Yeek! - full throttle hesitations/fuel cuts!!!

Discussion in 'All Things Technical' started by Graphite, Apr 27, 2007.

  1. Graphite

    Graphite 23rd June 2016 - Vote LEAVE EU!

    :shock: - horrible drive yesterday, hit my favourite bit of road for some 'pedal to the metal' driving and wasn't far along and got a nasty jerk & no power sensation, backed off throttle and carried on & it occured again. I got to the motorway and crusing at 3000 rpm, push foot to floor and jerk, pull, jerk, pull... this was repeatable :cry: - it wasn't nice - non full throttle seems to still pull OK though ???? - whats going on?

    History:
    ~ a year ago I had a small problem with this - then the car failed to start - traced it to a melted fuel pump connector block under the driver side of the back seat (apparently a common problem in classics :shock: ) - removed damaged wires and reconnected. It was then fine after this.

    A month ago of so fitted new 17" wheels... :? - I think it might have started there :shock: :wink:
    On the way to ScoobyTeknix a couple of weeks ago I noticed a couple of these 'hestations' on WOT whilst playing with a biker on the link road.

    2 weeks ago had a decat centre from KevC fitted at ScoobyTeknix (thanks guys :wink: )

    Last weekend loaned car to a mate who only used it for 60 miles or so but may have filled up the fuel with a couple of gallons of 'non-V-Power' fuel :shock:

    So is maybe the ECU learning with the better flow now one cat is missing or possible a few gallons of lower quality fuel has affected it, or is it something completely different.

    Actually thinking about it, when I did the RR day at TEG a couple of years ago there was a 'step' in my power curve :cry: - I was advised it might be ECU learning as I had just started using Optimax fuel...

    Any ideas?

    Thanks

    Mick :mrgreen:
     
  2. AndrewC

    AndrewC Active Member

    How much fuel in the tank when it did this?

    Do you have a boost gauge?
     
  3. Graphite

    Graphite 23rd June 2016 - Vote LEAVE EU!

    Just under 1/2 tank of fuel... round trip of ~ 40 miles & I topped up with £30 worth of V-Power when I got home.

    I don't have a boost guage...

    From the TEG plot my boost peaks sharply at about 3000 rpm ~ 1.08 bar & drops to ~ 0.9ish to ~ 5600rpm.

    Would it help to scan any of the RR plots? or are they too out of date or irelevant to what is happening now?

    Cheers

    Mick :mrgreen:
     
  4. AndrewC

    AndrewC Active Member

    Std ECU?

    1.08 bar could be very close to fuel cut depending on what ECU you have, changing a section of the exhaust may have just tipped you over the edge.

    Andrew...
     
  5. Graphite

    Graphite 23rd June 2016 - Vote LEAVE EU!

    Homer moment... DOH! - hadn't thought of that... I also have a STi7 rear box which will also be freer flowing - so that could be it.

    [​IMG]

    Don't know if that helps...

    Is there a way round this without spending a fortune on a mappable ECU?

    Cheers

    Mick
     
  6. Graphite

    Graphite 23rd June 2016 - Vote LEAVE EU!

    Here are the other plots if this helps the 'doctors' diagnosis... :wink:

    AFR
    [​IMG]

    Torque

    [​IMG]

    Cheers

    Mick :mrgreen:
     
  7. AndrewC

    AndrewC Active Member

    What breathing mods have you got, ie what's fitted before and after the turbo :wink:

    Might need a smaller restictor in the pipe from the boost solenoid back to the inlet or if your WG actuator has an adjustable arm try taking a turn off that.

    Andrew...
     
  8. Graphite

    Graphite 23rd June 2016 - Vote LEAVE EU!

    Pretty much standard... Pipercross panel filter in inlet & the 2 exhaust sections as mentioned above - that's all...

    It has an easy life mostly - wife driving to & from work - she's quite happy to drive quickly - but not aggressively :lol:
     

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