[s-cars] Chip upgrades

[Kevin Day]

On Wed, Mar 18, 2009 at 8:33 PM,  <s-car-list-request at audifans.com> wrote:
> From: "Scott Justusson" <qshipq at aol.com>
> IMO/E chipsets aren't what makes AAN motors run lean with boost, it's
> the stock injectors. IME, the RS2 injectors can be put into just about
> (if not) all AAN chipsets without throwing any air or fuel codes. A good
> idea for anyone over a "stage I" chipset.

Can the Motronic really trim the fuel maps enough to compensate for
the larger injectors at cruise?  I thought about doing that but
assumed my fuel economy would be terrible.  I would have bet on some
sort of "mixture adaptation" code.

I upgraded the fuel pump instead.  The problem -- at least in my case,
running MTM 1+ -- was insufficient fuel pressure at high boost.  I
recorded logs with a high precision fuel pressure transducer to
verify.  You can see them here:
http://www.boost-instruments.com/mtm044.html

> A K24 can routinely spike boost levels of 21psi (2.4bar) for peak
> horsepower, but can't support that in continuous horsepower due to
> heatsoak.  For a street car, 20psi boost levels on the k24 is pretty
> common and won't hurt the turbo. (2.5PR) 22psi>  IME is the boom level
> of the k24.  Or quoting Pitzo (tm), "the turbo wheels will disassemble
> themselves without the aid of wrenches")

I wouldn't claim it's wise (I don't really care, K24s are cheap
enough) but my car has been peaking to 26 PSI on a K24 for a while
now.  It was impossible with the stock fuel pump but it works OK with
the 044 pump.  It's not that 26 PSI is necessarily any faster than 22,
but the stiff wastegate spring which gives such nice throttle response
overwhelms the Motronic's  boost controller...

http://www.boost-instruments.com/fuel/BigSpring26PSI.png

-Kevin