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5 posts in this topic

Hi guys,

I have been reading alot about the Zetec S, mine is arriving in a couple of weeks. Could someone be so kind to explain to me exactly what Transient Overboost. I have seen it mentioned in a few review and such but I really don't have a clue how it works??


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Blasts an extra few Nm to the wheels for about 30 seconds on full acceleration; not sure how long the cooldown is though.

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I don't really get the point of it, surely it'd have been better to keep the torque figures up throughout, but I suppose it's something they can pipe on about :P

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Adds an extra 22 ft-lbs of torque between 1900 to 4000rpm by increasing the boost pressure for a short time on the 1.6 ecoboost, it reverts back to standard boost/ torque after that

Its useful for a bit of extra urge when in- gear overtaking (eg, in a high gear above 2k)

The short high- boost duration helps to prevent the turbo from overheating and the heat to build up in the intercooler /heat soak or detonation ocurring, after "thermal runaway" especially on a hot day, and helps with the long - term reliability of the engine

On a hot day (+22 degress or more) the intercooler does not drop the charge temp so well/ so much, the ambient temprature is critical because the intercooler relies on the temprature difference (in/ out) to work, added to that the soaring underbonnet temps raising the temps of the turbo hoses and further reducing the cooling capacity of the intercooler, on top of that the air intake charge temp (the temprature of the air going into the engine air intake) is already high

So the transient overboost may not come on on a hot day, also, on a cool day with quality fuel, it may be possible to run the overboost safely for longer

The car/ engine has to be designed to withstand different fuel grades and conditions in different countries ("world car") over long periods and with extended sevice intervals, with the (realatively) poor fuel available in some countries and the high ambient tempratures this helps to ensure the long - term reliability of the turbo/ engine

Aftermarket or approved tuners/ remappers may lift the boost to run at these (overboost) levels all the time but may do it in conjunction with other modifications such as an upgraded (bigger) intercooler and/ or a vented bonnet or "colder" plugs to keep tempratures in check (the bigger/ better intercooler is the most important one)

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