I've noticed two times by now, than when I drop my Fiesta into 3rd and floor it, it pulls harder than I'm used to.

What I'm wondering is, if it's because overboost normally isn't applied, and these two times it has actually worked.

Is there any way for me to tell if it's actually working properly ? (Aside from getting it on a dyno and have it read out)

I'm thinking about getting an OBD, it should be able to tell me the boost pressure right ?

Overboost has a cool down time of 35 seconds and only lasts for 15 seconds. It's hard to keep track of when it's on properly. You can hear it when it's going though, louder spool.

I can't even hear the normal spool, except if I turn the windows down - guess I'll try that tomorrow :-)

Something I have wondered about with overboost is this 15 seconds thing. Let's say you found a place where you could safely floor it for 10 seconds before backing off and lifting off altogether for 5 seconds before flooring it again.

When you floor it again, do you have only 5 seconds of overboost remaining because of the 35 seconds cool down time? Or is backing off before the 15 seconds enough to reset it?

This is starting to sound like the new rules of Formula one Racing

I could be wrong but..

Over-boost is semi-permanent, as in you always get it it unless;

-The throttle is wide open for over 15 seconds, in which the boost pressure is dropped (when full throttle is still applied). Full boost pressure is re-applied as soon as full throttle is engaged again after lifting off.

-I think a loss in boost pressure becuase the car is 'cooling down' is nothing to do with 'overboost', it is due to high ambient temperatures and a heavy right foot, in which case the ECU will limit boost in order to help cool the engine.

I don't know why they called it overboost or even have such a feature on the car. It realistically should be called 'under boost' as you do get full power at all times unless you exceed the 15 second limit of fully open throttle.

All other countries advertise the Fiesta ST as 197bhp.

And for the record, boost pressure is limited in 1st and second gear all the time. 2nd gear has a slightly higher pressure than first then 3rd gear onwards has a higher pressure than 2nd.

I hope this makes sense but correct me if I am wrong please.

Cheers

Other countries advertise as 200BHP as in the EU you cannot produce statistics on a limited basis, hence the 180 figure.

If you come off the throttle on OB the cooldown of 35s kicks in ( I've asked Ford directly how it works and they eventually parted with the info )

You should always be able to hear the spool, I can hear mine perfectly inside the cabin

If you come off the throttle on OB the cooldown of 35s kicks in ( I've asked Ford directly how it works and they eventually parted with the info )

But overboost is on constantly, there isn't a cool down of 35 seconds after every application of fully open throttle. Or do you mean after every application of a 15 second period of fully open throttle there is 35 seconds before you can have full boost again?

I talked to the dealer about it and what you are saying isn't what they said?

Cheers

This is what Ford say about it ...

Ford engineers made sure the overclocked EcoBoost engine would have a very robust cooling system. “The turbo itself is specified for sustained, high-output performance, but they’ve programmed the car’s computer to dial in more boost past 3,000 rpm to give it that extra something,” says engineer Lisa Schoder, who is Marketing manager for Focus ST.

“We limit peak turbo boost to maintain a wide margin of safety and durability over the life of the car,” Schoder adds. “But overboost is cool in that it tweaks more acceleration through the turbo for brief periods for performance-hungry drivers.”

Ford Focus ST increases acceleration through factory “overboost” turbo feature that extends torque curve from 3,000 rpm to 4,500 rpm for up to 15 seconds

What Rog Said, Overboost is always on yes... but Full max OB isn't always active and only becomes active after a 35s cooldown and becomes active for 15 seconds use.

I appreciate all the answers, but I think the overboost is slightly different on the ZS (which is the one I have) - I don't think they limited the power in 1st or 2nd (what's the point, there's not really that much power anyway).

And like I said I can hardly hear the spool, but then again the turbo is very small.

So I'm probably gonna buy an OBD and check the boost pressure.

Still an interesting read about the overboost of the ST :)

Does this mean that overboost remains active while you change up through the gears? I mean obviously you take your foot off to change gear, so we don't want overboost to reset just because of a gear change.

I think it will drop off with the recirc valve??

I think it will drop off with the recirc valve??

Possibly, I actually heard the recirc valve for the first time the other day, I don't normally leave the windows down so don't usually notice it. Floored it in 2nd and when I changed up I heard it, what a cool sound :). I couldn't tell if the overboost reset though cos I was coming up to the speed limit.

What happens if you power shift? Obviously without getting off the has does it drop off the boost after 15 seconds? If so rather annoying and it also annoys me that I can't brake boost my tdci, brake boosting is pure awesomeness.

Do you guys know if the fiesta St or focus st can brake boost?

Sent from my GT-N7105 using Ford OC mobile app

Possibly, I actually heard the recirc valve for the first time the other day, I don't normally leave the windows down so don't usually notice it. Floored it in 2nd and when I changed up I heard it, what a cool sound :). I couldn't tell if the overboost reset though cos I was coming up to the speed limit.

Good Boy keep er tidy :)

mixmasterlooney: This might be a dumb question, but what is powershifting?

mixmasterlooney: This might be a dumb question, but what is powershifting?

I'm guessing it's keeping the power on while changing gear, which I assume means you lose less speed when changing up a gear. Is this a technique that's used in racing?

I'm guessing it's keeping the power on while changing gear, which I assume means you lose less speed when changing up a gear. Is this a technique that's used in racing?

Yes exactly that, changing whilst still on the gas, it's very fast and it is indeed used in racing.

It's different from quick shifting where you do let off the gas but pull out of gear almost before fully pressing the clutch pedal.

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Surely doing that the engine just revs up to the limit as you put the clutch in, like flooring it in neutral? Can't see how that does it any good. Will be severely mismatched revs too when you bring the clutch up. Or is there more to it that I don't know? :D.

Also while talking about the turbo sound, the noise you hear with the windows down while the turbo is working, is that the turbo spooling or the air being drawn in through the intake? It doesn't sound that much like the whistle you normally associate with turbos but it also doesn't sound that much like air being sucked in. The pitch doens't really change through the revs either and I can't decide what it is lol.

Surely doing that the engine just revs up to the limit as you put the clutch in, like flooring it in neutral? Can't see how that does it any good. Will be severely mismatched revs too when you bring the clutch up. Or is there more to it that I don't know? :D.

I guess you have to control the revs carefully, but when you engage the clutch again the extra momentum in the engine / drivetrain will be converted to a little extra speed I think. I notice this when trying to rev match when I change down, I usually get it wrong and if the revs are too high you fell a jolt pulling the car forward.

Also while talking about the turbo sound, the noise you hear with the windows down while the turbo is working, is that the turbo spooling or the air being drawn in through the intake? It doesn't sound that much like the whistle you normally associate with turbos but it also doesn't sound that much like air being sucked in. The pitch doens't really change through the revs either and I can't decide what it is lol.

I'm not sure what the turbo sounds like, but I think I can hear mine with the windows closed, especially when flooring it on 4th as the revs climb it sounds like the turbo is also spinning faster.

Power shifting can do a lot of damage to your gearbox there is some gas pedal control required and TBH it's alot harder on a boosted engine, the redlining isn't so much of an issue when brake boosting and using a higher gear.

On my old polo i power shift alot when i bought it the gearbox it self had very little feel but it never actually popped out of gear those mk3 polos had gearboxes made out of chocolate anyways. the car took it very well, pulling out of gear without using the clutch etc (Cable clutch)

On the subject of hearing the turbo on my TDCI focus last year i pulled out of a road and accelerated heavily, i heard the turbo make a lovely whooshing sound, ever since then not once have i hear it again lol