Re: A4 isn't so special

[Orin Eman <orin@wolfenet.com>]

> 2.  Boost should be controled by a bleeder valve not the ECU.  (Turbo 
> Magazine used a EVC to control boost in an A4)

Scott J is probably having a good laugh at this point.  Fine if you
like replacing your turbo after it overspins and turns into
turbo schrapnel.  Those expensive chips are being very careful
to keep the turbo from overspinning (and some would say they
have stepped over the edge), something you just cannot do with
the bleeder valve mods as used on the VR4s.

> 1.  it uses a MAS sensor.  Therefore, only 1 chip is needed to raise fuel
> cut.  The only time a new chip is needed is when larger injectors are used. 

> 3.  This bullshit of re-tuning the ECU for every little mod is crazy.  When
> you add a free flowing exhaust, the hp goes up.  No re-tune of the ECU chip
> should be needed.  The MAS will see more air pass through it and send a 
> larger signal to the ECU which will in turn, send more fuel into the engine.
> (that isn't too hard to understand)  

There are limits.  It's more than just more air flow means more fuel.
Have you ever seen the fuel calculation?  Even with a MAF sensor, there
are tables of corrections which need to be extended - and you can't
assume that the relationships are linear.

Then you have the ignition timing.  Again, the ECU has tables for
timing based on 'load' and RPM.  More air flow means greater load.
Do the tables go that high?  If you buy a chip with tables that do,
then you have lost resolution in the lower RPM/load area - no-one
extends the tables that I know of.  You will sacrifice driveability
for top end potential you may never use.  So what happens if you
hit the end of the timing table?  You use the last values...
which will be too advanced for the higher load.  What happens now?
The knock sensor starts retarding timing.  What if it hits its limits?
It tries to reduce boost... _except it can't becuase you defeated
it with your silly bleeder valve_.  So you get detonation that you
probably won't hear leading to holed pistons and/or bent/broken rods
(at least that's what detonation seems to be causing on the 200 20V).

On the old 10V 5 cylinder turbo engines, you could get away with
stiffer wastegate springs, pressure regulators etc. with stock
turbo and ignition timing up to 1.8 bar absolute or so, but
not on the newer engines.

Orin.