As the Audi World turns...

[quk@sievers.com (Phil Payne)]

In message <199706140312.XAA17592@mail.rapidramp.net> "Ross" writes:

> The blowoff valve serves 2 perposes
> 1-keeps pressure out of the pipes during 
> shifts.
> 2-keeps the turbo freewheeling
> The reason it's not routed back into the
> system is,Who wants Hot air back and the kjet 
> really sucks!

I'm gonna have to think about this ...
 
In theory, dumping metered air from the system will cause enrichment.  The 
timing of this could be interesting, because (I presume) the purpose is to up-
shift - the engine's revs will be falling to match the new gear, and the 
mixture will be rich for a very short period as fuel arrives without some of 
its air.

This sounds very interesting.  The system would have _very_ different short-
term characteristics from a system that retained the air by recirculating 
compressed but uncooled air back into the turbo.  In such a system you would 
also see a short enrichment phase, followed by a short overboost phase with a 
"heat pulse" going past the air temperature sensor.

I'd sure like to see some traces made by some sort of high speed data capture 
equipment.  Some of this stuff is getting real cheap now - you can get data 
logging PCMCIA cards that fit into ordinary laptops for $100 or less.

--
 Phil Payne
 phil@sievers.com
 Committee Member, UK Audi [ur-]quattro Owners Club