discopotato03

Hi all , firstly would like the ID Tag no's from one of these if possible . I have found different figures for the turbines in these turbos , HKS USA site shows ~ 58 x 54mm which sounds like a mildly cropped GT30 turbine . Some pics I found from a string at Performance Forums shows the turbine at 63.99 x 58.8 mm which is basically GT32 turbine dimensions in 84 Trim . The compressor is shown as 82.46 x 60.64 so 54 Trim . If anyone has one of these turbos would it be possible to measure the wheels even if from the outside of the housings to confirm the sizes . The difficult thing to know is whether HKS got Garrett to crop a 68mm GT35 turbine or used a GT32 turbine with the GT30 or 35 sized shaft and bearing pack . Either way you could say the HKS GT3240 is a slightly reduced optomised GT3540R ie with slightly smaller trim compressor and turbine mid way between GT30 and GT35 to pick up the response . I think its power rated at ~ 570 ps where the GT3540R is around 700 Hp , 700ps ? If all my assumptions are correct , with a suitably sized (a/r) and T3 flanged turbine housing this would suit many that are asking for more than a GT30R can give with less lag than a GT3540R would have . Typically HKS want to charge a lot more for something thats a little less for their "Power and Response" monica ... Cheers A .

Like SK my vote goes to the Apexi PFC . Aftermarket engine management is reasonably complex to install - read expensive and time consuming . Even after that without a generic base programme to start with it wont even run . The Apexi PFC goes plug and run with all the std sensors and AFM . I used an Autronic SMC for about 3-4 years and every time I plugged the lap top in I wished it could have load sensed off a hot wire mass air flow metre . Its one thing to tune a Map or manifold pressure sensed system but difficult to get the correction maps for air and water spot on . To a large degree the hot wire sensor takes the hard work out of this because its load signal reflects mass flow ie CFM AND air temperature so the air density can be known as well . I've heard people say that they'd prefer the old gate type afm to map because it tells the computer how much air the engines ingesting not just manifold pressure . The map sensor signal tells the computer nothing about air volume or density so crude means of correction are needed to get the programming right . For burial rights - should you wish to remove the Autronic when the car is sold its a fair bit of work to refit the original computer/sensors/AFM/loom etc . If the constabulary were to find out (some of them are petrol heads and know what to look for) its much easier to refit the std computer/AFM/injectors . Apexi PFC will maintain its resale value better than a second hand Autronic . Cheers A .

First and third probably too big , serious doubts if no 2 is a GT28RS - looks dodgy . Cheers A .

Garrett family of GT30 UHP Turbine based turbos , aplication HKS / Garrett . Next time you say you have a "GT30R" it could be any of these or maybe others . Unit part no , CHRA , Note no . 700382-0001 , 700177-0001 , 01) Unknown but maybe 2835 48T , 84T Turb 700382-0002 , 700177-0002 , 02) 2835 52T , 56.6mm 84T Turbine . 700382-0003 , 700177-0003 , 03) 2835 56T , 56.6mm 84T with .64 a/r . 700382-0004 , 700177-0004 , 04) 2835 56T , 56.6mm 90T Turbine . 700382-0005 , 700177-0001 , 05) Unknown . 700382-0006 , 700177-0002 , 06) 2835 52T , 56.6mm 84T Turbine . 700382-0007 , 700177-0003 , 07) 2835 56T , 56.6mm 84T with .86 a/r . 700382-0008 , 700177-0005 , 08) Unknown , suspect GT3037 48T . 700382-0009 , 700177-0006 , 09) GT3037 (GT30R) 52T , 60.1mm 84T Turbine 700382-0010 , 700177-0006 , 10) GT3037 (GT30R) 52T , 60.1mm 84T Turbine 700382-0011 , 700177-0007 , 11) GT3037 (GT30R) 56T , 60.1mm 84T Turbine 700382-0012 , 700177-0007 , 12) GT3037 (GT30R) 56T , 60.1mm 84T Turbine 700382-0013 , 700177-0008 , 13) Unknown 700382-0014 , 700177-0009 , 14) GT3040 , 50T GT40 Comp , GT30 Turbine . 700382-0015 , 700177-0008 , 15) Unknown 700382-0016 , 700177-0009 , 16) GT3040 50T 700382-0017 , 700177-0001 , 17) Unknown . 700382-0018 , 700177-0002 , 18) 2835 52T , 56.6mm 84T turbine . 700382-0019 , 700177-0003 , 19) 2835 56T , 56.6mm 84T Turbine . 700382-0020 , 700177-0004 , 20) 2835 56T , 56.6mm 90T Turbine 700382-0021 , 700177-0004 , 21) 2835 56T , 56.6mm 90T Turbine 700382-0022 , 700177-0008 , 22) Unknown 700382-0023 , 700177-0009 , 23) GT3040 50T (.70a/r) , 1.12 Turb a/r . 700382-0024 , 700177-0003 , 24) 2835 56T , 56.6mm 84T Turbine . Real Garrett GT3071R CHRA 700177-0023 - GT30 Turbine with 71.1mm 56T GT35 Compressor . TO4S compressor Type GT30 Based BB Turbos . CHRA 700177-0010 , 56.6mm 84T Turbine , TO4S 48T 700177-0011 , 56,6mm 90T Turbine , TO4S 52T 700177-0012 , GT30 84T Turbine ....., TO4S 56T 700177-0015 , GT30 84T Turbine ....., TO4S 56T 700177-0017 , GT30 84T Turbine ....., TO4S 52T Garrett GT3040 56T CHRA 700177-0014 , GT30 84T Turbine ....., GT40 82mm 56T Compressor . Garrett GT 3082 BB ..... Not sure about this one , was once shown a 7/14 blade compressor "equivalent" of a GT3040R so could not be GT40 compressor . Turbo , CHRA , Turbine housing A/R . 714569-0001 , 700177-0018 1.06 714569-0002 , 700177-0018 0.82 714569-0003 , 700177-0018 0.63 Do not confuse this one with 714568-0001/2/3 which is the GT3540R series and uses CHRA no 706451-0005 Where there are repeats in CHRA numbers mostly its the compressor and housing A/R's/type ie GT28 or GT30 that differ and this shows as a different assembly number . Feel free to add or challenge the numbers as different lists often have conflicting numbers . Cheers A . Turbine housing breakdown to come plus specs of Garrett "GT3071R WG" and the HKS GT3240 if I can find them . Continued : HKS exhaust housings to suit the 56.6mm 84T Turbine GT2835 series T28 Flange . Integral Wastegate in .64 and .86 a/r . T3 Flange . Integral Wastegate GT Pro S style in .68 and .87 a/r . External Wastegate in .61 .73 .87 1.01 and 1.12 a/r . HKS exhaust housings to suit the 56.6mm 90T Turbine GT2835 series . T28 Flange . Integral Wastegate in .86 a/r only . HKS exhaust housing to suit 60mm GT30 turbines ie all GT3037 and GT3040 , also Garrett GT30R and GT3071R 700177-0023 CHRA . T28 Flange . External wastegate in .61 .73 .87 1.01 and 1.12 a/r . T 3 Flange . Integral Wastegate GT Pro S style in .68 and .87 a/r . T3 Flange . Garrett make ext gate versions in .63 .82 and 1.06 a/r . Cheers A .

Yep thats the one , Turbo number 714569-0002 = cartridge no 700177-0018 = GT30/TO4S 52T and being -0002 should have .82 a/r turbine housing if unaltered . -0001 = 1.06 and -0003 = .63 a/r . Cheers A . Edit : I may be wrong here , have conflicting information as to which of these two has the 7/14 blade 82mm compressor . Could be either 700177-13 or 700177-0018 though the -18 is more likely . Need to remove the compressor cover and measure the major diametre and count the blades . The smaller front or inducer diametre would be good so we can work out the approximate trim no . Cheers A .

Need the cartridge no (CHRA) . 700177-0014 is 56T GT3040R pt no . No time ATM , back tonight . Cheers A .

Hi Fantasy , when I get a little more time will bash it out here for all to see . What do your customers think of the GT28RS ? 180BFJ20DET , yep I believe close to 330 can be done with these . One thing I should have mentioned last time is that the ATP housing is .63 a/r as in GT30 turbine .63 a/r . The physical size and gas flow capacity of a turbine housing will vary with the family of wheel the housing was designed for . The ATP .63 can pass more gas than the Garrett GT28 .86 a/r so turbine inlet pressure will be less so less pumping losses and overlap reversion / inlet charge polution/pre heating etc etc . I think you'll find that the power curve produced by your last turbo was lacking because the thing probably didnt get up to boost revs untill fairly late in the engines rpm range . When turbo's like that get going they often make the torque but it doesnt feel responsive/torquey/progressive because you have to rev it to make it go and then its next cog time and likely to lag then come on and be a bit baulky . When you size it to work over a broad range it feels much better , more like a much larger n/a engine . I didn't make a habit of it but it was real easy to spin the wheels so torque was not a problem , it was perfectly suited to production gearbox ratios - usually larger turbos (for 2L four) that come on around 4000 are a pain to drive if you want some zip without being obvious to the constabulary . Difference between 2835 Pro S and GT2871 48T . Same series of compressor (GT35) , Pros 52T , 2871 48T = 48T . Comp cover on 2835 Pro S TO4E .50 a/r , 2871 = .60 a/r TO4B Turbine 2835 ProS 56.6mm 84 T (cropped GT30) , 2871 = 53.8mm 76T NS111 Housing 2835 Pro S integral gate .68 a/r GT30 turbine based profiled for cropped turbine in 56.6 84T . Housing GT2871R all trims . GT28 NS111 profile in .64 or .86 a/r . Cheers A .

I did , basically 60 trim 7/14 blade TO4S compressor in .70 a/r TO4S cover . Turbine is TO4 76 trim (TO4 P trim) in either .84 or 1.00 a/r twin entry T4 flanged turbine housing . The compressor looks to have been faced on the inducer blades sort of like the TO4R/Z compressor . So basically TO4 60-1 with P trim . Just for the record Garrett is doing what they call T3/T4R BB upgrade cartridges one of which is a TO4 60-1 and P trim combination . Easy upgrade to ball bearings if its what you want . I guess you could look at it as a 600Hp TO4Z with a slightly outdated comp wheel design . Cheers A .

Hi Fantasy , my listings show three different complete unit numbers (HKS GT3040) so there's bound to be some variations . 700382-0014 , -0016 and -0023 . They all show the same 700177-0009 cartridge . If I had to guess I'd say the optional turbine housing a/r is at the large end of the scale and the .70 comp cover upsized to suit . If you can let me know the ID tag numbers and turbine housing a/r it would help make my list a little more complete . Interesting about the larger comp cover on your spec turbos , it seems logical that the higher a/r would make for a little less resistance to airflow so faster rotating group acceleration rate . Its kind of a velocity pressure rather than a static pressure thing . I've no way of knowing if your machinist or parts supplier got the tip height of the compressor right with the diffuser section channel of the housing but a bit of mucking around here can move things round a bit - can also change efficiency islands on the map . Turbines I'd like to see used in BB cartridges are the GT32 , some including Garrett , use the TA34 76T (stage 3 in Turbonetic waffle) . Both from memory are around 64-65mm . 180BFJ20DET , getting better response than the GT30/TS04 can give should not be too difficult . I once wanted 400 from an FJ20 without knowing what 400 feels like , it seemed like a nice big number . What I should have looked for and eventually did find was a torque curve that started reasonably early say 2600+ but had very good low boost power at low revs and pulled like a locomotive from 3000+ . This felt responsive , torquey and fast because it could accelerate from low medium revs on an FJ20 - mine was the late higher CR intercooled FJ with way overkill intercooling by the way . It was in my old Bluebird with 16" wheels (205/50 tyres 3.9 diff) and could be driven round roundabouts in 3rd gear and pull away from 15-1600 revs . The answer was a Garrett GT28RS , they are not huge externally but use open bladed turbines in the all important .86 turbine housing . Mine was hung off a fabricated manifold made from 1.25" steam pipe which everyone said wouldn't work , they also said the turbo was too small but boy did it deliver . On a dedicated 2L street car I would choose it over anything out there at the moment and unless you're suicidal its plenty enough to give a 180B a very healty kick in the ribs in my book . Now its not for me to say what you can or can't have , will or won't do but my combination in a 1230Kg car put many smiles on my face . It embarassed many much more upmarket cars and a lot of people asked what the hell is in that . For me the result was fantastic and far more important than any number , the fact that it could respond so quickly and not become breathless never ceased to amaze me . Some Americans used one of these on an SR20DET powered Sentra SE/R (yank pulsar sedan and original Discopotato) and they found that they could largely modulate boost with the right foot and I found much the same thing . Fantasy what to your customers find with it - those that have all the right support systems and go to a bit of trouble to tune their engine properly ? 180B FJ what octane fuel do you use on a regular basis ? I think at that time I was using Shell Ultra 96 though Optimax 98 would have been coming onto the market and I try to get the highest pump fuel available . It would have been good if the 100 octane around now was available when I had that car , tis just an engine on a shopping trolley base and a heap of bits now . Cheers A .

The .50 a/r cover they mean is a .50 a/r TO4E cover . Actually I would have thought a GT30 based turbo was a little big for 330 RWHP , if you could afford it the 2835 Pro S may be better . If it were me I'd think seriously about the GT2871R 48 trim but with the .86 a/r turbine housing . In fact the GT28RS on its knees could nearly get you there . I haven't looked for a while but I think ATP was doing a special exhaust housing in .63 a/r with T3 flange to suit an integral gate GT28RS cartridge/comp cover . Have another look there as I think they got about 326 front wheel Hp out of an Audi of some sort . That housing is a custom one and looks like Garrett/Ford style T3 but GT30 passage and nozzle . I remember one fellow in the US that was drag racing A street driven Civic with this type turbo set up who really liked it . I could contact him and ask him what he got at the treads if you wish . Just for the record is the 330 RWHP number set for any reason ? Cheers A .

Hi Roy , some years ago Craig Allen from Allen Engineering in Mallala said they were using multiple coolant temp probes along the head of an RB30ET . This was done because when souped up the head was suffering localised overheating I think down the back and some plumbing alterations were used to get more even water flow and temperature along the length of its head . Most engines probably use water temp probes at the front or where the water outlet to the radiator is . Doing it this way should be ok but when power output is pumped up its difficult to know whats going on at the other end of the heads water jacket . Craig said something along the lines of 86deg at the front of the VLT head and 110 down the back . I think major dramas occur when there's localised boiling and steam pockets form in the jacket , where there's no water there's no cooling so localised thermal overload can cook/warp/crack the casting . I have seen examples of heads that have small water lines tapped into high points in the jacket to give any bubbles an escape path usually to a header tank which is the highest point in the cooling system . Any way I suppose another water temp probe down the back of your engines cylinder head would tell you if the coolant temp was even along its length . An exhaust temp probe between the head and turbo would be handy because if the temp got out of hand something may fail before the water temp gauge could tell you particularly if your racing and need all attention on driving the thing . The rally people tend to use a bright dash light and loud buzzer to warn them of imminent doom ie for oil pressure/water temp or whatever they choose to hook up . I think there is available head temperature probes for air cooled engines such as Dak Daks (VW's!) but I'm not sure if it would tell you anything useful on a water cooled engine . Either Allen Engineering or Nizpro have used a temp probe under spark plug type washer but not sure if its purpose was head or exhaust gas temperature . Gary is there any specific issues with the RB twin cam heads and water cooling ? Cheers A .

To round off ... Option 1) TO4S compressors have more blades because they were designed to move lots of air with limited wheel speed . To do this properly you need big turbines such as TO4's (74.2mm large and heavy) with lots of "sail area" to convert gas velocity energy into shaft power which drives the compressor . T3/TB31/TA34/GT28 and GT30 turbines do not have enough vane diametre/area to drive TO4S compressors properly . When combined they form a laggy combination because the compressor has greater shaft power demands than the turbine can provide . Option 2) Best mentioned but the 76mm 56T comp is still slightly overtaxing what the turbine can develop . Option 3) 56T GT40 comp (82mm) is far too big for the GT30 turbine , will again be laggy because the power demanded by the compressor is too great . The GT3540R is a better match , maybe laggy on an FJ20ET but thats because its a bit too much compressor AND turbine for most applications . This alone tells us that the GT40 56T comp was too big and that fitting a smaller less capable 60mm GT30 turbine was pretty pointless . Sounds more like a sales team spec decision than an engineers . There are a lot of these things waiting in warehouses for new victims . In a crude sort of way you could say a mis matched turbo is a bit like a mis matched overly tall diff ratio - a real sloth till the speed gets up a bit . Only with turbos the exhaust restriction comes on earlier and kills the fun or your engine . Cheers A .

Depending what you put it on yes , its a cheaper alternative to the HKS/Garrett turbo and more a reduction in wheel diametre with larger trim size ie 71.1mm 56T . It seems to take a bit of fiddling to get it right and is fickle with turbine housings . That compressor wheel in 56T may work better in a TO4B cover than the TO4E like 3071R's usually have . Given a choice the 52T wheel would have worked better again . HKS turbine housings seem to do it a bit better than Garretts because of better nozzle section and volute passage shape . I think a lot of the problems with GT30 based turbos is because of the style and trim of the GT30 turbine ie 60mm 84T . It was designed to be light and have high specific flow for Diesels which usually work over a narrower rpm range than petrol engines . Its a bit of a juggle to get it to work over the wider engine speed range and balance it against compressor speed and airflow to get a reasonable boost threshold and power range . I think the trim is a bit big which tends to make it too free flowing at lower gas flow rates . Personal theory but it dosen't work well over a wide range of exhaust gas flow . There is another 60mm Garrett turbine which I believe is used for Champ Car turbos that is the 60mm version of the 54mm NS111 that the higher performing GT28's use . I tried to get a production engineer from Garrett California interested in using this turbine in a GT BB cartridge but he said it would flow less than the GT30 , my point was it may have worked better over a wider variation in exhaust gas speed , but I'm not there doing his job . That GT3037 52T is a known but expensive to buy and then have to fiddle expensive turbine housings . I'm a bit surprised HKS didn't offer it in Pro S form for RB25's . I suppose they though the cropped GT30 turbine and the 52T 71.1mm compressor in the 2835 was a better compromise - could well be a case of expensive but best result and virtually impossible to copy on the cheap . Cheers A .

Hmm , roticeries (sp?) are a different thing to piston motors . I get the feeling that to make them scavenge properly they must have little or no backpressure hence the huge turbine housings . Everyone in the US that works with GT turbines will tell you that they have enormous flow potential for their size . In the past Garrett have not tended to use large family GT turbines with medium sized compressors probably because most of what they make is aimed at four stroke Diesel engines . I agree that the old TO4's are versatile but thats only because big turbines can easily have smaller family compressors fitted to form a hybrid that's very much exhaust side biased . I can't agree about the 1.5 times boost pressure in the turbine housing (turbine inlet pressure) being the roads to good power . Any measurable TIP is working against the engine so not a desirable thing , a case of least is best . In fact the ultimate is higher inlet manifold pressure than exhaust manifold pressure , I think the Americans call this "in crossover" . By the name GT3566 I assume you mean GT 35 turbine with Turbonetics T66 compressor . If so I'm not surprised - 68mm 84T (GT35 turbine) driving 92mm 52T (T66 comp) , not a real smart match . Guess only but GT40 turbine (72mm 76T) driving a TO4R (84mm 63T) should have worked better . Can get this one from the US in BB form ie GT4067R . If you search turbobygarrett site and some others in the US ie Full Race/Precision/ITS you will see that all the GT turbines offered in BB turbos and a few more are available in bush bearing shaft form . 180bFJ20det - the one you chose (2) is the pick of the three but arguably not the best depending on how much airflow you wanted , the 52T 6/12 blade GT compressor is said to spool ~ 500 rpm earlier than the 56T version so if it had enough flow potential its the better thing . For the record its called HKS GT3037 52T or cartridge no 700177-6 , fancy name for a GT30R with 76mm 52T BCI-18 compressor . Gotta run , cheers A .

Actually the early 82 MR30's used a better version of the L24 , the head had the normal L series exhaust ports rather than the late round type with the cast in "afterburners" . Later cars had the "L24E" skinny con rods and small crank pin cranks . They also used pistons with smaller diametre gudgeon pins which is not a strength thing . Early MR30 L24's had a different type of idle speed bypass on the throttle body but electrics I don't know . Cheers A .

I though SR20's used cast in iron liners . Cosworth alloy block 2L BDG's used it .

JVC the GT42/GT42R use either 94mm 56T (70.3mm inducer) compressor , max flow ~84lbs at ~ 22lbs boost 102mm 53T compressor , max flow ~ 95lbs at ~ 33lbs boost . Compressor type for both is BCI-18 or GT series . Turbine for both is 82mm 84T UHP or GT series . The once Garrett T66 , rights were sold to Turbonetics , is 91mm 52T (65.5mm inducer) with max flow ~70lbs at ~ 25lbs boost . I think these normally use TO4P trim (74mm 76T) turbines . Garretts answer to the T66 was I think the TO4R compressor which is 84mm 63T and good for ~ 75lbs flow at ~ 26lbs boost . The TO4R is said to be better spooling (lower boost threshold) than any of the above and judging by its major diametre and trim size it seems logical . The fact that its compact enough to fit in a TO4S compressor cover is a bonus . It is used in HKS's (rebadged Garrett) TO4R and TO4Z with TO4 P trim turbines and in bush bearing form just about any turbine practical ie T350 (75.5mm 70 or 76T) , TO4 O (74mm 69T) , TO4 P , TO4 GTQ (79mm 70T) , TO4 GTS (81.3mm 85T) and probably 82mm UHP turbine from the GT42 . The Americans really like this TO4R compressor up to about 750-780 Hp as its efficient at low and high pressure ratios and not prone to surge . If you go searching for it they sometimes call it the GT67 wheel - they like to call compressors by their inducer diametre (66.7 = 67) for some strange reason . There are some ball bearing alternatives to the TO4Z using it ie GT3567R and GT4067R which obviously use GT35 or GT40 BB UHP turbines in their native turbine housings . Cheers A .

Made from 60T steel whatever that is and fitted to any serious Datsun rally car . When you increase positive caster both wheels assume a camber in the correct direction . Outside wheel goes negative and inside goes positive which is what you want . What happens when the wallys use heaps of static negative camber and little positive caster is the inside wheel (relative to the corner) stays partially negative , so only about 1/3 of the available tread width is on the deck and not using its full grip potential . This shows up as unevenly worn tyres on the inside because when the outside tyres grip threshold is reached the inside tyre is dragged across the tarmack in understeer mode . I use 1/2 deg negative camber and ~ 6 deg positive caster , I have 205/55/16 front tyres on my DR30 and 225/50/16 rear tyres and the front easily outgrips the rear . The limit of positive caster is how heavy you can stand the steering being . At 6 mine is reasonable with pwr steer but not so hot for armstrong power steer ! Most modern cars use lots of positive caster which is why they have neutral or even positive static camber and they don't understeer off the road like the old dinosaurs did with positive camber . Easy fix this because you don't need the dramas of adjustable spherical bearing strut tops just the adjustable caster rods and a wheel alignment . Turn in is brilliant for an early 80's car . Also have the toe set to 0 ie no in or out . Noltec or nolathane caster rod bushes are good as well . Cheers A .

Need more positive castor not statric negative camber , that way you get the negative camber only when you need it ie when you turn the wheel . Much cheaper , much more effective . Ask Stu Wilkins to get some real ones made from the right grade steel , substitutes have been known to break and when they do its curtains in no uncertain terms . BMW started this caster trend with E30's which were the M3's raced out here many years ago - it works .

Many people seem to have issues with diff and gearbox ratios with RB30DET's in light R32 GTST's . My personal hate with Nissan production gearbox ratios is the big 1-2 gap , they must have figured the RB20/25 DET's had little torque off idle and used a short 1st to get the ball rolling . I have never been in a VLT so I'm curious to know what they felt like given a little stick off the line but nothing too harsh . When I crunched the numbers the ratio difference (VLT) is shorter 1-2 but a little wider 3-4-5 than the typical RB20 and RB25 turbo boxes . Most manual production boxes cop the worst hiding when snaching 2nd as the speed is low , flywheel affect retards engine deceleration and if the wheels were spinning they virtually stop when you leap on the clutch . All these things gang up on the 2nd coupling sleeve and baulk ring and they wont stand up to it for long . I'm wondering what people think of emulating the VLT's ratios ie its box with a similar maybe slightly shorter ratio diff to make up for the larger diametre wheels on a typical Skyline ie 16s . The reason why I asked about VLT's is that the overall ratios soon get reasonably tall you when get to the 3-4-5 end of the box . Most say that RB30's are pretty torquey but would they pull these ratios easily in a road driven R32 at 1250-1300 Kg . I have zero interest in race / drag / drift or spinning the wheels to impress the schoolies so there wont be any gorilla gearchanges at the redline for me . The last thing I want is a torquey engine and short ratios so what do you all think ? Only mechanical problems I can think of is speedo drive gears in the 3.5 to 3.6 range and what ratios exist ie whats the next step down from the S15's short nose 3.59 R200 ? Cheers A . Edit : Actually the OD looks pretty tall , whats a VLT like on the expressway in 5th ? By my calcs 3.7-3.8 diff ratio looks like reasonable compromise , any lower and 1st looks too short . Smaller Nissan boxes had variations in OD gear pairs and also the input and front lay gear pair . Is the situation the same with these larger 25T/VLT boxes ? Cheers A .

Food for thought but depending on the intermediate gear ratio spread maybe ~3.7 for wide ratio (GTST/GTS25T ~ 3.32 1st) or 3.9 for closer ratio taller 1st set . Anyone know the ratios for aftermarket gearsets - 2.9 1st and rest std works well in the Aust spec 260Z , I really hate the 1-2 spread in most Nissan boxes ie around 3.2-1.9 . I think the VLT Comode used a wide ratio version of the GTS25T box ie 3.6 1st but with tall 3.45 diff gears .

Actually there are a lots more of them though many are in the large or dinosaur categories . 2530R , TO4Z , I believe the GCG Hi Flow is ~ 65x69 so about 6.1% . The TO4B's had 74.2mm turbines with 70 mm comp wheels so turbine diametre was larger , large enough to drive 76mm compressors like TO4E's and the small shaft TO4S's eg 60-1 . The Americans (some) learnt that this 15% ratio works well with bush bearing turbos - lots of good and bad combinations can be bolted together so they had lots to experiment with cheaply . There is a bit of a leg up with the compressor/turbine diametre ratio thats not the best way but a workable solution . In some cases you may not be able to get a compressor to flow as much as you'd like for its basic size (major or OD) ie its not a family of wheels that is available in big trim numbers . You can go to the next size up ie 60.1mm to 71.1mm family and start with the lower trim sizes . A good example is the GT28RS at 60.1mm 62 trim . Had there been a 65 trim version of the wheel with good efficiency it could be a better thing spool wise that a small ie 48 trim 71.1 mm wheel . However no such 65T 60.1mm compressor is available so 48T 71.1mm is the next step ie GT2871 48T . So this is the grey area where the 15% rule may be bent a little . On paper the 2871's don't look famous but the small trim ones spool far better than the large trim one . As I keep saying HKS are not stupid - their 2871 (GT-RS) uses a 52T compressor so has fair response . My choise would have been the 48T comp which would have come on a little sooner (and have a bit less turbine inlet pressure) , but then HKS may have been chasing a certain power figure and have been prepared to wear the compromises . GT3040R - another classic example , 60mm turbine driving an 82mm compressor so nearly 36.5% difference . They both use 82mm GT 40 compressors , 50 Trim for HKS and 56Trim for the Garrett marketed versions . HKS knows the 50T wheel is a far better match for the GT30 turbine than the 56T so that is what they get made up . Sadly the sweetheart deal between HKS and Garrett means Garrett won't sell it to you at their prices . For the number crunchers the 50T cartridge no is 700177-0009 and the 56T one is 700177-0014 . I could not recommend anyone buy the 56T GT3040R or 56T GT2871R . They will be laggy and have more turbine inlet pressure (backpressure) than is necessary . Note the HKS uses a .60 a/r comp cover and the Garrett a .70 one . That GT2876R or GT2540R is an evil device and note what Garrett say on their site about this thing . The HKS version was equally hideous but had a later TO4E compressor with a smaller trim I think 46 vs Garretts 48T TO4S water pump wheel . I've dug up some compressor maps of the 71.1mm GT35 wheels mainly because I have the 48 and 56T maps . They run out of flow at ~ 18.5 psi (1.25Bar) and ~ 39 and 45 lbs/min so about 6 lbs flow the difference . That extra 6lbs at 18.5psi is more load on the turbine and if you didn't need the extra 6 lbs flow you've thrown away that energy for no gain , energy paid for at the bowser , energy to spool the 48T sooner and have less exhaust restriction . If you look around the mid frame size Garrett GT BB's you'd see the turbines are generally 84T and the compressors 56T , it starts to change with the GT40R's and TO4R/Z's , the turbine trims fall a bit and the compressor trims climb ie 76 and 63 for the TO4R/Z same approx trim and ratio as the 2530 . I think the future trend will be along these lines maybe with slightly larger a/r turbine housings . So yes I believe the 15% rule is valid but the compressor wheel type and trim is equally important . Don't fall into the trap of thinking small a/r turbine housings are the answer to laggy big trim big diametre compressors - its the compressor thats the problem not the turbine or housing , fitting a more appropriate compressor even if it means another cartridge or turbo is the real fix . Cheers A .

Silver mid 84 , clean original Volk wheels in Sydney .

I'd be laying the L24 head gasket on it just to be sure . You will find with the L4 and 6's helping the exhaust side works well . Unless you intend to use only high revs the 44mm inlets will cost you gas speed and torque . The first (early 81) MR30's got the best head and the large exhaust valves from memory - best chamber design sort of like L16 SSS 219 castings . I would use it over any L6 head . You can change valves but not chambers , welding is not cost effective .

Some people braze a coiled length of fine copper tube to a bung and screw it into the exhaust manifold ie O2 hole . The copper tube will conduct out a lot of heat , enough to clamp silicon hose to it and join it to a boost gauge . Its a fixed volume so flow and heat is usually not an issue . Cheers A .