Jump to content
SAU Community

How Do I Raise The C/r To 9.0:1 ?

Turbo_Knuff

By Turbo_Knuff,
in Engines & Forced Induction

 Share

Recommended Posts

The Dan Grand Master

The Dan

Posted
Posted

WTF? RB25DET's are factory 9:1 comp ratio

You are gaining nothing by putting RB26 gear in your RB25 block. Unless you have a spare crank lying around that you need to use. The stroke is slightly more but the extra 100cc is not going to do FA for torque or power.

Turbo_Knuff Enthusiast

Turbo_Knuff

Posted
  • Author
Posted

The reason I will use rb26 crank is because I have the block and enginehead but no crank,rods or pistons. So instead of buy an rb25 crank and then mount a crank collar on it would cost almost as much as an longnose rb26 crank. If 100cc doesn´t do anything then I wonder why so many high performance gt-rs from japan is stroked to 2,7?

Almost every aftermarkets pistons for rb26 is 8.5:1 but If the rb25 head is smaller cc maybe it is possible to get 9,0:1 then :)

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

^ umm but how do you have a RB25 now, without any innards?

It's not even 100c, its like 60 or something.

9:1 will be fine, pretty standard for anyone rebuilding in this day an age considering fuel advancements over the past 10 years+

Also just use GTR rods, they are fine for over 400rwkw and less than half the price of eagles

Turbo_Knuff Enthusiast

Turbo_Knuff

Posted
  • Author
Posted
^ umm but how do you have a RB25 now, without any innards?

It's not even 100c, its like 60 or something.

9:1 will be fine, pretty standard for anyone rebuilding in this day an age considering fuel advancements over the past 10 years+

Also just use GTR rods, they are fine for over 400rwkw and less than half the price of eagles

I bought a head cheap for about 1 year ago. The I found a block now to. So I will use them to build a complete engine of. A std rb25det cost about 2300Aud here and Im gonna change so much anyway so I think this would be the best way to go :)

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

You can buy a RB25 bottom end for next to nothing my friend... the head is the most expensive part.

Then just GTR rods ontop of that and you are set. Would be less than $1000 AUD easily. Not sure there you get 2300 from when you already have the top end :)

Beats buying a new RB26 crank IMO, unless you know the RB26 crank you are getting is fine but the cost to check, and if it needs repairing then its almost neutral.

Turbo_Knuff Enthusiast

Turbo_Knuff

Posted
  • Author
Posted (edited)
You can buy a RB25 bottom end for next to nothing my friend... the head is the most expensive part.

Then just GTR rods ontop of that and you are set. Would be less than $1000 AUD easily. Not sure there you get 2300 from when you already have the top end :)

Beats buying a new RB26 crank IMO, unless you know the RB26 crank you are getting is fine but the cost to check, and if it needs repairing then its almost neutral.

Im from Sweden and It´s alot more expensive with parts here. I have searched for a while for a bottom but didn´t find someting we don´t have so many parts here. So I had to order the block from England. I want the long oilpumpdrive to so I think the rb26 crank would be fine.

Edited by Turbo_Knuff
The Dan Grand Master

The Dan

Posted
Posted
Im from Sweden and It´s alot more expensive with parts here. I have searched for a while for a bottom but didn´t find someting we don´t have so many parts here. So I had to order the block from England. I want the long oilpumpdrive to so I think the rb26 crank would be fine.

The collar can be purchased and fitted for about $200 total. Being in Sweden might make things hard but there's always international shipping

James_03 Mentor

James_03

Posted
Posted (edited)

Don't think that getting a second hand rb26 long nose crank is the best solution, because IMO it's not.

Often times on a second hand crank you will see where the oil pump drive has rounded away on the edges of the flat even on the long nose. A collar with international shipping will be under $100AU easily, and then you know the drive is 100% OK after fitting.

Edited by James_03
The Dan Grand Master

The Dan

Posted
Posted
DO NOT shave the head more than just a surface because it'll stuff up your cam timing and possibly make the timing belt go slack.

Just order some custom 9.2:1 pistons. You won't be disappointed!

Sorry but that's the biggest load of shit I have ever heard. You aren't going to take enough off a cylinder head to have that much of an effect on the timing belt.

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

    • sunsetR33
      Unpeeling the Orange

      By sunsetR33 · Posted

      Update 3: Hi all It's been a while. Quite a lot of things happened in the meantime, among other things the car is (almost) back together and ready to be started again. Things that I fixed or changed: Full turbo removal, fitting back the OEM turbo oil hardlines. Had to do quite a bit of research and parts shopping to get every last piece that I need and make it work with the GT2860 turbos, but it does work and is not hard to do. Proves that the previous owner(s) just did not want to. While I was there I set the preload for the wastegates to 0,9bar to hopefully make it easier for the tuner to hit the 370hp I need for the legal inspections that will follow later on. Boost can always go up if necessary. Fitted a AN10 line from the catch can to the intake hose to make the catchcan and hopefully the cam covers a slight vacuum to have less restrictive oil returns from the head and not have mud build up as harshly in the lines and catch can. Removed the entire front interior just shy of the dashboard itself to clean up some of the absolutely horrendous wiring, (hopefully) fix the bumpy tacho and put in LED bulbs while I was there. Also put in bulbs where there was none before, like the airbag one. I also used that chance to remove the LED rpm gauge on the steering column, which was also wired in absolute horror show fashion. Moved the 4in1 Prosport gauge from sitting in front of the OEM oil pressure gauge to the center console vents, I used a 3D printed vent piece to hold that gauge there. The HKB steering wheel boss was likely on incorrectly as I sometimes noticed the indicator reset being uneven for left vs. right. In the meantime also installed an airbag delete resistor, as one should. Installed Cube Speed premium short shifter. Feels pretty nice, hope it'll work great too when I actually get to drive. Also put on a fancy Dragon Ball shift knob, cause why not. My buddy was kind enough to weld the rust hole in the back, it was basically rusted through in the lowermost corner of the passenger side trunk area where the wheel arch, trunk panel and rear quarter all meet. Obviously there is still a lot of crustiness in various areas but as long as it's not rusted out I'll just treat and isolate the corrosion and pretend it's not there. Also had to put down a new ground wire for the rear subframe as the original one was BARELY there. Probably a bit controversial depending on who you ask about this... but I ended up just covering the crack in the side of the engine block, the one above the oil feed, with JB Weld. I used a generous amount and roughed up the whole area with a Dremel before, so I hope this will hold the coolant where it should be for the foreseeable future. Did a cam cover gasket job as the half moons were a bit leaky, and there too one could see the people who worked on this car before me were absolute tools. The same half moons were probably used like 3 times without even cleaning the old RTV off. Dremeled out the inside of the flange where the turbine housing mates onto the exhaust manifolds so the diameter matches, as the OEM exhaust manifolds are even narrower than the turbine housings as we all know. Even if this doesn't do much, I had them out anyways, so can't harm. Ideally one would port-match both the turbo and the manifold to the gasket size but I really didn't feel up to disassembling the turbine housings. Wrapped turbo outlet dumps in heat wrap band. Will do the frontpipe again as well as now the oil leak which promted me to tear apart half the engine in the first place is hopefully fixed. Fitted an ATI super damper to get rid of the worn old harmonic balancer. Surely one of the easiest and most worth to do mods. But torquing that ARP bolt to spec was a bitch without being able to lock the flywheel. Did some minor adjustments in the ECU tables to change some things I didn't like, like the launch control that was ALWAYS active. Treated rusty spots and surface corrosion on places I could get to and on many spots under the car, not pretty or ideal but good enough for now. Removed the N1 rear spats and the carbon surrounding for the tailpipe to put them back on with new adhesive as the old one was lifting in many spots, not pretty. Took out the passenger rear lamp housing... what do you know. Amateur work screwed me again here as they were glued in hard and removing it took a lot of force, so I broke one of the housing bolts off. And when removing the adhesive from the chassis the paint came right off too. Thankfully all the damaged area won't be visible later, but whoever did the very limited bodywork on this car needs to have their limbs chopped off piece by piece.   Quite a list if I do say so myself, but a lot of time was spent just discovering new shit that is wrong with the car and finding a solution or parts to fix it. My last problem that I now have the headache of dealing with is that the exhaust studs on the turbo outlets are M10x1.25 threaded, but the previous owner already put on regular M10 nuts so the threads are... weird. I only found this out the hard way. So now I will just try if I can in any way fit the front pipe regardless, if not I'll have to redo the studs with the turbos installed. Lesson learned for the future: Redo ALL studs you put your hands on, especially if they are old and the previous owners were inept maniacs. Thanks for reading if you did, will update when the engine runs again. Hope nothing breaks or leaks and I can do a test drive.
    • Kapr
      What brakes on R34 GTT(Europe)

      By Kapr · Posted

      No those pads are DBA too  but they have colors too. I look at the and imo the green "street" are the best.
    • wizlb
      Who has a Infiniti Q60, Q50 (V37)?

      By wizlb · Posted

      I’m not sure what happened I told them about sonic tunes free OTS tune and the next the I know .. I was booted..   To funny 
    • Kinkstaah
      Starting again

      By Kinkstaah · Posted

      Yea - I mean I've seen my fuel pump which is decades old and uh, while I'm not saying this with real knowledge... but I sure get the ick at using anything in the fuel system that produced the state of that pump. Many years ago I went through multiple pumps (and strainers) before I dropped the tank to clean it out with extreme violence. I'm talking the car would do maybe 50km before coming to a halt, which resulted in me cleaning out the filter with some brake cleaner and going on my way. None of my stuff ever looked like what came out of your fuel tank. I don't think I'd be happy with it unless every single component was replaced (or at least checked/cleaned/confirmed to be clean here).
    • GTSBoy
      What brakes on R34 GTT(Europe)

      By GTSBoy · Posted

      I'm not going to recommend an EBC pad. I don't like them. Just about anything else would suit me better. I've been using Intima pads for a while now.
×
×
  • Create New...