Dale FZ1

I'll respond to the question with a question: If there was an advantage to be had in forced aspiration application, do you consider the Nissan engineers would have specified it differently? ie. there would have to be a reason why they gave the pattern makers in the foundry two different designs for turbo vs naturally aspirated RB25. Certainly sparked some conversation though. Good work

Basically you follow the same process as if changing a timing belt - because you remove the belt to install the gear. Suggestion 1: use a timing light to check (and note) the base timing setting before removing the CAS. Then you are able to reliably return to that setting after reinstall so your IGN tune is unaffected. Using a paint pen to mark existing position is of limited value because your base setting will change after altering the gear from zero. Suggestion 2: make sure you have access to a puller for the harmonic balancer - you will need to remove that in order to remove the lower cam belt cover to then access your belt tensioner Suggestion 3: do the job when the engine is cold. Much easier on the hands when working

I have to ask what appears obvious: No hardware changes other than the adjustable gear? What sort of tuning changes were made? fuel, spark, or fuel + spark? Were they necessary to make the cam timing work, or was there room for improvement prior to the tune? How did you arrive at the 4deg retarded setting? ie what were you targeting. Were you chasing top end improvement, or response? Reason I ask is that I have a high flow fitted and have been wading through the literature to find a worthwhile starting point. If I can achieve similar outcome then I will indeed be happy. cheers Dale

Thanks Gorjan. I'm likely to run with a replacement actuator rather than an EBC. Obviously each has its own advantages/disadvantages but I feel the actuator route will work well for me in this application. Choices are of either a 14 or 17psi setting so I will review the maths and maps to see if there is any real gain (without compromising reliability) to be had from pushing the extra boost. Gut feel is that it will nicely handle 14psi and crank some more power but that will be about it. It's about the size/capacity of the compressor impeller and I don't see the sense in over-speeding the rotating assembly. If those HKS housings were available economically I would be prepared to try one, but this really was intended as an off the shelf style high flow with cost containment being an important aspect. Similar issue with why/why not to use the RB25 comp housing as per an earlier post in this thread. Overall it was more expensive than a plain-bearing unit like Slide's (no, I don't want to get into comparisons), but it is showing itself as effective. I'd suggest this spec should mate well with an RB20, depending on performance targets. Meanwhile I'll work on smoother boost control and the cam timing to see just how good a result I can get. cheers Dale

Off topic gents...

Slightly off-topic, but relevant to this upgrade and tuning to suit: Some advice from Col-GTSX got me doing some research beyond old threads where I saw Sydneykid make consistent reference to +4 and -2 on inlet/exhaust respectively as starting points. I didn't find much meaningful info on what has worked with RB25 using adjustment only on the exhaust cam that seems to be the popular fitment due to the hydraulic advance unit fitted to the inlet cam. Col indicated ADVANCING the exhaust cam timing in order to give a stronger bottom end response and torque, which took time to fathom. Thankfully there is some good understandable literature from Muzzy's (US bike hotrodder) about degreeing cams, and what works and why. Have a look here: http://www.muzzys.com/articles/lobe_centers.html What I deduce from that is that Col's advice and experiences are on the money, and anyone looking to boost the mid-range should advance the exhaust cam timing. Obviously the dyno will tell the story, but it's great to get the technical info and use that for setting a starting point. I'll get another thread going on cam timing adjustments on RB25, but question to those who have done it, are there any obvious flaws in taking this approach when chasing mid range? cheers

Likewise. PFC opened the performance lid for me. In some ways it's a pity the R33 ECU is too difficult to alter. The results being pulled from R32 spec remaps are very noteworthy. Whether PFC is becoming scarce, the options are still wide open.

There is definitely room for good responsive results with other cartridges using the zippier 53.8mm GT28 turbine. This particular unit was obviously chosen to sacrifice big numbers in preference for response, and that may not suit everyone. Search on high flow with jmac to see another good result, regardless of critical comments raised at the time about his particular cartridge. My general view on the GT30 range is that the power numbers can be generated, and really open up the top end flow - but throttle response in a small capacity 6 cylinder RB25 is the first casualty of going in that direction. Depending on what is the primary performance objective, I think they can be a great fitment - and I have a mate who is running a GT3076. I like to share the results of upgrades with some meaningful appraisal of how and where it's better than stock, but also to uncover where the compromises show up. Some are very harsh on the driveline or demanding on the driver. With this one, it's just that it ultimately runs out of flow past a certain boost level.

Sounds like the ECU is in failsafe. Engine is breathing far better than stock, so it serves up a massively retarded ignition map to discourage any behaviour thta might damage the engine. And as pointed out, changing the ECU may give a cure but it will be (very) temporary. Many people (myself included) have hit the same hurdle by adding intake/exhaust/FMIC alone - no boost increase. And it is frustrating.

Using that larger housing will give some top end flow potential. Any ideas what spec cartridges or impellers you will be using? I'd like to follow things along.

Dave I'd say up front this unit may not suit everyone, but it's got my objectives very neatly covered. Check from the start of the thread. From the initial point of contact, various suppliers tried to steer me towards high flow units with bigger potential power capabilities. Response and power delivery (not the peak numbers) were always my concern. Some guys focus strongly on a gain of "only" 35hp, so they get the bigger units and are happy to accept a lag penalty. As is, I changed turbo, boost level, and tuning to gain 67hp, which is a 29% peak improvement. I received advice from a Garrett engineer that I should target a minimum of 30% peak improvement to justify the expense and effort. What you should focus on, regardless of whether you pick up 35 or 135hp from now is that you have removed the potential for ceramic turbine failure. Any upgrade is (to me) worthless in the long run if it introduces inherent unreliability. Anyhow, I'm not trying to tell you that what is good for me will be good for you. That's your decision. Hopefully the thread + pics will give an idea of what can be involved in doing an upgrade.

Not really, given the design and intended application - and how it's driven. It's just what they do.

As per post this morning, there is about 150rpm difference on the road when it hits boost transition. Roll-on in 3rd gear previously I was showing boost @ 1600rpm, now it's 1750. ** Revised comment - easily developing 1-2psi boost @ 1650. Maybe the stocker was able to start even lower?** That is just feeding the throttle smoothly too, not stomping on it. Comparing results on the dyno between stock and high flow are similar. It behaves like a stock turbo, just a lot more stick. Power delivery is very easy - it's tractable in the wet, and I have no slip out of a stock clutch. My baseline dyno run with stock turbo and boost (7psi) was 228hp. Some guys might consider it far too mild an upgrade to make them happy, but the car covers ground briskly without placing excessive demands on driver skill.

Check out how fast the flow requirements ramp once you load the engine in any rpm range, and if you keep sticking the revs into it. And if you've got more power, then you're going to use more fuel. If you want economy then you need to keep it in that light load zone. So the answer remains the same: mechanical spec (this includes injector flow rating) will play a part, but not as big as you might think tightly controlled AFR is important (yep, tuning) controlled use of the throttle is the major factor Hope this helps. cheers Dale

660cc injectors are overkill for that power requirement. Most guys on SAU have had good results with 550cc which will more than feed what you want. However, run what you have, and aim on good consistent tuning. Here's a development log I made in the past week: Pretty self explanatory, with the numbers being average AFR:1 logged during a run, with O2 feedback turned off. My target from P3 - P9 load is 14.7 but I tolerate a variance of between 14.6 - 14.8. Extensive data logging has shown that you do get variance from run to run, but multiple variance analysis shows that over the long run it is fairly tightly controlled. There is a bit (lot) of mucking around to achieve the consistency though. I'll pull up a shot of injector duty cycle too, just to demonstrate how much increase you get with load.

Yes, the dyno was calibrated off the FC Logit software so rpm scaled correctly. Tried a quick test of the VCT, altered from 4700 to 4000 switch point. Went backwards quite a long way and abandoned any other tests.

If I can get the boost control more even, I would entertain the idea of trying around 15psi. Beyond that, this compressor spec just runs out of flow. You end up running shaft speed increase of 10 - 15000rpm to pull another psi, so it starts to compromise the life of the turbo. Adrian I could have gone to a VG30/R34 turbine housing which has a larger A/R but basically went away from that one because it would have compromised transient response. As is, the boost transition is about 150rpm different from a stock unit, and roll on / roll off throttle response above 2500rpm is far superior. So I suspect any other larger housings would be a retrograde step away from my performance requirements. As you know a fat hp number is nice, but not much good on the road if it won't respond quickly. I'll get the cam adjustments made and check the difference this week. Perhaps someone with the experience (Sydneykid??) might have a suggestion what amount of exhaust retard typically works best?

The injectors are way overkill for the power you are developing. What is your power target? Obviously it would be easier to achieve fine control at light load with smaller injectors, but I'd suggest two main culprits: Your light load AFR Your driving style. Use lots of throttle and a bit of rpm, and you will use fuel; it's that simple. Injector sizing may be a small part of the issue, but I'd look at the other two as the main cause of fuel use. I have similar max power to you, but consistently deliver 400-440km per tank (50-52 litres to fill). cheers.

Mods: Garrett GT2871R 48T high flow @ 13psi PFC + Datalogit Splitfire coils NGK BKR7E copper plugs, gapped to .85 Bosch 040 pump S15 Silvia spec 440cc injectors Pod filter + cold air feed 2.5 inch split dump (cheap Chinese job) + 3 inch front pipe, 80mm Blitz cat-back with 2.5 inch restrictor at tail pipe FMIC Chinese room for improvement at top end - nosing over a bit quick. Probably tied in with richness and getting to the end of flow capacity for this compressor. mid range improvement likely to come with adjustable exhaust cam gear. very driveable unit

Dragging up the original thread, it's been a while as I learned about tuning through the Datalogit + wide band input. I'll let the graphs largely tell the story, but add the following: boost control with the $30 boost bleeder is not super smooth - fluctuations are evident, and there is a gradual drop away at the top end. I will look at changing boost control in the next couple of months, as a means to improving that torque dip @ 4000rpm The torque dip is also going to be attacked by trying an adjustable exhaust cam gear. I fitted it just prior to the dyno run but there is no way I could get in to adjust things while it was all hot. Happy to do that another day. AFR work was all done prior to dyno runs, with the only changes made being ignition timing. The richness at the very top end was intentional, to promote longevity. My target above 5600 was 11.8, so there will be a little work there yet to be done. Might pick up a couple of hp there, and with some effort I hope to see the power curve remain flat rather than nose over. Finally, my maths proved to be pretty good. I had actually calculated 290hp @ 14.5psi @ 6100rpm @ 12:1 AFR, using Sydneykid's observations of typical 2wd drivetrain losses. Further checks of my logged injector duty cycles suggested somewhere between 285-295hp, again using the rated flow of injectors and the power levels that would support. Overall satisfaction is still high Before/after shows the results of 9.5psi boost vs 13psi + some tuning.

Don't understand why it would be a last resort?? Pick up the phone and talk to them. I can't comprehend how you are going to fix it without knowing what you have. FWIW, Turbo Australia are a new company from scratch. Check their web page here http://www.turboaustralia.com.au/downloads...aliaOpening.pdf See how you go - best of luck!

I tend to agree with Adrian's views about the number of blades affecting how effectively the impeller can push air at lower shaft speeds vs something similar with fewer blades. It could be something as simple as that - often it's not easy to get a spot-on spec when trying something new/different. Older designs shouldn't be dismissed outright just because they're older. They just need to be matched to the application. 320hp @ 16psi is nothing to sneeze at BTW - obviously it has the mumbo to support good power but not able to work across the range. Garrett's tutorials in living colour in your garage?? If you want to know the spec of the impellers, I would recommend speaking with Ross or Josh at Turbo Aust. If they did the high flow job, it will be documented. Do you know what sort of characteristics or power target your mate had when getting the specs finalised?

Adam just as a point of reference, check this page: http://www.turbobygarrett.com/turbobygarre...bo_tech103.html which gives a bit of technical info on what causes surge. Basically, it's not the case that the engine is too small to push the turbo, rather it is too small to ingest the turbo's output once the turbo is allowed to crank up to a certain pressure ratio (ie. boost level). And yes, once diagnosed it's not easy to fix without some $$. Ported shroud housings and BOVs can/do mask the event, but you do need to be in the ballpark first off. Sometimes not too easy when you're dealing with high flows either. Best thing is there are some very knowledgeable traders out there with a wealth of proven high flow specs so you're not out on a limb. From previous posts you should be able to tootle around with a lower boost level without coming up against the surge issue. Let us know how it works out for you. cheers Dale

Check here http://www.turbobygarrett.com/turbobygarre...bo_tech103.html for the Garrett tutorial on what causes surge So the question is 1. how did you decide on the specs for the high flow? 2. do you know what size/spec impellers have been used? (if so, post them up please)

I agree on the point of it most likely being compressor surge. But not with you on the new ECU. The surge is related to the physical capacities of the engine vs compressor. Changing an ECU won't cure surge. But obviously it will give him the freedom to tune decent AFR + ignition once the surge issue is corrected.