Jump to content
SAU Community

Small Flat Spot On Boost Ramp Up And Fluctuating 2-3psi?

RaZ_TuRbO

By RaZ_TuRbO,
in Engines & Forced Induction

 Share

Recommended Posts

RaZ_TuRbO Community Regular

RaZ_TuRbO

Posted
Posted

Since getting my car tuned iv noticed i get a small flat spot immediatly after changin gears for only second, it mostly happens with big revs(7000rpm+) between 2nd and 3rd mostly. Also full boost in 4th gear and sometimes 3rd (18 psi) seems to fluctuate and the boost needle goes crazy from like 16 to 18 and it sounds like im slightly taking my foot off and on the gas making a chuffing flutter noise.

the car is a rb20det 306rwhp with safc management standard afm, but with everything else supporting. driving normal and below 15 psi its great and smooth.

Ideas? experiances?..

Cheers

R34GTFOUR Mentor

R34GTFOUR

Posted
Posted

are you running a bov?

that chuffing/flutter noise is compressor surge, which slows the compressor speed quite alot during gear changes or when you back off on the accelerator, which can cause lag inbetween gear changes.

what boost gauge are you reading off? also what turbo setup are you running?

also that standard airfow meter would of been maxed out ages ago, my bet its at 5volts at 4500-5000rpm, so get a z32 and get it retuned

RaZ_TuRbO Community Regular

RaZ_TuRbO

Posted
  • Author
Posted (edited)

I know what compressor surge is, its not when i back off the throttle its on throttle up hills, under load.. which it could be compressor surge, just different. So do you think its my afm causing the issues?..i think its compressor surge...as its fine when i give it enough revs.

Its a hiflow rb25 set-up by the way, im reading off the boost gauge i installed, its closest to the inlet i could get. Im running the std bov.

Edited by RaZ_TuRbO
  • 8 months later...

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

    • GTSBoy
      R34 gtt rb25det neo timing belt kit

      By GTSBoy · Posted

      Just don't use ChatGPT or any other artificial stupidity for the equivalent of googling. Their demonstrated inability to discriminate reality from hallucination should be enough to make them totally untrusted. LLMs don't know anything and cannot think to even the smallest extent. They are just predictors of the next word, and that should never be confused with capability.
    • GTSBoy
      Another little story of weird shit happening

      By GTSBoy · Posted

      I think, given the usage model described in the OP, I'd never ever experience the wonders of the 400kW upgrade. What I really need is boost from 2000rpm and probably no more than 260-270rwkW. But I suspect that the highflow is not actually the turbo for that purpose, so I may in fact need to get a G25 or 30 or something right sized and very spooly. We shall see after it is tuned. I've had to back the boost and boost ramp off to stop the thing from pinging since the highflow went on, so I've been almost living the NA life for 9 months now! Injectors are recently in hand. AFM is in hand. Dyno is fixed. Just need to clear a queue of f**king Supras out of the way (and probably fit my new gearbox). So....some time this year? Lol.
    • GTSBoy
      braided lines for the turbos

      By GTSBoy · Posted

      For what I gather is a Sunday/summer car....braided is fine. You're not going to be left without a vehicle and you have plenty of time for inspection/maintenance. Oof. I wouldn't use them that way. They can probably handle the temperature** but the internal corrugations means that their flow characteristics are a bit shit. Lots of extra friction and pressure loss. Makes them flow like the next pipe size down. ** They are stainless, and the stainless can usually be at least something like 304L, which is pretty good at higher temperatures (unlike 316L, which I would use for a wrt/corrosive environment, but not a particularly hot environment). But the welding needs to be top notch. And even then, because you usually need at least one cone-seat end on them (because you can twist the hose and do up both ends at the same time unless one of them is a union) they can be prone to coming loose with heat cycles.
    • sunsetR33
      braided lines for the turbos

      By sunsetR33 · Posted

      I don't have the OEM oil feed lines though and the turbo-wraparound line is torn, only has water. My plan is to get replacements for these and just connect a braided line to there. And make sure it's leak free. Hoses like these are also sometimes used to connect external wastegates, so for an EGR I think you're good using them.
    • sunsetR33
      Unpeeling the Orange

      By sunsetR33 · Posted

      Alright I understand. The most likely case is probably gonna be that I just keep the OEM unit in the car as long as it works.
×
×
  • Create New...