discopotato03

Not really , you want the exhaust gas to go through the turbine to drive the compressor . If you want less pressure you need a larger volute passage inside the housing - less restriction=lower gas speed=lower pressure . The problem with regulationg turbine speed (with a waste gate bypass) referencing off compressor outlet pressure is that exhaust manifold pressure gets ignored . An external gate doesn't fare any better but it can be placed so that exhause gas will flow through it rather than past it - if the manifold is properly designed . Cheers A .

If someone is running a Garrett GT30 0.82 A/R IW turbine housing on their 3071R/RB25DET I'd like to hear what they think of this combination . A problem that exists in IW turbine housings is that exhaust gas at high speeds has momentum and is not real keen on changing direction and going out through a hole in the side of the main passage . It seems that there is the usual juggle here of trying to get an early boost threshold whilst not having the hot side choke when its all up and happening . A larger AR housing will mean higher gas flow capacity but the compressor speed will be a little down so you may not get that "vertical" boost pressure rise - if thats what you are looking for . I reckon the thought that goes into turbos which favour the hot side (like GT2860RS's and these real GT3071R's) is low exhaust restriction , it sort of fits in with the not so much high boost but high air flow rates at modest boost pressure and low (lower than usual) exhaust manifold pressure . It probably means the engine needs to be set up to make reasonable low end torque ie good head/mild cams/bit higher CR/bit more advance . Having the larger rear housing in these circumstances should be less of a problem if the engine can stand on its own two feet in a pre supercharged state . Basically same circumstances as say a GCG RB25 Hi Flow with the RB25 or VG30 turbine housing , its what the factory wanted from the later R34 spec RB25DET . They just went about it with better cams and more effective variable cam control . Cheers A .

From what I hear about these real IW GT3071Rs they sound like they are if anying too responsive in the Garrett GT30 0.63 A/R turbine housing . Has anyone here used one with the next size up (0.82 A/R) IW turbine housing ? With IW turbine housings the exhaust can only go out past the turbine or turbine and waste gates vent path . If the wastegate cannot bypass enough of the overall exhaust gas volume then you cant't control the speed of the turbine or boost pressure . The waste gate valve can only get so big and after that the only way to get more gas though the housing is to use one with a larger internal passage - larger A/R . The closest Garrett turbo I know of (concept wise) is the smaller GT2860RS and it uses reasonably big housings for a GT28BB turbo . It has a 0.86 A/R turbine housing (largest in GT28 range) and its compressor housing is a 0.60 A/R T04B one - usually found on turbos with 70-71mm comp wheels rather than 60mm ones . The 3071R already has the upsized T04E comp housing (usually used with 76mm comps 3071R's is ~ 71mm) . I can't say for certain how much response you'd lose with a 0.82 A/R GT30 housing compared to the 0.63 version on a GT3071R but I can say that you'd get more gass through the turbine before the gate opened with the 82 size - if the exhaust system could support it . Until its tried we won't know for sure , cheers A .

Just for the record what is the difference between R33 and R34 RB25 turbo thermostats ? Cheers A .

Camshaft time for my late 96 R33 GTS25T so I need to explore options . I suppose for simplicities sake most would just grab a pair of Tomei pon Cams because they drop in and work . Now because I read posts about people using Tighe cam profiles I spent a bit of time and bashed out a few E mails to see just what they have . I got one reply from them saying that they are able to use Ford Sierra profiles on RB hydraulic type camshafts - lobes must be similar between YBB/BDA and RB hydraulic camshafts . So from their site the first 3 Sierra profiles (708C/805C/845C) are like this . 708C 13 59-62 10 , 252/252 , 215 at 50 , 0.345" (8.763) lift . 805C 14 60-63 11 , 254/254 , 220 at 50 , 0.355" (9.017) lift . 845C 14 60-63 11 , 254/254 , 224 at 50 , 0.402" (10.21) lift . From what I hear std camshafts (RB25 or RB26) need to be built up so that the lobes base circles say approximately the same to not screw up hydraulic buckets oil feed supply . STD RB26 cams must have greater lift so less to build up . For road I like the idea of shortish duration and as much lift as mechanically possible because I think thats the way to make torque without turning high engine revs . The shortish duration is supposed to keep up the cylinders trapping efficiency up and any extra lift gets the largest flow restriction (valve heads) further out of the ports . Extra lift while being good has limitations like the valves need to have a minimum distance clear of the piston crowns in the overlap phase (all valves open and piston moving over top dead center) . Also the buckets need to follow the lobes meaning the springs have to be up to the task . As the fella doing my head said "If the springs dom't close the valves the pistons sure will" ... Bent valves don't seal so big compression loss and exy repairs . The 64 dollar question is do you stuff around with local cams or just go with the tried and apparently proven Tomei drop in ones ? At this point cost rears its ugly head and if there is a significant difference either way the cheaper one will probably get the nod . I would really like to see what the R33 RB25 Pon Cams numbers look like but really its the result thats most important . So unless Tighe can offer me something worthwhile at a competitive price the answer is right there . Garys laughing at me again I can feel it , A .

Starting cams thread A .

So whats the going price for new Poncams ? Sorry OT , cheers A .

Is this to weld (build up/harden/grind) 25 cams ? What Tighe grind ? Cheers A .

Have you tried screwing some extra low and part load ignition advance into your RB20's PFC ? The std Hitachi RB20 turbine housing and turbine are much more restrictive than the HKS turbine housing and Garrett turbine wheel . I'd be looking into this first , cheers A .

I got an E-mail back from Tighe cams about what is suitable for RB25DET's , they said look under Ford Sierra because the lobe disign must be similar to the Ford ones . I was wrong about the 805's valve timing , it's bugger all longer than the 708 . It must have more agressive ramps to have the bit longer duration at 50 though lift and a little more total lift . The REAL interesting grind is the Ford Sierra one below the 805 one - very similar but ~ 10.2mm lift on from memory 254 deg duration . Very interesting , cheers A .

Someone else would need to chime in about std springs but I think the things to look out for are spring coil bind and not being too over the top rate wise . IMO the valve overlap period has a lot to do with trapping efficiency particularly at pedestrian engine revs . When you build an engine the CR figure given is the measured or "static" compression ratio , it assumes no inlet restriction (at all) so 100% volumetric efficiency . It doesn't work like this in the real world where you do have restrictions and the throttle/s are usually the greatest restriction - its how we control the engines speed/load - by strangling it . Anything that limits the cylinder filling itself on the inlet stroke governs how much air we have to compress on the compression stroke . What you get is a "dynamic" or effective compression ratio and the greater the inlet restriction (throttle/s etc) the greater the difference will be in static and dynamic compression ratios . At idle the throttle/s are making a huge restriction so less air reaches the cylinders so with less to compress the effective or dynamic CR will be quite low . Multi throttle inlet systems are a huge bonus because when fully open they allow whatever pressure ahead of them to reach the inlet ports/valves so the dynamic CR shoots up faster than a single throttle would allow . Cams with longer overlap periods tend to give that "lope" or what I call brittle idle and it's much more pronounced on a single throttle plenum type inlet manifold . The reason being that all inlet ports/cylinder can communicate with a single plenum manifold so pressure fluctuations do weird things to adjacent cylinders . To my way of thinking what the individual (per cylinder) throttles do is mostly block the pressure reversion waves in the cylinders (caused by earlier opening inlet vales) from spitting back into the manifolds plenum and doing weird things to the plenums air conditions . So in other words the long overlap cams designed to breathe and scavange at higher revs can have the chaff cutter effect reduced by using individual throttle type manifolds . If you have to use a single throttle manifold the engines low down manners are not going to be good with wide overlap cam profiles , as SK said the cam (valve timing) should be set to suit the engines desired usable rev range so if you don't need telephone number revs you don't need wide overlap cams . Nissan was obviously looking for more serious power from homologation engines like the RB26 and GTiR spec SR20 , both hade individual throttle per cylinder inlet systems and no doubt warmer cam profiles than the more mundane (single throttle plenum) RB and SR spec engines . This not doubt had a win win with performance and emissions in mind for road registered cars . I've always wondered about RB26 cams in RB20's/RB25's and hydraulic buckets aside its quite possible that more overlap in a single throttle engine caused them to lose out low down . My opinions only , cheers A .

And another more recent document called "Assessment of the Operation of Vehicles in the Australian Fleet on Ethanol Blend Fuels" . http://www.gov.au/atmosphere/fuelquality/p...uels-report-pdf The original link was to a doc dated 2004-5 (I think) so this one should be more up to date - I haven't read this one yet but the first is very informative I reckon . Cheers from the "Apple Juice Burner" - or so one here called me , A .

Hi all , no time to read this PDF Doc on Ethanol fuel blend Standards ATM but looks interesting . Sk possibly interested . http://www.environment.gov.au/atmosphere/f...ifqc-report.pdf Maybe good read , cheers A .

No edit function so this is best I could do . I guess another thing is how cam duration relates to compression ratio , I have to wonder if something like 9.3-9.5:1 and a good inlet manifold/multi throttle system would allow the use of the warmer cams in an RB25DET . It would have to have low restriction on the exhaust side to achieve anything worthwhile . Also I might contact Tighe to see if they are interested in doing a hybrid of the 805's ramps on the 708's centers and timing numbers , may be a bit noisy though and need good springs . While I'm here to what extent was your 32 25 head ported and does it use std sized valves ? Cheers A .

Sorry Cubes my mistake , on the left sheet its 14 not 4 BTDC on the inlet cam . Just not a great printout . Will edit my previous post . Back in a sec .

Ok so if I read the data correctly and the cams are timed correctly the valve timing/duration/lift/LCA should read : 708 = 4-61 63-11 In Dur 244.61/In lift 8.515 on 112 ATDC LCA , Ex Dur 254.23/Ex lift 8.510 on 117 BTDC LCA . 805 = 21-65 65-19 In Dur 265.38/In lift 8.913 on 110 ATDC LCA , Ex Dur 263.73/Ex lift 8.902 on 115 BTDC LCA . This probably begs another thread but it does still relate to the 30 series turbos and the difference with 20% extra capacity ie RB30 bottom end . Cubes I'd expect the extra capacity to tone everything down (maybe 20% ?) given the 20% increase in capacity but without 20% more port and valve area . So you could use the extra valve timing (duration) to fill the larger cylinders . I had to go back and check the 708 inlet cams opening time before top dead center (BTDC) because it looked very short . I'm guessing they made the inlet cam a shorter ~ 245 deg duration because customers may put those cams on engines with factory turbos and cop a fair bit of restriction and reversion . I suppose one way to have reasonable trapping efficiency and not too much charge pollution (from high exhaust manifold pressure) is to keep the inlet short and advance it up to keep the overlap short - 15 degrees . The situation would change with a larger turbine and housing (eg 3071R) , lower exhaust mani pressure I reckon would mean the engine could scavange a bit more effectively and possibly get away with the inlet valves opening earlier and the valve open period or duration a little longer . The thing I know nothing about ATM is how much an R33 RB25's VCT changes the inlet cams phasing . To the Mods , if this is getting too OT should I start a cam thread and maybe transsfer this post there ? Cheers A .

Hi Cubes , I asked in another thread about your cams but you may come here first . From memory you used an R32 RB25DE hydraulic head so are the LCA's native to that engines cams or all RB25 cams ie 33 25DET cams ? Very interested in these grinds - if they'll work in a 33 25DET engine . Cheers A .

One for Cubes or Simonr32 , these Tigh cams you've got - can I have some details about them as I couldn't see them under Nissan in that link . From what I can see they must have reasonably aggressive ramps to have the duration at 50 thou lift mentioned . I have to look into 33 25DET cams in the next few months and the price is looking good compared to Poncams . Cheers A .

Both housings should fit though the compressor one will be to suit the inducer diameter and exducer tip height of the 2530's compressor wheel . Did your site have pics of the compressor housing from the front ? Modifying the 2860RS's comp cover is not too difficult , single turbo (RB20/25) spec 2530's used basically the same housing with some inlet boss mods . Need pic to show how , cheers A .

One of the members here was showing me an S 1.5's lower section yesterday and I didn't notice any difference in the "heights" of the runners . That lower section had a casting line a little beyond where the std fuel rail mounts were and I was wondering if that was the point to think about cutting one . I need to find cheaply a std 33 25DET lower inlet manifold section to mock up . Do the members here think there is enough interest to consider a small production run of such a component if it can be made to work . I don't want to make any money out of this but if someone set up jigs to reproduce them it would be a bit more cost effective down the track . I like this idea because it allows people with 33 25DET's to reuse more of what they already have and the finished result should look like the factory would have had it . It's never going to be the same as a complete RB26 top end , all I really want is the throttle response and for it to look factory . I can live with the hydraulic valve train and VVT , poncams would be enough . Cheers A .

The single Z32 BB turbo should have the same ceramic turbine as the RB20 and RB25 factory turbos . Cheers A .

Well the theory being that both the "GT2530" and GT2860RS are both GT2860R cartridges they should interchange in any turbine housing intended for the generic GT25BB style center section - provided they are profile machined for the same turbine family/trim . I can almost see the confused looks over this GT25/GT28 terminology but there is an answer . HKS got into the BB scene early and at that stage all the small turbine turbos were called GT25xx . Going back a few years Garrett changed their turbo description system in an attemp to avoid confusion but the new system is not perfect and there is also the old and new systems to wade through . At this stage most people consider the 54mm turbine size to be GT25 and the 60.1mm one to be GT28 . The actual centre section meaning bearing housing and bearing pack is said to be the generic "GT25 BB" sized center section and covers most of the ball bearing turbo range from smallest (GT2554R) up to largest (GT3582R) , basically the guts excepting the wheels/compressor backplate/both housings is the same . I did once read that there was a very slight difference on the depth of the step or register where early GT3037's located in their exhaust housings but it's the only example I can think of that any variation ever existed . The fix was a very simple lathe operation so not a biggie . I read it years ago on some US board . OT again , the 60.1mm compressors is the "60" part of GT2860R or RS , the "30" part of GT2530 I understand means 60.1mm GT30 series compressor (don't confuse with the GT30 turbine family) . Old speak - GT2530 means "GT25" 53.85mm NS111 turbine in 76T + GT30 compressor in 63T . New speak - GT2860R means "GT28" 53.85mm NS111 turbine in 76T + 60.1mm comp in 60/62/63T . So a GT2860RS cartridge should go straight into a 2530's turbine housing , from memory 2530's (except the KAi) version used the same type of comp housing (T04B 0.60 A/R) as a GT2860RS if intended for an RB engine app . The snout was machined off and a 4 bolt flanged adapter tube was fitted to the front to get its barb size down to the same as an RB20/25 turbo so std inlet plumbing fitted . Capable turbo mobs or a machinist could sort this one out for you , cheers A . If you don't go with the shagged 2530 let me know , I could use some bits off it if the price is realistic . Cheers .

It was suggested to me this afternoon that the most practical way to get the six throttles on an Rb25DET head would be to cut the RB25 manifolds lower section just beyond the injector/rail mounts , then weld on a flat plate ported drilled and tapped for the RB26's 3 twin throttle sections and plenum chamber . The plusses would be retaining the Rb25's water outlet + log or bridge and the std fuel rail/injectors/injector loom . The IAC and TPS wiring would have to be altered to suit their different locations . Ah and the native VVT . Can someone confirm if R33 GTR IAC and TPS units are electrically same as R33 GTS25T - S2 ? Where it's going to be different for each individual is the budget and where they want to end up engine wise . I like the idea of one MAF AFM , one turbo and basically native electricals so the plate and bolt idea is probably about as straightforward as its going to get . Like most people my pockets are not bottomless and I don't want to be building an expensive pretend R33 GTR . So (this week) the plan is to look at modifying the R33 25DET head and investigating modifying the 25DETs lower manifold section . Cheers A .

Righto , it seems that RB26 heads and inlet manifold systems are the best available from the factory so assuming R33 GTST owners like myself can get them what would be involved in applying them to the single turbo R33 and its RB25DET . Actually I'll go one further and say that most would have either a PFC or some other tunable computer to start with . The problems I can forsee are : 1) Dfferent coolant/oil passages at the front of the block/head . 2) different sized stud holes (larger) in RB26 heads . 3) Fitting issues ie will the 26 IAC stuff fitt in with the 25DET water/oil cooler . 4) If required fitting the RB25DETs single turbo exhaust manifold . 5) Wiring loom mods to connect sensors in places foreign to an R33 GTST . 6) Sensor compatibility . 7) Injectors - all high/low impedance and top feed rather than side feed issues . 8) Water plumbing issues ? Anyone done this conversion or nutted out the fixes , cheers A .

Thank you everyone for your input to a hopefully ongoing thread . Arguably what we seem to have learned is : 1) Yes the RB26 six throttle inlet manifold/plenum can be adapted to an RB25DET Cylinder head . 2) With spacer/adapter plates fitted the RB26 mount injectors won't spray in the right direction (too low ?) . 3) Even with the injector mounts corrected (milled) you miss out many RB26 head features . 4) R33/34 VCT can create problems . 5) RB26 heads have different exhaust manifold stud pattern . Next thread will be fitting RB26 head to RB25 VCT type block/in R33/with R33 electricals . Cheers A .