stuarty Posted March 19, 2014 Share Posted March 19, 2014 I wasn't sure where to post this but could someone explain what "over boost" is when referring to cars with turbo's. The BMW Z4 35i e89 is twin turbo but the Z4 35is e89 is twin turbo but with over boost feature. Any help? Quote Link to comment Share on other sites More sharing options...
Jay-350z Posted March 19, 2014 Share Posted March 19, 2014 Over boost is actually a bad thing, when the turbo randomly spikes, I've never really understood it as a sales feature. Quote Link to comment Share on other sites More sharing options...
stuarty Posted March 19, 2014 Author Share Posted March 19, 2014 Over boost is actually a bad thing, when the turbo randomly spikes, I've never really understood it as a sales feature. That's what I thought Jay. But BMW are marketing the overboost as a good thing! Quote Link to comment Share on other sites More sharing options...
Jay-350z Posted March 19, 2014 Share Posted March 19, 2014 Over boost is actually a bad thing, when the turbo randomly spikes, I've never really understood it as a sales feature. That's what I thought Jay. But BMW are marketing the overboost as a good thing! The only thing I can think of is, the the fuelling and ecu allow the car to produce more boost for a short duration of time under hard acceleration, but if it's safe to do that why can't it do so all the time! Quote Link to comment Share on other sites More sharing options...
oVerboost Posted March 19, 2014 Share Posted March 19, 2014 Overboost on newer turbo cars when marketed in the brochures it's basically either a switchable increase in boost pressure or a mapped increase of boost at a certain point depending on gear selection or revs. Quote Link to comment Share on other sites More sharing options...
GMballistic Posted March 19, 2014 Share Posted March 19, 2014 Overboost on newer turbo cars when marketed in the brochures it's basically either a switchable increase in boost pressure or a mapped increase of boost at a certain point depending on gear selection or revs. Very apt that you should answer that. Quote Link to comment Share on other sites More sharing options...
stuarty Posted March 19, 2014 Author Share Posted March 19, 2014 Overboost on newer turbo cars when marketed in the brochures it's basically either a switchable increase in boost pressure or a mapped increase of boost at a certain point depending on gear selection or revs. That makes sense! Just noticed your forum name there. Lol. Quote Link to comment Share on other sites More sharing options...
docwra Posted March 19, 2014 Share Posted March 19, 2014 My old Delta had overboost by way of a little switch under the accelerator pedal, so when you floored it you got another 2-3 PSI. Why you couldnt just have that all the time I never really worked out Quote Link to comment Share on other sites More sharing options...
coldel Posted March 19, 2014 Share Posted March 19, 2014 R33 GTSTs come with a kind of over boost, it delivers boost in two stages so 0.5bar up to 4000 revs then something like 0.7bar after that - I think having it switchable means when stuck in traffic/around town your car is a bit more drivable on lower boost levels? Quote Link to comment Share on other sites More sharing options...
Ekona Posted March 19, 2014 Share Posted March 19, 2014 You're all kind of right, more or less. Basically the car will have electronic boost control, so the waste gate will be set to open at say 1 bar under normal conditions. If certain conditions are met (sport mode on, engine oil at right temp, certain throttle threshold reached etc) then the controller will hold the waste gate closed until 1.2 bar, hence the term overboost. 2 Quote Link to comment Share on other sites More sharing options...
richmillions Posted March 19, 2014 Share Posted March 19, 2014 I think the new Fiesta ST has overboost. In the states its power is listed as a couple of bhp higher than europe. In the states their rules allow the overboost figure to be the stated power whereas in europe it is not. If I remember correctly the overboost figure is only available for a few seconds at WOT..... 1 Quote Link to comment Share on other sites More sharing options...
Ekona Posted March 20, 2014 Share Posted March 20, 2014 Pretty much, yes. Same as with the 911 Turbo/S, you get two power figures and you always need to go on the lower one as the higher one is only ever available briefly. Until they launch a special edition and you can have it all the time Quote Link to comment Share on other sites More sharing options...
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