Dale FZ1

Looks like this thread is meandering a bit, difficult to fathom direct relevance of Mitsu 4G54B Astrons and KA24 to application of a GT30xx to RB25. I’ll add the bit that I can, from direct experience with GT3037 Pro S (0.87 turbine), GT3037 (0.63 IW Garrett turbine, water/meth injection) GT2835 Pro S (0.68 turbine, Pon Cams), and a piddly GT2871 high flow onto RB25 in R33 chassis, stock gearing. Max outputs of each were ~ 290rwkW, 300+rwkW, 265rwkW, 225rwkW and not running outrageous boost pressures or tunes to achieve those results. Reference to roll-on response is in 4th gear. Head to head the 3037 and 2835 DID NOT feel significantly different in the 2000-3500rpm range. There was a slight advantage to the 2835 in roll-on response, made you feel there was perhaps 5-10hp but nothing startling. Above that the 3037 just had bigger lungs and there was a clear advantage that widened beyond 5000rpm. I’ve said many times that the 3037 never felt laggy. The uninformed/inexperienced might use the term “laggy” when referring to matching a 3037 and RB25, but it’s just not the case. It’s linear, progressive, and with the 0.8x turbine housing gives a stock engine some pretty good high rpm breathing capacity so making and holding max power (in my instance) across 6300-7300rpm. That is holding peak for over 1000rpm, significant in my books. A superb match generally, but it did not quite have the zippy response between 2000-2500rpm associated with stock turbo and/or small capacity high flow turbos. It telegraphed exactly what it was going to deliver, and then delivered on the promise. Advice from a prominent Qld based Garrett distributor was that the 0.8x turbine was the best setup for an RB25 because amongst other things it permitted pressure drop across the head, and hence good scavenging. Also told to expect ~400rwhp @ 18psi. A comment made in response to whether it would deliver strong results under 2500rpm was to be prepared to change down a gear for best results. Dyno results of 390rwhp, some club motorsport, and 10000km on the road showed he was right. With the 0.63 housing I felt there was a slightly earlier sharpness in torque production, but you could feel things taper around 7000rpm. Not snappy, but it came on a bit earlier and peaked/fell away a bit earlier than the 0.87 turbine setup. Direct advice from a Garrett engineer was that the 0.63 housing would peak around 400hp, and not get the best (highest) output from the compressor but would give stronger transient response. Dyno results showing 400+rwhp and seat of the pants showed he was right. The 2835 was ”nice” which sort of damns it with faint praise. Cams let it breathe, and it produced power beyond 7500rpm. But (and my opinion only), it felt neither zippy down low, nor I’m-going-to-jail fast up top. That setup did need revs, and didn’t feel overwhelmingly powerful. It was fun and driveable, but for the money I’d want more. The 2871 high flow was in many ways a surprise packet, because of its strong torque beginning at 2000rpm, and running to 5500rpm. Didn’t look fast or sound fast, but covered ground fast and easily. Relatively low power was easy to handle and not at all intimidating. And it could beat any of the other three setups in a roll-on from 60 to 140. With respect to compressor trim sizes, I suspect it makes little difference to transient response capability in roll-on circumstance. A couple of posts out there trying to compare the 35 and 37 series compressors by trim size are wide of the mark. Best to get the actual inducer measurement, which tells most about the “gulp” capacity. Bigger mouth = bigger gulp = more top end power. That’s why restrictors work so effectively in rally cars to contain max power outputs. Comparison between the 56T 3071 and 48T 3037 (evidently now out of production btw…) shows their compressor inducers are within 0.15mm of each other, and they should hence be capable of roughly the same max flow capability. Required shaft speeds and moment of inertia will be different, and so they should perform differently – from a theoretical perspective. I had suggested to others looking for ~ 270rwkW that the 48T 3037 teamed with a 0.63IW housing would be a lively unit and better than a 3071 due to the lower required shaft speed to deliver a given air mass (ie power level). That is now impossible to tell unless someone built one special order from parts as a leap of faith. And it would not come cheaply. The smaller inducer for a 52T GT3037 will offer less max flow than the 56T 30307, and perhaps slightly less inclination to surge – good except that the 56T 3037 doesn’t surge on an RB25 in my experience. I’d concede that at sub 400rwhp the 52T might well offer a technical advantage, with marginally less power (drive) requirements placed on the turbine. There could be some difference in feel to a discerning driver, but until Disco (and a few others apparently) get theirs up and running that is conjecture. Most important is that the chosen compressor is running at peak efficiency across the range of peak engine torque, but not pushed so hard/fast that it’s cavitating and overheating the intake charge at max engine speeds. Not too difficult to grasp. Rule of thumb offered to me by both engineers mentioned before was that achieving enough compressor flow and efficiency is fairly straightforward but the choice of turbine plays a BIG role in how it responds, and over what engine speed range it runs best. And that is consistent with the turbobygarrett.com tutorials on turbocharger matching. In this case, smaller A/R = lower effective usable engine rpm, bigger A/R pushes things upwards. It really does depend on the use you intend to put the car to as to what is the best choice, not whether it makes 280 or 300rwkW. Power density or area under the curve counts the most. I know of only two people who used the 0.63 GT30 turbine combination. Mafia ran up around 19psi and did not observe boost spiking or running away. BHDave was looking to keep things down around 16psi and did experience issues. Both of them reported superb low end response – not surprisingly. Running a free floating (EW equipped) 0.63 turbine would offer a satisfactory cure, at a cost for those who demand that sort of torque delivery and usable engine speeds. If I HAD to have a 25DET running stock diff gearing, it is probably the path I would look at – provided I could wear the extra expense of a fabricated manifold and EW. And that also opens up the possibility of the ATP 0.78 A/R split pulse turbine option… Lithium’s comment about too many twisted undies is accurate. More hand wringing than action, and the 3071 is in my view the orphan that Wolverine referred to it as. Hypergear do offer their bolt-on version of a GT-RS (52T GT2871) for a safe bet of ~250rwkW and quick low rpm response / high power density. Check it at http://www.skylinesaustralia.com/forums/Ch...hp-t309952.html I’d back it to cover ground the quickest and easiest in general road driving, and probably the least expensive $:hp ratio. Skylinecouple has been running the GT3071 for some time, and his preference is to fit a GT3076 simply because it offers more headroom for flow and some power increase where the 3071 really can’t unless it is pushed beyond its efficient speed range. Final word: I don’t see the point in chasing middle ground between a GT-RS (or equivalent) and the GT3037 (trim size does not much matter). Go one or the other, and if you go for the big stick GT30, choose the turbine housing size according to use the car will be put to. And if funds/legalities permit, take the EW option.

Unknown quality of the metals used means porosity is a real issue to be aware of. Mine was stripped back for some extensive finishing work, but got a heavy coat of epoxy enamel before installation. The Chinese supplied it with a heavy coat of paint probably for the same reason.

You do realise the stock 25DET has a liquid:liquid oil cooler installed from factory? IMO no real value replacing it with a liquid:air unit unless for severe duty use (eg circuit work). For street running and drags you generally won't load the oil with enough heat to warrant changing what the factory did.

All the positive comments about the 3076 matched to RB25 are right. It will give you progressive response, 400rwhp, and top end breathing so it produces power to 7500ish on stock cams. Rather than play with the housing, you should consider fabricating a pipe into either the manifold or the spacer plate. Frome memory Simon R-32 has some knowledge of that method.

Poorly hung exhaust systems will often be accompanied by vibrations so shouldn't be that hard to spot. Agreed, the type of leverage they can place on the turbo and manifold are likely to cause problems. One thing I see as a possible plus for this particular manifold is that it's not stainless steel. Perhaps not as fatigue prone either? It's a bit of a judgement call, but at the price point perhaps worth a second look. I do agree that the other named brands are known quantities and come ready to bolt up, not requiring extra facing or bracing, or internal finishing that costs time and/or money.

Apart from using a Gibson Motorsport style hanger/brace, how do you avoid the weight of a turbo hanging off the manifold?

Bump.

What sort of torque/rpm characteristics would you be chasing from that change? Is there a real need to stay with the 2 litre capacity? ie. why not take advantage of readily available RB25 engines and reap the torque reward. Plenty of indicators out there that says a stock RB20 that's allowed to breathe via upscaled turbine will keep making good stick even up around 8000rpm.

http://www.turbobygarrett.com/turbobygarre...159-1comp_e.jpg Click on this link, a close approximation to what you should expect.

There are two plugs on the TPS, one on the flying lead, and the other onthe TPS body. There are two corresponding plugs on your loom. Simply plug them in. As per the tutorial you will possibly have to cut the loom to make things the right length and tidy things up a bit.

Complete Datalogit kit, comes with Beige box Cables Software access to the FC Datalogit tuners forum This kit used only for my ECR33, but I believe it provides for read/write access to other model PFC. If you want complete access to your PFC tuning potential, which is not available with the hand controller, Datalogit and your laptop is the way it's done. Asking $350 firm.

For the relative expenses involved, and considering the untouched internal engine spec, you'd need to play it cool with power targets IMO. Cheapest spend is on an adjustable cam gear. Try it, and if no major gain you haven't spent too much. Otherwise the marriage between KKR housing and GT35 turbine rotor may not be a happy one. Yes it is obviously dealing with the max flow rates, but no, it may not be driving the compressor early enough. Strongly consider a Garrett GT35IW housing if you wish to stick with the 3582 spec. Is the tune a good one? Getting fuelling and ignition right when spooling makes a big difference.

No amount of overboring a housing to accept larger turbine rotor will impact on the A/R. A = cross sectional area of the scroll R = radius from the shaft axis to centroid of the scroll at the point of measuring the cross sectional area. Basically A/R is fixed. I'd suggest a call to Hypergear and consult with Stao.

Unless for extreme use, external drain is over-rated and misunderstood IMO. Better value and results if the time and effort is spent drilling out the internal drainbacks in the head and block. Otherwise, yep, use a bung where the solenoid used to reside (make sure it is the correct type to seal), and have the feed hole welded or grub screwed as per the guide.

Front feed in the head is for VVT. If retaining VVT there are mods you can make in the gallery, otherwise run an external feed as per the RB30DET guide. If deleting VVT there is more than adequate oil supply to the front cam journals. You can also remove the solenoid and install a bung to simplify things. Be sure to check the lift specs in Pro Cams - beyond 9mm in a RB25 head will probably require machining to give adequate clearance and avoid coil bind on the valve springs. If unsure you should consult with a head specialist and get things measured on the bench.

Pump/reservoir unit looks neat. How big is the bottle? I'd like to see some shots in the engine bay too - I take it there is a single nozzle somewhere near the throttle body? Good to see the results are immediately obvious too.

Cage is coming together nicely. Will the height of the hip bars be a hassle in entry/exiting the cabin, or be something you whack your elbow on?

Keeping on-thread, and checking out zebra's build thread, I'll differentiate between the intended uses. For an occasional track machine it would be hard to deny the benefits of E85, and what Dave's mate achieved should be repeatable. The number of hours use it would realistically see during a year means E85 and >9.0:1 CR would bear serious thought. Good tuning would determine how well it lives. Keep us posted with progress.

There's a big difference between what can be done with direct petrol injection setups and the port injection setup we have with the RB. Even so, those factory setups aren't running much if any further than 10:1. The fuel is the secret ingredient there - looking through competition history books shows what has been achieved with high quality blends and rocket fuels. General availability puts a dampener on my enthusiasm for E85. Considering what the likely pressure ratio (say 12psi) is required to hit a streetable 350rwhp, I agree that perhaps up to 9.5:1 would strike a very good balance for output and fuel efficiency. I don't think I'd like its chances of surviving a hard day at the track though, unless it was running some sort of special fuel. Be a bit interesting to see/hear more on the results of this combination. Running a tune very rich (say 11.2:1 AFR) at high load does not mean it has to be rich at idle also. Time for a proper tune?

So exactly what spec are you running - 8.2, 8.5, or 9.0? Not sure why a 0.5 change in CR would make the thing any more/less difficult to tune. Run to your target AFR, and develop an ignition map that doesn't allow the engine to knock. The lower static CR should allow for greater knock resistance at a given boost pressure, maybe at a cost of overall engine efficiency/output. Also good tuning would/should provide suitable correction for changes in IAT. If you were in someone's draft for 4-5 laps everything would be hot, especially coolant temps?

Search for a thread on this one a few months back - has pics and all. The N/A Neo head evidently has smaller ports

Any idea what A/R turbine housing on that unit, and what engine it was fitted to? Comp cover looks physically smaller than the ported shroud version - optical illusion only?

Considering you've got the same spec as a GT-RS, look at the results others have achieved with them. Expect good results on-road, and don't worry about surge with either the 48 or 52 trim cartridges. The larger 56T would probably warrant use of a larger turbine.

Generally speaking, I would agree Lithium. The bigger turbine A/R certainly allows a stock RB25 to breathe as rpm rises, and gives one a lot of free revving zest (if that makes sense to those who haven't experienced it??). For bottom end and mid range urge, the 0.63 isn't a bad thing (quite potent in fact), but you'd then need to wonder if a full HKS GT-RS kit would be more suitable and probably near as quick in most situations. One of the tricks to a good outcome is having usable torque to suit the available gearing and speeds the car will be operated at. Only other thing I could add is that I enjoyed Mafia's car but would probably still go the 0.82 spec unless I could afford a split pulse setup. Then the price difference might lead me towards an RB30DET as a viable option...

GT3076, CHRA 700177-5007, with a Garrett IW housing 0.63 A/R. That spec has the 0.60 A/R ported shroud compressor, and 6 x 2 blade impeller. One of very few to run that spec turbine housing, and I can confirm it makes its power earlier than the 0.82 - but it also signs off a little earlier. I do believe that water/meth is a big aid in getting the best from this spec turbo. Best if you heard it direct from Mafia, but having driven it, it's certainly got some balls.