[s-cars] power loss question

[Michael Wakefield]

According to the Audi Service Training manual 218, page 16,  "The 
overboost condition has a time limit of 15 seconds.  The 15-second time 
limit helps ensure favorable drivetrain durability over the life of the 
vehicle."
Mike Wakefield
93S4
97 Cab

On May 25, 2004, at 3:05 AM, Paul Heneghan wrote:

>> From Scott Mockry's site:
>
> 'The 1992-96 Audi S4 in overboost mode will have boost set to about 
> 2.15
> bar absolute. The actual boost produced will vary depending on engine
> RPM, air temperature, fuel quality, and altitude.'
>
> Note: the overboost here is not the catastrophic gross overboost
> condition that causes the ECU to shut down the fuel pump and enter
> limp-home condition, it is a mild overboost deliberately produced by 
> the
> ECU under certain conditions.
>
> Is this what you're seeing?  It's quite pronounced on mine - if you do
> WOT, the boost and power build rapidly as you approach 2000rpm and then
> fall off a little somewhere between 3000 and 4000.  One the Avant, I 
> see
> a peak reading of 2.0 dropping down to 1.8, on the saloon, I see a peak
> of 2.2 dropping down to 2.0.  These are not accurate figures as they
> come from the notoriously inaccurate multifunction-computer boost 
> gauge.
>
> If you don't do WOT, but feed in the power gently then you don't notice
> this mild overboost.
>
> You probably all knew all this already, but I wasted a few days looking
> for a hose leak that didn't exist because of this slight power 
> reduction
> at higher revs.  Anyone know why it's there - engine longevity perhaps?
>
> Paul
>
> From: Elijahallen92 at aol.com
> Subject: [s-cars] power loss question
>
>> Hi,
>> I have been thinking about getting the car on a dyno soon and am not
> sure
>> what rpm they start at but if I am in forth gear and start at say 2000
> rpm's, I
>> floor it, the car gets to 3000 or so and builds boost, by 3500 I'm at
> full
>> boost but right after I hit full boost power cuts way off and boost
> drops. Its
>> not a violent shut off like overboost where it feels like you just 
>> left
> the
>> tranny in the road but more like if you went from full throttle to 
>> half
> throttle.
>> The only time it does it is if I floor it from a very low rpm like 
>> that
> which
>> is never but I am worried that on the dyno I will have a problem with
> this.
>> Any Idea what/ why this happens? Thanks,
>>
>> Elijah
>
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