discopotato03

Shanef I believe that's more a plenum chamber issue than a multiple throttle one , I also wonder how these single throttle manifolds fair on that score . If someone with the fabrication facilities and abilities were prepared to muck around with a couple of RB26 outer or plenum sections surely something could be made to work . If it were me (and I'm no gas flow expert) I'd consider making the plumbing /inlet /plenum volume greater than std so the incoming airs velocity was lower and possibly less likely to have that ram air uneven pressure at the back of the manifold . Maybe this is too deep and a simple computer adjustment (increase) of a few extra percent over the front 4-5 cylinders fueling could be done if the difference is known . SK ? Cheers A .

The factory RB26 inlet system is the tried and proven one and for the life of me I cannot fathom why people want to remove it . It does have more throttle area it does provide better throttle response and it does make the thing less of a cammy cranky pig if you do use long period cams . If people really think a 100mm or larger hole is required to get the air in under pressure then it'd be a simple matter to enlarge the inlet to a GTR style plenum and retain its multiple throttle plates as per std . My logic may be faulty but I look at it like this . If you measure the compressor housing outlets and combine the cross sectional areas this is what the turbo/s are breathing out of . Now lets just say that your brave and fit a pair of GT3076R's/GT3037's with a little less than 51 mm outlets . Now area of a circle is Pi x the radius squared or 3.14159 x 25.4 squared = 2026.8 mm square - times 2 (two outlets) = 4053.6 . The cross sectional area of a 100mm hole (Pi x 50 squared) = 7854mm square . It's not quite double but its getting close . Other things do have their say like for example a 100mm throttle body won't pass as much air as a 100mm hole because there are losses around the plate and shaft . Big NA engines need big throttle body's for a very good reason - all they have is atmospheric pressure to charge their cylinders so lots of capacity being charged with modest pressure requires a bloody big hole to let the air in . Once you force induce an engine the situation changes because the charge air density is (well should be) higher so hopefully a greater weight (mass) of oxygen is going in per cc of charge air . Ratbag rip tear and bust Jap 11000 rpm drag RB26's are a totally different story and totally inappropriate on anything less . Your calls but if Gibson Motorsport got real good power using that system then I reckon so can 90% of the rest of us . The Grp A cars also had to put up with inlet restrictors and most seem to agree that if they hadn't Holden and Whored might have not bothered running at all . Your call .

A matter of opinion but GT3076R's can do better than many give them credit for , don't think that just because some can't get 320Kw + from a 3076R equipt engine that its necessarlity the turbos limitations . As I mentioned a while back the real GT3071R has seen 440 Hp at the wheels in some apps but I think in single scroll form the turbine housing would need to be big and the power curve too peaky for most people . I think 280 odd Kw is not unreasonable to expect with Garrett's single scroll 0.63 A/R GT30 turbine housing - even an IW one . The thing that's impossible for me to predict is what it will feel like on an RB25DET at around town type revs and road speeds . My best guess (and that's all it is) is that it would feel pretty linear and controllable and hopefully not have that's lets double the engines torque output in 500 revs when it came on boost . All too often that shove in the back characteristic means virtually uncontrollable wheelspin which is not fast , dramatic yes fast no . A progressive climb into boost would be nice and possibly do a little in the way of hoof balanced traction control . Anyhow there should be results of such an upgrade soon . Cheers A .

Very briefly what bolts to RB20/25DET unmodified housing wise . Obviously the factory Hitachi RB20/RB25/VG30 single type turbochargers . HKS model specific turbos/kits . GT25/28 series - GT2530/GT2535/GT-RS . GT30 series ----- GT2835 Pro S/GT3037 Pro S . Real type Garrett GT3071R/GT3076R - possibly needing manifold spacer . Garrett GT3582R - but a bit extreme for 2/2.5L six cylinder powered RWD car . Note I have only mentioned integral wastegate turbos and in the forms you can buy them as complete . This is because most people want something they can buy/bolt on relatively easily . Cheers A .

Roy losing the VCT many not be the issue many think it is once you change the throttling arrangement . I tend to look at the RB26 and RB25 inlet tracts as complete sets and I think differences such as VCT/non VCT have a lot to do with what controls air into the system - throttle plates . To me RB25's have your typical single throttle valve into plenum type inlet manifold system which is cheap to manufacture and works well enough for MR MRS and street rat in standardish form . I believe the VCT on RB25's is about low down torque driveability and emissions in an engine with soft cams and a plenum manifold that allows all the cylinders to communicate south of the throttle valve . When you have the ability to change a cams phasing on a DOHC engine you can open and close the degree of overlap (phase in the 4 stroke cycle where all valves are open at the same time - well exhausts closing after inlets start to open) . At very low revs having stuff all overlap means the cylinders have greater trapping efficiency - this is about sealing the charge in the cylinders when the revs are low and the charge air is moving slowly and will flow backwards given half a chance . Once the revs are up a little the air (which has mass and therefore momentum) travels more easily in the desired direction and the cam phasing can be closed up to increase the valve overlap for improved scavanging . The easy way to tell if an engine like this has long period cams is how it idles , if more aggressive cams open the valves earlier and close them later the cylinders trapping efficiency is reduced at low revs and the reversions in the inlet tract give that chaff cutter idle effect . I don't think its a secret that RB26's were all about performance and homologation for race cars . Once an engine grows a throttle valve per cylinder - throttling restrictions drop markedly , this shows up as much better cylinder filling so the dynamic or effective compression ratio is higher . My thinking is that while an RB25DET has a static CR of 9:1 the dynamic (effective) CR may not be any greater than an RB26 which has a static CR of 8.5:1 . Another huge benefit of a throttle per cylinder set up is that the throttle plates actually block much of the reversion effect of healthy performance cams so the plenum air supply is much less affected than it would be if the throttle was a single one at the front RB25 style . The multi throttle system always allowed you to run more aggressive cam profiles than the single throttle plenum manifold and have much better manners at the same trime . ALL true performance engines have multi throttle inlet manifolds and good examples are RB26's and the GTiR type SR20's . Some of the later REX engines are like this and no doubt many exotic European ones . To have VCT RB25 style I think is a cheaper way to have some say in cylinder filling and emissions and drivability . They obviously went a bit further with the RB25 Neo's variable cam timing and this gave them the opportunity to increase performance with different cam profiles and a larger turbine housing and not lose the emissions and drivability , they actually had lower emissions than the R33 version from memory . Fuel consumption doesn't necessarily have to take a great hit with the 26 top end . GTR's may be a bit hard on the juice but so many things about them are aimed at performance that around town they toss it in - particularly if you must have that rush every time you open the throttle . Out of time cheers A .

What fits - the exhaust manifold . Lots of people come here asking if XYZ Turbo will be a winner for me on my Skyline without knowing anything about Turbo XYZ . Before we look at any of the performance aspects of any turbo we need to know if it will physically fit as in bolt to the existing or alternate exhaust manifold . Skylines in standard form (R30 - R34) use one of two distinct exhaust manifold mounting flange sizes and the crossover is from single to twin parallel turbos (RB26 GTR) . The single turbo Skylines such as DR30/HR30/R31 RB20DET /R32/33/34 all use a format known as the T3 mounting flange and stud pattern . The GTR with its twin turbo'd RB26 uses the T25/28 (same) flange size and stud pattern . There are minor variations in the actual manifold and exhaust housing port sizes but the essential thing is that a T3 flanged exhaust housing bolts to a T3 flanged manifold . When assessing a turbo upgrade probably THE first thing to know is does it have the correct size mounting flange because if it doesn't or can't be corrected its a wastes of time . It has to be able to fit . Most people seem to go with Garrett Turbochargers or versions of them sold through performance houses such as HKS . There is a lot of confusion out there because Garrett makes the turbos in generic form and HKS sells them in slightly different form to suit a specific car/engine . Back to the flanges . Garrett makes T28 and GT28 turbos but they only sell them with T28 flanged exhaust housings . HKS also sells GT28 turbos but for single turbo Skyline applications they have T3 flanged GT28 turbine housings made for them so they bolt to a Skylines T3 flanged exhaust manifold - they also have the Skylines std dump flange pattern so std dump pipes bolt up in the std location . The bottom line is that if you want a properly engineered exhaust housing to mate a GT28 turbo to a single turbo Skyline (R32/33/34) you need HKS's exhaust housing . The HKS turbos that have this housing (and are any good IMO) are the GTST/GTt Skyline specific GT2530 , GT2535 , GT-RS which is their name for a GT2871R 56T . This exhaust housing is only available in the one 0.64 A/R ratio size . This housing also bolts up to Garrett BB GT28 turbos such as the GT2860RS and the 3 GT2871R's . Some people like the idea of boring their Skylines original T3 flanged Hitachi exhaust housing to suit a Garrett turbo but its a compromise because its designed for a smaller diameter ceramic turbine . Aftermarket T3 flanged housings are available but how much actual development went into them is anyone's guess . Once you leave the GT28 turbine based turbo series the performance ask is higher and so is the lag or boost response (boost threshold) potential . The next larger Garrett turbine series is the GT30 family in two forms . Firstly the cropped or ground down 56mm version and secondly the full or 60mm sized version . Exhaust housing wise there is a lot of potential to f**k up here because again only HKS make a proper T3 flanged housing to suit that cropped turbine and a single turbo Skyline and they are on their GT2835 Pro S turbos . Both Garrett and HKS screwed up badly by offering these cropped GT30 turbine based turbos in bored out GT28 exhaust housing to suit CA18 and SR20DET applications . Avoid them like the plague . They won't bolt to you Skylines single turbo T3 flanged manifold and adapters only make the situation worse by forcing the exhaust gasses through a smaller than necessary port . For the full sized GT30 turbine based turbos ie the "real" GT3071R and the "real" GT3076R the situation is much simpler and easier because Garrett now sell propper GT30 T3 flanged integral wastegate (IW) exhaust housings which will bolt to your single turbo Skylines exhaust manifold . You may need a spacer plate between the exhaust housing and the manifold so that the compressor housing clears the exhaust manifold but thats easy and cheap . The real GT3071R and GT3076R have the potential to make power way beyond traction in a 2WD Skyline and if pushed to their limits can support ~ 420 and 540 Hp . The GT3582R (AKA GT3540R) is also available through Garrett with T3 flanged IW exhaust housings and may suit some though I think a bit over the top for a street RB25DET let alone an RB20DET . Out of time more later . My opinions only , cheers A .

No the biggest factor is it won't bolt to your exhaust manifold , T25/28 flanged exhaust housings are too small at the inlet for 6 leg exhaust manifolds . You really need someting with a T3 flanged exhaust housing . A .

I think you'd find that GT40 based turbo a little hard to mount . Your call people , if you want I can bash out the basics of what fits , what can be made to fit and don't bothers . Other than that people really need to get and idea of how much air (in lbs mass) is needed to make X amount of horsepower so that they can look at compressor maps and have some idea of whats possible . Temper that around appropriate exhaust flows and I think thats about as close as you'll get in such a broad field . A .

Yes that seems to be the complete solution . I'm beginning to think that using the complete 26 head and inlet may be a good transition from 26 25 (26 upper/25 lower) to 26/30 . It now remains to be seen what can be done to get the 20/25DET exhaust manifold on the other side of the 26 head .... I spoke to SK a while back about having extra bosses welded to the exhaust manifold side (head) so that either pattern manifolds could be catered for . Even an adapter plate should not be too difficult . Cheers A .

As was mentioned in a similar thread Walbro pumps suffer volume wise at higher fuel rail pressures - ie on a forced induced engine . You can put this down to the "high pressure" relief valve settings these pumps have . The real question is are people continuing to buy these pumps purely on price and if so how much more does a more appropriate one cost ? My R33 GTR pump 2nd hand owes me $100 and there's no way I'd swap it for any Walbro out there . Be VERY wary of Walbro pumps on E bay or shady suppliers because there a Chinese copies out there even worse than the original . A .

Sometimes the easiest and best economic method is to sell the R32 and buy a clean R33GTST , it has the things you want + the better gearbox and brakes standard . If you shop around and you can get 33's with good extras too . True the styling is different , its a little bigger and heavier but its RB25 has a lot more potential than any RB20 - more so than the ~ 500 cc difference suggests . Younger fresher and worth more to sell later . Cheers A .

Garrett has turbine maps with lines representing the three GT30R turbine housing A/R sizes , you can see them at turbobygarrett.com . Turbine housing size is a trade off between boost response and exhaust restriction , the lower the boost threshold the lower the maximum exhaust flow you'll have and vice versa . With turbocharging often exhaust manifold pressure rise becomes the limiting factor because you start to suffer reversion/charge polution/charge pre heating proplems on top of pumping losses . The inducator is mostly detonation . Possibly the best generalisation I know of is try to aim for lots of air and exhaust flow rather than lots of boost pressure . We don't yet have conclusive results of a real GT3071R on an RB25DET as its only just being done as we speak . The chief difference between a GT3076R and a real GT3071R is the extra speed you need to spin the 71R's compressor at to move enough air to make good torque . The one being attempted ATM is using a propper Garrett GT30 IW 0.63 A/R turbine housing and my gut feeling is that it will work quite well . It probably won't have the top end punch of a GT3076R but I think it will be more linear in its power delivery on an RB25DET . Anyway real world results should be available soon , cheers A .

Yes Mafia's answer was the one I was waiting for . So 314 Kw on not stratospheric boost in the smallest of the three propper GT30 turbine housings . Depending on how you like to work the numbers in potato theory the larger housing supports between 1/5 and 1/4 extra gas flow which is a huge change to the world the engine see's . More numbers for the numerically agrivated . 0.63 GT30 = ~ 20.5 lbs/min ......... 0.63 GT35 = ~ 23 lbs/min . 0.82 GT30 = ~ 23.5 lbs/min ......... 0.82 GT35 = ~ 27 lbs/min . 1.06 GT30 = ~ 26.5 lbs/min ......... 1.06 GT35 = ~ 32 lbs/min . From these approximate numbers you can see that for the sameish flow rate the GT30 turbine needs the next A/R size up to be about the same as a GT35R turbine and housing combination . The point I am trying to make is that if the GT3076R's compressor can move more than enough air to meet your goal and its turbine with the 1.06 A/R turbine housing can handle almost as much gas flow as a GT35 turbine in its 0.82 A/R housing do you really need to go any larger ? Your call but I reckon the GT3582R is getting a little big for what you're doing and T04Z's are really a ball bearing large frame dinosaur . HKS housings make a big difference to the Z turbo but you pay dearly for them . Over to you , cheers A .

Compressor wise the GT3076R can make the wind for 375-400 Kw easily enough but you have to size the turbine housing to suit the engine capacity . Cubes here uses a GT3076R IW with a 0.82 A/R housing on an RB25DE based RB30DET and it starts early from memory . If you were to use the largest available 1.06 A/R housing it would start a bit later and make the power more easily through less exhaust restriction . From Garretts turbine flow maps for the GT3076R the flow rates in corrected lbs/min are as follows - approximately . 0.63 A/R - 20.5 lbs/min . 0.82 A/R - 23.5 lbs/min . 1.06 A/R - 26.5 lbs/min . Food for thought , cheers A .

The real propeller heads used to say that a large A/R turbine housing on a modest turbine was better than the other way around . The reason mentioned was that the expansion ratio was higher across the smaller turbines blades in a large housing than with a larger turbine and smaller housing . You could take a leaf out of Nissans book with the Neo RB25 and use a slightly larger A/R turbine housing and have the response evened up with the more sophisticated VCT . Personally I'd have the head off/ported/larger exhaust valves and Poncams in before contemplating large turbochargers . The better you can make it breathe the easier it is to make power with modest pressure - in inlet / exhaust / fuel rail . IMO going any larger than a GT30 series turbo is too much for any 90+% road only driven RB25 . In large housing form a GT3076R/GT3037 can support ~ 540 Hp and the HKS spec GT3082R 50T a bit more again . This is snapping on the heels of what many get out of GT3582R's on basically std engines , the overall power delivery would be better with the improved engine and 30 series turbo I'd think . Cheers A .

Your call but I think there are much easier ways to get those R30 semi trailing arm rear ends as good as they're going to be . If you muck around with ride heights you'll find a sweet spot where camber and caster are acceptable . If you want it to handle then you need to fit large enough anti roll bars to minimise body roll and geometry change . Being a RWD car large rear bars should make the front turn in better depending on how well its set up camber/caster wise . The sad fact of life is that the greater the arc those arms move in the more the camber/caster is going to change , if you can limit the travel via higher rate bars (increased roll stiffness) the geometry change will be less . All your going to achieve with expensive adjustable bits is in theory neutral camber and caster at one set point , as soon as the arms rise or fall its changed both anyway . Semi trailing arm is a legacy of wanting IRS on the cheap , independant yes but geometric excellence no . In an R30 you are stuck with this and mac struts and drag link steering . When I had my DR30 I hated hearing how and why R32's and later can run rings around R30/31's handling wise . I think the term used to me was quantam leap .

Dennis the issue is finding new bits for R30 power steering boxes , when I had my DR30 I could not find rebuild parts anywhere . All the 2nd hand steering boxes were no better than mine . I think you have two choices with R30's , you either find an alternative steering box or convert to power assisted rack and pinion steering . The racers had non std quadrants and worms to make for faster steering so to speak . Basically the steering and suspension issues are what made me sell that DR30 because the fixes were uneconomic . Easier to buy a car with multilink all round and five stud hubs and four piston calipers std etc etc . You know what my R33 drives like , its no E36 M3 but closer to it than an R30/31 . We differ because you like the classic and I like the tecnology , I just cant afford the best there is out there . Must share an ale sometime , cheers A .

Someone will know but I was under the impression that the R32 GTST top end was better than R31 gear . I believe that GTS-R aside the R32 engine made more power than than R31 versions did for the same capacity . Affordable RB25 can do better than any of these . Cheers A .

The basic GT3037 cartridge is the same as a GT3076R cartridge - if the compressor wheel is 56 trim and most 3037's seem to be . What you are paying for is low volume car specific housings that enhance a specific engines state of tune . Also generally these housings help with packaging a non std turbo on a production car . HKS kits supply the 101 fiddly bits in one box , if its a Pro S kit they also supply their Micky mouse dump pipe . It's possible sometimes to cheat price wise by buying 2nd hand HKS housings and bolting them onto a new Garrett cartridge . For example if you found a 2nd hand 3037 Pro S turbine housing they fit straight on GT3076R cartridge . I don't know about the RB22 and 400 Hp , obviously it can be done but most would take advantage of a better breathing and slightly larger RB25 . I think RB20 based engines are limited valve area wise so after appropriate cams I guess the boost pressure has to rise . If I had to guess I'd say something along the lines of a GT2835 Pro S or a real GT3071R in 0.63 A/R could get you there with an aftermarket turbo . There's always the GCG Hi Flow option and a choice of RB20 or RB25 or VG30 turbine housings . Cheers A .

Take 2 , lost another longish post to wifi . CR too low IMO , modern turbo with free breathing tracts can do much better than dinosaur bits from the 70's . Parallel twins not worth the weight and complexity on a I4 or flat 4 , most boxer 4's have the wrong firing order to hang a turbo off each head . IMO a TS single with twin external gates (very easy to do with flat 4 tubular headers) would give the best results . If regs allowed possibly water/methanol injection , highest octane fuel available and as much timing as it takes to make the most torque everywhere . Lots of effort needed to get airflow around the heads/barrels and effective oil cooling to keep it alive . My 2c , A .

The fact of the matter is that Garrett don't make a proper turbine housing for that turbine - in any form . The one they do sell with the T28 flange is a bean counters botch job , bored out GT28 turbine housing that was not designed to work with a GT30 based turbine . Don't let the term "GT2835" fool you because there is NOTHING remotely GT28 about that turbocharger . The "GT2835" Pro S turbos work best with HKS's housings - period . To use anything else IS a compromise not aimed at power or response . If you want the best from it use your 0.68 A/R HKS housing because it was designed for your application . I know it means another dump pipe and thats because their housing/dump combination works better than Nissans original system . If the 0.71 A/R housing is what I think it is then it's a sort of copy of the Hitachi OP6 or single bb turbo VG30 - sort of . GT30 based turbines will always give their best results when used in a GT30 based turbine housing . IMO the HKS Pro S GT30 housing would have less restriction than the other probably aftermarket one even if its A/R number is lower . A good example is this , Garrett's 0.86 A/R GT28 turbine housing won't outflow their 0.63 A/R T3 one . The A/R number is relevant to the turbine family that the housing is made for - nothing else . Anyhow I'd use the HKS housing because its a known quantity and designed for the purpose . Cheers A .

8/16 blade compressor wheel - very likely dinosaur T04B wheel . Good if expensive paperweight .

IMO the right anti roll bars are essential and for those you need to talk to SK - Gary . Also I'll be blunt , I think you can buy much better than the Jap name brand stuff namely the Whitline/Bilstein kit parts . No guess work involved , buy bolt align handle . Cheers .

Provided your car has the std DR30 rear disc rotors and calipers with the larger pistons I reckon there's little if anything to be gained here . More likely you'll alter rear geometry designed to be in the back of a DR30 . I'm pretty sure the rails are wider in an R31 and the rear A arm height on the cross member is different . IMO if you must use the R31 rear brakes/back plates/E brake graft those onto R30 rear arms . I think this is more trouble than its worth and will create more problems than it solves . DR30 rear brakes work fine and if they aren't broke .....

Hi Steve , your call but I think something more practical than a GTR such as an Evo 6 is a good look . Godzilla has the aura but its a heavy expensive complex car and they financially break people all the time . The Mitsy is smaller lighter and cheaper to hot up , bolt in suspension goodies are readily available and easy to fit . In club level motor sport Evos eat GTR's . I'm glad you enjoyed that DR30 as I did , but like with many things there comes a time ... I really like the R33 I have , the more I drive other things the more it impresses me . Its hardly an E36 M3 but neither was the purchase price . The Subie RX Turbo has its spider Vortex EA82T engine in the build phase and the constant AWD transmission is done , just looking for a closer ratio Liberty gearset . The "SK" suspension is progressing well and I think it will bite a few unsuspecting Rex's in the twisty windies . Its my toe in the water with turbo AWD though an Evo 6 is my destiny . Best of luck with the sale , cheers A . BTW DR fans , still have front struts/brakes and FJ ET manifolds taking up space . Also complete factory engine management system minus CAS . Dennis , must get that DR rear X member to you . We have suspension contact at Minna so must pass it over one day - need the space in the cave . Cheers A .