Gt2871 Based Hi-flow Into Rb25

[Dale FZ1]

Nice work Dale.

Sounds like a good package.

If I was to upgrade I would think about this.

Are you sticking with the Rb25 AFM and standard injectors?

Have you got a PFC?

How much did the turbo sey you back if you don't mind me asking?

Thanks

Is this what you got?

http://www.horsepowerinabox.com/HPIAB2/prod414.htm

Currently running the std AFM, but suspect that I will get better/more accurate full load tuning with either a Z32 or Q45 - higher voltage scale. Injectors are S15 specunits, nominal rating of 480cc but I believe at stock pressures delivering 450cc.

Yes, the PFC is fitted and in my opinion, the essential key to the whole upgrade route. Other ECUs are available and just as good, the importance is to have freedom in adjusting the fuel and ignition strategies.

The turbo, as per pictures, uses stock Nissan housings on a Garrett core 446179-31 CHRA. You may see it referred to as a SB8031. Check the turbobygarrett.com site for full details.

The link you have picked shows the full Garrett unit with their housings and the T25/5 bolt inlet/outlet flange that makes fitment to a Skyline more difficult.

Cost-wise, check my last post. The seller I bought from was Turbo Australia, operating out of Brisbane. Depending where you are, any of the other reputable sellers (GCG, MTQ, etc) can replicate what I got. There is no rocket science in the machining, but I believe there is some science in matching the specs to intended application.

cheers

[RS500]

Currently running the std AFM, but suspect that I will get better/more accurate full load tuning with either a Z32 or Q45 - higher voltage scale. Injectors are S15 specunits, nominal rating of 480cc but I believe at stock pressures delivering 450cc.

Yes, the PFC is fitted and in my opinion, the essential key to the whole upgrade route. Other ECUs are available and just as good, the importance is to have freedom in adjusting the fuel and ignition strategies.

The turbo, as per pictures, uses stock Nissan housings on a Garrett core 446179-31 CHRA. You may see it referred to as a SB8031. Check the turbobygarrett.com site for full details.

The link you have picked shows the full Garrett unit with their housings and the T25/5 bolt inlet/outlet flange that makes fitment to a Skyline more difficult.

Cost-wise, check my last post. The seller I bought from was Turbo Australia, operating out of Brisbane. Depending where you are, any of the other reputable sellers (GCG, MTQ, etc) can replicate what I got. There is no rocket science in the machining, but I believe there is some science in matching the specs to intended application.

cheers

hey dale,

i've been following this upgrade path of yours and noticed that there haven't been any updates since your last one.

how did u go, have u managed to tune the engine with more boost?

the reason i ask is b/c i am considering this same combination for my R32 GTS-T (RB20DET).

i look forward to your updated info.

[RS500]

hey dale,

i've been following this upgrade path of yours and noticed that there haven't been any updates since your last one.

how did u go, have u managed to tune the engine with more boost?

the reason i ask is b/c i am considering this same combination for my R32 GTS-T (RB20DET).

i look forward to your updated info.

no updates i guess.

[The Mafia]

give dale a chance, poor bugger is usually tied up with work (even though he's lazy anyway) and he also just moved house.

I'm sure he'll be back soon with a nice informative reply.

[Dale FZ1]

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.

Edited February 23, 2007 by Dale FZ1

[The Mafia]

Not bad at all dale, you've done well. I can't get over how flat that AR is - and you tuned on the road!

I don't think 13psi is enough though, get 15psi - 16psi into her and you'll get a better figure.

[discopotato03]

There are also a few recent developments in direct fit turbine housings for RB20/25 , GCG has had one cast up in (I think .70 A/R) and is supposed to be dimensionally same as RB25 houing ie std T3 flange and dump side flange . I think one of the Victorian mobs has a similar thing but can't remember who .

My latest research is into twin scroll housings to try to get similar response but with a GT30 turbine based turbo ie Real GT3071R or GT3076R 52T though this is not going to be a budget option .

Cheers A .

[BHDave]

Are the rev's displayed at the bottom accurate?

Assuming they are a bit out you may benefit from messing with the VCT switch off point to remove the dip in the power. Atleast you know it's got nothing to do with the af ratio.

[Dale FZ1]

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?

[Dale FZ1]

Are the rev's displayed at the bottom accurate?

Assuming they are a bit out you may benefit from messing with the VCT switch off point to remove the dip in the power. Atleast you know it's got nothing to do with the af ratio.

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.

[Chris_R33GTSt]

Nice work Dale, I am looking to do the same sort of upgrade to my S2 R33. Midrange punch and reliability over big power. Now that you have it sorted how would you rate it over the stock turbo? I am very interested as to how the boost comes on and how low in the rev range it starts building? (on the road not the dyno sheet)

Edited February 24, 2007 by Chris_R33GTSt

[Dale FZ1]

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.

Edited February 24, 2007 by Dale FZ1

[MANWHORE]

awesome work. I love what you said above, about not expecting to finish it in 1-2 days. That's so true.

If the skyline is your daily driver, it'd be really hard to start working on it on saturday expecitng ot be able to make an appointment for work on monday

[Cubes]

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.

To set the VCT up optimally you set the vct switch point to an rpm point that you won't reach (8000rpm for example)

Adjust ign and afr's around the 3500rpm+ point optimally. It only takes 10minutes or so to do this. Then give it a power run,

Move the switch point to 3000-3500rpm and give it another power run. Overlay the two graphs and there's your absolute optimal switch point for the given setup.

[NYTSKY]

I pulled a 260hp at the wheels on my dyno run.At 13psi and stock turbo and injectors.So when i put my highflowed RB25/VG30 BB turbo on ill only expect a 35hp gain.Doesnt sound right to me.

I have my dyno sheet but for some reason cant post it so ill email to anyone if they wanna look.And hopefully put it up for me.

[Dale FZ1]

I pulled a 260hp at the wheels on my dyno run.At 13psi and stock turbo and injectors.So when i put my highflowed RB25/VG30 BB turbo on ill only expect a 35hp gain.Doesnt sound right to me.

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.

[NYTSKY]

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.

I totally agree anyone who changes from ceramic wheels to steel is giving themselves the option for big power.In your case just this mod alone would be a big saftey barrier.Meaning with your application your turbo will last forever at the boost levels you are running.Me on the other hand my goal is to have as much power at 3500rpm.At present the stock turbo reaches 13psi at 2700rpm in 3rd gear rolling on the throttle.So i have a lot of room to play with.

It seems you have researched alot, so congrats with your result.Im sure if we were next to each other on the freeway it would be an interesing couple of squirts of the throttle.

[Lithium]

Nice to see how a GT2871R behaves on an RB25 - sounds pretty cool. Good work and cheers for sharing results I had been looking into it and decided a GT30 based turbo would suit me more...

My latest research is into twin scroll housings to try to get similar response but with a GT30 turbine based turbo ie Real GT3071R or GT3076R 52T though this is not going to be a budget option .

Strange, I mentioned our discussions and decision to go with a twin scroll "real" GT3071R on a particular car and you seemed to consider it a wasted exercise?!

[Dale FZ1]

Nice to see how a GT2871R behaves on an RB25 - sounds pretty cool. Good work and cheers for sharing results I had been looking into it and decided a GT30 based turbo would suit me more...

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.

Edited February 25, 2007 by Dale FZ1

[Dale FZ1]

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?

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