discopotato03

Mafia my train of thought is that it will work better everywhere because the cylinders can exhail so much more easily throughout the rev range . A turbine housing is really just an extention of the exhaust manifold and in the RB25's case this is where the pressure rise occurs and cross contamination takes place with the single scroll housing . The twin scroll housing takes the exhaust path of each pair of 3 cylinders all the way to the nozzles - just like an RB26 does . The main difference there is that the twin turbines are only getting an exhaust shot half as often as the twin scrolls single turbine does . By off boost I mean sub atmospheric inlet manifold pressure , and the higher exhaust gas velocity (gas always flows from an area of high pressure to lower pressure faster when the pressure difference is greater) to enhance that windmill effect (compressor pushing more air into the engine than it would get if it was only being charged by atmospheric pressure alone ) . BTW someone mentioned only one available TS A/R ratio and thats not the case . There is another family of TS housings thats being used OS in .82 and 1.06 A/R . You get a leg up with the cast HKS manifold because it has the larger T4 flange but with split T3/T4 Euro ports and stud hole pattern , in other words if you found a split T4 flanged housing in the ratio you wanted you simply drill and tap four more holes and bolt it on . Hint , its not uncommon to find TS T4 flanged housings with split T3/T4 Euro sized ports in them . Cubes I'm in no great hurry with my Skyline , I fully intend to do lots of stiring in the sorts of places that may get noticed so with a bit of luck and a tail wind we may get Garrett (or aftermarket) TS turbine housings with the twinned passage/swing valve integral wastegate . Just like the single scroll integral gate housings were TS ones really are the missing link . Could you imagine what the demand for such a thing would be if it was made available ? Who would bother with the ordinary housing ? I have mentioned in the past that Brett Lloyd said Garrett have no intention of making them but if they thought the volume sales were there who knows ? The single ones we have are manufactured here in Australia not the US or Japan , admittedly they had the advantage of having a similar OEM (Ford XR6T) to work off . Can someone please tell Mr FoMoCo how much better a TS GT35R integral housing could make the XRT6 go ... ATM the best I can do is put feelers out round the world to see what sort of interest (sales potential LOL) exists for TS/split integral wastegate GT30 and GT35 turbine housings . My current daily will probably get a TS turbo before the Skyline but thats OT so I guess we need another TS thread . Cheers A .

Mmmm I'd dispute the part about have to be on boost to do any good . In part throttle operation often the inlet manifold pressure is lower than atmospheric where the exhaust manifold pressure is almost always higher . The pressure differential is not going to do you any favours - sort of EGR action I suppose . Any serious NA engine even production ones in some cases use decent pulse divided headers/extractors . I won't argue that a properly specced twin scroll turbo on an RB25 will do better than a larger single scroll on an RB30 but we are not talking about a bolt on either . I aimed for the RB26 head on an RB30 because I think an RB30 needs all the port and valve area it can get to justify the extra 20% capacity . Getting way off topic but many agree if they did the RB30 DOHC again it would have the best head . Tearing up 10G's very easily . Hell I already own the 26 top end and the delux JE pistons and gapless rings but I still think my R33 will get the HKS manifold/gate and some sort of twin scroll turbo . My problem is that I can see this car costing a bomb and not getting upwards of 30G when I'm finished with it . I've noticed that people here generally have to sell the RB30 separately to get anything worthwhile and then re power the car to sell it . Lot of work for lot of loss IMO . Bolt on bits unbolt and std bits rebolt so this is the issue . My other big issue is that an R33 is no flyweight and while impressive power can bolt in how do you get it to the ground ? The answer is obviously all wheel drive and thats not an economic reality in a 2WD Skyline . It urks me to say it but smaller /lighter AWD cars are out there with similar power to weight ratios BUT 100% of that weight is available for traction . I also think to have a road rocket that won't put you in gaol needs to have giddy acceleration out of the blocks to feel great and not smoke your points - too quickly . No AWD Skyline is what you'd call light and this is probably a big part of why the Evos (and Rex's possibly ?) beat the GTR's in production class motorsport . If the legend can be beaten I don't need to explore the limits of great power but with less that half an R33's 1380 odd Kg over the driving wheels . I still believe I can get enough power from the sold in the car engine to make it a nice drive and not shred the treads too much . For me any more is pointless and the money I'd rather have in the bank . Truly sorry I'm not printing the stuff , cheers A .

Hi , yes RB26 heads and inlet manifolds are a bit of a sea of hoses and tubes . If it were me I'd be trying to take water from the low point on the block and feeding it back into the system at the engines highest point which is at the top water outlet on an RB26 . The reason for doing this is that this turbo coolant system will thermosyphon coolant when the engines shut down provided the turbo itself is not a high point . Its important to realise that should there be any localised boiling going on in the engines cooling system (anywhere) gas (steam) bubbles must have an escape route otherwise the area they get trapped in gets no cooling and differences in temperature can result in cracking/warping expensive things . If the turbo or even the engines top water outlet is higher than the radiator inlet you really need to look into header tanks to avoid problems . VL RB30's had these issues and I think turbo Sierra's had a header tank into which the turbos top water outlet returned its coolant (turbo sits high on Sierra Cosworth YBD) . Something else to think about is returning hot water post turbo into the back of the inlet manifold , I'd prefer it go direct to the radiator via the front than into the back of a relatively long inline 6 . The longevity of the engine would be more important to me than how it looks . Lastly if it decided to leak I'd rather be tracing it round the front of the head than the back . Just my thoughts cheers A .

The Haltech should have its own rev limiting device just can't remember if its fuel or ignition . Don't get busted with an afterburning exhaust , not good for turbo or cat . That second link talks about Apexi PFC's being a piggy back ? Cheers A .

Busky personally I don't like dyno graphs because they're not a good indication of what an engine/car feels like in real world operating conditions . There is that much variation between different ones and all sorts of tricks used to make print outs look good or bad depending on what the operator sets out to do . Dynos are a valuble tuning tool don't get me wrong but there is this want to flash the hard copy around showing peak Hp/Kw figures , the fact that very few drive at that point has to mean something . Gary once mentioned that he'd like to see dyno plots at half/three quarter/and full throttle loads - I guess to have a better overall idea of an engines power and torque characteristics . And torque that reminds me , you often see power figures quoted for turbo diesels and the Kw count looks pretty limp . But , your average death bringer punting his 3 tonnes of Cruiser/Patrol etc around is not exactly going slow so what gives ? Torque and lots of it but without our cure all (Kw being torque numbers x revs numbers) . What this all means is that its entirely possible to have a road engine make a lot of torque over a reasonably wide range BUT if you put the vehicle on a rolling road dyno and stand on it (go pedal) it may not generate glowing Kw numbers . So busky I don't know how to go about giving proof that it works . All I know is that everyone I can think of thats done it half right is over the moon with the results . The night and day bit has been said a few times so those individuals are impressed . This may sound like I'm up myself but if you look hard at the four stroke cycle and do some research on what piston engines do and don't like - from a gas flow perspective - its difficult to draw any other conclusion . The split system will allow a piston engine to make more torque and over a wider range than the single system . Manufacturers of large slow reving diesel engines are taking advantage of it and have for some time . When you look at an engine with a short usable rev range its even more important to pull the bottom end torque up because there's not too many up "high" to play with . Performance car manufacturers are using this system as well because I believe they are running out of ways to get respectable power without moonshot revs from small/light/compact engines . Look at it this way , if you made cars and you found a way to get more low down torque from your current engine design do you A) throw some better technology at it B) go back to the design room and start the larger engine design process . Out of time now , cheers A .

Hi , one of the fellows on FJ20.com forums has ordered and landed on his doorstep a real GT3071R with the .78 A/R twin scroll turbine housing and a TiAL external gate for a little over $2200 . They came from ATP Turbo (in US) via Fedex and now all he needs is an exhaust manifold and some plumbing to make it happen . He's posted a couple of pics of the turbo and gate at that site . One to watch , cheers A .

Hi Cubes , can't say for sure . From a dollars and cents point of view its more practical to see what I can reliably screw out of the RB25 . Cheers A .

Nice , gives me more time to get around to building mine .

It sounds to me like the system he's using is what David Vizard thought up and called Electronic Boost Lag Eliminator . The launch part of that system uses a two stage rev limiter which controls rpm by degrading and retarding the ignition timing . At a pre set inlet manifold pressure the limiter changes from low to high ie launch revs to maximum desired revs . In operation it means the driver can sit on the line with the acceleratoor floored and the primary ignition timing limit used to hold the engine speed at the desired launch revs . In this state the engine is turning fast enough to generate enough exhaust gas to spin the turbine and make measurable boost . DV managed to get 8 lbs of boost with his car stationary in neutral and this was with a low tech 2L Ford SOHC iron lump carburetted (atmittedly at 8000 revs !) . I reckon if you could get an aftermarket management system to retard ignition at certain revs and wide open throttle/s you could probably generate enough extra exhaust flow to pull the boost threshold down a bit . I also think its easier (not necessarily cheaper) to size the turbo to suit the application and take the flow restrictions out of the system - both sides . As for the Turbo HKS has not done everyone any great favour by only offering that GT2835 Pro S in the largest available compressor trim (56T) in that wheels family . Enough of my theorising . It would help if you'd tell us what exactly your power curve feels like and where its not to your liking . If its on a road circuit and the boost threshold is too high maybe something a little smaller like a GT2530 would suit your cars weight and gear ratios better . Food for thought Cheers A .

If I can find it I'll get a link to one of Geoff Raicers (FullRace Geoff here) posts where he talked about developing a Honda 4 cyl drag engine using a Garrett GT4088R . I may not get the numbers exact but you'll get the picture . I believe it started with a single scroll .8x A/R turbine housing (possibly the Precision Turbo one) and power production was up somewhere in the 800's range . He progressed through native GT40R divided housings in I think .95 and 1.06 A/R ratios (obviously with one of his own manifolds) and power I think rose while boost pressure went from 40 to (can't remember) to around 24 PSIG . Thats pretty incredible when all thats changing is the manifold gate/s and turbine housing . Its pretty obvious to me that the turbine inlet or exhaust manifold pressure has dropped away markedly allowing the cylinders to be charged and blown down much more effectively . This is an extreme example but the principles haven't changed . The bottom line I believe is that if you can't effectively empty the cylinder (actually I should say clearance volume) at the end of the exhaust stroke you can't effectively fill it on the induction stroke can you ? Where there is hot exhaust gas there can't be cool charge air and fuel so you lose some effective cylinder capacity , whats worse is that the spent gas is not combustable and will dilute the once clean charge air AND its hot so will pre heat it costing you charge density - hot air is less dense than a cooler air so its mass is less inc its oxygen content . Lower mass means less so less to burn fuel with to develop pressure to drive the pistons down on the power strokes . Anti detonation strategies can be effective but there is power to be found beyond best mean torque timing when there is restrictions in the system . Remember when SK talked about ported heads and improved cam timimg and their effects on gas throughput vs boost pressure ? More of the same only its a bit further south beyond the exhaust ports BUT these things radically change the world the engine see's . I'm out , peace all A .

After re reading my last post I should have said exhaust manifold pressure and temperature are lower with properly sized and developed divided manifold/turbine housing components . I see elevated EGT's as a lack of tuning or control over AFR/Ign timing or restrictions in the system . I get the feeling that the point some people are missing is that the engine evacuates its cylinders far more easily and completly with the split system . The big issue is that to get sufficient gas velocity to make the turbine responsive overall the A/R ratio will be compromised with the single scroll housing , this generally results in the exhaust manifold pressure rising out of proportion to inlet manifold pressure . The cause is restrictions now in the exhaust system and the fact that the non segregated exhaust pulses and pressure rise is more than happy to backflow into the cylinders when all valves are open trying to scavange the clearance volume (everything above the piston at the overlapping end of exhaust stroke/beginning of induction stroke) . Back to the old detonation demon , as we know it's possible to defeat it with anti detonants be they high octane fuels or in Mafias case water/methanol injection . Good as they may be they don't stop the exhaust side pressure rise or reversion so progressively more horsepower is used trying to force the exhaust gas from the cylinders - the term generally used is pumping losses . The well put together entirely split system will have more effective scavanging/lower charge temperature/lower combustion temperature/lower EGT/less crank power loss to pumping inefficiencies so its all cream . To get even close to this with even a split manifold/single scroll turbo means using a very large A/R turbine housing and then you lose the gas velocity to accelerate the turbine at low/medium engine speeds . Extreme methods to get around this are available such as ALS (anti lag systems) but I think you'll agree that this wouldn't go unnoticed in a road car . Anyhow to each their own . I have the HKS manifold so with a suitable external gate and TS turbo I think it would work quite well . Sadly my resources are going into the daily driver ATM so some other will no doubt do it before I do . Cheers A .

Dale the trick with welding these manifolds is partly getting the weld material right for the high nickle (sp?) iron alloy . The parts I've seen welded used stainless steel fittings were TIG welded and the welds actually look really neat . You'll find that EGT's are not going to be higher actually lower with properly sized and developed components . Out of time more tomorrow , cheers A .

Or go to a Garrett dealer (ie GCG) and buy the propper GT3076R in 52 or 56 compressor trim . If turbine lag is an issue go the 52 compressor trim and the .63A/R Garrett Integral Wastegate GT30 T4 flange exhaust housing . I think you can do a lot better than 3+ grand for a similar outcome . Cheers A .

Actually the modern equal (ball park) of the GT3271 would be the real GT3071R cartridge no 700177-5023 . I believe the same family compressor but in 56 rather than 52 trim . The GT3071R (real one) uses the 60mm 84 trim GT30 UHP turbine where the GT32 is from memory an ~ 64mm diesel design maybe HP series . Virtually everyone who's used the .78AR twin scroll turbine housing on the real GT3071R raves about the result , gotta be something in it . Cheers A .

Forgot to add , a surprising number of twin scroll turbine housings are manufactured here in Australia and all you have to do is find one with similar (prefer fractionally smaller) turbine dimensions to the GT30 and have it reprofiled to suit . Obviously it helps if the flange is split T3 and a has a useful Area Radius Ratio . ATP is a box company - they sell bits in boxes from a warehouse . I am only 99.99% certain that the .78 A/R turbine housing is a reprofiled GT32 and if you search the net everyone elso thinks so as well .

Dale I've been thinking about the costing of the twin scroll system and depending on what you pick the bits up for it may not be anything like 6.5K . With manifolds its been seen that the std lump of iron can support 300 odd Kw so all its really missing is the facility for an external wastegate (1) . I seem to remember ages ago JMS did a project car I think called OneEightVia (reverse panel Sileighty) and they managed to weld a section onto the RB20's cast manifold to mount an external wastegate . If you read that thread at FreshAlloy.com you'll remember that Geoff used one gate on the SR20 manifold but the path to the gates valve is divided as well . I think welding techniques have developed to the stage that this would not be the end of the word to do reliably . In the US they do it often to production manifolds and if done properly they don't seem to fall to bits . You may have also noticed that HKS's cast low mount RB20/25 manifold has a divided gate mount as well . Either of these gets the whole shooting match on the side of the head so thats the manifold and gate for what 8-1200 ? A ball bearing turbo from Garrett to support 300Kw /400Hp is probably going to owe you 1500-2000 depending on taxes etc . You won't get one out of the box with a twin scroll turbine housing but they can be supplied with them if required . The idea is to not buy one with the expensive Ni Resist GT housing but to get the TS one instead - it could be line ball or even cheaper depending on the cost of the TS Diesel housing and the machining cost to reprofile it for the GT30 turbine and cartridge . If you'd opted for an IW GT30 turbine housing your up for the cost of fabricating a dump pipe anyway , the twin scroll one only requires a bend and V band flange plus what it takes to plumb the gates outlet back in . I get the feeling that the numbers chase is lurking again with the question being how little can 300Kw cost . My point is I reckon the twin scroll system done properly will give the RB25DET more of the larger N/A engine type power curve than a single scroll one and not lose any top end . This is a difficult thing to achieve but from an RB six point of view I think its a cheaper option that removing and gutting/replacing the bottom end in the search for larger capacity torque . Sure at very low revs it won't pull like a 20% larger RB30 but it wont cost like one either . BTW I'm not nocking what Mafias does , great effort and learnt by doing it himself . Cheers A .

Garretts GT3267 and GT3271's are not bad really for a plain bearing turbo and it looks like the more modern centre section than the old T3 and small shaft T4 turbos had . They are availabe with a couple of different compressors and the 71mm I think using the 71mm GT35 series (BCI-18) family . If thats the case its basically a plain bearing version of the wheel that the GT2871R 52T and GT2835 52T use . Wheel backspacing and bore size are different for BB vs plain bearing cartridges . If you look at the compressors from some GT BB turbos you'll notice they have a hexagon behind the compressor lock or jamb nut . This is because when used in a ball bearing cartridge they were modified from the plain bearing form . In plain form they generally have a threaded bore and the hexagon is used to screw up and tighten the wheel on the turbine shafts thread . BB spec turbines usually have a smaller diametre where the wheel lives and fixed with a locknut so most but not all of the original hexagon gets machined away . With backspacing ball bearing spec wheels can sit closer to the shorter BB bearing housing because there is no need to allow space for the non existant plate/collar thrust bearing . The BB wheel just has a bit more off the back and a smaller plain hole through the guts , spot face the outer end for the nut to bear on and toss it on a BB cartridge . I'm not certain but the turbine is probably an early diesel design . If you search GT32 turbos you will find that people in the US have played with them on some Subaru engines and a few others . There are dyno plots of the 67mm vs 71mm compressors although they speak of them in terms of pounds (pounds of airflow capacity) . I wouldn't get too excited over the wastegated housings because I'm pretty sure they only vent one side of the divided housing so no good for a petrol app . As a cheap twin scroll external gate turbo they're probably not a bad thing on an RB25 though I'd prefer the Nissan/Garrett style T04B compressor cover (two bolt in / 3 bolt out) to make it a bit more compact . The .78 A/R twin scroll non gated turbine housing looks a lot like the one turning up on real GT3071R's and real GT3076R's doesn't it ? Cheers A .

I really like the idea but the composite material they're made of worries me . I've seen too many "plastic" radiator tanks fail and I just don't have faith with non metalic materials in this app . If it cracks and dumps your coolant quickly it stands a good chance of damaging your engine . If/when Davies Craig make an aluminium cased version I'll give them serious consideration . There is a lot to be said for a pump thats not mounted on the engine block - generally easier to service/replace . The one down side is that should your alternator fail its something else to draw electrical current . If they can make system reliability better then more people would buy them . OT but I'd even consider elec fans (one large one) provided it sensed off the radiator temperature rather than the engines jacket temperature . When you think about it for fans the rad temp is very important because this is where the cooler water comes from provided 1) its got some and 2) the thermostat lets it flow in . Meanwhile back to the elec water pump (EWP) , cheers A .

LOL , I didn't claim it was any new form of rocket science but there are some important difference nowdays . From a mechanical perspective the turbos are more modern and so can be specced to respond better than the older ones . Some of these GT UHP turbines can be made to handle quite high flow rates and provided thats what the engine wants its a win for turbine power and the pressure balance across the engine itself . I'll quote Corky again for the umpteenth time , "Turbine inlet pressure is an evil and should be delt with accordingly" . When you do you throw away a large number of the things that gang up and promote detonation . They WILL restrict power development even when detonation is no longer the limiting factor . This is why I used to harp about measuring EMP and IMP because when EMP is significantly higher its trying to tell you that the exhaust side flow restrictions are getting out of hand . Cheers .

About controlling combustion chamber temps not combustion temps ? I must be missing something here . David Visard did some interesting write ups on water and water/methanol injection . He mentioned that Spearco used to do a sort of programmable type system that only fed the fluid in when the engine was likely to detonate . I have to wonder what distribution between the cylinders would be like even with a fine misting system , multi point would be best but more complex to apply . I think there would be a chance to actually lose some power by injecting water if it wasn't doing anything ie no detonation . Before I go any further if possible its best to find out why your engine is detonating because as I'll show you may find some power lurking behind whatever was causing it . Only because Dale can't sleep at night : Drum Roll .................... Twin scroll turbine housings and properly designed pulse divided equal length exhaust manifolds . Make a pot of coffee because this'll take some time . I'll start with the exhaust manifold because they get discussed a lot but the people who make or obtain them swear by them . The reason behind having all the runner lengths the same is that the time it takes the slug of exhaust gas to reach the turbo needs to be the same in the engines sequential order ie 153624 . If you have a manifold with different lengths the short ones take less time for the gas slugs to travel between the exhaust valves and the turbo and vise versa with the longer ones . The best situation is when they are evenly divided so you get a sharp pressure/velocity rise at the turbo followed by a pressure drop then the next cylinders event etc etc . The aim is not to have them overlap when avoidable because a cylinder blowing down into an area of higher than avoidable pressure will lose some of its velocity attempting to overpower the raised pressure in its path . A non divided manifold is not very efficient because it does a good job of tyring to pressurise every other exhaust port . The turbo (turbine) much prefers to have slugs of gas rather than a constant feed so to speak to benefit from the highest pressure/velocity just as the exhaust valves first crack open . With a divided exhaust manifold on an in line six the exhaust ports are grouped together 123 and 456 , with the firing order being 153624 the exhausting cylinders alternate between the front and rear groups in theory timing the gas slugs evenly to the turbos mounting flange . When you have a divided or twin scrol turbine housing you are separating the two groups all the way to the turbine nozzle - actually there are two nozzles . So we get the high pressure/velocity gas slugs evenly time feeding pulses as widely but evenly divided as possible doing the expansion thing into and through the turbine blades . You don't tend to get a cross feed occuring between the parallel nozzles because the exhaust gas finds it difficult to flow backwards through the turbine blades . There are some important things to understand about divided and undivided turbine housings of the same family and A/R size . If you had for example a .82 A/R divided housing its really more like two .41 A/R housings in a common casting . This is why you need to increase the A/R ratio with divided housings compared to non divided ones because while yes the combined area is similar the same sized engine cylinders have to flow through them and .41 A/R is a bit restrictive . So ideally the gas slug leaps from the cylinder out of the port and through the split manifold into an area of lowish pressure not losing to much velocity and barrels into the turbine blades via the divided nozzle . The divided housing was say 1.20 A/R giving ~ .60 A/R so again not a lot of velocity robbing restriction in the separated passage . Wastegating needs to be done properly ie separate gas flow paths from the manifold or turbine housing all the way to the wastegate valve other wise you lose the pulse effect at the turbine . The properely designed divided system achieves pretty much what twin parallel turbos do , two separated groups of three cylinders pulsing into separate nozzles but this time with one turbine and one compressor . Twin GT28's obviously have their own integral wastegates but the same thing can be achieved with two vent paths and integral flat valves in one turbine housing . Toyota did this with one version of their CT20 turbo on some GT4's , Mazda did it I think on an RX7 Rotary and more recently Subaru have it on some Rexes and Legacy's (JDM USDM Liberty) . I've got some pics of IHI's (MHI) VF36/37/38 and for emissions clean cars they make pretty good torque . Current JDM Legacy GT makes 430 Nm at 2400 rpm from a 2 Litre 4 . The people that get this system right and tune the engine properly tend to REALLY pull up the bottom end torque and generally make more torque and power everywhere - right throughout the range . They do this with much lower exhaust manifold pressure and EGT and the engine suffers a lot less of a thermal thrashing when worked hard . At the moment firms in the US like Full Race Motorsport and ATP Turbo can sell you a real GT3071R or GT3076R with a T3 flanged divided housing and FRM (see above) is doing some for the GT3582R AKA GT3540R . Last time I spoke to Brett Lloyd I asked him if Garrett was going to make divided turbine housings for the GT30 and 35 turbine based GT BB turbos and he said no , the high temp resistant iron is difficult to cast reliably so none in the near future . Their loss I reckon because the aftermarket is already modifying workable generally Diesel divided housings and the results speak for themselves . Who would have thought a twin scroll GT3071R could help crank 400 ft/lbs out of an SR20 at 4500 rpm with porting better cams and injectors etc . I think its entirely possible to make an RB25 feel a lot better than they normally do without lifting the engine out of the car . I still think porting and mild cams help a lot but how close to a mild RB30DET can we get the RB25 ? Night all .

The turbine housings should interchange as RB26 turbos have to be located in the factory position to have all the plumbing line up . I've never had the two side by side but it'd be hard to resist using the High Kost Spec ones given a choise . You could look inside them to compare the shape of the passage and nozzle . I'd reckon HKS had their own made originally because there would have been nothing else available in that model specific app . Who knows maybe even Garrett made them . The divider between the turbine and wastegate outlets would be worth having . I haven't looked into the HKS GT-ZZ for ages , I think they were something HKS was cooking up for a twin turbo conversion on the Z33 350Z . If and when they materialise it won't be too long before someone whips the housings off and posts a few pics so wont be secret for long . It'd be hard to justify buying expensive name brand turbos and then rebuilding them . Cheers .

That HKS spec T04E is not a T3/T04E hybrid its a full "T04E" meaning it's got a heavy T4 turbine and in its smallest trim size - 62T AKA "N" trim . Its compressor is 57 trim which is not real small either . Any full T04E turbo is going to be big/heavy/not very responsive . Also a lot od misinformation on what a "T3/T04E" really is . When built in America they use the TB31 turbine (NOT some ancient small series T3 turbine from Nissans RB30/FJ20/280ZXT/Z18 ) . The TB31 turbines are ~ 64mm OD not 59mm like our early Nissan/Garrett T3 turbines . If you used the TB31 turbine with a med trim T04E turbine ie 50 trim they can work reasonably well . Garrett actually make turbos called from memory TA34's and they do work , I seem to remember posting picks on this board of the "TA34-1" so do a search on that . It runs a .58 A/R turbine housing in T3 flange and the word is they work reasonably well depending on your expectations . I did see one at Turbologic (Port Kembla) and Fred did say the RB20 people thought they were a good cheap upgrade though that was a few years back . I wouldn't throw HKS dollars at a T04E when there's noting you can't have built in them . Cheers A .

Making a "T04R" is laughably easy . Take one garden variety plain bearing T4 centre section and fit the "R" wheel to it with a T04S compressor housing . HKS cropped the common as dirt T04 P trim turbine but I wouldn't bother . Or you could just buy a T04 60-1 turbo and Garrett even now do that with the larger sized BB centre section . Your call .

The truth of the matter is that Honeywell Garrett make a generic GT25BB centre section and use it for everything from GT2554R right througt to GT3582R including the HKS spec cartridges (centre sections) . There is available a slightly different BB pack itself but I'm told the only difference is the cage that separates the balls , some high temp composite vs the slightly more expensive ceramic cage . HKS cartridges use the normal one as well as the usual Garrett range . Garrett calls any of their high performance GT25 BB turbos GT28XXR now days - the ones using that 53.85mm 76 trim NS111 turbine that is . Garrett has optioned quite a few different GT28BB cartridges using the 60.1mm OD GT compressor and that NS111 turbine . The HKS spec GT2530 uses a 63 trim version though its not impossible that because of the age of these cartridges that it may even be a T3 wheel . Garrett also does two very similar cartridges where the compressor trim is 62 and even then the inducer diametre is fractionally different . The most significant difference I know of is the extucer tip height and the greater one is that used in the GT2860RS (AKA GT28RS) . The other is I think used in the 2530 type offering . I'm not in the cave ATM so I can only quote cartridge numbers from memory , pretty sure the 2860RS uses CHRA no 446179-5066 and the other one 446179-5056 . I think the 2530 is CHRA no 446179-5021 but have to confirm that . These differences are not going to be massive in the real world but they will have some influence on boost threshold and adiabatic effeciency at the bleeding edge . My best guestimate (not based on experience) is that the Garrett marketed equal to the 2530 has a bit going for it . Firsty if new its zero mileage and its compressor being a fractionally smaller trim thasn the 2530 may have very slightly better spool and transients . I've never measured a 2530's 63T compressors tip height so I can't compare it with the two 62T wheels . The price is probably going to be better than any HKS vendors particularly if they discount for the matching identical pair . I tend to be a little conservative with turbos and in a GTR's case I reckon I'd be more interested in what happens between 3500-7000 than 4500-8000 . Again I don't know through experience but I think GT-RS turbos (GT2871R 52T) would make the usable power range a bit peaky on a std capacity RB26 . I think HKS were silly not to use the GT2871R 48T cartridge as the basis for the RB26 spec GT-RS turbo , it would have been a better incrimental offering over the 2530 and been more user friendly . Your call , I hate low compression slugs that you have to get angry with to have any decent squirt . It you have to drive around everywhere at 3500 revs so you can get some push when you crack the throttle/s it gets very tiresom and expensive at the pump . Why bother cheers A .

The ones that spoke to me said that the compressor/housing combination (map confirms it) maxes ~ 53-54 lbs air at around 2.75 PR or 25 pounds of boost (PSIG) . I'm conservative and work on 10Hp per pound of air (mass not boost) but a lot of people say 11 . So I guess you could say that turbocharger compressor wise is capable of supporting 530-540 Hp conservatively or 580-590 not so conservatively . Down round 60% adiabatic efficiency increasing the rotating assemply revs doesn't pump significantly any more air (mass not boost) . That GT30 .63 A/R turbine housing will to a degree give the turbo the lowest boost threshold (of the 3 available) but as the boost climbs so does the turbine inlet or backpressure . It will run out of gas flow capacity on the exhaust side before the compressor side . The water/methanol injection is very obviously working for you to supress detonation but what it can't do is control exhaust manifold pressure (EMP) . BTW By IMP I meant inlet manifold pressure . You've proved that you can supress detonation to the degree that advancing it past the point of BMT (best mean torque) no longer makes anything worthwhile . As I said in the past I would have tried to use the 52 compressor trim version of that turbo because it may have enabled you to get away with the next size up or .82 A/R turbine housing . Its still capable of moving 50 lbs air by mass but takes a little less turbine energy to excite it . Out of time but if you really want to uncork the hot side you now have to address the turbine inlet pressure and reversion issue otherwise volumetric efficiency and reversion will become the impass even if detonation is not . Later tonigh or tomorrow , A .