i have heard this phrase so many times can anyone tell me what it means and what symptons you get
except for the obvious to much boost

 

what happened when i had nine was when driving on turbo it felt as though someone had grabbed me from behind, nearly throwing me through the windscreen

Rob

 

dose this mean plenty of people have had overboost but dont know what it is

 

It happened on my old MY94 WRX when the speedo cable broke. Believe me when it happens you will know about it. You expect to see lots of oily bits in the rear view mirror.

 

Obviously the boost pressure rises to a level that the ECU deems unsafe, the ECU will the cut the fuel..... this leads to a very sudden drop in performace (meeting the windscreen!).

I think the odd occasion will be ok, however, if your car is constantly overboosting, I would have it checked over....

I have had this a couple of times, both have been at high motorway speeds on very cold/foggy mornings.... the denser air will produce more boost.

Any clearer?

Cheers

Paul

 

On late cars the overboost is really subtle unless you go over big style.

 

you guys have just described overboost cut. ot overboost.

Overboost is a symptom of non critically damped boost control. The car over shoots its desired boost target. If the level of boost is too high (influenced by temperature and pressure) then the ecu will cut fuelling and the car feels like it has suddenly braked very hard indeed.

It is perfectly possible to overboost without hitting the overboost cut eg, my car used to overboost to 1.5 then fall back and hold 1.3.

 

Hi

I suffered OB on my MY98 due to excessive oil in the engine. Had to drain out some oil and clean all the pipes out with brake cleaner around the boost solinoid.

The Oil fumes condense on the sensor/restrictor and give the ECU false readings producing the 'ran in to a brick wall' feeling. Not a nice feeling.

Cheers

Neal

 

I had a similar problem with my MY00 that my head would hit the dashboard everytime I changed up over 5000rpm. It turned out to be a faulty 'purge valve' whatever that is, which has since been replaced (20 mins) and the overboost problem has gone away.

As for my head hitting the dashboard that still happens, only now it's everytime someone pulls out in front of me.

Next brake replacement