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

    • Dose Pipe Sutututu
      Dose's Sometimes DIY and Pay Someone Home & Boat Improvement Thread

      By Dose Pipe Sutututu · Posted

      Wife wanted basket things in the wardrobe in our temporary house. Thought about ripping our the wardrobe and fitting the entire IKEA set, but it's a temporary house and we want to move in a few years. So IKEA advertises this as a 50cm unit, however the actually basket and rails measure 46cm wide. Only issue was depth, IKEA stuff is quite deep, where as the builder special junk is super shallow at less than 40cm. Send it, chopped the rails, then offset the mounting holes, job done, happy wife, less shit scattered all over the bedroom. Did the same to the other side too. Also drove the Skyline shit box today, dropped off oil at Supercheap Auto. I didn't realise they only now take max 2x bottles per visit. I visited 2x Supercheap Autos.  
    • Kinkstaah
      Strange issue RB25DET wont start

      By Kinkstaah · Posted

      I've seen similar actually in my situation. You never know what tables are attempted to be used when the car thinks it's -99C or +200C. The fail state is not usually that extreme but you know what I mean - it was in my case though! This is where being able to read all the sensors is useful cause you see this stuff really quickly.
    • Kinkstaah
      First time Skyline owner

      By Kinkstaah · Posted

      The above is very important. However as long as you keep timing relatively low, it's plausible to make your own knock ears and plausible to learn to tune with a modern ECU that can do wideband O2 correction like a boost controller. I mean if you only have one viable road to even drive the car on, learning to tinker to this level may be worth doing given you can't do much else with the car...?
    • Kinkstaah
      Chris' Toyota Mark ii JZX110

      By Kinkstaah · Posted

      I find the fact that the rear plate has to be bent inwards at the rear not so bad: but the front is just awful: It's like come on. (these are my very old, now retired/turned in plates) TBH it is a lot of money to fix a minor issue, the fact I said "I'll never really spend the money on doing this" is why people ended up buying them as a gift for a 'car guy' who can be hard to shop for.. for car guy things.
    • GTSBoy
      Chris' Toyota Mark ii JZX110

      By GTSBoy · Posted

      I just bent the ends of my premo plates. It even went through Regency like that after the engine conversion and the inspector (a great bloke!) just squinted his eyes and said "I didn't see that". Plates, and how they look, are just something that have zero importance to me.
×
×
  • Create New...