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Advice Needed - Rb25det Neo Vs Rb25/30

QRI05E

By QRI05E,
in Engines & Forced Induction

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RB25DET Neo Vs RB25/30  

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QRI05E Mentor

QRI05E

Posted
Posted

Hey Guys,

My 2002 R34 GTT shoud be arriving in a couple of weeks and just planning my build so I need some advice.

I'm contemplating either one of two options:

Option 1: RB25/30 Rebuilt + TO4Z = 400+rw/kw

Option 2: RB25DET Rebuilt + GT3540 = 350+rw/kw

However I have a couple of issues to address:

1. It wil be a drive in/drive out build therefore labour will be a killer (RB25/30 will be very fiddly to fit)

2. Will I have trouble engineering the car with the RB25/30?

I spoke to Jim from DART and he recommended to build the RB25 as its a street car and that I will be very happy with 350rw/kw and not have the hassles of RTA compliance issues. However, CRD recmmended the RB25/30 as there wont be much difference in the build cost however as a dollar value, will net much more power and torque than the RB25.

I am so confused please advise!

Regards,

Sarkis

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NYTSKY Grand Master

NYTSKY

Posted
Posted

RB25FTW :D

There isnt much of a price difference when building a 25 or a 25/30.

The only fiddly part about the 25/30 is drilling a hole in the block and plumbing up the VCT. If you have done it before its not hard at all.

It all comes down to preference in the end.

Anyone can make tough 30s, tough RB25s are the new black :)

Ill take you for a spin after my car gets tuned.

QRI05E Mentor

QRI05E

Posted
  • Author
Posted
RB25FTW :)

There isnt much of a price difference when building a 25 or a 25/30.

The only fiddly part about the 25/30 is drilling a hole in the block and plumbing up the VCT. If you have done it before its not hard at all.

It all comes down to preference in the end.

Anyone can make tough 30s, tough RB25s are the new black ;)

Ill take you for a spin after my car gets tuned.

Hahah I promise Dave, your car is the ONLY thing making me consider an RB25DET build ;) Can wait to see yours after the tune!

However being a daily driver it wont be tuned on E85 :D so im not expecting more power than yours. However the RB25/30 will make big power on pump fuel.

NYTSKY Grand Master

NYTSKY

Posted
Posted

If you had a T04Z on both engines they will make roughly the same power.

Its the way and where that power is made that is the key.

For a very responsive 25/30 i would consider the new GT3788.

QRI05E Mentor

QRI05E

Posted
  • Author
Posted

Yea thats what Jim from DART said... That they will make the same top end if setup right however the RB25 will need more boost and the RB25/30 will be less lag with more torque.

Dave what power would should a RB25DET + GT35R make on PULP?

MBS206 Grand Master

MBS206

Posted
Posted

For a street car... I'd be going the 25/30 but actually probably looking at the 3540 or a touch smaller.

On the street, for a very tractable car, you want and need response.

Also, in the comparison of a 25DET VS 25/30DET, think about the fact, they may both make 400KW, but the 25/30 will do it roughly 1000RPM earlier... Meaning there is way more torque being put down, which is what makes you go fast.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
lol 400kw street car.....

save yourself some dollars and just get a hiflow and shoot for 250kw will be more fun than a 400kw lag/no traction monster on the street.

but if you got $$ to burn rb30 for sure!

I was going to say a similar thing. 400rwkw in a RWD street car is I’m afraid, nonsense.

However I wouldn’t say 250rwkw :D

QRI05E - have you even seen how pointless 350rwkw+ is in a RWD car on the street???

I was driving around with a RB25/370rwkw on the street for a while, utterly pointless.

You had to constantly be thinking about when it was going to break traction - as that is all that the car did. Would just turn tyres as opposed to moving anywhere.

The first 3 gears also serve no purpose so you have to be over 150km/h before you can even hope to have some use of the throttle without frying the tyres.

My advice - GT3076, make your 300-330rwkw, put it on a 25/30 like Al has done. A nice setup, responsive and most importantly, controllable & progressive.

Less in terms of power, is actually more in terms of how fast it will be.

And a NEO25/30 will be even nicer again, really nice low end.

One of the reasons i have a RB26, with around 300-330rwkw max - once it's done.

The 280-330rwkw power range is the best compromise between having solid amount of power to make you giggle as it will turn tyres if you want, while actually still being a solidly fast street car because it's controllable at the same time.

So what turbo am I looking at for 380+rw/kw?

TO4Z with a 0.81 Ex?

A GT35 will do 370-400rwkw on PULP on a decent motor.

A T04Z is 400-450rwkw on PULP, again with a decent build.

MBS206 Grand Master

MBS206

Posted
Posted
I was going to say a similar thing. 400rwkw in a RWD street car is I’m afraid, nonsense.

However I wouldn’t say 250rwkw :D

QRI05E - have you even seen how pointless 350rwkw+ is in a RWD car on the street???

I was driving around with a RB25/370rwkw on the street for a while, utterly pointless.

You had to constantly be thinking about when it was going to break traction - as that is all that the car did. Would just turn tyres as opposed to moving anywhere.

The first 3 gears also serve no purpose so you have to be over 150km/h before you can even hope to have some use of the throttle without frying the tyres.

My advice - GT3076, make your 300-330rwkw, put it on a 25/30 like Al has done. A nice setup, responsive and most importantly, controllable & progressive.

Less in terms of power, is actually more in terms of how fast it will be.

And a NEO25/30 will be even nicer again, really nice low end.

One of the reasons i have a RB26, with around 300-330rwkw max - once it's done.

The 280-330rwkw power range is the best compromise between having solid amount of power to make you giggle as it will turn tyres if you want, while actually still being a solidly fast street car because it's controllable at the same time.

A GT35 will do 370-400rwkw on PULP on a decent motor.

A T04Z is 400-450rwkw on PULP, again with a decent build.

I run a "250RWKW" RB25/30DET... It turns the tyres at 130KM/H in 3rd...

No, it's not a nice power delivery, nothing below 3500RPM, full boost at like 4000 - 4500RPM... Turning tyres from 4000RPM onwards...

Power isn't the main thing to worry about (Power from a 25DET isn't really comparable to that of a 30DET as they make the same power, lower revs, more torque)

I believe a couple of the guys are running 25/30s with stock 25 turbos on them and are able to turn the tyres in 2nd/3rd with just a prod of the throttle too... The torque from a well setup 25/30 is just unbelievable...

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
I run a "250RWKW" RB25/30DET... It turns the tyres at 130KM/H in 3rd...

No, it's not a nice power delivery, nothing below 3500RPM, full boost at like 4000 - 4500RPM... Turning tyres from 4000RPM onwards...

Power isn't the main thing to worry about (Power from a 25DET isn't really comparable to that of a 30DET as they make the same power, lower revs, more torque)

I believe a couple of the guys are running 25/30s with stock 25 turbos on them and are able to turn the tyres in 2nd/3rd with just a prod of the throttle too... The torque from a well setup 25/30 is just unbelievable...

What is your traction setup? (diff/tyres/suspension)

Even someone with a RB25 and a stock turbo can get their tyres to turn coming onto boost if they have a poor setup and only 190rwkw.

See it all too often unfortunately that people sped 10k on power, and only $1000 on tyres and some silly hard jap suspension.

I'm also assuming the OP will make a decent turbo choice, one that is progressive rather than older style 'light switch'.

MBS206 Grand Master

MBS206

Posted
Posted
What is your traction setup? (diff/tyres/suspension)

Even someone with a RB25 and a stock turbo can get their tyres to turn coming onto boost if they have a poor setup and only 190rwkw.

See it all too often unfortunately that people sped 10k on power, and only $1000 on tyres and some silly hard jap suspension.

I'm also assuming the OP will make a decent turbo choice, one that is progressive rather than older style 'light switch'.

Semi slicks (A048), on stock suspension (Squats down VERY well). (This is on the track too frying in 3rd after warming the tyres up)

The main killer, is as you said, the "Light switch" delivery. It is very much light switch, and I'd like to head down to something like a 3076. (Turbo is quite large and laggy... Won't really "come alive" till I'm pushing 24+ PSi, only on 14 atm)

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Well that kinda answers your own issues doesn't it? :D

Non progressive power delivery, turbo not suited for the application (im assuming at least a 700hp by the sound of it), which is what i said initially would not work well anyway...

bubba Grand Master

bubba

Posted
Posted
I believe a couple of the guys are running 25/30s with stock 25 turbos on them and are able to turn the tyres in 2nd/3rd with just a prod of the throttle too... The torque from a well setup 25/30 is just unbelievable...

Maybe as Nismoid said, with a poor suspension/tyre setup.

My 32 has bulk traction and that's with -2deg camber on the back, rolling on boost in 2nd and 3rd wouldn't light up but a 3000rpm clutch drop in 2nd from standstill would light the hell up.

I'm hoping with the GT35R it lights up rolling on in 4th :)

TiTAN Grand Master

TiTAN

Posted
Posted

bubba, you will do 3rd easy but i haven't had troubles with 4th gear so far even with some nitromethane additive in the WMI (good for 30-50hp apparently, seat of the pants dyno says it makes a noticeable power gain assuming the 50hp boost thats 490hp @ the rears)

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