discopotato03

It works like this . You can't measure a vacuum because it is nothing zip zero zilch . Anything abouve a total vacuum is positive pressure even if it isn't as high as sea level atmospheric pressure here on earth . The confusion exists because cork head humans got in the habit of measuring air pressure using two different base lines or datums . 1) Absolute Pressure Psi"a" . The correct way is to say a total vacuum is zero and anything above is positive pressure and it puts sea level airpressure at around 100 kpa/1000 millibars/14.7 psi (same). Some engine management systems read off absolute pressure with a manifold pressure sensor so 0 would be a total vacuum and 100 kpa sea level atmospheric pressure . Abouve 100 kpa is said to be positive pressure ONLY because its higher than atmospheric pressure . Anything from 1 to infinity is positive compared to absolute 0 . 2) Gauge Pressure Psi"g" . This is where pressure is referenced using sea level air pressure as 0 . When you have a compound gauge it trys to show you pressure thats lower than its 0 when the pressure is lower than atmospheric . They are really just a means of making a distinction between atmospheric pressure and anything thats added to it . The silly thing is gauge pressure can make people think you can have a negative pressure when in fact technically speaking you can't have less than nothing . From a tuning perspective I think absolute pressure (psia) is better to use because the graduations rising from absolute zero are easier to comprehend than ones rising either side away from an atmospheric pressure 0 datum . Next time you look at a turbos compressor map pay attention to the pressure ratio (PR) scale . Because these pressures are a ratio of anything above atmospheric pressure to atmospheric pressure they will say for example PR = 2 when a compound guage shows 100 kpa/15 psi . This is because the first 1 bar (bar means barometric sea level air pressure) is just this and the second bar is the pressure above atmospheric . An absolute pressure gauge would show atmospheric pressure as 100 kpa/15 psi and the second bar as 200 kpa/30 psi . A .

If using a Garrett small frame BB turbo re use the banjos from the std T25 based turbo . Most of the hydraulics suppliers sell -4 AN weld on fittings , you drill them to suit the std shortened steel banjo tube and braze them on . Simple and looks factory because the banjos are . You'll find they are the most compact too and compact is good with turbo fittings . A .

What you are calling a "VL Hi Flow" just means someone has made up some kind of Bitsa using a Garrett T3 water cooled bearing housing . Generally the reason why this is done is because T3 bearing housings , centre sections if you like , are dimensionally quite similar to the Hitachi ball bearing one . I seem to remember the water cooling holes being the same size and thread but don't quote me there . It is possible to "Hi Flow" these RB25 turbos with a Garrett ball bearing center section but these are shorter and a bit more fiddly to work on . I wouldn't say you can flog plain bearing centers harder than ball bearing ones , often people assemble Hi Flows that have a lot higher turbine end pressure than the cold side so with huge end thrust they overload the thrust bearing . Just about everything except cost and availability goes in favour of ball bearing center sections . One exception with Garretts small frame ones is that they are based on a smallish GT25 dimensions so shaft and bearing wise can be on the limit with larger heavier wheels like say GT3582Rs have . If you put some pics up we may be able to see what turbine and compressor your Hi Flow has , what you won't be able to see is the condition of the bearings and the turbine end seal . To be sure it needs to be gutted and everything inspected no short cuts here . To be hon est I'd do it anyway because its a major PITA to fit it and then find it has problems . I'm very wary of Hi Flows unless they've come from someone whos played with them over time and basically found out what doesn't work . My experience when I was mucking around with the things is that the turbine and turbine housing are the hardest things to get right and there is a lot less choice with them compared to compressor wheels and housings . Also the learning path is very expensive and often frustrating . My advise is to go to someone thats been down this road or just buy a manufacturers std something ie Garrett etc . I would also be conservative size wise because it is so so easy to lose power you use every day and gain more higher up where you don't go so often . I go the conservative way because the end result tends to feel more like a larger engine than a more highly strung rev happy std one . This is a difficult point to get across mainly because people want 300 RWKWs without actually knowing what a 300KW 2.5 litre engine drives like . If anything Mr Mafia sounds to have struck the best trade off on power and a reasonable boost threshold . He didn't worry that everyone reckoned that 0.63 AR housing on his GT3076R would choke , over 300 Kw and 700Nm of torque speaks for itself . A .

GO33GO got by with poncams GCG OP6 Hi Flow and I think the Gready knock off and an OE GTR front mount . I think it had adapters and GTR injectors plus an 32 GTR pump , 33 ones drop in . Later it was rebuilt with slight porting and slightly oversized pistons . Gary said it cranked out 266 at Insight and went real well for an S1.5 GTS25T . Same same , if 266 can float your boat you won't need the expense of 300 Kw injectors pumps etc . It may be worth waiting to see what Garrett turns up with when the GT28 based GTX turbos arive . I'm seeing hints that they want to have T3 flanged twin scroll turbine housings to cover the GT28 to GT35 BB turbo range . Me thinks that if you can screw 265 odd out of a GTRS you may get a bit more out of a twin scroll GTX2867R depending on housing sizes and wheel trims . With the right housings they may even put together something a little better than a GT2871R/GTRS and if it added up to 270 at the treads its convienent isn't it . Personally I would do the turbo last but have a realistic idea of what 250-270 kw feels like because over builting is money wasted . A .

I don't agree that the GT28 NS111 turbines in GT28 turbine housings are restrictive , particularly in twin form on an RB2570cc engine . Its a different thing when theres only one of them on an RB25 and the housing is 0.64 AR . Its fine if you want to have boost at normal production car like revs but not when looking for 300 Kw . There is good reasons for using larger than 60mm compressor wheels on the better GT28 turbine and I don't think the small and medium trim GT2871Rs are such a bad thing . The issue with GT28 turbos in twin form is that the larger diameter compressor wheels don't make them terribly responsive things but you have to look at the capacity of the compressor wheels themselves . The other significant issue is compressor housings namely port shrouded ones . In the past I don't think Garrett was famous for using them on aftermarket road car turbos and it took some pushing from HKS to make that happen . Actually many of the PS'd compressor housings on HKS spec Garrett turbos have ones made by someone else I think because they didn't have a market for them on OE spec turbos . IMO if Garrett is smart they'll offer T3 flanged IW turbine housings in 0.64 and 0.86 because there is a market for them . I think the GTX2863 and 2867 may already have port shrouded compressor housings std and this will mage a significant anti surge difference . If they are really smart they will offer these to suit GT2871R turbos and kill the HKS GTRS monopoly . One I haven't looked into is the GTX2860R because it may have a larger trim/airflow range than a "GT2530" which in todays speak is a GT2860R with a 60mm 63T compressor wheel . It could be interesting to try to make RB26 specific port shrouded compressor housings though its difficult to know if Garrett thinks a market is there to justify their development . I reckon the bottom line is that you won't get a torquey responsive std capacity GTR engine without a higher static CR and specifically tuned turbos like GT2859R/GTSS turbos . The sad fact is that a low compression ratio 2568cc I6 cannot make enough torque to drag a tonne and a half of AWD Skyline around in style at conventional car type everyday revs . Last time I spoke to SK about this he said the first thing a GTR needs is an RB30 conversion just to drag the pork around without a boot full of revs . If I was into GTRs thats what I'd do to make one a real good dual purpose car . A .

Full Race Geoff played with RB26s some years ago so you could do well to ask him . You should also at least look at T51Rs because they are essentially a GT4294R with arguably a more responsive T51 (I think) 76 trim turbine wheel . Its the one HKS uses and I pretty sure you can buy the same cartridge but with Garrett housings . Your call but I would base the engine on an RB30 because every inch counts . A .

No I reckon if I wanted to use a 76 or "P" trim T04 turbine I'd use a 60-1 compressor . Garrett actually seel a ball bearing T4 60-1 turbo , it looks just like their T04Z externally but with that 60-1 compressor in it . I think better to use like technologies where possible . From memory T04 turbines are 74.4mm OD and not exactly light weight things . To me it looks like the GT35 68mm OD turbine was intended to be a more modern replacement turbine for the T04 but being smaller in diameter I reckon the trim needs to be larger to compensate . From what I see GT35 turbines are not prolific things in truck turbos and they often use twin entry T4 flanged GT40 turbine housings with them . The biggest issue for the small frame (GT25 BB center section) GT3582R turbos is that there is no propper GT35 turbine housing made for them . A .

Well boring out turbine housings for larger turbines does increase their flow potential but given a choice a designed for the turbine housing is a better bet . There is no real T3 flanged GT35 turbine housing so what you get is a bored out GT30 one from Garrett . If you go to turbobygarrett you can compare the exhaust flow differences between a 0.63 AR GT30 and a 0.63 AR GT35 based turbo . I'd have to look again but I'm pretty sure Robert Young at FP uses 0.70 AR T04S compressor housings on his GT30 based HTA turbos , I think these are port shrouded too . Yes Buschur is a bit of a whis with Evos in the US . Its a bit hard to compare a stroked 4G63 to an RB25 because the engine dynamics are so different , as are the cars themselves . The sort of power a well sorted Evo can put to the ground isn't possible with a RWD Skyline . I don't qnow the full story yet but the version 9 Evo heads are different and its not just the MiVec variable inlet cam biz . They changed the water jackets and spark plug size so that they can raise the detonation threshold a bit and that would make a significant difference in itself . I suspect Nissan did something similar with the last version of the RB25DET in the R34s and if I wanted the best from a 25DET I would base it on a Neo head and pistons designed to work with it . The best part of those TR30Rturbos was that 60mm NS111 turbine wheel , actually TR30Rs came with four compressor wheel options and two trim sizes for that gun turbine (73 and 76 from memory) so they are not just one turbo rehashed . Ironically many of the old T series turbines were also 76 trim and can actually work quite well for their era . I think Garretts aim with the production GT30 and GT35 turbines was to use the larger 84 trim size so they could increase their flow potentials without increasing the turbines major diameters . The ODs are approx 60 and 68mm (GT30 GT35) and while they do allow high flow it comes at a price and that is turbine response . The 60mm TR30 turbine does not flow as much as a GT30 but it is lighter and a lot more responsive in the real world . The TR30Rs aim was to make brutal torque from a lot of boost without a lot of engine revs , to do this you need a free flowing but responsive hot side so the EGT doesn't melt everything . I think killer road car power comes from brutal mid range torque and the maximum kw output is less important . I honestly don't know what the ultimate RB25DET turbo is but I do know that any engine thats making good torque off boost tends to hammer on boost even if it doesn't rev to the moon . If you can make boost reasonably early without choking the hot side engines tend to be torquey as was proven with the old FIA Grp A rally cars . Its history that TR30R turbos work and not surprisingly better than std GT3071Rs do . I reckon if you could option a TR3071R or even the TR30R with the 76mm 56 trim motorsport compressor they could be pretty shit hot things . I don't think the GTX compressor/housing pairs are fully developed yet and I think Garrett can do better than these now old GT30 and GT35 turbines . A .

I'm reasonably sure that VL turbos used the same size banjo bolts at least at the turbo end . If you can confirm OE ones work because they are the right length . Good second hand ones do the job too so import wreckers can be good places to look . A .

AFAIK Garrett have never made a twin scroll turbine housing for the GT35 turbine in a small frame turbo - which is what a GT3582R is . I think you'd be better off with a GT4088R or even a T04Z because at least you can get propper TS T4 flanged housings made for their turbines . Plus they both use the larger frame and ball bearing center section . Jeez even a BB T04 60-1 is at least correct housings for its wheels even if the wheels are long in the tooth . Twin ext gate twin scroll is fabbed semi race car stuff that most will never use , TS IW is the only practical hope because its the easiest and cheapest method for the end user to apply . It works but only economies of scale through a big manufacturer using it as OE could make it happen . A .

Something of interest for those looking at Garrett GTX turbos . http://www.motoiq.com/magazine_articles/articletype/articleview/articleid/1802/an-inside-look-at-the-new-garrett-gtx-turbochargers.aspx Cheers A .

The caliper brackets are modified Z32 ones and moved out std R33 GTS25T calipers , I think std R33 rotors are 297 and GTR 320 so half of that . I did actually drive the car that used them and while the brakes are very good the bias has changed because the front braking increased significantly with no change to the rear . I just wanted to know if the rear 322mm rotors fit and would caliper extentions work . A .

Read this again and I still think the affordable reality for most punters is some form of twin scroll twin integral wastegate turbine housing . In the real world most people are not going down the road of twin external gates and or fabricated exhaust manifolds , some may but most won't . I'd like to see Garrett alter the Evo 10 TS twin gate GT30 turbine housing so that it uses the Euro T4 (T3 twin) inlet mounting flange . Big power engines can work better with the larger T4 International sized mounting flange but would they sell in acceptable volumes ? Very early in this thread there was mention of a 300Z with a single twin scroll T04Z on it . I think I'd be going with two turbos purely because of packaging reasons with V bank engines , inline ones are easier for obvious reasons . The debate will go forever with GTRs and TS singles vs twins . My reality is that RB26s are designed to rev and will never be something that makes good low to mid range torque - not without a 30 under them anyway . A .

If its affordable I'd base it on a Neo head and matching pistons because I think the later revision has some combustion advantages over the R33 version . I'm not sure what the story is with the CAS here , would the late plastic cover R33 CAS mate the R34 cam drive with R33 engine electrics ? Also is an RB30 short an option for you ? A .

Hi all , I've found a larger front disc and caliper adapter conversion for my GTS25T and need to know if 322mm rear discs can be made to work and to avoid brake bias issues . The people with this front conversion used different pad materials to help the bias situation but I'd like to increase the rear brake size if possible . I did search first but didn't find much . Thanks in advance , cheers Adrian .

Yes what most people call a GT3582R is the same as a GT3540R - at least center section and wheels wise . From what I've seen there has only been two cartridge variations and the other was the HKS spec GT"3240R" which has a cropped GT35 turbine (roughly GT32 turbine dimensionally) and its compressor wheel is a slightly smaller trim 82mm GT40 one as well . The early Ford XR6T version started the integral wastegate ball rolling because at that time Garrett didn't have T3 flanged IW turbine housings for GT30s and GT35s . No way Ford was going ext gate so had to organise a suitable turbine housing . The compressor side was different in that they used a smaller T04E rather than T04S compressor housing and adapter ring , possibly to keep the air speed up in a low boost application . I think these days Ford went to a GT3576R , probably same compressor as a real GT3076R , which possibly works better in the T04E compressor housing . They would have tested different variations of wheels and housings and came up with the easiest cost effective solution that suited their purpose . A bigger 4L six should make reasonable torque in four valve form and done right it shouldn't need huge turbos to make tractionless RWD performance . I wouldn't think Ford'd splash out for high rev engine internals so enough performance to please the average rat bag is adequate . A .

What people call the OP6 turbine housing is a slightly larger version of what R33 RB25DETs get std , and dimensionally are almost the same . Nissan seems to have had a habit of using larger , but not huge , turbine housings on larger engines in low boost pressure apps . Examples that come to mind are L28ETs RB30ETs and four cam VG30DETs . The idea is to not restrict the exhaust path too much in a larger low boost and sometimes non intercooled engine . I believe with the Z32 300ZX the reasoning was to get a heavy car going from low speeds and just cruising around - not a real high performance application . If you use these turbine housings on smaller engines ie RB20s or RB25s with no other changes what it does is reduce the gas speed through the housing and reduces the turbine wheels speed for a given engine speed . Some people like OP6 housings on RB25s because they fit straight in and allow more power to be made at higher revs at the expense of low rev turbo response . If they modified their 25 it can make a bit better low speed torque than std which covers what they lost initially . Some later R34 GTt RB25s use this housing too but its part of a system including different cams chambers and piston crowns slightly larger intercooler etc . All together they boosted the performance from ~ 184Kw to I think 206 kw . I don't remember reading of anyone who liked these housings on RB20's because they slow the turbine response too much in an engine that probably needs boost as soon as possible . For a budget upgrade on RB25s they are good and probably essential if you built an RB30/25 and had to run the std turbo for some reason . Hi flows are a different story and particularly the plain bearing ones , these will have more oil shear drag than a ball bearing centre sections do so theres a lot of potential to gain extra turbine lag with larger wheels and a larger turbine housing . The good news is that Nissans , Hitachis , ceramic turbine is small in diameter so these turbine housings can be machined to accept Garrett BB cartridges and conservatively sized ones can work quite well ie GT2871Rs . The main thing to remember is that these housings and Hi Flows will always be a compromise and not quite as good as a turbo designed for a specific purpose . A .

Lith from what I read Ford went from a GT3582R to a GT3576R in the upspec XR6T thing , can't think of the name of it - Typhoon ? The original XR6T GT3582R did use a T04E 0.50 AR compressor housing which looks a bit small in the flesh , though I think they only ran 6 pounds of boost . A GTX 76 compressor may pump close to what the GT82mm compressor does while having a little less innertia . I agree that GTX compressors seem to make more flow at higher pressure ratios (boost) , I think Garrett could experiment with larger compressor housings on them to see if they can gain flow at more normal PRs . As has been mention with turbines I too bitch about these because Garrett couldn't not know that these need work as well not just the compressor end . They could start with the TR30R turbine which like the GT30 is 60mm but unlike the GT has 9 blades instead of 10 and comes in 73 or 76 trims rather than the largish 84 trim . Even easier would be to option the GT30 and GT35 turbines in 78 trim like they did with GT37 and GT40 turbines in their big frame BB turbos . Garrett should take a leaf out of HKSs book and try to understand what "Power and Response" really means , it was never intended to mean ultimate power number turbos because ultimate performance and response don't go together . A .

Facts: 1)Generally the only time you hear about cropped GT30 based turbos being called GT28s is with the HKS GT2835s , who knows why they did this . My best guess is that they used some of these "GT2835" cartridges in GT28 turbine housings ie for SRs and RB26s . Some of these HKS spec units date back to the early 90's and in those days both TB25 and GT28 turbines were called "GT25xx" ie in GT2510 and GT2530 and GT2540 . 2)What you are calling a GT2876R comes with a GT28 NS111 turbine and a 48 trim 7/7 bladed T04S compressor wheel . It is not the same as the one HKS had in their spec "GT2540" turbos . The 2540 use the same GT28 turbine but its compressor was a 46 trim 6/6 bladed T04E wheel . Neither is really a gun combination but the Garrett marketed one truly is an exercise in stupidity - by Garrett that is . You have to wonder about a marketing dept that advertises turbos like this GT2876R and then tells you its not suitable for virtually anything . RB20's seem to need something that spins up reasonably early but doesn't choke up too easily on the hot side . I did hear that Garrett may be tooling up to make twin scroll T3 flanged turbine housings for these new GTX2863R and GTX2867R turbos and if they have twin integral wastegates it sounds pretty good for RB20s or even 25s with 2871Rs . With whats around now GTRSs sound like good things for RB20's . I'd think GT30 based turbos like GT and GTX3076Rs would be a bit laggy for and RB20 unless you ran big revs all the time . A .

Deleated .

Hi all , I stumbled across this at Evom net and dif a few searches to confirm . This is a link to ATP and shows a few compressor maps ie the GTX2863R , GTX2867R and a comparison of a GTX2863R and GT2860RS compressors . Note the caption for the GTX2876R is a typo and should read GTX2967R - you'll see if you expand it . http://www.atpturbo.com/root/releases/release110101-1.html Note the port shrouded comp housing in the pics . Elswhere there's mention of a GTX3576R and some of the much larger 55 series as well . Its significant that some of these later GTX variants are 63 and 67mm OD because thats where some of the extra flow capacity comes from ie it isn't just because of the GTX blade count and profile . It remains to be seen if the GT28 turbines can keep up though in a Utube vid of Garrett at Sema this year there's mention of twin scroll T3 flanged GT28 turbine housings on the way . Get down on your knees and pray they have twin integral wastegates like the GT30 Evo ones do because this would give these turbos a huge lift in performance affordably . Watch this space , cheers A .

I think most will tell you that a 6 cyl engine in a four cylinder bay makes life difficult because hot post rad air has to find its way through the bay and out underneath . The very best radiators in the world do jack if the air through them has restricted flow downstream . It could be worth sticking this car on a hoist and having a look from under and behind the engine at where the air flows through - and removing anything thats not essential in the flowpath . Note that includes in the gearbox tunnel as well because if you have the large 25T box in there it takes up more room than the Ss one did . Back to basics , you make more power you make more heat though rough rule of thumb is that only 33% goes down the cylinders and the other 66 is split between liquid cooling and exhaust heat . Any exhaust restriction won't help and if the tuning is iffy that could show up as elevated EGTs and coolant temps . I don't know what oil cooler packaging works on S series cars but I do remember some Mazda Rotaries having reasonably effective oil coolers and they may have been long and not very tall , something to look into maybe . I only ever had one GTR rad and that was a Koyo in a Bluebird . It has all single tubes as in the full thickness of the core and worked really well . I think multi row radiator cores are a bean counters decision not an engineers one because the gap between each layer does SFA for cooling . A real radiator has alloy vanes inside its tubes to break up laminer flow and make the coolant reject its heat properly . My personal opinion of multi pass rads is small cores in series and you have to hope each one can flow enough water to work properly . I'm pretty sure most/all Skyline radiators have vertical flow because more tubes is better for flow and cooling than fewer longer tubes , its the same with intercoolers but packaging and costing means most are not . Anyway as mentioned that viscous fan hub needs to be fully functional and a new genuine Jap one is probably the way to be sure . I'd be running a real good group 4 synthetic oil as well if you have high heat issues and a high poundage rad cap to make sure the coolant doesn't actually boil . The real danger isn't 120 degrees coolant temperature , its the coolant boiling and steam bubbles forming in the head and localisaed head temps cracking/warping things . I don't think its real well known that water boils at higher temps with higher cooling system pressure and its the rad cap that sets the MINIMUM pressure once warmed up . You have to make sure that all pipes hoses everything is fact is in good order so elevated pressures don't blow anything . Just back to oil again I'd be watching oil temps and if its getting high enough to be a worry you may need a higher viscosity one to keep the film strength up . One that comes to mind is the highest of the three Mobil 1 Racing 4T bike oils , its a 25W50 and called "V Twin" and intended for Harlry Davidson V Twin tractors and the like . I know everyone has their favourite brand and theories on performance engine oils , mine is that real performance 4 stroke sport bike engines beat the christ out of the oil far more so than any car engine . BTW I realise that Hardlys are not sport bike engines (IMO) but this oil is in the same group of 10W40 15W50 25W50 so its good gear . 4T Racing has high concentrations of ZDDP or Zinc Di Alkyl Dithiophosphate which is the gun anti wear additives taken out of most of todays oils for Green Socialist Psycopath reasons - it poisons cat converters over time . Hope this helps cheers A .

I'd just replace the std cracked fan with another one , you won't beat a fan that runs all the time with others that don't . A .

If you think about it low volumetric efficiency leads to a lower dynamic compression ratios , you have to have something in the cylinders to compress to start with . The longer the valve (cam) timing gets the harder it is to keep the gasses flowing in the right direction at lower revs . This is obviously why engines are cranky at low revs with big cams , the valves are opened early and closed late in an effort for the engine to fill its cylinders at high revs . Just on this ITBs tend to reduce some of the camminess (reversion) at low revs and small throttle openings because the throttle plates act as a partial barrier to reversion pulses back from the inlet ports . To each their own , A .

Individual throttle valves play a big part in dynamic compression ratios because it means a engine has a lot of throttle area on a per cylinder basis . With single throttles all cylinders have to breathe through the one and you reach a stage where it can't feed them all enough to get adequate cylinder filling . If you want an engine to breathe well - read fill its cylinders as best as possible - then individual throttles are the best way to go about it . Look at it this way , take an 8.5 to 1 static (measured by volumes) compression ratio engine and give it individual throttles . Then take the same engine and fit your typical manufacturers single throttle and plenum type inlet manifold . ITBs give the very lowest restriction throttling because they give the least path of resistance to the atmosphere trying to fight its way into your cylinders . Dynamic CR is all about how much air the cylinders have in them to compress , therefore if the cylinder is only 80% full its dynamic CR will be lower than if it was 100% full - for any given static compression ratio . The way to make a less expensive to manufacture engine , ie single throttle one , feel good in part throttle conditions is to raise the static CR . In other words we didn't get as much air in as an ITB system could but what we did get was squeesed into a smaller space so the dynamic CR didn't die in the ass as badly as it could have . Yes cam profiles play their part and the general rule of thumb is that the larger (longer) the durations are the higher the static CR needs to be in order to not lose low end torque . The reason why long period cams lose low end power is because they keep the valves open too long to allow good air trapping efficiency in the cylinders at lowish revs so the cylinder has less air to work with meaning less to compress . The thing is that if people wish to do silly things with real long cams then its not the engines fault if it cylinders trapping efficiency is low and the static CR too low to do anything helpfull for them . Any engine is a sum of its parts and if the "system" is designed to all work together to make power over a given range then lifes good . A .