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Old 6th July 2017, 09:43 AM   #1 (permalink)
GTB is unaware they can edit their status
GTR.co.uk seasoned Member
Join Date: Aug 2006
Location: Somerset, England
Posts: 27
RB25DET headgasket and fuel pressure questions

I'm starting to order parts for my project but have a couple of questions.

Engine is an RB25DET and I plan on keeping stock internals at the moment.
  • I will be running a Borg Warner EFR7064 0.83 A/R T3 undivided, on the standard manifold with a turbosmart dual port wastegate actuator.
  • I will be converting to top feed rail and running ID725 injectors
  • Engine will be controlled by a Haltech Elite 2500

I plan on having it tuned up t 19-20psi, but will see how it goes once I have it mapped.

My main questions at the moment related to the above modifications are, with that turbo and possible boost pressure, will standard Nissan headgasket be okay? I was thinking of pulling the head off and installing ARP head studs and fitting a new genuine Nissan headgasket.
I know for a metal headgasket I would need to have both head and block skimmed to ensure they were perfectly flat in order for it to seal, and at the moment I don't want to get involved in stripping the bottom end as I know I would get carried away, and for now this is something I would like to leave for the future.
While the head is off I was going to have it stripped/inspected and cleaned, and have valve stem oil seals replaced, is there anything else worth doing to the head while it is off?

With the ID725 injectors is states the flow rate at being 725cc at 3.0bar, am I correct in thinking 3bar is standard RB25DET fuel pressure? In this case is the standard fuel pressure regulator going to be okay, or will I still need to purchase an adjustable fuel pressure reg?

Lastly (for now) who is good for mapping the haltech ECUs? I am in Somerset, but am happy to take the car anywhere for the right tuner.


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Old 7th July 2017, 04:08 AM   #2 (permalink)
Lith is lurking
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Join Date: Oct 2006
Location: Wellington, NZ
Cars owned: R33 GTS25t
Posts: 2,458
All depends on the fuel, the quality of tune etc.. 19-20psi is really starting to get up there for a stock HG/displacement RB25 BUT plenty of people have run that for ages with no issues, I ran my stock RB25 at around 17-18psi for years and did ~100,000km with a GT3076R (fairly comparable size) on stock HG and that engine is still running fine

I tuned an RB25 a couple of weeks ago with an EFR7064 with the open housing on stock exhaust manifold and it goes very nicely, we ran into issues with the medium actuator supplied so it couldn't hold >1bar at the high end of the rev range so the Turbosmart dual port actuator is a great idea. It's running stock cams etc, the owner was going to just do a HG but discovered his ring lands were cracked so ended up building the motor - though it's all stock head stuff still... albeit reconditioned probably similar to you.

Cams didn't seem necessary, however I'd consider going to a different trigger setup to stock if you're running that much boost on a stock motor - you want the most reliable triggering possible, but I'm a stickler like that. No idea on tuners in the UK, I'm from NZ.

Pretty sure the stock FP is around 3bar.
'97 Skyline GTS25t
12.6 @ 112mph
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Old 7th July 2017, 04:38 PM   #3 (permalink)
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Thanks for the reply Lith,

I had been following your posts on the SAU Efr thread, and that was what made me choose the turbo smart actuator as an upgrade, so thanks for posting all the information as at least I can sort a possible problem before it gives me trouble. I look forward to seeing how it goes with the car you are mapping, as it will be towards the end of next year when mine should be complete, so will be nice to see your updates in the thread.

Boost wise, I am happy to keep it at 17-18 instead of 19-20 if it means it's going to be safer in the long run. I will see how it goes when I get to the mapping stage.

Would the AEM replacement CAS trigger wheel be good enough upgrade, or is a complete replacement trigger setup required?
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