Overboost Feature

Discussion in 'Fiesta ST Chat and Discussion' started by Neely2005, May 27, 2014.

  1. Neely2005

    Neely2005 Member

    Can anyone give me a better idea on how the Overboost Feature works and how to best activate / use it?

    This is all that I've been able to find in the Fiesta ST Supplement:


    Your ST vehicle offers a period of additional torque delivery referred to as overboost or overtorque. This feature of the engine calibration broadens the RPM range of the peak torque curve. This gives improved performance during maneuvers such as passing and vehicle launch.

    Note: The overboost feature controls a variety of engine parameters to deliver additional torque. Overboost is built into the engine calibration on your ST vehicle and no action is required by the driver to engage.


    There's also a paragraph on Engine Overspeed on the same page. (Page 18)
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  3. djdennehy

    djdennehy Active Member

    The simplest way of putting it, in first and second the car is limited to about 18 pounds of boost, when you get into third under full throttle, the ECU will allow a period of 22+ pounds of boost. This will only last a few moments, but essentially its a short burst of extra power. The boost isn't available in first or second to prevent wheel spin. I may be off with some figures, but essentially that is what it is (as I understand it to be).
    Neely2005 likes this.
  4. reddog99

    reddog99 Active Member

    What djdennehy said. Basically, just floor it!
    Neely2005 likes this.
  5. Kevin R

    Kevin R Member

    From my understanding anytime you floor it (possibly not 1st and 2nd gear which is torque limited) the car will give you 'overboost' for 20 seconds. If you somehow manage to keep the accelerator floored for more than 20 seconds the ecu will lower the boost. Once you release the accelerator the 'overboost' is reset and you will have it for 20 seconds the next time you floor it. So basically anytime you floor it you'll have overboost unless you somehow manage to keep the throttle floored for more than 20 seconds.
    Gpfarrell and Neely2005 like this.
  6. eRic

    eRic Active Member

    Car and Driver explains it best: "Peak power is made in “overboost” mode, when the turbo is squeezing in a maximum of 21 psi. To stretch the engine’s durability, Ford programmed the computer to cut pressure after 20 seconds at wide-open throttle, a situation you’re likely to encounter only at Bonneville or the Nürburgring, or when fleeing the cops. But lift just once, and the overboost timer resets."
    Gpfarrell and Neely2005 like this.
  7. SirSlaughter

    SirSlaughter Member

    Oh why thank you for this thread. I was actually curious as to how to activate it as well. Now I know.
    I must say, every minute I have my Fiesta I just start loving it even more.
    dislegal and Neely2005 like this.
  8. ryst

    ryst Active Member

    If I'm not mistaken, you would have to be doing at least a 4th gear pull to go WOT for over 20 seconds... there's no way you could stay in 3rd gear long enough to hit this. Anyone know what the gearing in 4th is like? Redline = 130 MPH?
    Neely2005 likes this.
  9. WScottCross

    WScottCross Well-Known Member

    According to my spreadsheet, redline (6500 RPM) would get you 118 MPH in 4th. In third, you hit 90 MPH. If you have the Cobb tunes, raising the limit to 7K would get you to 97 in third and 127 in fourth. I agree that you would likely hit the rev limiter before running out of overboost in third.
    ghostwhite likes this.
  10. ghostwhite

    ghostwhite Active Member

    4th seems to run out at about 110

    Sent from my iPhone using Tapatalk
  11. BlackBird

    BlackBird Active Member Staff Member

    There's a pedal that is furthest to the right.

    You press it, and hold onto the steering wheel. Smiling wide helps.
    Sil3nt611, SpaceFish and iLiptiKal like this.
  12. MasterPooBaa

    MasterPooBaa Member

    There is a youtube video of someone doing an Autobahn run from 0 to 225km/h.

    In 20 sec the car gets to 175-180km/h and is reaching redline in 4th.
    Neely2005, iLiptiKal and F1ST like this.
  13. WScottCross

    WScottCross Well-Known Member

    Smiling wide is inevitable!
    Firesail and BlackBird like this.
  14. Neely2005

    Neely2005 Member

    Nice! Do you have a Link?

    EDIT: Never mind it wasn't showing up on my phone but now that I'm on my PC I see it.
    Last edited: May 30, 2014
  15. An additional fly in the ointment is it seems that I have access to more boost with stability control in sport or disable mode. Same gear, same section of road, I can consistently show more max. boost (3psig more) in any other mode than default.
  16. BlackBird

    BlackBird Active Member Staff Member

  17. Zormecteon

    Zormecteon Active Member

    I presume that you have a boost indicator of some sort and can read the extra boost. Have you done any testing to see if that equates to a measurable difference in acceleration?....

    Perhaps this is how to get 6.7 sec to 60 instead of 7.0?
  18. moff3tt

    moff3tt Active Member

    I have noticed this as well. I think this is a function of just with less traction control in play the car isn't forcing less throttle to keep the tires from spinning, or whatever it is that it does.
  19. BlackBird

    BlackBird Active Member Staff Member

    Are you on the stock engine tune? Because 1st and 2nd gears are torque (and boost) limited, TCS on or off. You can only make full boost in third or higher on the stock tune.

    Sent by my GS4 via Tapatalk.
  20. In the instance I was talking about I was in 4th WOT up a slight incline. Stock tune but in default mode I only see about +19psig or so. If I select sport or disabled node I can see 21 or 22psig under the same circumstances.
    BlackBird and Neely2005 like this.
  21. BlackBird

    BlackBird Active Member Staff Member

    That makes sense.

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