Jump to content
SAU Community

R33 Gtst Huge Flat Spot + Boost Cut

MBar93

By MBar93,
in General Maintenance

 Share

Recommended Posts

MBar93 Apprentice

MBar93

Posted
Posted

Hey everyone

Recently I've been having troubles with my 33. I bought it last year, and at the time it was running 14psi, with a high-flowed stock turbo, and nistune-chipped ecu (not a great tune, runs rather rich). Had no problems when I bought it. Other mods the car came with were splitfire coilpacks, upgraded fuel pump, turbosmart bleed valve, FMIC.

A couple of months ago I added a Greddy type s bov (car was bought without bov), which I had a few issues with setting up, because I tee'd it to the same vacuum line as the boost gauge, and it leaked boost. I turned the boost down for a while until I got around to fixing it (this car is also my daily driver so it took a while), but now I've fixed that up and both now have their own source of vacuum. I then turned the boost back up to 14psi.

Lately, when at WOT I've been hitting boost cut when it spools close to 14psi in 3rd and 4th gear, and also there seems to be a massive flat spot which is very noticeable through 2nd gear, which wasn't there before and seems to be getting progressively worse.

I've already changed the spark plugs, as I thought maybe the rich-running engine might have fouled them and caused the engine to run excessively rich, although the old spark plugs were not fouled when I took them out and the new ones haven't made any difference.

Any ideas of what else could be causing this?

Link to comment
https://www.sau.com.au/forums/topic/459633-r33-gtst-huge-flat-spot-boost-cut/
Share on other sites
MBar93 Apprentice

MBar93

Posted
  • Author
Posted

Could be the nistune falling into the knock map if it's Z32 ECU and the knock sensor mod on the board hasn't been done properly.

The ecu is r33 gtst

Are you running an airflow meter?

Block off the bov and see if it fixes it. If it does then I think the tune needs a bit of tinkering.

It's running a stock rb25 airflow meter. I'll try blocking off the bov again

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
Posted

Are you sure it's a nistune OR just a re-flashed R33 ECU?

Because R33 Nistune Type-6 boards are still in prototype and I don't believe they have gone to market yet..

Anyhow, these days you can use a RB20DET ECU with the new feature pack that controls VCT woots

  • 2 weeks later...
sonicz Rising Star

sonicz

Posted
Posted (edited)

Maybe the spark is giving out above 4000rpm. I know you have spitfires but that doesn't rule it out. Maybe you are running overly rich, fuel pressure regulator busted etc?

What spark plugs are you replacing it with? I hope you are not one of those guys that uses iridiums and gaps them down to 0.01mm. 0.8mm is low enough and use coppers.

The boost cut you are hitting because the AFM is running out of reading range. Nothing you can do about that unless you change to a bigger AFM, so just keep it under that point.

Edited by sonicz

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

    • Haggerty
      RB25DE NEO with Haltech ECU

      By Haggerty · Posted

      I guess one thing that might be wrong is the manifold pressure.  It is a constant -5.9 and never moves even under 100% throttle and load.  I would expect it to atleast go to 0 correct?  It's doing this with the OEM MAP as well as the ECU vacuum sensor. When trying to tune the base map under load the crosshairs only climb vertically with RPM, but always in the -5.9 column.
    • CF.Panda
      R34 25GT Engine Light 21

      By CF.Panda · Posted

      AHHHH gotchaa, I'll do that once I am home again. I tried doing the harness with the multimeter but it seems the car needed a jump, there was no power when it was in the "ON" position. Not sure if I should use car battery jump starter or if its because the stuff that has been disconnect the car just does send power.
    • Haggerty
      RB25DE NEO with Haltech ECU

      By Haggerty · Posted

      As far as I can tell I have everything properly set in the Haltech software for engine size, injector data, all sensors seem to be reporting proper numbers.  If I change any injector details it doesnt run right.    Changing the base map is having the biggest change in response, im not sure how people are saying it doesnt really matter.  I'm guessing under normal conditions the ECU is able to self adjust and keep everything smooth.   Right now my best performance is happening by lowering the base map just enough to where the ECU us doing short term cut of about 45% to reach the target Lambda of 14.7.  That way when I start putting load on it still has high enough fuel map to not be so lean.  After 2500 rpm I raised the base map to what would be really rich at no load, but still helps with the lean spots on load.  I figure I don't have much reason to be above 2500rpm with no load.  When watching other videos it seems their target is reached much faster than mine.  Mine takes forever to adjust and reach the target. My next few days will be spent making sure timing is good, it was running fine before doing the ECU and DBW swap, but want to verify.  I'll also probably swap in the new injectors I bought as well as a walbro 255 pump.  
    • AnimalGarage
      spot the stagea

      By AnimalGarage · Posted

      It would be different if the sealant hadn't started to peel up with gaps in the glue about ~6cm and bigger in some areas. I would much prefer not having to do the work take them off the car . However, the filler the owner put in the roof rack mount cavities has shrunk and begun to crack on the rail delete panels. I cant trust that to hold off moisture ingress especially where I live. Not only that but I have faded paint on as well as on either side of these panels, so they would need to come off to give the roofline a proper respray. My goal is to get in there and put a healthy amount of epoxy instead of panel filler/bog and potentially skin with carbon fiber. I have 2 spare rolls from an old motorcycle fairing project from a few years back and I think it'd be a nice touch on a black stag.  I've seen some threads where people replace their roof rack delete with a welded in sheet metal part. But has anyone re-worked the roof rails themselves? It seems like there is a lot of volume there to add in some threads and maybe a keyway for a quick(er) release roof rack system. Not afraid to mill something out if I have to. It would be cool to have a cross bar only setup. That way I can keep the sleek roofline that would accept a couple bolts to gain back that extra utility  3D print some snazzy covers to hide the threaded section to be thorough and keep things covered when not using the rack. 
    • GTSBoy
      R34 Handbrake light saying ON and intermittently flashing

      By GTSBoy · Posted

      Probably not. A workshop grade scantool is my go to for proper Consult interrogation. Any workshop grade tool should do it. Just go to a workshop.
×
×
  • Create New...