Full throttle = full boost?

[drummerdimitri]

Is that how it works?

The boost gauge seems to increase when there is a load on the engine so even if one revs the engine in a low gear without accelerating the boost is non existent.

It seems to shoot up when the car accelerates under load so does full throttle = max boost?

 

[S32B]

I think it's a gimmick and never look at it!

 

[Sean_Jaymo]

The boost levels are electronically controlled and the throttle pedal doesn't control the throttle body. The throttle input is analysed by the ecu and boost and throttle body inputs are made and controlled by the ecu.

If you slowly put your foot through the bulkhead, The ecu interprets that as wanting to go quicker but not as fast as possible. If you were to slam the throttle pedal through the bulkhead, The ecu interprets that input as wanting to headbutt the horizon and controls the engines response accordingly.

 

[drummerdimitri]

The boost levels are electronically controlled and the throttle pedal doesn't control the throttle body. The throttle input is analysed by the ecu and boost and throttle body inputs are made and controlled by the ecu.

If you slowly put your foot through the bulkhead, The ecu interprets that as wanting to go quicker but not as fast as possible. If you were to slam the throttle pedal through the bulkhead, The ecu interprets that input as wanting to headbutt the horizon and controls the engines response accordingly.

So if boost shows as maximum that doesn't mean the car cannot accelerate any faster in that particular gear right?

 

[Sean_Jaymo]

In a word, yes. But not in that gear but that particular car status for that time. Lots of factors are taken in by the ecu when it's deciding on the engine response.

These include (if applicable) but are not limited to:

Traction control settings (on, off, limited)
Actual Traction (inputs from the abs)
Drive select mode (eco, sport etc)
Steering angle (straight on or full lock? )
S-Tronic status (what the mapping of the S-Tronic box allows)
Haldex inputs (condition and Traction distribution requirements)
Abs inputs (faults logged, wheel speed)
Engine fault codes (cam sensors, turbo pressures, intake temps)
Ambient temperature (hot air doesn't reach full boost as quickly)
Throttle input (type of input made by the driver)
Clutch switch status (if manual, won't give full performance if it feels that the clutch is engaged)
Brake switch status (most modern switches have an output for lights and another for the electronic control units of the abs and or engine ecu)

 

[cuke2u]

Some engines had a timed overboost as well...

 

[Gazjs]

I was wondering about the boost gauge also. First car I have owned with 1) Crazy power and 2) Boost gauge.

Driving around today, it seems the boost flickered up to 2 bars driving on the motorway, and when giving it some, shot up to its maximum.

What does it all mean? The description above is good ... but is there anything I should be doing to control things etc ?

There are no stupid questions as they say .....

 

[desertstorm]

Generally boost is created in response to the amount of fuel that is being requested to be injected into the car. To get the correct combustion conditions the ratio of fuel air has to be correct. The turbo is driven by exhaust gas and the more boost you want the more exhaust gas is needed to turn the turbine that drives the compressor.
Thus at say 3K RPM part throttle the boost gauge could be reading quite low, as the amount of fuel being injected is small and the amount of exhaust gas volume will also be low. Floor it and the amount of fuel injected increases rapidly, this produces a lot more heat and exhaust gas volume which drives the turbine in the turbo a lot quicker producing a lot more boost. And with the increase in airflow will come an increase in fuel flow.
Don't look at the boost gauge too much when driving, better to look at the road.

 

[Gazjs]

Very informative. Thanks very much! Exactly what i was looking for.

 

[Tony1982]

Nice description of how turbos work and how boost is applied. However the boost gauge in the S3 isn't worth the plastic and led lights its made from and doesn't give a true representation of what is going on with regards to boost pressure, it's a gimmick if you ask me and a bit of a let down, audi knew S3 drivers wanted a boost gauge when they developed the 8v and came up with this rubbish! A proper boost gauge can be much more informative and can let you know if things aren't right. One of the only things I believe lets this car down in my opinion.

 

[musicegbdf]

I would swap it for a oil temp gauge...

 

[sjbarneS3]

I would swap it for a oil temp gauge...

Find someone with vcds or whatever it's called. Took a kind gent 3 mins to do it on my car

 

[musicegbdf]

Find someone with vcds or whatever it's called. Took a kind gent 3 mins to do it on my car

Though thia is only on the digital speedo , would like it on all dis screens

 

[sjbarneS3]

Though thia is only on the digital speedo , would like it on all dis screens

It's normally only
On the S3 lap time screen but I now have it on any DIS page/screen/speedo