Jump to content
SAU Community

Rb25det With A "real" .82 A/r Gt3076r

Lithium

By Lithium,
in Engines & Forced Induction

 Share

Recommended Posts

huddy Veteran

huddy

Posted
Posted (edited)

yes RB24DET

Tomei pistons, GTR crank, rods etc...

hence with the way rb20's and rb25's flow gasses differently, i'm after some sort of assistance in trying to figure out best setup for my car. also assumin my 20 based engine will rev more, also after opinions, that is why i would like peoples opinions on my questions.

thanks for the links, i have spent time reading them, and in mafia's thread he is relating to RB25... but i will have another look at them

thanks

-Matt

Edited by huddy
  • Replies 56
  • Created
  • Last Reply

Top Posters In This Topic

Popular Days

Top Posters In This Topic

Popular Days

Cubes Grand Master

Cubes

Posted
Posted

If you stroke out the bottom end and leave the head untouched it will make its peak power earlier in the rpm and nose over earlier. in other words rev less.

Your going to have to get the head breathing better with a set of cams.

Dale FZ1 Veteran

Dale FZ1

Posted
Posted
Stock ECU that dip is normal, its the rich/retard kicking in most of the time... plus average mapping i would suspect.

PowerFC/Tune = gone.

I have to say that I've seen that mid range dip more than a few times. Ignoring any stock ECU that's going into rich+retard, it's more with unopened engines but uprated turbo specs and with a new ECU. I see that Lithium has a Link setup.

Which area of mapping should be used first to attack the problem? ie fuel or ignition? If it is fuel (and assuming that the AFR in that area is a "nice" repeatable value, should it be leaned off?

Simon-S14 Grand Master

Simon-S14

Posted
Posted

i too have seen that dip in plenty of RB25 dyno's... and thats with aftermarket ECU's, stock bottom ends and supporting gear with decent turbo's... any idea what the cause is there??

Huddy: the prob with making 300 rwkw with your set us is you have the bottom end support to do it... but the head is still an rb20 head... it just wont flow the air to support the big numbers... no matter what turbo you run.

Lithium Grand Master

Lithium

Posted
  • Author
Posted
I have to say that I've seen that mid range dip more than a few times. Ignoring any stock ECU that's going into rich+retard, it's more with unopened engines but uprated turbo specs and with a new ECU. I see that Lithium has a Link setup.

Which area of mapping should be used first to attack the problem? ie fuel or ignition? If it is fuel (and assuming that the AFR in that area is a "nice" repeatable value, should it be leaned off?

The fuelling on mine was nice and consistant, and the timing is all fairly sensible though we / he didn't play with the VCT point. The tuner is a very accomplished tuner, he tunes some NZ GTR who went over to Australia last year and turned a few heads.

1400r Veteran

1400r

Posted
Posted (edited)
i too have seen that dip in plenty of RB25 dyno's... and thats with aftermarket ECU's, stock bottom ends and supporting gear with decent turbo's... any idea what the cause is there??

Huddy: the prob with making 300 rwkw with your set us is you have the bottom end support to do it... but the head is still an rb20 head... it just wont flow the air to support the big numbers... no matter what turbo you run.

time to buy Blinkies head then

Mach Go Go style 405rwkw on low boost

rb20 head

http://www.geocities.jp/akfw1_rbx32/free/car.html

rb20 head 3lt bottomend 600ps hmmm list it as a 25 head in specs?

http://www.eonet.ne.jp/~7thmeister/2003914zen.htm

2.2lt rb20 272 cams 500 ps http://www.dragster.st/dragster/mizo/mizo.html

Edited by 1400r
R31Nismoid Grand Master

R31Nismoid

Posted
Posted
I have to say that I've seen that mid range dip more than a few times. Ignoring any stock ECU that's going into rich+retard, it's more with unopened engines but uprated turbo specs and with a new ECU. I see that Lithium has a Link setup.

Which area of mapping should be used first to attack the problem? ie fuel or ignition? If it is fuel (and assuming that the AFR in that area is a "nice" repeatable value, should it be leaned off?

Dunno, i didnt tune the car, i leave that to my tuner/builder.

But there must be something people arent looking at/changing as no car i know of that gets tuned has a problem and a few RB25s have been done there.

I dont think its bottom end related as that largely has no effect IMO.

Dale FZ1 Veteran

Dale FZ1

Posted
Posted

I guess it comes down to what the budget will stand, and whether you can feel a difference on-road.

VCT change point on a mechanically standard engine can have marked impact, but usually in a negative way if you alter it a long way from standard. But + or - a couple hundred rpm might be worth a try.

I've seen using an adjustable cam gear also work well in terms of smoothing the torque curve - but no actual increase in my case. Just minimised the peaks/troughs so it was evident the engine was running in a happy mechanical zone.

With that slightly saw-tooth appearance, I'd think that the ignition map might be worth a look. If it was mapped to the best output without knock, some columns will take less timing, meaning that as you advance through the rpm range the map is not moving smoothly through a curve. Can give the up/down appearance I'd commented on.

None of this is a smart-arse commentary, just looking to see how the end result came about and whether it's possible to improve with comparatively little effort or $$. I like to know the how/why rather than just leave it to a tuner.

The fuelling on mine was nice and consistant, and the timing is all fairly sensible though we / he didn't play with the VCT point.
series2r33 Collaborator

series2r33

Posted
Posted

Shit hey, i had just ordered the GT3082r with the .63 the day before i posted my question. Now i read u guys reckon it'll be crap and i've got it! I hope your all wrong lol. I'll post the dyno results when i get it all fixed up.

SilverECR33 Veteran

SilverECR33

Posted
Posted (edited)
I have to say that I've seen that mid range dip more than a few times. Ignoring any stock ECU that's going into rich+retard, it's more with unopened engines but uprated turbo specs and with a new ECU. I see that Lithium has a Link setup.

woudlnt this have something to do with the Profiles on the cams?

Edited by silverbulletR33
Dale FZ1 Veteran

Dale FZ1

Posted
Posted

I'd say probably, yes.

He should be in a position to work with what he's got though. I posted a few ideas on #51.

Changing to non-standard cams may well just move the characteristic (I won't call it a problem) around and upwards. The saw tooth torque curve I would think is the bigger issue to address. And there are things that can be done that cost more in the way of time than anything else.

Again though - Lithium has got a generally good result. I'd just like to see something done to make it "happy".

woudlnt this have something to do with the Profiles on the cams?
Lithium Grand Master

Lithium

Posted
  • Author
Posted
Changing to non-standard cams may well just move the characteristic (I won't call it a problem) around and upwards. The saw tooth torque curve I would think is the bigger issue to address. And there are things that can be done that cost more in the way of time than anything else.

Again though - Lithium has got a generally good result. I'd just like to see something done to make it "happy".

Yeah me too. For what its worth, you really can't feel any of it on the road. All passengers etc perceive it as just building up and having strong power all the way through, the only "weakness" is that the thing doesn't go straight to 15psi and hold it. If it did that it'd be so much more solid, nonetheless there are definitely gains to be had by removing that slight dip.

The plan is next year to go to a built motor etc and then give it some boost and revs, this tune was just to get it safe and fun to drive - not to hunt every last hp :thumbsup: For what its worth, I gave it a run on a rolling road dyno for fun and the dip wasn't anywhere near as extreme.

  • 2 weeks later...
huddy Veteran

huddy

Posted
Posted (edited)

did you guys get custom lines made up to suit? just got my 3076r... :)

LITHIUM

-i cant see pics of your dump, can you please post up, mine phsically looks the same as yours with the antisurge front, and same stye rear exhaust housing.

-how did it go for standard intercooler piping to the top of the turbo? (well maybe not standard, as mine had previously been modded for the hks turbo...)

-was there any difference noticably with the change in manifold? (even noise??)

cheers

-Matt

Edited by huddy

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • hoodedreeper
      Chris' R34 GTT Series 2

      By hoodedreeper · Posted

      Sorry for resurrecting an oldish thread Not much has happened in the past year since the last update. The car did another 1000 miles or so and failed the MOT for the first time in October (failed on tyres which had been advised for a couple of years) In October the car got put up for sale and was removed in November due to no interest, being so close to christmas it was to be expected. The roads were dry in February so I decided to tax it early and get the new tyres fitted.   Fast forward to April, I got someone in to give the car a good clean after sitting for the winter.                                 The car got re-advertised and today (Saturday 3rd May) the car sold. The new owner is planning a GTR conversion at some point and a respray in the same pearl white. It's bitter sweet, it's a shame to have the car sit there for half the year and then only do 1000 miles. The kids are growing too quick and space in the back is getting limited. It's been a great 6.5 years of ownership
    • MBS206
      Rb26/30 build

      By MBS206 · Posted

      And if you want more power, more reliably, and cheaper, go get the Aussie RB... The 4L Barra and put that in instead.
    • MBS206
      Nismo rear spats

      By MBS206 · Posted

      No cats will keep discolouring the rear bar. Sends white paint a weird yellow stain. Cut and polish normally gets it out, but you'll be doing that every fortnight I found.
    • Butters
      Rb26/30 build

      By Butters · Posted

      Both heads will be equally reliable or unreliable depending on what you do to them.  Stock the RB26 head will flow more. You have access to the stock intake ITB manifold on the RB26 cheaply which flows really well(1000hp+).   Arguably more aftermarket support for RB26, though in Aus we love our RB30 SOHC heads too.    The only downsides to the RB26 head is if you have a VL commodore and want to keep the SOHC look.  Where you may have an issue is drilling out the rb30 block for the bigger head studs but if you are building a big power motor you'd probably put bigger studs on the SOHC head too.  This is just about finding a good machine shop, sometimes easier said than done.  RB30 head worked can make big power just like a Rb26 head, so really it actually more comes down to what your preference is for your car.  People now even making billet versions of both.
    • GTSBoy
      Rb26/30 build

      By GTSBoy · Posted

      2630s work perfectly well. There is something to be said for just using the 30 head, as it saves all the pain of the conversion, still makes tons of power, still sounds cool, etc etc. 2630 will obviously make more power again, but the differences are not stupidly big. It really depends on whether you're racing for sheep stations or not. If it's dead serious, then it's a 26 head. If it's just for fun, it could go either way. But the 26 head and the effort to get it set up, etc etc, is part of the fun.
×
×
  • Create New...