discopotato03

Exhaust finally fitted today and looks good from underneath . Consists of 3.5 dump to 3.5" 200 cell XForce metal cat which tapers to 3" for the cup joint and the rest of the system . They used the largest longest straight through mufflers that physically fitted - the rear one is 20" long . The outlet is a straight section of polished 3" stainless tube . I asked for quiet and that's what I got , if anything it's a little too quiet and I didn't previously think that was possible with straight through 3" mufflers . If you can remember what a factory std VL NA sounded like it's a little louder than that . The old exhaust is a HKS one and available if anyone wants a cheapy . The ceramic cat is in good nick internally with its matrix very clean at the temp sensor end . I'm interested to see if mixtures and consumption changes much , also turbo transients . A .

Yes and that hose is a bastard to get to in situ . It went on my 33 and in the end I had to remove the idle air control valve to get at it . Nissan did it the right way on RB26s and piped it up to the front of the head on the turbo side and returned it into the top water outlet . Works well because any steam bubbles go out to the top rad tank and out past the cap into the overflow bottle . A .

Yep , many petrol heads will have the recirc valve and boost solenoid covered so extra bulk and clutter is often not needed . If omissions like this make EFR turbos cheaper lighter and easier to package it's a no brainer . I would prefer to see BW do this but if not the aftermarket may be able to cater for it if BW is prepared to sell their cartridges separately . From memory EFR 7163 does not use port shrouded comp housings so simple all round you'd think . Geoff , plain Jane B1 comp housing available - in aluminium ?

Tao that's looking similar in size to Garretts GTX3067R comp wheel and housing wise . Does anyone have graphs of the baby GT30 on an SR20 ? I really want to see someone use a copy of a TR30R turbine , NS111 60mm 76T 9 blade , since the pricks at Garrett won't use it in production turbochargers . A .

GT2554R to GT3582R from Garrett anyway are based on the GT25BB sized centre section . T4R is the larger centre section inc P/60-1 T04Z GT37Rs GT40Rs T51Rs etc . Imagine water cooled T25 and T3/T04B centres converted to BB . I've also heard about GT3582Rs bending turbine shafts and lunching their compressors , from memory the section of the turbine shaft that the compressor fits over is slightly larger on a GT35R possibly to make it stiffer . I also wondered how they were getting GT37 turbines into GT25BB centre sections and making them live . A .

What compressor housings do the Indy cars use ?

Evo 4 was the first one with the engine turned around and a reverse rotation twin scroll turbine housing , they used the smallest or 9 cm housing . 5 had from memory an optional 10.5 for the RS can't remember other variants . AFAIK 6s all used the 10.5cm housing even the TMEs with the smaller 15GK compressor wheel . The larger and heavier Cedia based 7and some 8s used a slightly smaller 9.8cm turbine house to get back some of the squirt the 4g63T lost with tightening emissions legislation in 2001 . From memory 8MRs had the 10.5 standard as did most 9s which all had inlet VCT to pull the bottom end up . There are aftermarket 11.5 housings which works well on std turbos with exhaust upgrades . The 8s and 9 had a revised version of the 10.5cm turbine housing using a single flap and mirror imaged D shaped outlets like the TSIW EFR housings . The early ones had two holes and two flaps and most have probably cracked now anyway . So the story goes the Evo turbos were the closest production turbos got to being a true competition unit especially the small comp wheel types for restricted rally engines anyway . Not exactly a TR30R but I don't think any other manufacturer got as close - for Grp A rally anyway . One 7 I know of goes pretty well with an 11.5 housing on a bog stock turbo . On a 9 spec turbo with the larger comp housing and diffuser it should have gone better . The best overall was supposed to be the second series 9RS turbos with the Titanium Aluminide turbine and the super back or tulip shaped if you like magnesium compressor wheel . The early version had a flat backed comp wheel and these can lunch themselves if leaned on too hard . The TiAL turbine is said to be boost limited and if you overdo it the wheel separates from the shaft destroying itself . These 9RS turbos are supposed to boost 3-500 revs sooner than a conventional 9 units and its possible the 11.5cm turbine housing puts that back near standard but with less exhaust restriction . A .

I have not seen them side by side but I seem to remember people saying that R33 and R34 RB25DET inlet manifold gaskets are the same , something to check on . If I was building up another engine I'd leave the Neo head for that one and get pistons to suit it . Maybe even buy a complete Neo to rebuild . A .

A GT2835 KAI would be good if you can find a 2835 Pro S turbine housing for it . In T3 flange and IW from Garrett their GTX3067R is rated at 500 crank horsepower , no ones tried one AFAIK on an RB25 yet and is possibly similar power wise to a GT2835 Pro S 0.68 AR . GT3076Rs are tried and proven 300+ RWKW if the engine and exhaust is up to it . A .

Tao you know about the GT28 76T NS111 turbine , can you do something similar in a 60-63mm OD ? Cheers A .

Was back at Kirrawee mufflers this afternoon to look at the Xforce cat I wanted ordered , 4.5" OD 3.5" bore 200 cel one they normally use on XR6Ts - looks very adequate ... They've also ordered in mufflers and the rear one is huge , from memory 11 x 6 x 20" long . They reckon they can get it in - just with a couple of tight radius 3" mandrel bends . The middle one looks the part too , not as deep as I'd like but between the 3 "cans" they reckon it'll be very quiet and flow well . At the time they had a GTR on the hoist with an interesting looking 4" exhaust on it , custom mufflers and they think it will be quiet too . Hmmm . I just need time to get the work done and fingers crossed it will uncork this GT3076R and make it come alive . A .

Interesting times Tao , it's about time someone delved into turbines and housings to unchain us from Garretts aging GT30 turbine variations . You seem to be using quite large turbines for your compressors Tao , is there any chance of finding and using something a bit lighter and more open bladed like the GT28 turbine only larger and in similar trim sizes ? Cheers A .

Yeah sort of GT30ish , be interesting to know its trim size . A .

Didn't realise he'd already built it with NA RB25 pistons , why is another story . You'd think the original pistons with the Neo 25s more compact chambers is easiest as long as valves and pistons don't meet . There are workarounds but I think fitting the right pistons is the answer . Longer cams with more overlap would reduce effective compression to a degree . Water injection reduces combustion temperature and pressure . Absolute minimum exhaust restriction so it can reject the heat in its exhaust gasses most effectively . All these things cost money and only the individual can know their financial vs convenience priorities . I'm guessing the cheapest option may be to grab another RB30E short block , hunt around for a Neo 25T head and start again . Cheap cheerfull rings and bearing rebuild whilst driving the current setup . A .

What about an RB25 Neo head and RB30 NA pistons , smaller chamber should bring the CR up to a reasonable figure . A .

Well this thread is about exhaust restriction and anything significantly positive behind the turbocharger under load tells a story . I just picked on the sensor location because it's an easy place to tap from . If that exhaust is restrictive and gets fixed the dump pressure should fall and so should the exhaust manifold pressure . Boost and power characteristics should change as well . A .

How about this , where your oxygen probe goes get a plug and drill/tap/braze whatever a take off into it and measure the pressure in the exhaust behind the turbocharger . Compare it to boost pressure and note the difference . It may not be a bad idea to pull the cat out and see if its blocked or collapsed as well . Changing that mid muffler shouldn't be a biggie surely . A .

60-1 or from memory 409535-1 is a 76mm 60T wheel . I think there were half a dozen trim versions of that compressor with 60T being the largest . A .

My experience with a GTRS on a 25 with E70 was it wanted to boost at 2200 revs and it felt like it couldn't breathe and did the ethanol "wobble" thing . I suspect that until the waste gate cracks open there is more air going in than the turbine housing itself can pass out so you get I suppose a locked up volume situation that the engine can't handle unless you back off or allow the gate to crack open at that point . You can drive a GTS25T up some surprising grades in 5th gear and silly low revs with a GTRS and E70/85 - if you can get the exhaust out through the combined housing and gate . If you go with the stay shut f**k you gate theory I think you'll choke the thing at low revs trying to get boost in when the engine can't really use it . The surge slotted compressor housing gets around compressor surge issues but you really need the gate to crack early and some electronic means of boost control to get adequate exhaust flow out of the engine . Really people have to think about how much boost you jamb into an engine at low revs and how much it pays off - or doesn't actually . If you had a multi needle gauge showing boost and exhaust manifold pressure you'd be surprised what happens at times . I never ran my GTRS on straight PULP but I'm sure the ahh hot side restrictions would have shown up as detonation and countering that would stop you forcing them into boost at real low revs . Ethanol is good stuff but I reckon it can resolve detonation issues in a setup that's trying to tell you it has a problem . I'm choking even if I'm not detonating ... A .

Yeah GT"3040" means GT30 turbine with GT40 82mm compressor wheel . These were originally an older HKS spec turbo and the difference between theirs and the Garrett marketed version was the compressor trim - 50T vs 56T . You basically got a bit more airflow than a GT3037/GT3076R 56T with the 50T 3040R . Even when HKS went to a cropped GT35 turbine in their GT"3240R" they kept the 82mm compressor trim at 54 . And yep I reckon a larger turbine housing on the original turbo would have been the simple and cost effective option . From Garretts maps you get a healthy flow increase with the GT30 turbine going from 0.82 to 1.06 turbine housings , logical step with an RB30 in mind . If the ask was 330+ I reckon the way to keep the turbo responsive is to increase the housing size because the rotating groups inertia doesn't increase like it will with larger wheels particularly the turbine . Garrett already gives you a 0.70 AR compressor housing on those "7 blade" GT3076Rs so changing turbine housings if required is straightforward . One further , I'm not so sure the 7 blade wheel is a T04S . From memory their blades have a leading tip if you know what I mean where the S and 60-1 series had perpendicular blades . The 7 blade one could be TB41 series but whatever . GTX is the foreseeable future . A .

Don't forget that the "-9"s use a smaller trim turbine than many of the GT28 based turbos , from memory 62T vs 76 . I haven't looked to see but I assume all the GTX28s use the larger trim one . A .

I think the roads to good economy are CR injectors and gearing . An RB30 with at LEAST 9.5 static CR should make real good part throttle torque . I also think good injectors like EV14s help heaps because they have fine control (if tuned properly) at short pulse widths . Most R series Skylines were geared to suit the std RB20/25/26 and Japanese roads , depending on the lump you removed the gearing can be pretty short for a 3 litre . I don't think any turbo R series was taller diff wise than 4.1 and a 3.9 would allow you to better use the extra part throttle torque . Note the difference in rear gearing between some JDM and some Aus spec S series cars , 4.1 to 3.7 in one case from memory . Lastly and very importantly , turbine back pressure . If the turbine/housing combination is small this hurts consumption too . A .

Someone above mentioned 500mm which is about 19.6" and that's about what can fit with a tightish radius bend into it . Depth wise will probably depend on how low your car is and how likely it is to get hit or torn off . Somewhere around the 7-7.5" is probably about it height wise and maybe 11" wide . Stageas obviously have long range tank space for the rear can ... A .

In the bad old days people used to get NA exhaust manifolds and bolt "J"pipes on them for a cheap high mount manifold . I've never seen an NA R25 manifold so I don't know if that's practical . If you could get fabbed 26 twin shorties can Js fit them into a single ? POV stuff but you never know ... A .

I think there's a bit more to these Japanese cat back mid mufflers than meets the eye . They're more difficult to see on the car let alone look through and Jasma systems were made to be quiet . If your bolt on import only got modest upgrades some restriction may not have been a big issue . There are limits to how deep that mid muffler can be and from memory there is a bracket bolted across the tunnel in a 33 anyway that limits the length of that mid muffler . The numbers I wrote down are 5 x 10 x 16 inch and that's a Nismo in cat back one - no idea what it's like inside . I spoke to Wolverine about this stuff yesterday evening and it's beginning to sound like the best mufflers need to be made because the generic ones are too big or too small . The rear ones like that Xforce could be slightly longer and deeper for Skylines but they're obviously intended to go into other cars with a little less space - so one fits all . The best scenario would be a run of the biggest straight through mufflers that will fit 32 33 34 made up and a group buy , 3 and 3 1/2" would keep most inc the GTR people happy if quiet . A .