Re: Dancing on Mods

[zm@mhcnet.att.com (Zafer Mehmood [209])]

> 
> "Obsolete" is a word that's been haunting me all weekend....  You're correct
> in that the guage reads fairly quickly, tho there is a delay, not sure why
> (not sure I care or should), but on my car it approaches a couple
> seconds..... 

The delay that you notice is due to the low sampling frequency of the
analog-to-digital circuitry that drives the boost display. For the
non-EE folks here, let me elaborate a bit. The output of the pressure
sensor is analog, i.e., continuously changing almost instantly with
the pressure being sensed. This sensor output is "sampled" very so often
(lets say once every second) and its value is displayed on the LCD
readout. So, on a car where the boost is rising rapidly, the display
seems to lag by a second and is displaying an accurate reading only
once per second.  The sampling frequency can be higher and then the
display would change sooner, every few milliseconds if so designed.
But generally, digital displays do not lend themselves to being driven
very rapidly. The human eye finds it hard to focus on rapidly changing
numbers. So such systems are designed conservatively and have a low
sampling frequency. Here's a case where a conventional analog gauge
would give an accurate reading of a continuously changing input with
virtually no delay.

I think that for most normal driving conditions, the stock Audi digital
boost display is adequate, except for tuning or race applications.

The choice of the word "obsolete" by Trevor also hit a jarring note
with me. The TAP mod either makes the boost gauge's readout inaccurate,
non-functional or leaves it as accurate (or inaccurate) as it was before
the mod. Which of these three is it?

Zafer