In my readin on this forum i have come across this "overboost" feature that allows you to run higher than stock boost for 12 seconds? Can someone explain this to me? Also im assuming this is a "feature" and not just referring to "if" you overboost stock ecu will allow 12 seconds vefore pulling timing? Sorry for the noob question, just trying to learn as much as possible. Also, i have only had my r56 for about a month, it has 57k miles. I have noticed that on cold startups it will have a slight random misfire. Is this normal? Or should i look at plugs? Or maybe even start gathering the necessary equipment to perform the diy walnut blasting?

 

Overboost is activated when you floor the pedal momentarily (try it with the car off, you'll feel a little click). The engine will momentarily give the engine a little extra power and it is usually accompanied with a downshift a gear or two (if you have the auto box). This is indeed a feature for emergency maneuvering situations or if you need that extra passing power.

 

Ahhh ok

 

I call it the temporary sport mode when you aren't in it but need to punch it

 

Actually "Overboost" is a gimmick phase by marketing people who don't really understand what's really going on. What really happens when you push the Sport Button is it makes the throttle more sensitive to your pedal therefore opening the throttle further open than it would be while not in Sport Mode.

There's nothing temporary about it.

 

One may not know everything, and I certainly would not pretend to be an engine scientist by a long long shot, but obviously many people here don't understand what is going on... yes the "Overboost" is temporary or it would fall in the sport mode, or tunes, camp of engine operation timing and would pretty much loose its "Overboost" terminology purpose.

I would not say it is gimmicky, as real processes change during specific conditions of driver's input demand, so to balance power output with continuous engine performance efficiency. One would not want to continually be in a power priority mode and unecessarely over spend $ on gas. But I agree that the use of the specific word "Overboost" certainly sounds a bit gimmicky for what happens when it has more to do with detecting a change of driver's input behavior to adjust engine management settings under specific condition such as pushing more quickly on the acceleration pedals. A lot of it is about timing really. This is something that turbo engines and electronic timing have really enable car makers to play with. And there will be an sharp increase in turbo and twine turbo engines within this next decade as it is a powerful element to manage gas consumption and power efficiency.

And fyi, there are more to the sport mode than throttle opening...

 

From what I understand, overboost is simply a function of the ECU, which allows extra boost over the normal limits during extra-hard use. Normal boost is limited to let's say 15 PSI, overboost allows 17 PSI or so for limited times. Can anyone confirm or deny this? I have seen 17.3 max boost on my Scangauge 2. This is after installing a JB+. Just installed a Forge BOV 2 days ago, so will track my boost numbers. I don't expect much more boost, but have already felt the difference when shifting....boost recovery is MUCH quicker! Best mods so far? JB+, larger rear swaybar, and now the Forge BOV. Totally different animal now!

 

From my operator's manual:

Maximum hp 181 @ 5500 rpm
Maximum torque lb ft 177 @1600 to 5000 rpm
with overboost – 192 @1730 to 4500 rpm

Overboost briefly increases the highest torque during rapid acceleration, for example when passing another vehicle.

 

If everyone just read the Book, we could all be experts! Thanks, hsautocrosser!

 

I have been running the Forge DV for almost two years and couldn't think of switching back to the stock DV! You won't get more boost with the Forge DV, you'll lose less boost between shifts which means when you get back on the throttle you'll be nearly where you were before the upshift. I have done a ton of data logging and everytime I see higher boost levels while not in Sport Mode, however I see higher sustained MAF readings while in Sport Mode. Turbos are by nature exponential meaning they build there max boost over time rather that instantly like a supercharger. Our stock factory turbos are out of there efficiency range past 18 psi.

 

Sport mode and Overboost are independent of each other. Overboost is exactly that, a momentary bump in boost for quick power - works with or without sport mode. Sport mode doesn't give the car any more output, but it makes the power available quicker by changing throttle mapping, shift points (on an auto), and by tightening the steering.

 

Systemlord, you are correct! I am not feeling any more grunt or pull, but the recovery time is amazing! Even when shifting quickly with the stock diverter valve, I would loose boost, and have to wait for the turbo to get back up to full spool. The Forge BOV gives me pretty much instantaneous power when changing gear while hammering the throttle. Turbo lag is almost completely gone, and my shifts are actually much smoother! Perhaps the best mod I have done so far! So much for my MPG. LOL. That BOV sounds so sweet!