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What is Overboost?

61K views 20 replies 14 participants last post by  ChrisG23 
#1 ·
in a GSR.

How much overboost is bad?
What are the side effects of overboost?
Long term effects?
How does it effect drivability.
Etc.

I have always been a little unclear on this subject, can someone clear it up?
 
#2 ·
I believe (and please, correct if I am wrong) that overboost is when the turbo boosts higher than the wastegate controller is set to allow it to boost. The ECU isn't tuned to the excess boost, and therefore doesn't operate with a proper mixture for it (more than likely, at least, depending on how much over). Long term effects, it could damage components that aren't properly set up to run with that extra pressure. You probably wouldn't notice it daily driving, but it's a problem. Basically, your car is doing something it isn't prepared to do.

**note: the validity of these statements has not been verified by... well, anyone. grain of salt, please.**
 
#3 ·
overboost, it's like a balloon put too much air it will explode. the motor has a limit. not sure how much before it will ka boom, now stock tune you will get a code when you overbooost, prevent you from ka booming your motor. custom tune it's up to the tuner if he set the limit too high.
 
#5 ·
thanks for the info.

My car hits 26 sometimes 27 psi, when the stage 2 AP map is set for 25 peak.
Car seems fine. Don't know if it's a problem.
 
#7 ·
I hit 29 sometimes and maybe 30....this error always comes on soon as I hit high boost...I never really sat down with my tuner to get rid of this but we will on the next tune.
 
#9 ·
Overboost as a condition is where your engine is running more boost than what it is tuned for or outside its controlled conditions. Overboost as a feature is generally offered in sport cars which are turbocharged which they tune the car to run extra boost in certain conditions to make more power.
As a condition, it is caused either by malfunctioning parts or an improper tune etc.

Yes, overboost is bad. Side effects are an overall lean condition, knock and ultimately a blown motor.

I would only worry about your car if you are getting excessive knock or you're running lean when you are spiking at 27psi.
 
#10 ·
we hit 32psi on the dyno and had no knock.....we backed it down cuz thats scary hahah My injectors are maxed out 101% duty cycle now I'm on 92%. Need injectors and a red :)
 
#16 ·
With just a Works drop-in filter and Sakura UICP, I have found it quite easy to overboost. I've especially noticed this during cooler temperatures. I am not tuned for these simple upgrades, so my solution thus far has been either to roll on the throttle instead of matting the accelerator to the floor when I'm driving spiritedly, or simply to refrain from shenanigans all together until I complete my exhaust upgrade and am properly tuned.

From these responses though, it seems that even after I'm properly tuned an overboost condition may still be prevalent. Just a side effect of operating a boosted car, and I'm okay with that.

The talk of running lean at WOT is what has me more concerned though. I have no way of monitoring my AFR, but I've assumed that since it has become common knowledge that the MY07/08 run very rich from the factory that I'm on the safer side of the spectrum. Not exactly a scientific approach, but it'll have to do for now. Smells damn good when I get on it! Lol
 
#19 ·
So, ideally a tuner could set up your afr's to be perfect at 28 or 29 lbs, then set your ebcs to 25 or 26 psi and you would be golden. Yeah?
 
#21 ·
That's true, and as long as that thing is pinned on 11 you should be fine I guess.
 
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