I was driving the other day and noticed that my boost level in lower gears (such as 2nd and 3rd) when full throttle does not go past 11 psi or 15psi on overboost mode respectively. While on the freeway, booking it and floored in 5th gear, I notice the car boost closer to 18 or at 18 PSI and then drop off.

I am trying to figure out why the car does not boost all the way to 18 in 2nd or 3rd gear. Is this normal? I am guessing it is because the gears are too short and it takes awhile to build the boost? I know in first gear that is definitely the case, but it seems like 2nd and third are much longer gears.

If someone could weigh in I would greatly appreciate it.

 

Software?

 

No software yet.

 

its normal to not hit the higher boost levels in the lower gears i.e. 1st and maybe 2nd. Ive found that unless you really step quickly on the 'go' pedal in 2nd gear it wont hit overboost mode (i.e. the arrow) but nail it promptly and it does.

Note overboost usually only works in 3rd at 3k or higher but when I installed my Cargraphic, even with stock software at the time, overboost would occur in the lower grears which I assume is due to the reduced EGT's.

 

there's more load on the engine in higher gears

 

I had same problem with my turbo, the boost will not pass 0,9 bar with sport chrono and 0,7 bar without sport chrono. Service guy told me to drive more than 10 sec more than 3500 rpm with sport chrono off and than to turn on the sport chrono, after that I change the petrol station where I use to fill the car an now the boost show 1,2 bar with sport chrono activated.

 

Bump - I have the exact same issue as the original poster. Do I need to take it in for service? Thanks!!

 

It may not necessarily be an issue at all.

My understanding, after having read many posts by far more knowledgeable people is this:
- The amount of boost is a function of load on the engine, the higher you load your engine, the higher the boost.
- With other things being equal (such as fuel, IATs, etc...), the acceleration demands you place on the engine in lower gears where revs can build up much quicker actually load the engine a lot less than the same acceleration demands when in higher gears where revs require longer to build up.

For example, if you are, say, in third gear doing 45mph and stomp on the gas pedal, you are definitely placing less load on the engine than if you are in fifth gear doing 45mph and stomp on the gas pedal.

Another example will be if you are climbing a steepish incline, even without hammering the gas pedal, you will load the engine more if you are in higher gears than lower gears.

Hence, under such conditions, you will definitely see more boost when in the higher gears.

If this is the kind of behavior you are seeing, I would say it is perfectly normal.

I am sure others will step in to correct me if I'm wrong.

 

they always do...LOL!

 

K_ddsl - thank you. That makes perfect sense.

My question is why I am not seeing more that 12 psi under higher load (say 3 or 4 th gear WOT)?

 

Gotta love 'em for it

Is that in Normal mode or Sport Mode?
At what RPM are you starting when pressing the gas pedal to WOT?
Have you felt a deterioration in your car's performance of late or is it unchanged?

 

It's in normal mode. RPM was around 3 to 4k RPM and WOT. I believe there was some degradation in performance but due mostly to warmer weather? I will try more runs today and report back.

Thanks again!

 

bad or low octane gas or bad sparkplugs may cause that.

 

3 to 4k rpm and going WOT is not going to load your engine much.

Try starting at 2k rpm in 4th and go WOT.

Do that in normal mode and in sport mode.

I think you'll see higher boosts then. If not, something gives.

And yes, I can definitely vouch for power degradation due to warmer weather.
Ask me how I know.

 

How do you know about power degredation in warmer weather huh?