discopotato03

Thanks Guys , its really the diffuser section I need to see rather than their glitsy port shroud hunk of Swiss Cheese . The diffuser is the bit where the funnel section transitions into the flat section which is parallel with the backplate just beyond the compressors exducer blades . The ask is because I'm cooking up a BB hybrid that I don't think has been used in Aus before and its not GT35R or T4 turbine based . Cheers A .

Hi BSK , off the top of my head 446179-20 is a HKS spec Garrett BB GT28 series cartridge . The HKS GT2510 is basically a GT2530 with the more OEM style GT28 60T turbine . The GT2510 and 2530 both use the same 63T 60mm compressor which I've not seen in Garrett marketed GT BB 28's . Garrett normally use one of two very similar (to each other) 62 trim 60mm compressors ie in the Skyline GTR upgrade GT2860R and the GT28RS (GT2860RS) . Both 2510 and 2530 were early GT BB developments and have been improved upon by the GT-SS and that GTR type 2860R with the NS111 76T turbine . And no its not the std turbocharger . Cheers A .

What I mean is the front cover (compressor cover) removed so we can see from the inside . The diffuser is the flat section that forms a funnel shape that the compressor wheel vanes are profiled to fit inside . Mitsy is also crowing about widening the diffuser section of the Evo 9's std turbocharger to help pull up the bottom end of the power curve . Cheers Adrian .

Hi all , am interested to know if anyone has a HKS TO4Z or comp cover lying around . The little doers at High Kost Spec have found ways to improve on the diffuser section of their compressor cover and I want to see what it looks like . So any pictures of the inside or wheel side of one of these covers would be real handy . Cheers Adrian .

Yes I would be interested to see them too . I have driven an MR30 with the Bluebird manual rack which was heavy though it did have shortened steering arms . If you were lucky and had the Bluebird pwr rack and matching cross member it would be nicer . Bluebird lower control arms are shorter than R30 so you may need to use them as well - unfortunatly then the caster rods no longer fit . The one I drove had its lower arms cut and shut (Bluebird inner to suit the crossmember and R30 outer to suit the caster rods and strut foot ) . The critical thing is to match the racks inner joints to the inner pivots on the cross member width wise . Otherwise it'll bump steer - badly . Cheers A .

This could have been called compressor selection . Garrett aren't going to too much trouble to show how to work out the turbine side of the turbocharger equation . Also its very easy to fall into the trap of using their formula which shows up the maximums ie engine air requirement and compressor capacity at the redline . I like to look at it as where the engines torque peak is and aim to have the compressors peak efficiency round about that point which is also supposed to line up with peak volumetric efficiency . Also note the compressor map with the port shroud map comparison on it . A lot of good aftermarket (did someone say HKS ?) turbos use them with good reason . Road car turbos with smallish turbines/housings tend to do this because the need to make them responsive often overspeeds the compressor in relation to how much air the engine can take initally . Note how the surge line is higher to the LHS in that case . Often the main difference between HKS and Garrett marketed BB turbos is the housings themselves . The HKS TO4Z is a good example . The fancy drilled and increased AR comp cover with diffuser alterations actually works . No doubt the turbine housing if tested back to back with the same AR Garrett diesel housing would work out better as well . Cheers A .

Hi all , has anyone used this turbo on anything ? Some punters from the Supra (2JZGTE) have mentioned it and one fella has one on a 3L V6 Camry in the States . It has some very interesting wheels and trim sizes and is supposed to be very responsive for its size . Just on that it looks HUGE which is a pity because its map looks real good in the 1.5 to 2 pressure ratio area . I really like its choise of 78 trim for the turbine rather than Garretts garden variety diesel biased 84 trim size . Am trying to find out if the 82mm GT40 50 trim comp can be grafted on to the GT4088R cartridge with a .70AR TO4S comp cover . If Precision in the US can put the 84mm TO4R comp on them (GT4067R) it must be possible to do an 82mm one . Another issue is the exhaust housing flange pattern . It hard to find information on these larger frame turbos as to whether the flange is twin entry (split pulse) T4 or "T4 International"/T45 . I think I need std split T4 but have to confirm that too . Cheers Adrian .

Still researching this one . Been looking at the GT40 turbine based turbos to see if I can move the exhaust flow up and the compressor flow down a little so that pressure is not too high on either side but the volume flow is high . Still waiting for some info from OS about the GT4088R on 3L 4 valve engines . Garrett appears to have played about with turbine trims and comp styles/housing AR with the BB GT40R so it may work well in a lowish boost application as it is . I would still prefer it with the 82 rather than 88mm compressor but the cost to change it may be out of the question . One thing I have learnt is that generally increasing a compressors cover AR generally widens the islands of the map , so being big is probably no great disadvantage provided the lower gas speed is not an issue . Cheers A .

Hi Stocky , this part of the Garrett catalog is the closest I could find to that GT40's turbine housing AR . Search Turbochargers GT40 Family GT4088 703457-2 . It shows the turbine as a 77mm 84 trim in a 1.34 AR housing . I am not trying to say you are wrong it just seems to line up with that pages specs . I checked out GT42/42R's and they are shown as having 82mm diametre turbines . If you can give me the turbos ID tag numbers it would confirm the wheel sizes . Its also curious that the pics of the turbo (yours) at the ATP site show a different style of turbine housing on the GT4088 . The outlet is V band and the profile of the inlets looks more like two capital "D" miror imaged around the divider rather than two 00 shaped T4 style inlets . I think I smell a rat here and want to know if ATP is passing T4 housings off as GT40 housings . As for your cars boost rise , do I remember you saying it has a 50mm wastegate ? What pressure is it set to regulate at ? Cheers Adrian .

Actually you will find that most compressor maps are graduated in pressure ratio vs the mass of the air pumped in lbs/min . The problem with measuring airflow in cfm is that it gives no clue as to the air temperature and therefore density . Because of the mores law factor the maximum choke flow is usually considered to be what the compressor can dish out and horsepower worked from ~ 10-11 Hp per pound of air . This really is a nonsensical way to rate a turbochargers power or I should say mass airflow potential . It makes the huge assumption that the turbine can get the compressor/housing combination to perform as it did on the test flow rig . All too often it can't so the result is not an accurate real world achievable one . Cheers A .

That theory makes the broad assumption that the manifold/turbo can pass enough exhaust gas while running on boost . If it cant the exhaust manifold or turbine inlet pressure can go ballistic and eat your pistons/valves/head gasket . Cheers A .

Hi again StockyMcStock , I looked into these GT40's a bit closer and the one I think you have is the GT4088 unit no 703457-2 / cartridge no 449739-34 . The specs say 88mm GT40 54 trim compressor in a .72 AR port shrouded cover and 77mm GT40 turbine in 84 trim . We should give you a round of applause for getting any boost before the red line with that turbine housing ! As the map shows 40lbs exhaust flow with that housing/turbine LOL . The later C117 compressor in the GT4088R (88mm 52T) is a bit more efficient and wider across the 1.5 PR line on its map but probably costs more than double what your turbo did . No doubt the wheel will turn up later in bush bearing turbos so may be able to be fitted if needed . Does your turbo use a T4 mounting flange or the larger T4 International which also gets called T45 flange at times . I am looking into BB GT4082 and GT3582 custom hybrids ATM , I just have to be careful not to be too greedy with exhaust flow and lose too much shaft/compressor speed . One thing that does concern me with the GT40 turbine side is the size of the exducer outlet , I'm not sure if I can shut the noise of the exhaust up with outlets that big - only really want to run 3" pipe . I also have a bad feeling that the larger GT40/42/T51R sized BB centre section is very expensive compared to the GT35R's if US pricing is anything to go by . Cheers and good luck with your project , Adrian .

Hi Stocky, what spec of GT40 do you have ? I've been looking into various bush and BB GT40's of late . All I can remember is that your using a large 1.32 ? AR turbine housing . There's a bit of variation in GT40 turbine trims ie 73 78 and 84T . Compressors can be GT37 76mm , GT40 82mm or GT4088mm - so many variations . Pics ? Thanks cheers Adrian .

I would avoid it like the plague , note the specs say TO4S compressor . There are only three off the shelf full sized GT30 turbine based turbos worth having for petrol engines in my book . They all use the same 60mm 84 trim UHP turbine so its only the compressor/housing that changes . From small to big .... 1) GT3071R - Uses GT35 71mm compressor in 56 trim . Usually has .50 AR TO4E comp cover . Uses cartridge or CHRA no 700177-23 or -5023 2) GT3037 - These are available from HKS and use the GT37 76mm compressor in 48 52 or 56 trim . The 3) GT30R 56T version you can buy through Garrett as the GT30R . You MUST specify turbo no 700382-12 if you want the same cartridge and wheels that HKS use in their GT3037 56T . To get the 52 trim GT37 compressor you would need to buy the HKS or get someone like GCG to make one up new which I think would be cheaper . The cartridge ID tag numbers to look for are 700177-0007 for 56T or 700177-0006 52T . As for exhaust housing AR numbers many see them as being small medium and large (.63 .82 1.06) . Its really to do with running the turbine /compressor rotating group at the right speed to make the desired airflow . For example HKS generally specify a smaller AR turbine housing and compressor cover for the GT3037 52T ie .73AR turbine housing and .50AR comp cover , .87 and .60 for 56T . My gut feeling is that a 1.06 exhaust housing would be a bit laggy on an RB25DET , I reckon the .82 housing on the 52 compressor trim version would be nicer to live with and better suit the std gearbox ratios . If they're still available the T3 flanged HKS .73 housing could be worth a go . Cheers A .

That was for an RB25DET . I think the 3L really needs the GT35 turbine and even its 82mm GT40 compressor in 56 trim is not ideal and could have been offered in 50 and 52T as well . Its all about getting the load down on the turbine to enhance the transients . I don't want 700Hp , I also don't want to pay the lag penalty of the big trim wheel . I may be stuck with an 84 trim turbine (still researching that one) but if I give it the best chance I reckon it will be more responsive and I couldn't care less about the 10 lbs less maximum flow that is the trade off 56 to 50T . Garrett has turbos that use the GT30R and GT35R's compressors (GT37 and GT40 series comp wheels) with many different turbine options . For example that GT37 comp wheel is used with their GT37 turbine which is 72.5mm diametre ie 76mm comp 72.5mm turbine . The GT40 comp is offered with their GT37 turbine or their GT40 (77mm) turbine . Interestingly these diesel turbos tend to use smaller trim compressors of the same family than their ball bearing cousins . I think Garrett may have had more faith in the BB/reduced friction/faster spool school of thought than possibly was ideal . HKS obviously knew and speced many of their turbos for power and response - sound familiar . The bottom line is you may be restricted in your type and trim of turbine but compressors can be changed . The right sort of replacement can reduce the turbines negative atributes . Cheers A .

I would not fit a .63 housing to a GT3540R because I can't see the sense in choking the hot side of a reasonably large turbo . If you have to go to this length to get the desired response out of it thats telling you it (the compressor anyway) was too big to start with . This really is overkill for a 450-500 Hp RB25 . A GT30R (700382-12) with a large 1.06 AR turbine housing could get you there with a LOT less lag and much less chance of compressor surge . Even this would be pretty laggy on a std street engine and more than capable of killing a bog std one . If I was going to use a bog std R33 25DET and had to have a GT30 based turbo it would be a bought GT3037 52T or a GT30R with the 56T compressor flicked for a 52T wheel . If you get it built new its no where near as expensive as the HKS . A cheaper alternative may be to use the REAL GT3071R like someone else is doing here on an RB20 . As I've been saying Garrett are soon releasing a T3 flanged .82 GT30 integral gate housing which may make an easy convienent package for an RB25 . Take note of how much a GT35 turbine doesn't flow with the .63 housing . Also look at the GT30R's turbine map . I tend to think along the lines of small compressor trim/smaller turbine housing GT30R's for RB25's and similar deal with GT35R's for for twin cam RB30's . The smaller engine can't generate the torque of the 3L at low/med revs and needs a turbo that can come on song earlier to get it going . I know its been said that large exhaust housing GT30R's can handle similar gas flows as the medium size GT35R but don't forget that with 3L under essentially the same size valves and ports the gas velocity is going to be higher so larger AR housings is the way to keep things flowing out of the larger pots . Cheers A .

I only ever used one non std FPR which was the hateful Malpassi rising rate lump . The propper fix was larger injectors/pump and the std FJ FPR . Next time around it'll be a new std or Nismo adjustable FPR but only because its new . Cheers A .

Generally its a case of heating the exhaust housing with the oxy (no not the cutting torch) and tapping it gently and evenly away from the cartridge . A small knockometre is generally easier and I would be using a copper one given a choise . Cheers A .

Only my 2c but I hate rising rate fuel pressure regulators , the pump is often on its knees and not always for any good reason . Roller cell efi pumps will trade volume for pressure and so if the pressure is not required it costs volume anyway . If injector flow is limiting then higher pressure is the only answer but its a bit of a band aid . Cheers A .

Congrats on a fine result , many would probably agree that the RB20DET is difficult to get good responsive power from particularly from under ~ 4000 rpm to over 7 . That GT3071R happens to be a very good match ie 71mm GT35 comp with 60mm GT30 turbine . In theory both the turbine and compressor run out of puff in the 450-480 Hp range (assumes 1.06 exhaust housing) . The turbine would go a little further than the comnpressor which is as it should be . I imagine you are running the .63AR Garrett T3 flanged housing on yours ? These would be an interesting turbo for RB20's with the 52 trim comp as well (56T is std) , it would be sort of similar to some versions of the HKS GT2835 but with the unmolested GT30 turbine . My orphan opinion is that this is the propper way to go rather than bigger compressor with GT28 turbine ie GT2871R 52T/GT-RS or 56T . A GT3071R would not be difficult to build from a GT2871R in any of the three trims . If a GT30 turbine was exchanged with 2871's GT28 turbine (identical GT25 centre section bearing/housing/shaft dimensions) you end up with the same thing except your choise of compressor . The same thing could be done to a GT3071R WG to fix its woes . The tune should have made the car feel much better down low than std , the extra timing these can use when un corked should make a marked difference to the low speed torque . Im wondering if it could use the next taller 4.1 final drive to take advantage of the extra torque and give the turbo a little more load to push against . Before I go the cartridge no. on that turbo should be 700177-23 , if so its a rare bird in Australia - for the moment .... Cheers Adrian .

Hi Roy , from memory the ext gate housings are 61,73,87,1.01 and 1.12 . I think the integral gate GT Pro S integral style turbine housings in T3 flange are .68 and .78 ar . I not sure if there is a direct comparison of Garretts AR measure and Trusts cm measure . I believe that with Trust housings the measure is just a base line to know if you need to go larger or smaller ie if 8cm is too laggy use a 6cm and if too restrictive use a 10cm . I never did think to ask what sort of power your talking about so what do you reckon ? This equates to airflow and desired response . The RB25 people seem to think the GT2835 Pro S runs to about 380-390 Hp . The things to avoid with 2835's are the 56T comp and Garretts bored out butchered GT28 T28 flanged turbine housings . Most of these turbos come with the .68 ar housing . Cheers A .

I tried searching but can't find pics of the GT40R (GT4088R) hot side . It is available in a T4 flanged 0.85 A/R turbine housing for its 78T 77mm GT40 turbine . The turbine map at turbobygarrett looks very interesting . Am interested to know if its split or twin entry . Cheers A .

Yes very interested . By 66mm comp wheel do you mean the Garrett/Turbonetic T66 compressor ? If so it could prove laggy ie 52 trim ~ 90mm compressor . There is alternatives with compressors for the GT35 cartridge . Thanks but not too keen on the GT3040R because the total turbine/housing flow ~ 27lbs with largest 1.06 a/r turbine housing . The tip speeds are very different between the comp 82mm and the turbine 60mm for any given rotating group rpm . I want to be able to use the GT35 turbine in a large a/r housing and get the response by reducing the load imposed by the compressor , I'm working on the theory that with little work to do the large and low restriction turbine should zip up to speed quickly . I can live with limited airflow potential (if you consider ~ 55lbs limited) and am not likely to need any more than 1 bar max . Am still not sure whether to use a large trim GT37 compressor or a small trim GT40 . I had been under the impression that the Garrett plain bearing GT4082 which uses the 50T 82mm GT40 compressor was using a .58 TO4E cover but I think its a GT40 or TO4S cover . Arguably the GT30R's GT37 compressor end can move the air but will the GT35 turbine in the big housing spin it fast enough ? Cheers A .

Since the turbines dead making the shaft useless all thats any good is the bearing housing and compressor wheel - if its aluminium . You could break up the remains of the turbine wheel and tack weld a cross piece to the flat bit so that it can be held and the compressor nut removed . Or you could very carefully grind the nut and shaft away till the compressor can be removed though the burr may be a problem . Its ages since I looked at a Hitachi with a damaged turbine . If enough of the steel section of the shaft protrudes from the bearing housing you may be able to slot it with a saw and use a large plain blade screwdriver in a vise to hold it still while you undo the nut . Two pairs of hands helps .

Actually I told a lie , this was not their car but it is on the HKS USA site . Cheers A .