discopotato03

Neo RB25 ? More money but more std go and really nice with the 6 spd box and matching final drive ratio .

The Discopotato GT28RS AKA GT2860RS is really a slight compressor variation on the HKS GT2530 but its housings suit 4 pot 1800-2000cc better . It tends to like being used in .86AR (GT28) exhaust housing and the TO4B compressor cover is fitted because it can turn some big revs and pump a lot of air for a 60mm compressor . I do remember someone fitting it in this form to an RB20 and found it laggy - sort of the all in with a bang at 4000rpm . If you were lucky and had the HKS T3 flanged 2530 exhaust housing (.64AR) it would no doubt pull the bottom end up but then its not operating as its designer intended so no promises . I don't have time to get into an SR20/RB20 debate but it is obvious that the RB20 was designed to rev where the SR20 was not . The whole 4 cyl/6cyl thing is going to revolve around individual cylinder capacity and breathing so they really are worlds apart . For convienence sake I reckon DP for SR20 and either Hi Flow or model specific 2530 for RB20 . Because I'm obstinate I would build (get built) a variation of the real GT3071R with the slightly smaller 52T compressor so that it would not have high boost anywhere but a broad power range to roam around in . It would have to hang off the HKS manifold and be externally gated so not cheap easy or convienent . Cheers A .

Its the same cartridge with similar housings used by the GT2871R 52 trim SR20 application . HKS does a Skyline GT-RS variation but it uses a T3 flanged turbine housing and a port shrouded compressor cover because they knew it would surge on the six cylinder . There is a very good chance that HKS uses minor variations in the diffuser and nossle sections of their housings . Cheers A .

The whole idea of the GT30 turbine based GT3071R is that it uses T3 flanged turbine housings . The fact that it uses a 71mm compressor , like 2871R's/GT-RS's and 2835's do means its more responsive than the 76mm compressors that GT30R's normally use . It is an inbetween Garrett hybrid , sort of a productionised version of their TR30R competition turbocharger . I would not purposely put a T28 flanged turbo on a six cylinder because its difficult to get a propper compact manifold collector to work well .

Thats going to depend on your finincial situation . If it was rebuilt with the GT35 turbine - technically making it a GT3540R it would be ok for an RB30 .

For my money since you have the extra capacity it would be the real GT3071R with one of Garretts soon to be released T3 flanged integral wastegate turbine housings . Someone here recently put one of these on an RB20 with good results so with 2.4 even better . If you want to get fancy you could get someone to stick a gt30 turbine up the guts of a 2871R 52T (Garrett now sells what HKS calls the GT-RS ie 2871R 52T) to make a GT3071R 52T . Very responsive , integral gate T3 flange , and Nissan Garrett style compressor cover with bolt up air inlet and outlet flanges . Cheers A .

A lot of this is going to depend on how much + you want on that 250 RWKW . I would have though the 1500-2000 rpm boost threshold is way too low for an RB30 - any RB30 . For 250Kw you could get that NA if everything was spec'd to achieve it ie CR cams and no loss throttling . For turbo I would keep the CR up in the 9:1 region , cams could be std for that power level . I would size the turbo to come in around 3000 minium and you wont need a lot of boost for 250 Kw . I guess I would look at Garretts GT30R (unit no 700382-12 specifically) and have a think about their .82 or 1.06 AR turbine housings . The .82 should be availabe soon with an integral wastegate and maybe a 1.06 as well . I have to say that this would be a very expensive 340Hp , its probably easily done with an RB25 Neo or the 33 version if everything is well thought out and applied . In those cases I would run the real GT3071R or the 52 compressor trim HKS GT3037 . Both of these run out of air at about 42 odd lbs so more than enough for 340 Hp . Cheers A .

That will depend on what feels good to you , that 63 housing may make it surge a bit . Cheers A .

Probably going to be fairly laggy . GT40 large trim compressor is not the GT30 turbines best friend . I would resell it and go for less compressor next time . A GT3037 52T or propper GT3071R (cartridge no 700177-23) are much better GT30 turbine based turbos for the smallest capacity RB six . Sorry to say it but GT3040R's are a bad mismatch of compressor to turbine especially the Garrett marketed 700177-14 cartridge because it uses a larger trim compressor than the similar 700177-9 HKS GT3040R ie 56 vs 50 trim . I was just reading today some posts from US sites about some wanting to use them in .63 turbine housing form on high performance Hondas . They are not common in the US and most people in the know can't understand why they were made in the first place , they are not optimal on anything . There's nothing they can do that the real GT30R can't do better and even it would be a bit laggy on a sedately driven street RB20 or 25 . I reckon the GT3071R modified with the 52 trim compressor like the 2871R 52T uses would be quite good . PM me if you want to know how to go about it without spending way too much . Cheers Adrian .

Want more ? There is a bit more dogma to add about turbine trims and turbine housing AR ratios . A couple of different approaches can be taken to "tune" the turbine/housing combination around desired shaft torque , shaft speed and mass flow vs gas speed which ultimately means turbine inlet pressure (TIP) . Because of production costs the turbo manufacturer may decide to cast only one turbine housing in a fixed AR ratio . To be able to vary the turbine speed for different applications they would need to make several trim sizes of the basic turbine and profile machine the housing to suit . Or the other way round , make only one size and trim of turbine and cast several different AR ratio turbine housings . In the past plan B has generally been the case and makes economic sense when you remember that for example Garrett uses say the GT30 turbine in heaps of different turbo cartridge options , so the three basic AR size housings covers the whole range of turbos that use this turbine . The best situation would be if we had different trim turbine (and compressor) options and a choise of turbine housing AR ratios but the spare parts side gets more involved and expensive . And besides mobs like HKS need a bit of latitude to change things and charge a premium for their technological magnificence/thermonuclear protection and titanium show off tag . Cheers A .

Paul turbine maps are a graph of exhaust gas flow in pounds per minute vs exhaust manifold pressure in pressure ratio/atmospheres/Bar . 1 pressure ratio is equal to 1 atmosphere or 1 bar meaning atmospheric pressure at sea level . The coloured line tells you how many pounds of gas the turbine/housing combination will flow as the turbine inlet pressure rises . Note that when it reaches its peak generally the rising turbine inlet pressure doesn't increase its flow rating . Also note that higher AR turbine housings do increase total flow . Most people tend to spend more time thinking about the world beating compressor that what drives it . The very best compressor is useless without something to support it and spin it . Spooling or accelerating a radial compressor is all about bringing it up to a high enough speed to make it pass enough gas to provide positive pressure in this case into an expanding volume (accelerating piston pump) . Turbine and housing design are critical to how a compressor performs . The turbine ideally weighs nothing , absorbs heaps of velocity energy from the hot expanding exhaust gasses and creates no resistance to exhaust gas flow . The turbine needs to be large enough to adequately drive the compressor ie enough vane sail area to take maximum advantage of the exhaust gas energy . Choise of compressor is very important as well as the turbine in the spool stakes . The rule of thumb is that the more blades and thicker section these blades are , more turbine energy is required to accelerate the compressor . The bottom line is that the easier you make it for the turbine load wise the more likley it will rip the compressor up to boosting revs . In other words the turbines with the least work to do will accelerate much faster than those with high work loads given the same exhaust gas velocity . Turbine blades are like levers so the longer they are the more axial force (shaft torque) they generate . The greater shaft torque you have the greater power you have to drive the compressor . Rule 1) Spec your compressor to have a little more (10-15%) than you flow requirements . This way you put a reasonable work load ceiling on the turbine , not major overload through wanting an extra 200 DHP (dream horsepower) somewhere between next week and never . Lag is free so if you want it go for it . Rule 2) The 15% rule (keep compressor and turbine within 15% of each other diametre wise) is valid . It keeps the Gemini graduates from wanting to put 102mm GT42 compressors on 56mm T25 turbines . Actually it keeps the tips speeds manageable and ensures the turbines "levers" are long enough to drive the compressor . Wheel trim sizes . The smaller the compressor trim size is the less air it will pump . The less air pumping capacity also means less workload for the turbine to shoulder . Ever wonder why Garrett turbos use big trim compressors while the HKS equivilent uses a smaller trim and spools earlier/faster - now you know . Turbine trim size . The major or basic turbine diametre size dictates how much torque it developes . The trim size (and housing AR) dictates its maximum flow and velocity . With all else being equal reducing turbine trim increases the gas speed and trades gas speed for mass flow volume . So the response is increased but the flow limit is reached sooner . Garret have done this with the GT4082 which is also on that turbobygarrett site . Note the turbine is 77mm like the GT4088 and 4088R but its trim is 73 rather than 78 or 84 . Also its 82mm 50T compressor is of a smaller lower flow design that the 88 or 88R's different 88mm wheel designs . They obviously wanted more response and less airflow possibly for a smaller engine or lower power (airflow) requirement . As I mentioned yesterday Garrett is beginning to come down a little on turbine trim size so it could allow them to go up a turbine family for each compressor wheel family and maintain response via the slightly smaller trim number . This could assist spool and lower turbine inlet pressure at the same time . It may be like a 3071 rather than a 2871 , a 3576 rather than a 3076 , 3782 instead of 3582 and so on . Everyones snoring for some reason ? Night all ......

Hi all , people are starting to ask the power potential of the TO4Z and its worthwile discussing some of the available alternatives . It no secret that the TO4Z cartridge is an evolution of the Garrett/HKS TO4R turbo and now has a modified GT40R/GT42R/T51R style ball bearing centre section . It also uses the TO4 P trim turbine which is getting pretty long in the tooth . Its surprising that they chose that turbine given that the ball bearing GT40R was being developed though to be fair it was not then being tested in its final form (Garrett were still playing with the 84T GT40 turbine) . Garrett is starting to change their ideas about turbine trims for petrol engines and moving down from the agricultural 84T to lower sizes such as the 78T in the final release version of the GT40R (GT4088R) . The old P trim measures about 74.2mm OD and is 76 trim , its rather heavy and uses I think 11 blades compared to the 10 Garrett uses on the UHP family ie GT35/37/40/42 . Many people are saying that the 68mm GT35 turbine can pretty much do the same job while being more compact and have less innertia to overcome at the spool phase . It sounds good to me though The 68mm turbine compared to the 84mm TO4R compressor wheel makes me think hmm are the turbine blades long enough to get good easy low gas speed shaft power , did the TO4Z use the P for this reason ? I think Garrett should have looked at using their 72.5mm GT37 turbine in an appropriate trim to replace the aging P when it grew balls . The fact that the GT40 ball bearing cartridges turbine is 78 trim rather than 84T sent me after its turbine map to see how it weighed up compared to the GT35R's turbine map . The smallest .85AR turbine housing for the GT4088R comes out at a similar ~ 32lbs of corrected flow to the GT35R with its largest 1.06AR turbine housing thought the 40R reaches this point at lower pressure ratio than the 35R . Then I started to find mention of a hybrid GT40R 67 (67 is what the Americans call the TO4R compressor) which is the GT40R hotside and the TO4Z compressor end combined . A company called Precision Turbo and Engine get this combination made up and market it in the US as the GT4067R . The as sold GT4088R is no slouch either though it has gone to a new 7/14 blade GT compressor of the C117 family . It uses a huge .72AR GT40 port shrouded cover which looks like a carry over from the TA45 series turbos . The debate over GT4067R/GT4088R is ongoing in the US but the power developed is easily in the 7-800Hp and beyond with the best optomised housings and engine setup . The Honda/Lancer/Supra people are developing all sorts of things ATM and much of it surrounds these turbos or the even larger GT42R/HKS T51R . Just on these last two take note that HKS's T51R gets the 76T 82mm turbine while the Garrett GT42R gets fobbed of with the 84Trim 82mm turbine - Power and Response by High Kost Spec ..... So anyway the TO4Z or GT4067R or GT4088R are all vying for the 650-750Hp arena with the US performance crowd pushing the two GT40R based turbos . I have a feeling that the Precision GT4067R will be the best all rounder and very tunable with turbine and compressor housings . Its unfortunatly going to be the most expensive of the non HKS options because it has to be disassembled and balanced plus its unique backplate machined up and fitted . Garrett could do a lot worse than offer it themselves . Any of these turbos are not for the faint hearted and probably need a high reving RB26 or preferably an RB30DET to do them justice . Cheers A .

Provided everything else is working properly ie wastegate / fuel system / tune / no inlet leaks the .87 will bring the boost threshold down . It may be worth asking Doughboy if he has the .60AR comp cover as well as it was a HKS GT3040 option . I know OT but the 3037 52T would be a fair bit more responsive in a daily driven RB25DET . Cheers A .

HKS have to cater to mad Japanese putting big turbos on CA18's , also their GT30 turbine housings should bolt up to GT3037's in 48 and 52 compressor trim . The smaller AR housings are for these smaller compressors to spin fast enough to make some boost on 1800-2000cc engines . Cheers A .

That Turbo will probably be unit number 700382-23 and cartridge number 700177-9 , check its ID tag if you can get at it . GT3040's use the same turbine as many of Garretts GT30R family and HKS's GT3037 family ie 60mm 84T . Garrett do T3 flanged housings in .63 .82 and 1.06 AR . HKS do them in T25/28 flange .61 .73 .87 and your 1.12 AR . I would be hesitant to use HKS's .61 or .73 or Garretts .63 because of surge reasons . Probably the logical step would be the .87 HKS in T28 flange or the .82 Garrett in T3 flange . Cheers A .

If it were me on a std RB25DET I would do the HKS GT3037 in 52 comp trim or ask GCG if they can make a similar combination up for you . A lot of people find the GT30R (the real one which is same cartridge as GT3037 56T) is laggy and you have to push it to get good squirt which is a pain in a road car . Small AR turbine housings only make them surge so that 52T compressor is a must and makes 40lbs airflow in .50AR TO4E cover so 400 should be no prob . A bit OT but we need Garrett Japan to make GT30 and GT35 turbines in smaller trims than 84 , the current GT40R uses a 78T and the High Kost Spec GT42R (T51R) a 76T turbine . Cheers A .

I think its sufficient to say that an 800Hp turbo is a long way out of place on an RB25 , it would be extreme on an RB26 and laggy on a street driven RB30DET . If you go this way and I strongly advise you don't , use the HKS version which is called T51R as it uses a smaller trim turbine than the Garrett marketed GT42R ie 76T vs 84T . Very very laggy , very expensive and very likely to destroy your RB25 . Why bother . Cheers A .

BHDave , I would talk to Brett at GCG turbos because he knows what alternative compressors are available and although popular opinion is that these ball bearing cartridges can't be altered or rebuilt its not the case . You would be surprised what custom combinations are floating around out there for those who go to the extra trouble and effort to improve upon whats available off the shelf . Its often not as expensive as High Kost Spec turbos . Something in the GT30 turbine family should be on the money , either a GT3071R CHRA no 700177-0023 or a GT3076 52T equal to CHRA no 700177-0006 would be pretty close . Maybe GCG's BB Hi Flow would do if your using all the original fixings . I am not keen on the .63AR turbine housing on a GT30R/GT3037 particularly in 56T compressor . It would probably be ok on the GT3071R because its a cartridge with a little more turbine bias than most . The 76mm (GT37) compressor versions seem to do better with an 82 turbine housing . Also with GT3071R's from Garrett the -23 cartridge is the one to have , their other two versions are more like HKS GT2835's in 56T and not too brilliant in my book . No T3 flanged turbine housings available for them from Garrett either . Cheers A .

BHDave , as a start we really need to know which turbo you are talking about because many different ones can use a .63AR turbine housing - must know compressor and cover as well . When you look at turbine housing area radius ratio its not simply a case of small = good response and large = poor response . Small AR housings will give higher gas velocity through the turbine blades than larger AR ones given the same exhaust gas heat/flow . A small AR housing is NOT the way to make a large turbocharger responsive . The theoretical perfect turbo uses mid trim wheels and housing AR's BUT it all hinges around what is trying to be achieved . Turbine maps are usually a two dimensional graph of exhaust flow in corrected pounds per minute vs the pressure ratio of the gas . What it tells you is that once a certain flow rate in lbs/min is reached increased turbine inlet pressure (TIP) wont make it pass any more . Note changing the turbine housing AR will increase or decrease the flow rating for larger and smaller ratio housings . The balancing act with gas turbines is tuning the turbines trim and housing ratio to get adequate shaft power vs low gas flow restriction . Looking at the turbine/housing combination purely from a flow rate perspective wont tell you the full story either . You could have a small diametre large trim turbine flow the same amount of gas as a larger diametre small trim turbine so they both do the same thing right ? wrong . What generally changes is turbine shaft torque or twisting energy to drive the compressor with . The larger diametre turbine makes more shaft torque in that situation for the same turbine gas flow rate . The compressor wheel has a large say in how the turbine performs eg throw a huge high trim compressor on your typical turbine and it just cannot power it properly . Turbine lag city . Someone in the States once came up with the 15% rule of thumb meaning the OD of the turbine should be 85% or greater of the compressor OD . This was from the days of bush bearing turbos so it can probably slip another 5% or so and still be a reasonable theory . The people that get the best results have it closer to ~10-12% where possible . So that gets you basic turbine to compressor dimensions . If you look at lots of turbo specs and maps you start to see a pattern forming of maximum exhaust gas flow in pounds versus compressor flow in pounds and its easy to work a ratio of one to the other . You start to see the extremes such as Garretts GT2540R and GT3040R where turbine size and flow is lower that the norm in relation to compressor flow . This alone should make you think hang on thats not what it should be . It can go the other way with turbos like eg the GT3071R where the turbine size went up a family and the compressor did not . This should make you think hmmm - more exhaust gas flow and turbine torque for the same compressor that a GT2871R has so less restriction and more power to zip up the compressor . Out of time more later . Cheers A .

I would forget staged turbochargers as well . One thing they do garantee is high exhaust manifold pressure at low/med revs because of the primary turbos small turbine and housing . Also the changeover from primary to secondary is difficult to achieve smoothly . What is supposed to happen is the larger secondary turbine gets a small but increasing amount of exhaust flow to spin it up to useful speed . Its nearly impossible to do this without robbing the primary turbine of enough energy to slow it and the engines torque development . The secondary compressor has to attempt to come on line and provide enough volume and pressure to take up the supercharging effort smoothly . It quite complex with the secondary compressor having air valves to prevent air from the primary compressor backfeeding to atmosphere through its air inlet . Far more trouble than its worth and very expensive to develop and manufacture . Subaru tried it with the B4 and ended up prefering the larger EJ25 with its twin scroll or split pulsed single turbo . One of the late Mazda Rotaries (was it ser 5 or 6 ?) used it but it ended up being so complex and unreliable that no one wanted to know about it when it acted up . In fact one of the rev head magazines had an article about how to convert them back to a Hybrid Hitachi HT-18S / TO4B single turbo . I think the most successful solution is to have as many cubic inches as is economic to build and if necessary turbocharge that . The RB30 should make enough torque off boost to make a Skyline feel pretty good (provided final drive gearing is not too short) and spool the sort of turbos that make BIG power if everything else is made to support it . Cheers A .

Will get back to you on this one tomorrow - stay tuned . Cheers A .

It should be using the standard GT3540R cartridge which is CHRA 706451-5 . That Turbine housing is a one off design Ford had made specifically for that turbocharger . What colour is the turbine that makes you think its ceramic ? Cheers A .

Guys unfortunatly with RB twin cam engines the only propper low inlet manifold type is from the GTR - meaning head + manifold because the flange patterns are different on RB26 compared to RB20/25 . It gets better , the exhaust manifold pattern is unique also meaning std or aftermarket RB20/25 manifolds don't fit . Single turbo low mount manifolds are rare and no longer in production from HKS . Even then the manifolds outlet flange is T4/TA45 footprint (it wore a HKS spec TA45S in its kit) so you can forget std T3/GT30R/GT35R turbos bolting up . ATP Turbo in the US do custom T4 flanged turbine housings for the GR35R but do you really want a GT35R ? Its expensive but a std RB26 is the most straightforward way to go , good luck . Another option could be A 2JZGTE ie the late VVT single turbo version . Cheers A .

I'm all ears Dennis about larger than std rear anti roll bars - wacha got ? You'll hate the easy solution to the rear X member bush problem . Simply remove the member and glue up the air gaps in the std bushes with Stickerflex (sp?) . You need to do it in 2 or 3 stages to get it to set properly - on each side ie right side up then upside down . You end up with a solid rubber bush with about works type consistency which means some but VERY limited compliance . We also cut out some rubber discs from rally car mud flap material to put between the body mounts to prevent vertical movement of the x member . Worked really well . Had to use nolathane bushes in the rear diff mount because it was a custom for a Bluebird with DR30 IRS . I was going to do this to my spare DR30 diff mount but lost interest . The bum of the Bluebird was much better behaved than my DR30 is now . Don't hate me Dennis - I'm sure I've posted the Stickerflex "works" bush upgrade on this board before . Ask Jacko and Stu about this "fix" . Cheers A .

I would have thought plumbing stepping up between the 90mm Q45AFM and the turbo inlet would offer no advantage . Since the comp covers are aluminium it would be very easy to have the inlet boss turned down to 90mm , its only 5mm off the radius of the boss and the plumbing can be one size - no expensive silicon reducers required . Cheers A .