaller because I've never seen anything to show it . I know that on some later/last versions of some engines manufacturers went to long reach spark plugs so they could improve cooling galleries around the chambers , do Neos use different style plugs to R33 RB25DETs ? Anyway I gather Neos use the same sized valves and if pistons are same/similar the static CR must rise if the chamber volumes are less . What truly gives ? A .

8-10cm housing on what ? I thing the Garrett GT28 based turbos are the go for SR20s , either the GT2860RS or any but the biggest trim GT2871R . The reason being that they use either a GT25 or GT25 BB turbo std so the GT28 ones go on easily enough . I'm not really an SR 20 person but if I was it would have the early high inlet port non VCT head and the GTiR four throttle inlet manifold . A

I don't know of any twin entry T3 , Euro T4 , GT30 turbine housings but the non gated one I see most is the GT32 plain bearin one - search for GT3267 in 0.78 AR . The only real GT30 TS IW housings I know of are the Evo 10 ones but they have a different mounting flange . Possibly the best response GT3076R (IMO) would be the 52 comp trim one with a 0.63 AR GT30 turbine housing . If it were me the 0.63AR with a good smooth up job in the turbine housing and maybe exhaust manifold would be good enough . I dunno about a lot of boost at 7500 but more that enough to be a tractionless pig in a RWD car with the boost turned up . If you could go inside the engine and fit a tad more capacity ie 26 crank and 1mm over pistons it all helps . I would touch anything under 9.3 to 9.5 static CR and Poncams don't go astray . Then just bolt a 56t GT3076R on with the 0.82 housing and tune the thing properly . On the cheap , a std freshened up RB30 short and if you could spare the cash higher compression pistons . My conclusion is that twin scroll systems are either too expensive or too defectable on single turbo Skylines so tried and proven single scrolls and extra cubic inches end up being easier . A .

Between Garrett and HKS neither really got it right with GT28 based turbos for RB25s . I get the feeling that back in the early days more emphasis was put on catering for RB20s than 25s and thats possibly why HKS had a GT28 IW turbine housing made with the T3 and single turbo Skykine outlet flange in 0.64 A/R only . I'm 99% sure its the same one used on 2530s and 2535s for many years now and the chances are slim of them doing a 0.84 AR one now . I think I'll just leave it as it is (GTRS)and save the involved mods for the Lancer , I want to lose the AYC for an RS clutch LSD rear end . 240-250 in the Skyline is fine for me . A .

Now you mention it I think I did once see a pic of one of their housings . Flange adapters are a pain and from memory the GT28 turbine housings have the flange and throat section offset with the volute for packaging reasons . Could potentially screw up and have wastegating issues with adapters . The other half of a GTRS or GT2835 KAi is the port shrouded compressor housing and it woulde cost something to re create . The upside of the larger AR turbine housing is it would slow the turbine down a little and offer a bit more exhaust throughput - maybe something like 20% but thats a pure guesswork going off the turbine map differences . If you feed guesstimation into the Tardis computer does it reckon needing 20% higher revs t get it going ? Woolverine would it be good or bad having a GTRS start boosting 400 odd revs later , what eventual difference did you find between the GTRS and 2835 Pro ? A .

It occured to me to go back and have a look at Garretts turbine maps for 0.64 and 0.86 housings on that GT28 turbine and the difference is a little better than I thought . Have a look at the flow rates of the GT28 0.86 AR and te GT30 0.63 AR . http://www.turbobygarrett.com/turbobygarrett/images/catalog/Turbochargers/gt28_images/739548-1&064turb_e.jpg http://www.turbobygarrett.com/turbobygarrett/images/catalog/Turbochargers/gt30_images/GT3071R_turb_e.jpg Interesting that the GT28 turbine in its larger housing slightly outflows the GT30 in its smallest housing . Hmmm .

Very interesting , Woolverine I was just looking at the GTRS pic and the one in your link and it hit me that the GT2835 KAi uses both of the GTRSs housings but a slightly different style of port shrouding on the comp housing . Sorry if I've asked before and forgot but do you have any results from the 2835 KAi ? I'm not interested personally because that GTRS should suit me fine , just pondering using an adapter and a 0.86 turbine housing I have on it but thats another story . I don't really know how to do these things on the cheap without buying 2nd hand , I suppose if you had an 0P6 turbine housing and 25 comp housing you could Hi flow it with one of the GT2781R cartridges but with the machine work and custom lines I can't see it being much cheaper than a GCG Hi Flow at Grp buy rates . One way or another having BBs costs , A .

Imo big revs are not the answer , big revs mean a lot more wear and tear and a higher chance of handgrenaded engines . Bottom line is that a 2mm stroke difference is SFA and while a slightly shorter stroke could work better with a large bore diameter they don't go into RB anything blocks easily . The reason why big bores work so well is that you can fit a lot of valve area and breathing ino the head above easily . Probably what limits an RB20 most is the inability to do much with bore and valve size bcause of that 78mm bore . As for 12-14 pounds of boost and that power level the turbo would have to be really big and really laggy so not a wide ranging thing . The practical thing is good rods and pistons in an RB25 or DOHC 30 . 100Kw/litre should be quite straightforward and I wouldn't think RB30s would be grass seeds in the US . A .

I think some of you people ask for the impossible at times . I highly doubt that a turbo exists that will make significant boost at 3000 revs and still do it at 7500 revs . The problem is that automotive turbochargers use rotary non constant displacement compressors and their pumping abilities are not linear . The car manufacturers go to some pretty extreme lengths at times to attempt to have a wide flat torque band but its not endless . Some of the methods used are about making the engine have good cylinder trapping abilities which generally means some kind of variable valve (cam) timing and sometimes lift as well . In a perfect world we'd have actuators of some kind to give virtually infinite valve timing flexibility . Take it to the grave , in the world of engineering RB engines are not exactly high tech things and the best of them can only move one cam without lift alterations and whilest ITBs are available they only bolt to RB26's . None of them have twin scroll or VATN turbochargers and from a competition perspective parallel twin turbos are as good as it gets . Gearing also has a lot to do with how a car performs and Skylines in some areas could be better . You find if you want to thrash a car everywhere close ratio gears work better but keeping a car on the boil , particularly an at times traction limited one isn't always the fastest way to go . As per having a 4000 rev flat line full boost maximum torque band , thats just not going to happen . All engines have a sweet point where volumetric efficiency will be highest and it falls off either side of that point . This is actually an interesting discussion topic because I think people should worry more about torque than horsepower chiefly because at revs torque can go south with killadorks still climbing . Its torque that gives you the forced induction shove in the back and when it drops off you pull another gear , ideally you want the rev drop to land the engine at a point where it will pull strongly and accellerate you across the middle of its best average torque range . Some cars are geared to take advantage of the torque they make in every gear , did someone say RS Evos ? They may run out of revs at only 230 but they can pull 3rd 4th 5th like it was 2nd 3rd and 4th . Skylines are geared to be sort of sporty road cars and that big 4th 5th gap is easily felt . How fast is a Skyline geared to go at the redline with a 4.1 diff and a 0.76 5th gear ? If it could get there how long would it take ? The RS Lancer would not be the gun thing to cruise to Melbourne in and let me tell you close gearing is an awkward PITA round town but thats what it takes to have unholy thrust in every gear . Its this sort of thing that has the potential to make a car a missile and not need 400 Kws to do it . Getting strong accelleration with production gearing all the way through is a big ask and it needs a LOT of torque to achieve it . Manufacturers put tall gearing in road cars because it makes for relaxed cruising and better fuel consumption . They also set the enines up to make good part throttle torque because thats also needed to pull tallish widish spaced gear ratios . Its another one of those areas that you can't really have both ways and so the manufacturers build what the market wants which is smooth quiet and economical . With gearing the zoomers need shortish diff ratios and close tall gearbox ratios which is not difficult in an indirect transmission . Direct boxes like most RWDs have should probably go with a direct 5th because thats strongest and set the diff ratio accordingly . This is something like what the R31 Skylines used when raced here and the trans was actually a Hollinger if memory serves me correctly . It had a splined countershaft so the individual ratios could be changed with the gears fitted casett style . I think Nissans 240RSs were also set up with tallish , for rally , 3.9 diffs too . A .

Purely from what you see through the comp housing of a GTX3076R . These compressor wheels appear to be eleven bladed where the GT37 series BCI-18C wheels have twelve . As we know the GT37 ones halve six full height and six splitter blades and only the full height ones sweep over the radial slot in a port shrouded compressor housing . One of the things you notice when looking at GT series compressors and turbines compared to T series ones is their axial length and it would be interesting to to compare this on GT and GTX compressors . I'm a conservative in the turbo world and that makes me think that they are looking to get higher airflow rates at mid range wheel speeds but at higher pressure ratios . To me the islands on the maps are a bit narrow and thats why I think they could do with a larger compressor housing - if not a higher A/R one . Garrett do make a 0.70 A/R T04E compressor housing but its an ungainly looking thing with the same inlet and outlet diameters as and isn't much if any more compact than the T04S housings which are more common things anyway . In the State FP makes up "HTA" compressors for upgrades to Garrett BB turbos and I think they use a T04S housing on their HTA30R turbo . I can only go off trends I see with other compressor wheel families in sometimes a number of different compressor housing families and I think these GTX wheels are getting to the stage of needing larger housings than the GT25BB center section can support . Also making up adapter rings to get say GT40 compressor housings on GT25BB center sections means more inventory for a very low volume , aftermarket , rage of turbochargers . This is really where the larger center section/frame Garrett BB turbos come into their own , native to larger housings both sides but they are starting to get away from being "compact" turbos . Also few are itegral wastegate and many use T4 international flanged single and twin entry turbine housings . I work for the Intermodal Division of one of the interstate rail freight carriers . A .

Cartridge numbers for GTSS turbos . Remember the SR20 spec GTSS is a GT2860R turbo where the RB26 spec GTSS is a GT2859R . The turbines are the same family in 76 and 62 trims . SR20 spec GTSS cartridge no 446179-53 RB26 spec GTSS cartridge no 446189-65 A difference , not mentioned often , is that std RB26 turbos use compressor housings moddled on T25 or T3 internals - can't remember . From memory R34 RB26 ball bearing turbos are a unique GT2556R . Once you get into 60mm compressor wheels in the BB Garrett turbos they generally use a T04B 0.60 A/R compressor housing thats styled on the Nissan Garrett CA/SR one ie two bolt inlet flange three out . I think they do something similar but styled to suit RB26 twins in T4 as well . The issue these days is that people seem to ewant 2530 performance with GTSS low and mid range , theres not a whole lot between GTSSs and 2530s for RB26's . I don't think its possible to have the best of both worlds without an engine capacity increase to boost the engine only torque low down . I guess thats the compromise of having a GTR or RB26 . I sometimes wonder if people would be happier with a Stag block and all the GTt gear for 280+ in a GTR , the single turbo RBs with the conventional inlet system can easily support 300 and things like VCT help pull the bottom end up . A .

I honestly cannot remember where but I thought I read about a 68 or 70mm compressor version . Possibly something on a GT28 turbine but No details come to mind . Purely using the force here but I think it could be possible that the 76mm GTX compressor in the port shrouded T04E comp housing may possibly benefit from having all blades exposed to the radial slot , unlike a GT37 6/6 bladed wheel where only the full height blades sweep over that slot . GTX compressors appear to have all full height blades and I guess if they can run in a "partially unloaded state" it could help the turbine spin them up a little sooner . The telling factor is the transient responses compared to a conventional GT3076R . Looking purely at the GTX3076R comp map I get the impression that the islands are taller but possibly narrower than a std GT3076R and I have to wonder if it can gain from a slightly larger port shrouded housing . Anyway good results particularly with no tuning , cheers A .

Yes that inverted flare should have the correct sized hole through it . Its actually a mushroom shaped device that fits into the oil hole in the actual bearing cartridge ande locates it in the turbos center housing . A .

Cartridge number 700177-12 is a GT30 turbine based one but with the 7/7 bladed compressor wheel in 56 trim . It is not part of the HKS range of Garrett GT BB turbos/cartridges which includes the better version of that -12 cartridge from the 56 trim GT3037/GT3076r which is 700177-7 . To confirm the GT2835 56T HKS turbos use cartridge number 700177-3 according to my lists/notes . It should be in that list I posted some years back of most of the GT30 BB turbo family . Cheers A .

Some mobs can rebuild Garrett GT BB cartridges and the economics revolve around whats worn or bent/broken . The things that ae expensive are new turbines if the blades are amaged or the piston ring has eaten into its groove . When there is piston ring damage to the back of the turbine wheels hub you often find it in the same part of the cartridges bearing housing and its not economic to change both . Buying locally usually costs a bit more but if the new item has issues getting exchanges can be more complicatede from OS . New std cartridge is the way to go I think , if your heart is set on 300 Kw sell the 2835 and buy a GT3076R . A .

I may have missed it but what sort of power are you making and what are you looking for ? I would have thought a 2835 Pro S would've made quite reasonable squirt though they may lose you the bit right down low . I think you're at point where changing turbos could be expensive and maybe other upgrades like say better cams could help a bit . A .

No you can't really machine out those HKS GT"2835" Pro S housings . Interestingly HKS used the same turbine housing castings in 0.68 and 0.87 A/Rs but they offset the housing in the Lathe to do the GT3037 version because the full sized GT30 turbine has a larger exducer diameter and would have broken into the waste gates outlet flow path . With port shrouded compressor housings the radial slot is machined to suit the height of the lower or splitter blades leading edges and most wheels are different . The thing people used to do to get a bit more out of a GT2835 Pro S was to use the larger 0.87 A/R turbine housing if they didn't already have one . A .

I think a low CR RB30 is a big handicap but to each their own . 9.3 would be noticably better IMO . A .

Well Lithium that may depend on where that 1 bar comes up and how far you want to rev the thing . I remember being surprised the first time I looked into an RB25 Hitachis std turbine housing and thinking how the hell do you get 184 Kw through that straw yet is there any boost at 1000 revs ? I can understand how people look at a GT30 turbine housing and then laugh at a GT28 one particularly the smaller 0.64 A/R one . Those GT28 NS111 turbines are pretty good things as in very open bladed + 9 only and the tip height is quite wide for a 53.8mm turbine . The real interesting thing is where HKS optioned the GT2835 KAI as mentioned earlier and got surprising power from them given that they're still using the same GT28 0.64 A/R turbine housing . To get that extra power with a larger or cropped GT30 turbine means that obviously the housings throad and volute are not the major restrictions in these things . You'll find the same thing when looking at 0.63 A/R GT30 turbine housings compared with first a GT30 turbine in it then a GT35 one . I must go back and look at the turbine map of this GT28 NS111 76T turbine to se the differences in flow for the 0.64 and 0.86 A/R turbine housing sizes . Something else to remember with a GTRS is that the compressor is 52T and its housing is based on a T04B rather than a T04E like the GT3076Rs normally use . The wheel speed is going to be higher as will the air speed out of the compressor housing so its probably not as bad a situation as you think , better than the std 184 Kw capable RB25 Hitachi anyway . These GTRSs aren't obviously going to pump and vent as high up the rev range as a GT3076R can but the word on the street is that 250 wheel Kws is pretty easy . If you look at 250 GTRS Kw and compare it to 300 GT3076R Kw the smaller option still gets you 83.33% of the way there . If the GT30 got you to 280 Kw the GTRS got you virtually 90% of that figure . It still depends where you want the spread of power to be and what the torque delivery feels like . I don't think any of the EJ20 powered STis ever felt real good , the Subaru header system is woefull and generally nothing happened much under 4000 . A .

Well as history has shown I never used my GT3076R 52T because a RWD Skylines lack of traction turned me off , I don't think they would be a real stable thing cranking out 300 kw to those two rear wheels . Anyway that's irrelevant here . To the OP I would have used higher compression pistons something in the 9.3-9.5 area because the extra part throttle performance from reasonable static CRs is too good to throw away . Its the sort of every day torque/throttle response and if tuned properly fuel consumption that is improved here . The other thing is that if you can get all of the above there is less need for an early boost threshold just to zip around . So straight engine power most of the time and more power from boost when you feel like having a go somewhere . I always think about cams and static CR because the two are tied together with the actual or dynamic CR . The way to make healthier cams work and not lose at low revs is to raise the static or measured CR . The low down trapping efficiency you lose by opening and closing the valves earlier and later you regain with the higher static CR . As per the turbine housing I wouldn't use anything but a proper Garrett or HKS GT30 one and If you have the elevated static CR you can think seriously about using the largest 1.06 A/R one . Bigish turbine housings are better at making boost pressure rise at a controlled rate than smaller ones , often its the wide open throttle and a turbo suddenly accelerating as the exhaust gas becomes sufficient to drive the turbine that makes the torque increase really quickly . Trying to control the situation with boost pressure often doesn't help because its the transition onto boost thats the issue here - IMO anyway . Now a grey area exists because no ones been game to use that 1.06 A/R GT30 turbine housing I think because people think it makes the GT3582R turbos a little lazy . I'm not sure thats really relevant because what a GT30 turbine does in a big GT30 turbine housing won't be the same as what a GT35 turbine does in a big GT30 turbine housing . I'm sure I've mentioned a number of times over the years that if you look at GT30R and GT35R turbine maps the flow rates are different for the three GT30 housing A/R sizes and the GT35 turbine "sort of" roughly equates to being one A/R size up flow wise for the same actual housing size with a GT30 turbine . Now its your calls but I would have thought that the whole idea of having the big 3L RB30 was to make easier lazier torque than an RB25 or 26 does and not need to chase low to mid range torque that a 9.5CR 3000cc engine should have to start with . I dunno , maybe the thing that people worry about is not getting the almighty rush when an engine suddenly leaps on to boost and feels to go like buggery . The thing that amazes some people is watching a factory supercar like say a Porsche make the leap to light speed , I watched one do this once and it didn't look at all violent or particularly dramatic . But when the brain caught up to just how fast that car disappeared towards the horizon I could tell that it was a missile . Out of time back later . My thoughts only , cheers A .

No its still in its box at the moment . I wouldn't mind giving EFlex a go in that car because it does so few miles that an exotic fuel wouldn't be a problem . It has 740s a Z32 and PFC already , and a 33 GTR pump . I'm wondering if EFlex and a bar of boost would give it the 250-260 RWKWs . Also people keep asking about the mythical perfect RB25 turbo and they want to hang an RWKW number on it . Id prefer people to have an "adequate" performance level because a set number seems to bother them . If they get it their chuffed and if they don't they're crestfallen . The performance level could be great for them but its the number that worries them . This is a personal hack formula and quite conservative , I think along the lines of 100Kw/Liter capacity being quite good ie RB20-200 RB25-250 and RB30-300 . Its not difficult to think that if you throw an extra 50 Kw at each engine size you possibly risk losing that nice bottom squirt road cars thrive on . In the case of E70-E85 you can possibly get a bit without increasing the boost pressure and that most likely comes from more efficient combustion - timing set around best torque rather than best detonation protection on PULP . The trouble with going larger than the 100Kw/L state of tune is that you begin to need larger turbine housings biased more towards high performance exhaust flow than lower engine speed boost response , and so an unhappy compromise starts to set in . Typical examples might be say RB20+GTRS/RB25+GT3076R/RB30+GT3582R . Now you can come back on turbine housing size on all except the GTRS and unfortunately its the one you can't easily go larger on either . Personally on my hack formula to not really lose anything but gain everywhere it looks more like RB20+GT2530/RB25+GTRS/RB30+GT3076R . Now as mentioned not much can be done with the GTRSs turbine housing aside from flange adapting a T28 flanged 0.86 housing but you can certainly use a 1.06 GT30 housing on an RB30 with a GT3076R . With turbos its virtually always the hot side that causes all the grief , the cold sides by comparison are generally easy . 16yrs ago I wanted T3 flanged GT30 IW turbine housings , now they are here but now I want them twin scroll and IW . I still want that 60mm NS111 turbine in 76 trim and I'm off to another board to chase more on them . A .