Rb25det Neo In My R31 - Questions

[fr05ty]

Hi all,

I'm new to this forum and I've been on CalaisTurbo and R31skylineclub forums for a while and have had RB30E and RB30ET setups on my R31's I owned. I have now recently purchased an R31 with an RB25DET NEO motor, RB20 box with Extreme racing button clutch, R31 silhouette 3.9 LSD, 3 inch turbo back exhaust, AM front mount cooler, and dual stage boost controller (8psi on low and 13 psi on high). Currently the power I'm getting is 187rwkw @ 8psi and 212kwrw @ 13 psi with the stock R34 GTt ECU, stock injectors and bosch 040 pump

with my current setup my questions are:

*What turbo does the RB25DET Neo have and how much boost can it be wound to?

*How much boost (safely) can I run on the stock internals of an RB25DET Neo with stock ECU & A/M ECU?

*What is the limit on the stock injectors (power/boost)?

*What is the best aftermarket injectors with my setup without changing the fuel rail?

*What is a good suggestion for an aftermarket ECU to run higher boost?

*How much power can my drive line possibly take (RB20 box/extreme racing clutch [rated at 1600 kg's..so I've been told by previous owner], and R31 silhouette 3.9 LSD)?

*I've heard of KKR turbo's being a decent/cheap upgrade; are they reliable and substantial in comparison to power output/price wise on other turbo types?

Sorry I'm still pretty noob with all this

What I'm basically after is a high power output....maybe somewhere between 250-300rwkw without having to change internals (if that's even possible) and most of the current setup; yet at the same time be on the safe side. Maybe looking towards upgrading ECU, injectors and Turbo, most likely ECU if anything.

The usage of this car is basically a mixture of street/drag/weekend use. Trying to keep costs at minimum (if that's even possible LOL) and to increase a power output on my setup safely. Any suggestions?

[Bennett]

Mate before any of that you are going to have to upgrade your gearbox before you blow 3rd gear. RB20 boxes always seem to blow when behind rb25's

Edited January 7, 2009 by Bennett

[nIsMo86]

Mines pushin out round 270kw and my rb20 box hasnt broken yet. Trackdays and drags etc. Just look after it.

When it breaks...replace it

[JonnoHR31]

stock silo lsd's are crap, if it spins double now it wont for much longer once you start using it, a few rings and it'll spinning single, the diff itself will handle the power no worries

[Adriano]

is yours an rb25?

[Bluprint]

I have an R31 with an RB25 Neo.

In no way do I claim to know everything, so - to my knowledge...

*What turbo does the RB25DET Neo have and how much boost can it be wound to?

The turbo has a VG30 style exhaust housing and the compressor wheel is made of a nylon composite material, making it more fragile. Most people say that 10psi is the safe limit.

*How much boost (safely) can I run on the stock internals of an RB25DET Neo with stock ECU & A/M ECU?

The R34 internals are probably a little stronger overall then the R33. They are known to have GT-R RB26 style conrods (mine did when it was pulled apart) which are good for the power level you want. Also has GT-R style shim & bucket solid lifters instead of hydraulics.

The stock ECU has an overboost protection which I think comes in at 12 or 14psi(?), I think it basically richens the hell out of the mixture and retards the timing all the way.

Aftermarket ECU I'm not sure, because I don't know if the R34 motors have the same issue with R33 RB25s where they break piston ringlands. I guess if you're not worried about rebuilding it then wind the boost up and tell us how much psi you had in it when something breaks

*What is the limit on the stock injectors (power/boost)?

215rwkw? Don't really know for sure. They're smaller than R33 injectors (R34 are 340cc vs R33 370cc or something like that)

*What is the best aftermarket injectors with my setup without changing the fuel rail?

Nismo 440cc?

*What is a good suggestion for an aftermarket ECU to run higher boost?

Apexi PowerFC is very popular, also the new Vipec range.

*How much power can my drive line possibly take (RB20 box/extreme racing clutch [rated at 1600 kg's..so I've been told by previous owner], and R31 silhouette 3.9 LSD)?

RB20 gearboxes are very similar to series 3 R31 RB30 boxes. With the power you want you'd be better off with an R33 or R34 gearbox. If you did that you'd have to get a custom tailshaft made. Mine is a single piece using a Z32 300ZX twin turbo gearbox yoke and bigger universal joints.

Australian R31 diffs are pretty weak. I drove on mine for about a year with the Neo and the gears inside the diff centre pretty much collapsed. Had that rebuilt to stock Silhouette LSD specs with a Pintara 4.11 crownwheel & pinion and now 2 years later it's groaning and whining like it's the original diff. I don't drift the car, do burnouts or drive like an idiot, it's just weak. The fix is a Kaaz LSD centre. $1500 last time I heard. Have fun trying to break it after that

I suppose if you drive like an idiot then fairly quickly you'll have to replace the diff, then either the gearbox or the universal joints.

*I've heard of KKR turbo's being a decent/cheap upgrade; are they reliable and substantial in comparison to power output/price wise on other turbo types?

Have no experience with KKRs. You get what you pay for I guess?

Edited January 7, 2009 by Bluprint

[JonnoHR31]

is yours an rb25?

yer?

the diff's start making lots of noise but they dont break easily, just whine louder and louder.

gearbox all depends on how you drive, can kill it 100kw if your an idiot, but probably a good idea to get a 33 turbo box, 34 is pull type clutch which makes it harder

as for the tailshaft with a 25 box, easiest way is to get a shop to put a vlt/33 yoke on your standard tailshaft, or if you wanna spend a bit more get a custom single piece made up

[fr05ty]

Thanks for u'r input guys (especially to bluprint),

I will be considering changing the box and diff...after they blow I guess ;-p.

[R31Nismoid]

rb20 box wont last

i killed a perfectly good RB20 box with 270rwkw/RB25, i did about 15 passes, on 225 tyres so it wasnt as if i was launching on sticky rubber.

if you plan to use the power, plan to change the box and you might as well do it while the motor is out

[discopotato03]

As for Nissan live rear axles I can add a bit .

From memory one of the larger so called luxo barges like 260C or 280C had a Japanese H190 differential and those are reasonably durable - compared to a Borg warner 8. something "Ford Diff" . Damn local content in Nissans of that era .

LSDs are a bit exy though some JDM Nissans had a production plate LSD in them .

If you can find one and are keen enough to fit it the JDM semi trailing arm IRS gets you into a long nose R200 and is a step up from a live rear end but not as good as multi link IRS like R32/33/34s have .

You are at a cross roads here where you can spend a lot and risk painting yourself into a corner with an R31 .

Their limitations are 4 stud hubs (limited bolt on brake options) , macpherson front struts and at best semi trailing arm IRS . They are also heavy cars . The Aus spec interior is a bit plasticy in some peoples opinions .

Now your call but you get a quantam leap (quote SK) in technology going from R30/31 to R32 and beyond and I'd think you could probably find a clean R32 GTST for not too much money in the scheme of things .

You could plonk the RB25 in an R32 which already has 5 stud hubs , far better suspension/brakes/std R200 and is wired and plumbed for an RB twin cam . Add the R33/34 turbo RWD gearbox and have a pretty good package .

I built a Bluebird with the whole DR30 driveline and was not happy with it , I then had a DR30 and was not happy with that either - just added dinosaur steering into a longer better trimed package .

Your call , cheers A .