discopotato03

Generally the greatest drama is always the dollars . Just as there will be a choise of bush or ball bearing turbos theres choises in cross plys/retreads/radials etc . There are many benefits from later designed turbos , it goes a lot further than the bearing system . It probably starts with materials that better resist heat corrosion and wear , continues with lighter weight internals which need less energy to accelerate , better aero wheels that create less exhaust restriction and impart less heat into the compressed air , use a bearing system that is far more durable with less drag and low pressure/volume oil supply . A huge advantage is that open bladed wheels and a high speed bearing system allows high gas flow abilities is a reasonably compact lightweight turbocgharger . The sad fact is that trying to spin a shaft at high speed in bush bearings was never going to be long term reliable - mainly because the contact area of the supported shaft is quite large even on its oil film . Basically the bush itself revolves so its inner and outer surfaces are floating but create a lot of oil shear drag particularly at slow speeds . The thrust collar and plate type bearing to counter end float also has a lot of oil shear drag and is virtually impossible to make reliable in high speed high boost applications . If you get the chance look into the compressor of an idling engine with a bush bearing turbo and compare it to a ball bearing turbo . The "idle" speed of the BB one is much higher than the bush one and as many find the BB one turns for some time after the engine is shut down . I don't think its possible to get the transient response and durability from the bush/plate system . Annular contact ball bearings use hardened balls running on hardened surfaces so the point contact area is small , they require a lot less oil to lubricate and because the surfaces are hardened and not brass/bronze/aluminium stand up to the heat far better . I'm not sure where the "ceramic" ball bearing comes in . I did see a sectioned Turbonetic turbo once that had a "ceramic" ball race bearing on the compressor end and a bush bearing on the turbine end . I did enquire later and it was suggested that some high speed ball races have a cage to separate the balls within the races and the cage can be made of a ceramic material to resist heat and wear . Thats not confirmed just what I was told . Anyway I think the bottom line is all these things cost money which many don't mind spending provided it does the job and gives no trouble . I used to tell people that one you've had a bush turbo off and rebuilt a couple of times its cost more . I realise that people like to experiment with turbos in the quest for the holy grail but its a long labor intensive costly program . One thing you can be certain of is that hard worked bush bearing turbos will fail with monotonous regularity because of their bearing systems . The only alternative if you want reliability is to use larger capacity bush turbos that wont need the shaft speed or boost levels to generate the power - but this means larger heavier wheels and higher boost threshold and worse transient response to go with the extra weight and bulk . As for heat and "oil coaking" this will depend on the temperature of the bearing housing via the turbine and housing . Water cooling generally fixes this because the thermal mass of the turbine and bearing housings is not that great . How well the high contact area bushes deal with the turbine heat is hard to say . All turbos are a compromise - some more than others . I would have a conservative but good turbo before the 20" wheels or the 6 stacker or air con or the Louisville intercooler because my priorities run that way . I want the best end result so using a well thought out BB turbo is a necessity. I have better things to do than R/R turbos . Best of luck but its not going to be easy building bush bearing hybrids based on older parts because they have been drying up for some time . If it were me I would be exploring one of the GT BB cartridges with sensible wheels for the Hitachi housings and doing production runs of the oil and water lines to make it bolt up . Cheers A .

While on this GT2530/GT-RS(2871R-52T) has anyone thought of using HKS's GT2535 turbo's ? From their specs they use the same turbine as 2530's and GT-RS's but the compressor is an unusual 69mm diametre so may prove a little less laggy than the GT-RS's 71mm compressor depending on wheel trim and housing AR . I have to assume its compressor is a special by Garrett for HKS which they do at times . I'm not sure if its available with housings to suit an RB26 but its food for thought . Cheers A .

1) Early 70's T3's share the same turbine shaft and bush bearing dimensions with std shaft T4 turbos , larger series T4's used larger diametre turbine shafts and bush bearings to resist breakage with larger series compressors . Plain bearing T25's and T28's were based on the smaller T2's internal core and shaft dimensions . I was curious to know if someone was attempting to use the T3 sized shaft and bearings in a T2/25/25 core . 2) As I said if Garrett plain bearing cartridges are going cheap it can be more cost effective to go buy/bolt rather than rebuild a worn cartridge . Its common to find the shaft/housing worn for all sorts of reasons and the machining + balancing operations can sometimes cost more than just buying a new cartridge and fitting the original housings . Garrett are a business just like a supermarket chain so at times parts or units will be cheap and other times expensive . This is very frustrating for businesses that service turbochargers because they are trying to keep prices down while Garretts supply and demand tactics are unpredictable . Its pretty certain Garrett never intended ball bearing turbo cartridges to be serviceable , they wanted total control by selling only cartridges or complete units to dictate price . 3) T3/T4R's . Do a search on these . Garrett is trying to tap into the T3/TO4E market in the US as the plain bearing bastard hybrids as like grass seeds over there . As I said most of them use the incorrect Turbonetics term T3 Stage 3 (actually TA34 76 trim) turbine with a small selection of 76mm TO4E compressors ie 50/54/57 trims . If your in the US and your "T3/T04E" keeps shitting itself you can buy a bolt in cartridge that has basically GT25BB internals with your same wheels - all you have to do is add the water lines and banjo bolts . Pitty the wheels aero technology and balance of compressor to turbine may be up the wall . The interesting one is the P trim/60-1 because it uses the larger turbine shaft and ball bearing unit like TO4Z's , GT40R's and GT42R's do . You could look at it a bit like a TO4Z but with the 409535-1 or 60-1 compressor . 4) The TB31/TA34 series turbos could be likened to the later development of the old dinosaur 1973 era T3's - from a turbine point of view anyway . These turbines are far better aero wise and people love to put them in reprofiled T3 exhaust housings , they are same shaft dimensions as T3 though they are normally longer at the threaded end and have a left hand thread . The turbine housings used on the Ford Sierras are not strictly speaking T3 housings but integrally gated housings designed for those turbines . They may have had a T3 flange and fitted the hot end of a T3 bearing housing but internally are different . If for example you changed the Sierras turbine housing with a machined out VLT housing performance goes backwards - big time . Buick Grand Nationals used a 4.1 L version of our early Commode V6 and had a Garrett Turbo based on the large series T3 turbine (~ 65mm diametre vs the baby 59mm version we got on FJ's/Z18's/VLT's) in an unusual looking exhaust housing with a 3 bolt mounting flange . Its the turbine housing that suits those 65mm turbines that takes to those TB31/TA34 turbines because they are dimensionally similar . The compressor wheel from the GN turbo happens to be quite good and is of the TA34 family . Its part no is 410299-0004 , it was known years ago as the T3 hi flow wheel but is a little laggy when teamed with the small series 59mm T3 turbine . From its map it maxes out at ~ 45lbs air at 2.2 bar though its highest efficiency "island" is wide and long - from approx 17lbs/1.4bar to approx 34lbs/2.2bar and around 5-8lbs wide on the horizontal scale . I'll get back on the trim number which I think is either 60 or 80 - more likely 60 . Actually just found it 69mm OD , 52.5 inducer diametre 58 trim and 6.25 bore size . Its sort of like a 2/3 scale 60-1 airflow wise and the large trim number makes for good efficiency . The rest looks self explanatry but ask if not sure . Cheers A .

Aron I'm not really sure what you mean by problems with shaft/housing/bush dimensions , I'm a bit rusty with plain bearing cartridges but I thought all those old T3's/TB31's/TA34's and small shaft TO4's used 1/4 shafts and a standardish bushes . I suppose the plain bearing T25/28's used a smaller shaft - um ... As I'm sure you know buying Garrett cartridges can be cheaper than assembling one from new components though prices can be all over the place - worse than supermarket chains ! I know Garrett has been pushing what they call T3/T4R ball bearing cartridges cheaply in the US , they are basically the 76T TA 34 turbine with a choise of TO4E compressors - water cooled as well . One different one actually uses a TO4 P trim turbine with the old 60T TO4S (60-1) compressor . I sort of reckon the TA34 family are a good look for high flows but the GT turbines and compressors are far better aero wise . Having said that the Buick GN's were not so bad in some ways .... I don't want to sound like a smart alec but those housing pics are Hitachi RB25 or VG30 , the only thing T3 is the mounting flange . Gary's experience of more power EVERYWHERE with decent turbos is absolutly correct , mainly because the turbines in the Hitachi's are so woefully small . Anything you can do to offset exhaust restriction pays off from idle up , its to do with pumping losses and reversion I believe . When you start to compare the GT BB turbines with the ceramic Hitachi's they look much larger as do the passages in their native GT turbine housings . Anyone that ever put a 2530 on an RB25 found the difference hard to believe particulary since its compressor is slightly smaller than the Hitachi's - different story on the turbine side though . Anyhow bush or ball I think response is better when the spec is slightly generous on the hot side and a bit conservative on the cold side . Had I realized this years ago my bitzer hybrid plain bearing turbos would have been more effective . On a last note take every old 8 blade TO4B compressor and hit it with a hammer , they should never be used in petrol engine hybrids . Cheers .

I can tell you it looks to have an 8/16 bladed TO4B compressor in it , either a -24 or -25 and is almost guaranteed to surge . Turbine side is usually a 76 trim TA 34 or series 4/5 RX7 Hitachi HT18S . I believe ATS came up with this failed concept for the JMS RB20 "One Eight Via" some years back . To have any hope of it working flick the 8/16 blade TO4B compressor for a 6/12 bladed one . At least then the dinosaur hybrid won't surge .

You'd find your turbo / manifold / dump burning up on re entry as well . What Bart said .

If you think the differences between GT-SS's and 2530's is technology I can tell you this . The compressor wheels are same family though different trims and no doubt tip heights . The turbines are different types not just a trim difference . It pretty obvious that the SS's are designed to spin faster given the same mass exhaust flow than 2530's so they will make positive pressure at lower engine speed . If I had to guess I'd say some people don't like their GTR doing the gratification thing from 4000 up so want a bit more torque in the sort of rev range wot t' good tawd ausie six pac does . They are a 1400+ Kg car with a low compression ratio 2570 cc six off boost after all . The 2530's were designed to give little away to the std T28's but make far better mid range and top end so they are a win if you want more of the same so to speak . There is no way that GT-SS's will make ultimate 2530 power with higher boost pressure , it can't be so because their housing passages are smaller and their turbines more of a closed blade design - that which gives them earlier response goes against them at the other end of the gas flow range . They really are horses for courses and the user needs to decide what sort of power and rev range they want to have . So whats it to be , a true grand tourer or an urban blatmobile ? Given a choise I reckon I'd use 2530's and do my damnest to tune the lower end to be the best possible . Who knows maybe those new Tomei R Poncams and goods dumps/exhaust plus a little smoothing of the head/exhaust manifolds/turbine housings plus a little more static compression may make the better overall package than just bolt on SS's . Good tuning as always critical . Just my 2c , cheers A .

Ok , I had thought the RB25DET Neo gearbox would have been of similar strength to the R33 RB25DET box . Are the R34 gearboxes basically like the R34GTR box minus the transfer case and FWD bits ? Cheers .

I'm interested to know what people think of the R34 GTt's box and diff ratios , does it solve the R33 GTS25T's gear ratio problems or is is really just a marketing bling thing ? Also does anyone know if they will fit in an R32GTST and how the box compares strength wise to the R33 RB25DET box . It was mentioned recently that the VLT box ratios are pretty wide which I thought an RB30 would not have a problem with but it would make for slow changes and short baulk ring life . Getting a first gear ratio change would be expensive on top of the cost of an R33 gearbox so I'd like to know if the R34 gearbox and diff fits and works ok in an R32 . No doubt alternate ratio syncro/helical gearsets are available but most likely cost squillions . Cheers A .

No , not all GT30 turbine based GTBB turbos need to run the large .70AR ratio TO4S comp cover . These are only used with the 76mm 7/14 blade TO4S dinosaur compressors or the 82mm GT40 compressors . The GT3071R runs a 71mm compressor and can use the TO4B cover (like the 2871R's do) or the TO4E cover they normally get and like GT2835's do . Compressor cover families go T3 T04B T04E TO4S . The basic GT25 ball bearing centre section is almost the same ftom the smallest GT2554R up to the GT3540R (GT3582R) and all that really changes is the flange on the compressor end of the bearing housing . The smallest compressor stages are 54mm and the largest 82mm so the bit behind the compressor has to grow to suit 54 , 60 , 71 , 76 and 82mm wheel families . Then you have an aluminium backplate or adapter ring to make what are basically "T" series covers bolt to modern cartridges , once they are internally profiled to suit the compressor wheel that is . This adapter ring has a groove machined in it and butts up against a lip on the compressor end of the bearing housing and is locked in place with a large internal circlip . It fits on from the front and has a O ring to seal it up . Cheers .

I'm not sure of how a GT3040R would compare to the Apexi RS6 . I can say that the GT3040R is a weird Garrett hybrid of GT30 turbine and the smaller of the two GT40 series compressors ie 82mm (larger is 88mm) . Depending on your point of view the GT3040R has either too much compressor for the turbine or not enough turbine for the compressor . Big size mismatch between the turbine and compressor diametres . I would not knowingly use a GT3040R on anything , my gut feeling is a GT3071R (the real one has a full sized GT30 turbine and a T3 flanged GT30 turbine housing - CHRA no 700177-5023) should work well on an RB25 with std pistons etc . It is an off the shelf Garrett turbo + housings so getting housings is reasonably easy . Have a look at the ATP Turbo site and the 3071R they offer . I would steer well clear of the "GT3071R WG" or waste gated as it uses the wrong flange (T28) and is a dog anyhow . Cheers A .

By my calcs you'll need ~ 67lbs of air for 500Kw (670Hp) so about 33.5lbs per compressor for 2 . Something like a pair of 48 or 52 trim GT2835's should get there easily enough . I don't think I'd go beyond 52T GT3037's if the rev ceiling is 6500-7000 . A pair of GT3540R's could potentially do 800Kw but I don't know of any T28 flanged turbine housings for them which you will probably need to keep the turbos and manifolds compact . Cheers A . Actually would a VQ35 be a better option given the limited rev range ?

A GT4088R on an RB26 is getting fairly big for a tarmac racer , what sort of power are you looking for and where do you want it to go from rpm wise ? There is a wild cat hybrid (non Garret conversion) of the GT4088R cartridge called GT4067R that uses the TO4Z's compressor wheel (TO4R wheel) instead of the 88mm C117 wheel . The TO4R wheel is supposed to max out at from memory 75lbs air and the C117 about 68lbs . The TO4R wheel is ~ 84mm OD (63Trim) and is usually found in .70 or .80AR TO4S comp covers . The C117 wheel is ~ 88mm (52T) and comes in the .72AR GT40 cover . Its difficult without back to back testing to know if the TO4Z has enough capacity to cover most of what a 4067R or 4088R can do particularly with HKS's optomised housings . Cost wise the generic Garrett TO4Z works out a lot cheaper and the HKS exhaust housings are available if needed . I think Datsquick once said that 700 odd Hp is not difficult to get from the Garrett marketed TO4Z and I'd reckon response would very likely be better than a GT4088R . Geoff Raicer tells me that the 4088R is not a turbo that likes to be toned back with small AR housings as this kills a lot of its potential . A TO4Z with mid-large sized TO4 turbine housings may be a better thing . Food for thought cheers A .

Need rear windscreen wiper and motor if its a two door . Cheers A .

If its all about response WilliamsF1 was very happy with his setup . I think it uses GT-SS turbos and mild cams with possibly an Apexi PFC and a few other goodies . I'm not the right person to ask about twin turbos or GTR's because I've had very little to do with them . I think the single is way to go but thats another story and not what you want to do . Cheers A .

Search GT3567R , pics at Full Race Motorsports . Cheers .

Not hard to work out really , the RB20 and 25 std turbos Ive seen use different sized turbine housings so if they modify what was the RB20 version the gas speed will be higher than with the RB25's housing . Cheers .

Yes the turbine housings from HKS would be .73 and .87 AR ratio . Always remember that going up in housing AR increases the gas flow ability at the expense of gas speed . I would be wary of going too big because you are basically doubling the difference with two turbos . Any increase in turbine housing AR and compressor trim will make them come on boost later that what you have now . I would be doing the sums on the cost of a pair of HKS GT2835's vs either a HKS TO4Z or a Garrett GT4088R or Precisions hybrid GT4067R . Actually I'd Email Geoff Raicer from Full Race .com in the US as he's had lots to do with the GT4088R and GT4067R . Arguably you can probably make the power with good response and low turbine inlet pressure if you get the manifold and turbine housing AR spot on . Geoff has used twin external gates on split pulse manifolds for single turbo engines so maybe you can re use yours . In Americanlish twins may look "bling" but the modern single is hard to beat from a weight and complexity point of view and costs often a lot less . OMG the twin turbo terrorists are in coming , bye - ducks ...

GTS25T there only ever was one production gearset out of Nissan I found that was on the money . That was from the Aust spec Datsun 260Z , 1st was 2.906 and second was 1.901 . It was really good to use and much easier on the baulk rings , just the thing for the old "Wonnie Bends" in the wet with the snap crackle and crash Detroit diff . The V8 Ford aircraft carriers never could catch me there . Cheers A .

I remember working out the overall ratios of VLT's and R32GTST's and I think the VLT set up is better for the RB30 engine . Yes the final drive is taller but the VL's intermediate ratios are shorter . The 1-2 gap in RB20 and 25 gearboxes is wider than the VL's though 2-3 and 3-4 are closer so innitially too much and then too little . I think they got the VLT right for its RB30 , it could be worth look at what the 300ZX used in the way of gearbox/diff ratios and wheel OD's . The VLT box is probably getting hard to find and is supposed to have some minor differences with the slave cylinder mount and gear shift . I did a search on Navara VG30 boxes and they used the same ratios as the VLT (except shorter OD) so the gear set is around . One of the wifes distant lations has a manual VLT quietly rusting away in a small central western town and I hope to get the box and bottom end when its beyond help . Cheers A .

That 7/14 blade thing related to using 76mm TO4S compressor wheels with GT28 and GT30 turbines . You need to understand that the more blades/vanes a compressor has for a given diametre and trim the more air it tries to push at a given wheel speed . The more air it tries to push the greater the drive load it places on the turbine . Also GT series turbines (and compressors) are true high speed wheels and don't like having to lug wheels around that are designed to work at lower speeds eg TO4S compressors . To turbine housings , you can't alter a housings area radius ratio by boring a larger hole through the housing . If you had a sectioned housing (across its axis not along it) you would see the volute curving around like a snail shell and the nozzle section which feeds the accelerating gasses into the turbine blades . When you fit the housing in a lathe and start boring you are removing material from the nozzle section rather than the volute so while the diametre is larger the volute is not . So the cross sectional area of the volute remains the same and the radius from the centre of the volutes passage to the centre of the housing remains the same - result no AR ratio change . What has happened is that the nozzle is now altered and often doesn't work as the designer intended . Also the larger diametre turbine probably needed a larger volute passage to pass the gas required to drive it with its native compressor in the turbo the turbine was designed to work with . At the end of the day knowing what the AR ratio of the turbine housing is only helps you to know which direction to go if the one you have is not right ie too big go smaller and vise versa . I believe Bretts Hi Flow works because the diametre of the turbine and compressor are closer than any Garrett GTBB turbo I know of and the trims are on the money for a responsive turbo . The wheels are also not worlds apart speed wise like a GT30/TO4S is so compliment each other rather than fighting each other . I'm not going to blow the whissle on them and I'm only nearly certain what they actually are from looking at pics of them . Its enough to know that they are not super high tech or thermo nuclear protected but just a good combination that he managed to package in a cartridge and housings that are std to Skylines so go bolt with ALL the std fittings . Its handy that they can be tuned with a few different RB20/25/VG30 housings to suit different sized engines . Compressor housing AR does make a difference which can be seen in the maps . With higher AR's the map islands grow wider meaning the surge lines are steeper and the wheels pumping efficiency increases in the lower pressure ratios . Note HKS often don't have comp housing AR numbers cast into them eg TO4Z and T51R , they are often a little larger than the similar sized Garrett to help avoid surge and pump more efficiently down low . The turbine housing will have more say in the speed of the turbo than the comp housing but then its up to the compressor size/trim /housing style and AR ratio to do the air pump thing .

The problem with the GT30R is that its a bit short on turbine area itself . Its maps show it as having ~ 53lbs air capacity but the turbine map "flat lines" at ~ 26 and a bit lbs (and thats in its largest 1.06AR turbine housing form) so not really enough . If you divide the turbine flow number into the compressor flow number you get .50 or 50% which is not enough ideally . The original Garrett bush bearing GT37 turbo (GT30R turbo uses a GT37 compressor as does HKS and why they call theirs GT30-37) is powered by a 72.5mm GT37 turbine which is not short on exhaust flow . A better match for petrol would have been something in between the GT30 turbine (60mm) and GT35 turbine (68mm) PROVIDED you really needed all that the 56T GT37 compressor can pump . If you compare the 56T GT37 compressor map to the 56T GT35 map (GT3071R's comp) the 35 map is not too far behind the 37 in the flow stakes . Some of this is because the GT37 compressor is in a TO4E housing which was designed for 76mm compressors . The GT35 compressor is also in a TO4E housing in GT3071R form though the AR ratio is .5 rather than .6 and its snout is not port shrouded . HKS had a fair idea that the GT30 turbine GT37 compressor combination could be a bit laggy in large or 56 compressor trim so they offered it in 48 and 52 compressor trim as well . This is part of the reason why some of their GT3037's respond better and get some boost and torque happening earlier than the Garrett GT30R can . A while back Garrett was developing a competition turbocharger for CART and WRC (probably Indi as well) known as the TR30R . The GT3071R ended up being the productionised cousin of the TR30R and is a better way of achieving what the smaller trim GT3037's can do . Compressor maps of the 48 and 52 trim GT37 maps are hard to find but the results are very similar to the 52 and 56 trim GT35 wheels . Just in case you don't know GT37 compressors are generally 76mm and GT35 71mm . Garrett could have used smaller turbine trims earlier than they have which would have allowed them to go up a family on turbines for much of their compressor range . The GT3071R is one example of the turbine upsize though the trim at 84 did not change . It has happened with the recently developed GT4088R where the turbine trim is 78 . It is also significant that the HKS marketed T51R is using a 76 trim turbine while the garden variety Garrett marketed GT4294R makes do with an 84 trim turbine of the same family . There is nothing to stop Garrett using 76-80 trim versions of their GT30 and GT35 turbines , the GT40 and 42's are already in use . I think the way you should look at it is that rather than the GT3071R's wheel being near the limit its closer to being in sync with its turbine sides flow potential . Cheers A .

Ceramic turbines were all about low innertia rotating groups . With the Hitachi's the sad fact is that they are too small and the blade sections too thick . This is why some modest sized GT28 turbos (with the right turbine ie NS111) kill the std Skyline Haitchi's performance wise . The std turbo was about having low engine speed boost but the cost is exhaust restriction particularly with a boost increase . When you look at a turbo such as a GT2530 its not much if any larger than the std one but it performs MUCH better mainly because the hot side is higher flowing . No good stuffing more air in if you can't get the exhaust gasses out . Metalic turbines have developed way past the point of being light and heat resistant enough to do the job on high performance engines . Super alloys like inconnel can use thin section blades which is far better from an aero point of view , high speed turbines need to be as light as possible out towards the tips to keep the polar moment of innertia down . Cheers .

Because the GT30R uses a 76mm 56 trim compressor capable of more like 400Kw . The extra unused compressor capacity has to be paid for in turbine energy regardless of if it used or not . So basically you'd get extra lag for no worthwhile reason . Cheers .

As always it depends on what else is upgraded to suit and if you intent to spend much time at that 280Kw level . To make 280Kw divide by 3 and multiply by 4 to get approx Hp or ~ 375 . Divide 375 by 11 to get required lbs of air = 34.1 plus 10% = 37.5lbs . 0.6 times air in lbs gives a fair air flow to exhaust flow ratio so 22.5lbs exhaust . The closest match I can find is the GT3071R which has ~ 45lbs air and ~ 23lbs exhaust flow with a GT30 .82AR ratio turbine housing . It does not have an integral wastegate . That particular GT3071R is cartridge no 700177-0023 or -5023 , it does not have a turbo unit number because its only sold by Garrett as a cartridge to which you add your choise of Garrett exhaust and compressor housing kits . ATP turbo in the US can supply it complete with a choise of .63 .82 or 1.06AR ratio exhaust housings . The closest thing in a HKS would be the GT2835 Pro S which also has a T3 mount flange but also an integral wastegate . This one may be a tad shorter on exhaust flow but some want the convienence of the integral wastegate . Garrett is supposed to be releasing a new .82AR ratio GT30 integral gate T3 flanged housing which has gone back to late July - production lead times I'm told . This on the above mentioned GT3071R would be my choise ATM . The HKS Cast low mount exhaust manifold would help but can't promise the turbo would clear the engine mount and bodywork . You need to be real sure 280Kw is what you really want and that the engine can stand up to that figure reliably . I reckon 240 Kw and the state of tune that could have would be nicer to drive and easier to live with in a road driven R34 but thats my ideals only . The R34 Neo's turbo in GCG's high flow form may just about reach that 240Kw figure with the right supporting mods and goes - bolt . Your call .