Dale FZ1

A few good points made. VNT is somewhat off-track, but also something I think we'll see more of in due course. Early adopters will pay through the nose, as with all new technologies. The issue has evidently been getting the system to withstand the peak temps associated with petrol engine exhaust gases. At the moment I'd just like to see if there is a reasonably priced split pulse setup that could be configured to suit an RB. I don't really have an opinion on the AWE headers, but their pictures and diagrams helped with explaining exhaust gas dynamics and the how/why certain designs work better than others. FWIW, I don't believe any ceramic coating will hide shoddy workmanship or poor design. Its main objective is to work as a thermal barrier. One thing I did notice was the sandwich construction used by Audi in the OEM manifolding though.

Not necessarily Paul, that's why I'm looking around. From a maximum system efficiency viewpoint, the properly engineered manifold is desirable - but in the power range I've nominated we don't know if it's ESSENTIAL. Depending if an IW split pulse unit is available economically, there may be good gains without having the big shift away from stock appearance. FWIW, the Holset range are evidently not expensive. The model families of relevance seem to be HX30, HY30, HX35, and HY35. More tomorrow.

With a bit of research, I've found that MHI is running a technology and product sharing arrangement with Holset - similar in some respects to Garrett/HKS. I think their main business focus is on diesel engines. The main point of interest here is that both MHI and Holset market split pulse turbo units, possibly (hopefully) within the mass-flow and efficiency ranges that could work for the petrol RB. Available specs seem limited, but two things caught my eye: 1. they are available both free floating (non gated) and with IW, in a range of A/R 2. they produce units with titanium aluminide impellers (resistant to extreme heat) There is evidently a HUGE range of options, and it would take a fair bit of work to find what could be built, but there could be something in it. Perhaps we might be able to unearth some specs and flow maps?

It’s interesting to check out the market and see what machines are generally fitted with split pulse turbos. We’ve seen evidence of Toyota having a go with MR2 running 3SGTE and (unconfirmed) early Supra fitted with 7MGTE; but generally otherwise in the Japanese market it’s mostly been the domain of the 4wd rally rockets which require (and can use) maximum torque, early and rapidly. The other common fitment is for various diesels, which as Adrian correctly pointed out in Mafia’s thread have a narrow effective operating engine speed range, so also NEED to develop maximum torque early and rapidly. Common theme? I’d say yes, particularly when the issue of using full throttle on the rally rockets is factored in. Full throttle = maximum mass air flow for the petrol engine, and diesels do not have a throttle – they get the full whack of flow 100% of the time. Is it possible that the 2wd Skyline with a split pulse turbo might suffer traction and driveability problems if either 1. this turbo configuration requires full flow (or lots of throttle) to get the pulsing effect and respond (ie. not progressive in delivery)? 2. this turbo configuration responds so vigourously that boost/airflow/torque rises very rapidly (ie. not progressive in delivery)? OR – do we follow the compromise through, by running a larger A/R housing, with the technical advantage of split pulse partly off-setting the dulled turbine response, with a gain up high because of increased flow + lower turbine inlet pressure? ie. on balance lose little down low, and gain something up top? It sounds a bit of an airy-fairy question, but one that is reasonable (I think) because of the existing typical application. Hopefully it’s obvious that I’m zeroing-in on whether it’s possible to achieve good transient response and linear delivery at less than 100% WOT, as well as the targeted beefy torque curve on the dyno sheet which is at WOT.

Not entirely sure of availability within Aust. But will be interested to find out. As I said initially, we had focused on Garrett product, but there are other options. I would say the T04Z range would be pretty well outside the 300rwkW cap too. It’s pretty clear that a true “tuned” split pulse setup relies on correctly designed and built manifolds that use the same principles as N/A extractors. I found this link that helps to explain with pictures: http://www.awe-tuning.com/media/pdf/2.7T_h..._comparison.pdf After viewing the pics there, I’d have to say the stock RB20/25 manifold is configured rather like a pair of joined log manifolds. It does seem that Nissan found benefits in keeping the flow from 123 separate from 456 until the turbine inlet though. If it was a tuned manifold, both the diameter and length of the runners have to be important, and would affect both the mass-flow capacity, response time, and engine rpm where it all works most efficiently (just like extractors). This design approach is about getting efficiency by correlating the timing and strength of exhaust pulses at the collector point, using pressure waves to assist “drafting” the waves emerging from neighbouring exhaust runners. Here’s another link on manifolds and exhaust systems generally, that might be useful: http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm Pretty much what I gained from that is ANY form of manifolding has compromises, and there will generally be a leaning either to the bottom end, mid range, or top end performance. Sounds like the rest of the engineering in your RB, and makes it clear to me that we should be looking to complement the rest of the engine with manifold and turbo.

Well there was plenty of discussion on Mafia’s 300rwkW on-a-budget thread, regarding split pulse turbos. Discopotato03 has been urging for the use of a split pulse housing in this higher power range, which roughly equates to 475-500 crank hp. The idea of starting a tech discussion focused on split pulse application for RB series engines was suggested, in order to keep that thread on track. No-one else took the challenge, so here it is. I’m very interested to keep this thread on track too. Firstly, my intention is to investigate and discuss more of the theory behind split pulse and what makes it work. I don’t mind if we get technical here – I want to learn more than I currently know about this subject. Secondly, I’d like some effort from you blokes (and girls) to see if we can find out what actual options there are to economically configure a split pulse turbo for an RB over a certain range of streetable power outputs; let’s say between 200rwkW and 300rwkW. I DO mind if we get over the top with cost here – we want some viable, cost-competitive alternatives to the various single scroll units currently fitted to RB engines to get in that range. We’d previously focused on the Garrett range, but I believe there are other brands out there that should be checked out for suitable spec. We are after a unit that will give as high and wide a torque spread as possible, and within the standard rev range. Early/quick spool, and free breathing high rpm power? Sounds like the “average power†concept that Sydneykid proposed quite a long time back. I’ll take it a step forward, and say that it is about maximum area under the curve. Let’s not get hung up about torque and power; we know that power is merely a function of torque and rpm. My personal preference is to look at the torque curve, but that counts for little. What does count is getting the curve up high, early in the rpm range, and keeping it there for as long as possible. So who’s up for it?

The unit BHDave suggested has a CHRA #700177-5023 on the ID tag. A pretty good unit overall, more responsive but less overall mass flow capacity than the 3076. It'd be good if someone can source a legitimate flow map for that 52T GT37 compressor assembly, but I'd suggest it would support somewhere in the vicinity of 290rwkW. The 3071 mentioned above will probably support 260-270. As always it will depend on the systems that support it, and especially the tuning. Pixel8r sounds like he has similar experiences to others using a turbo from the GT30 family. A bit slow to come on, and then breathes well higher in the rpm range. Those who use the 60mm turbine with the Garrett GT30 IW housing will get even higher max power results but at the cost of some response. It may not suit all needs/tastes.

I have no claims to fame, but here's a couple of suggestions: 1. The OE comp housing may strangle the potential flow capacity of the impeller. Physical size difference between this and the .70 A/R housing Garrett normally mounts up to that impeller suggests that the mass-air flow will be reduced. By how much is a guess but that side should (guessing) be able to support 240-250rwkW - maybe slightly more. I'd reckon with a .70, the compressor would be good for 280-290. 2. The OE turbine housing normally mates up to a MUCH smaller rotor. This one MAY present an excessive restriction at higher flows, leading to tuning issues to control knock if you wanted to run big boost. Still, if it was machined correctly and profiled to match up to the rotor, it may be quite ok. I'd guess this one is also likely to run out somewhere around the 240-250kW mark. Overall? A bit slow to come on, pretty big mid range hit but top end petering out by comparison. Again, a guess only. Keep us informed how it goes. EDIT: I don't think it would be directly comparable to any off the shelf item, given the specs (and assuming they are correct of course). EDIT 2: While you have the turbo off the manifold, get someone to drill and tap a suitable location near the collector to take a nipple/bung. With VERY LITTLE mucking around you could run a temporary pressure gauge and monitor what sort of backpressure this turbine actually created. You may have seen some other discussion that focused on that issue at length. On consideration, that is what I will be doing if I remove my turbo again. Low cost, and better understanding of what is going on.

I'm not going to argue the toss. He said it was NEW cartridge, and supplied the CHRA number off the ID tag. No suggestion of interference or modification, just a new cartridge installed between Nissan housings. That -0017 tag equates to a 52T T04S compressor mated with an 84T 60mm turbine. That data comes off a spreadsheet sourced directly from Honeywell. Unless there was some big quality control problem, it's unlikely that Garrett got it wrong. Given the tag number, that's what I would say is in there. HOWEVER, those who disagree, can. At this stage all that matters is probably giving the thing a run and seeing what it does.

The way to confirm easily is to read the numbers on the ID tag attached to the centre section. If you can, post them up please. I'm aware of a GT2876 BB cored high flow, using the OP6 housing that performed without surge problems and supported around 250rwkW. Be interested to see if this unit is the same specs. The difference in that approach to my 2871 48T was in the turbine, with lower gas velocity the compressor was not evidently enough to cause surge issues.

Have a look at Mafia's thread with a 56T GT3076: http://www.skylinesaustralia.com/forums/in...howtopic=167572 There is a bucketload of detail there, and some discussion about alternative turbine specs too. I've not seen any compressor maps for the 52T GT37 compressor, but presumably they are about 40hp shy of the 56T for maximum power capacity and would offer a bit quicker transient response. Suggest having a look around freshalloy and ns.com for other discussion about the 3071.

I don't think anyone doubts the brutal efficiency of the rally rockets. They are short, relatively light well powered and put it to the ground. For me, the 2wd Skyline was all about how it FELT to drive. Balancing traction and drive coming out of a bend (not just a tight roundabout) with something reasonably powerful (or really powerful) is what the experience is all about. Having said that, every grass motorkhana I go to, I rue the decision to pass up a R33 GTS4 for a lot less money. Surely the intelligent thing to do is target a certain power level, and aim to make it as progressive and driveable as possible. Good torque both on and off boost is the key, and in the engine speed range that we use. Cubes is right on the money with earlier posts about that. I don't need 300kW, but at that level, the cubes certainly count for something. And I think that regardless of engine size, putting it to the ground is most important. How about some real discussion on this point? Surely there are more people than BHDave that have had to deal with this.

I'd have to say that in my case the rear suspension settings have made small but noticeable traction improvements. So the mechanical diff made the big difference? What spec are you running?

R&R is how the Nissan engineers made a fail-safe ceiling. They intended it to make around 240 crank hp. Bigger mass-flow represented by more boost allows the ECU to see higher than specified max values from the AFM. It MAY be possible for the mass-flow to hit the factory-set ceiling if you have a free flowing inlet and exhaust. We don't know if it has a pod/FMIC/exhaust system upgrade. (EDIT: yes we do, didn't see the comment) Notice the problem is associated with colder conditions? Higher air density makes it easier for the engine to get the staggers. FWIW, mine did the same thing with just those changes, and running on stock boost.

Don't take me too seriously Dave, I will happily confess that I don't belong to the 300rwkW club in terms of driving ability. That was something I had to come to terms with in deciding the development path for self and car. So... chassis development? How does yours put the power down, and what did you do (if anything) to make it better?

Looks like it's nearly time to start a split pulse thread to keep this one on-track. The WRC rally rockets use split pulse designs in their restrictor-equipped engines which are basically strangled for mass-flow up high and therefore have a fairly narrow useable rev range. Those things punch hard down low in an un-Godly manner, and the setup works. BUT they are also designed / intended to run at full throttle / load as much as possible AND have 4wd to put the grunt down. I agree with Cubes in that the most appropriate road-spec Skyline is the one that gives the ability to respond in lower gears without simply frying the rubber because of the quantity and delivery of torque. Put simply, it's got to be USEABLE as Adrian indicated with half and three-quarter throttle delivery probably more important for general road use. The ability to transition from light to full load torque with power-down to the road has got to be the smart way. If Mafia had the option of a split pulse housing, with A/R options (important as Cubes said) then he'd have been mad to not go that way - price dependent of course. Useless dreaming though, because there are only so many options, and only one split pulse housing size. Back onto the main thread. Mafia's been off line for a little while so until he's back who reckons they could justify/use 300rwkW? I've never experienced that on 4 wheels, but have had about twice the power:weight with my bike - and LOVED it.

I’ll take the last word before bowing out of the turbo aspect of this thread. Make sure the information is complete. I couldn’t deduce any change other than in turbine A/R, which still dynamically affects the turbine inlet pressure. Here is the link for all to see: http://forums.freshalloy.com/showthread.ph...6028&page=2 There is absolutely no doubt that effective cylinder scavenging through low turbine inlet pressure is important. Note that the maximum boost pressure reduction was also associated what were admitted to be “aggressive” camshafts. with The cited case though, is EXTREME. 300 more hp, from 39% less capacity, using a significantly larger framed turbocharger? That is in another league guys. Agreed, it highlights the importance of reduced backpressure. That was identified very early with Mafia’s setup, regards my comments about “effective volumetric efficiency”. ie. better scavenging through reduced backpressure results in better cylinder filling = more power. 50rwkW gain at the same boost pressure validated that. The sticking point for me – and there is NO absolute right answer – is that at this particular power level, for this particular engine spec (internally bone-stock) the technically elegant split pulse system probably can’t stretch its legs well enough to show a practical superiority on-road especially once the tuning aspect is factored in. At best, I could only surmise that the split pulse system would see a couple of psi drop to run the same output. The underlying issue remains Mafia’s early comment about “bang for the buck”. Mr. Full-Race obviously has business interests, but he rightfully indicated that simply installing a split pulse turbo on a split pulse manifold won’t necessarily get the desired results. http://forums2.freshalloy.com/showthread.p...scroll+question He’s saying “buy mine, at 2300USD + shipping”. For the money involved, I’d keep the edge on Grandad’s axe and run the WI and live with the compromise. Meanwhile, maybe Wolverine should pick up that HKS manifold from Adrian, run the split pulse + WI, and put me back in my place with the results? Top discussion, and Peace.

Not an entirely valid comparison to make, but interesting to see what the freshalloy blokes achieved running the same compressor as Mafia, but with an internally modified 2.0 litre SR20 and the technically superior split pulse system. Whether the actual recorded outputs are closely comparable to Mafia’s is unknown, but I noticed that Mafia 397hp @ 18psi, freshalloy 410hp @ 16psi. Assuming the hp results ARE directly comparable, in many ways it validates 1. The capacity of the BCI-18 compressor and 2. The impact of improved volumetric efficiency through cam specs. The theory, and the practice says that bottom end and mid range improvements are there. At this stage, until we see the results, there is no evidence to demonstrate whether it has any PRACTICAL on-road superiority to Mafia’s spec, especially when the cost is factored in. I’m all for finding technical improvements, but they have to equate to the on-road experience in a demonstrable manner. I’ll keep off the cost issue. What I won’t keep off is the tuning issue. We are in complete agreement that fine control of fuel and ignition are critical components of achieving the potential of the mechanical spec. WI – equipped engines can (and do) run more efficiently at leaner AFR similar to a naturally aspirated engine. They do not rely on extra fuel to cool and suppress detonation. The coolant (water or water-meth) allows significantly more aggressive ignition timing which is worth LOTS of reliable torque through the ENTIRE range. More aggressive ignition improves spool off full-load, and torque through all speed ranges. Whether the split pulse system offers that degree of improvement despite any reduced pumping losses is debateable – but I would say not. I would also say that the split pulse system would not allow as aggressive ignition timing, primarily to control the demon knock. Conclusion: WI equipped system offers better scope to achieve the optimal, knock free fuel + ignition tune, and it is probable that both will be more aggressive (read: power productive) than the non-WI equipped split pulse system could achieve. At least our RB25 hot-rodders who work on a budget have options. Go for the technically superior turbine spec with fabrication or manifolding sourcing issues, or go for a technically less advanced (I won’t call it inferior) turbine that bolts-up and get to work giving it an aggressive knock free tune with the WI system as an integrated component. Then spend the leftover on event entries Again, it’s great that there ARE options, and it depends where the owner’s priorities and finances are. At this stage I think we’ve tossed the issues of WI, compressor, turbine, and exhaust manifolding around as aspects of Mafia achieving the 300rwkW mark as far as need be. Mafia can you tell us whether you’ve looked at the inlet manifolding as a hurdle? And you still haven’t told us what the car is being used for.

Variable vane possibly slightly off-track, but some stage in the future they will possibly see service on a Skyline. At this stage, the gear they are fitting to the Porsche wouldn't have quite the mass flow capacity to hit Mafia's power target I suspect. KKK are part of the Borg Warner conglomerate. Thanks for the info on the 7MGTE units. No doubt size would be a bit on the small side there too, but there could be options for other lower powered upgrades.

Yes, that was the trick that the boilermakers I've spoken to said was the problem. The right material isn't known, and while they can make the weld look neat there is no strong guarantee that the mix is correct. So the advice I got was that even after heating the manifold red hot and THEN welding, and THEN following a proper cooling process, there is a good chance of there being a problem with cracks after a while. I don't have enough technical knowledge to do other than repeat what I was advised. The JMS experiment obviously worked, but that was a few years ago. I wonder if that car is still running, and wearing that manifold? Undoubtedly someone will have a manifold that they've modified successfully, so I'm not going to say it can't be done - but it might be big task to find someone who can do it properly. EGT comments were looking at the difference between diesel vs petrol. At full load this could be something like 650-700 degC vs 900-950 deg C pre-turbine which is significant. The other heat related issue I would see is RETAINED heat within the housing itself. No doubt they are robust, but there are reasons why they use different cast iron alloys for high temp applications. As a matter of interest, who/where are these split pulse housings available, and are they a direct fit to the GT30 cartridge? Typical cost? At this stage, I found 6Boost style (non divided) manifold ~ 1400AUD, Trust style manifold ~ 1800AUD, and Full Race style ~ 2800. There would have to be a good 500-600 to have the OEM manifold modified and faced if you went that way. Typical external gate should be ~ 600 - 800AUD and another 300 - 500 to get all the exhaust + gate pipework done. So depending on the reliability of manifold mods, it might be possible to get within distance of Mafia's costs. The question is though, how good is the tune with this split pulse setup going to have to be in order to get within distance of his knock-free tune and inherent reliability that goes with absence of knock? And is the potential for lower turbine inlet pressure with the bigger A/R split pulse going to help combat knock as effectively across the range? I agree with GeeTR - best to use the best components and get the best overall result. At this level though, I think WI is too valuable to dismiss. I think we need someone with balls like Mafia who's willing to give it a run.

And the emphasis is on SERIOUS. Do you want ~ 300rwhp, or ~400? Response, or power? or a big dash of both. That 3071 would be a great unit, but leave you without the stock-feeling response at the very bottom of the rev range. The 2871 based units will also be great, feeling similar in delivery to stock, just lots stronger. A 3076 won't be to everyone's likes/needs/abilities. As long as you know exactly what you want out of your car, you can get something that will meet your demands.

It’s a big ask to get 2.5 litres to produce torque like a 3 litre on and off-boost. But Mitsubishi have done a great job with their 4G63 which is equipped with a split pulse TD-05 turbine. The torque numbers quoted from about EVO 7 onwards are outstanding (equal to R34 GTR), and from low rpm too – just what you want to punch a rally car hard out of corners. The thing with the TD-05 is they appear to have a significantly wider range of housing A/R options and it’s possible (at least for MHI) to tailor spec to exactly meet their performance needs. Going on their results, there is no reason to expect that an RB25 couldn’t produce some very impressive results using the same approach and thinking it all through. I admire your never-say-die attitude in trying to get the absolute best out of the RB25, and agree that up around this 400rwhp mark an external gate setup is more desirable. The trend in high performance petrol-spec housings and impellers is to cope with extreme temps – somewhere around 1000+ deg C. Not so sure that a diesel spec housing will have the right metallurgical qualities to resist cracking, and trial is the only thing that will tell if the manufacturers can’t/won’t. Welding mild steel to a cast iron manifold is certainly do-able, but I’ve had plenty of rejection from skilled boilermakers approached to do just that. Their basis of concern was not knowing exactly what the mixture of metals were used in makeup of the manifold, as that affects the ability of the bodies to fuse effectively without the join cracking. And that is even with using the proper cast iron welding techniques. None of them said it couldn’t be done, just that they couldn’t guarantee their work long-term. I’ve not tried to source a HKS low-mount manifold, but comments around suggest they are out of production and fairly rare/expensive (is this true??). Logistical and financial hurdles notwithstanding, I reckon that the split pulse manifold spec would be great, and there would have to be a great opportunity for a skilled pattern maker working in a foundry to produce a ‘foreigner’ if a HKS unit was made available. Wouldn’t like to pay full freight for one though, given what current workshop charge rates are. That numbers chase is something we can’t get away from, and for this discussion I can overlook immediate product availability. I don’t expect Mafia to lay his exact costs open, but a ballpark of turbo with IW GT30 housing (~2100AUD?) and custom dump (~500AUD?) + the ~850AUD for the water injection system would add greatly to this side of the equation. One thing Mafia has in spades is balls and perseverance so hats off to him. Plenty of reading and understanding of the theory, then the willingness to have his results and experiences discussed for the benefit of all. At this stage he’s well out in front, having installed pretty much the turbocharger spec that was discussed about 12 months back when his first upgrade was installed. Out of time tonight, more later.

Did a bit of searching, and came up with IHI - VF36, VF37, VF38. Used by Subaru on EJ20 , EJ25 engines, rated up to 350-370 crank hp MHI - TD-05, maybe TD-06. Used on 4G63 EVO rally car, rated up to 370 odd crank hp. BW - K-04, rated to 250 crank kW. The trend is to build them in size and power capacity to suit sub 2.5 litre engines, but specifically to build early/strong torque and get the smaller engines performing like big ones. The MHI units are spec'd with titanium-alloy turbine rotors, and thin-wall turbine housings, and apparently cost/durability issues have pulled them back from wider use outside the EVO Lancer range. Everything I could reasonably locate was rated 100-150hp lower than Mafia's requirements. Can anyone else find more?

Check ATP's website, but that's the only one I could see. Check hp-inabox because it seems they might have access to OE replica housings as an alternative to getting your own unit high flowed. All of the 2871 cartridges are good in their own right, and you can choose a spec that meets your performance needs in the 220-240 rwkW range, with zippy performance. The major difference between this option and the big brother 3071 would be in the very bottom end 1500-2500rpm and top end 6000-7000rpm ranges. Better breathing up high will yield stronger power at lower boost without it tapering nearly as noticeably, but I doubt you'd get that zippy/flexible response down low from the 3071. There MAY be split pulse options from other manufacturers, if that is something you really want. Might be worth a search, and let us know?

It does look an oddball. I've looked at this unit before, thought it was probably best suited to a larger capacity/lower revving engine not chasing bucketloads of power but looking for linear delivery. Perhaps something like a Falcon or Commodore running mild boost. Turbine efficiency and flow capacity data provided by Garrett does not look fantastic, but the T3 flange means it should bolt on to a stock RB25 manifold. I tend to agree with BHDave. The GT3071 with 60mm 84T + .63 IW housing is probably a far better option, but if you want zippy immediate low-down response then any of the three trim options in a GT2871R based high flow would do the job quite nicely. FWIW, you should definitely look at the split pulse option 3071 available from ATP or full-race.com and check the price/availability.