[s-cars] Chip upgrades

[Scott Justusson]

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] On Behalf Of Kevin Day
Sent: Wednesday, March 18, 2009 10:18 PM
To: s-car-list at audifans.com
Subject: Re: [s-cars] Chip upgrades

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.

IME, the RS2 injector (Bosch green top) has better resolution than the
AAN stock injector.  I too assumed this might be much, but have done
many of these injector conversions, even on MTM stage I cars without any
issue or CEL.  I'd venture they would work fine on a stock Motronic box.

>>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

Took a while to get thru what you did there (or it's relevance), but if
we believe Probst book that 12.6:1 A/F is 'peak power', it would appear
your larger fuel pump is not making the resolution in A/F 'better'.
Maybe a better test would be on the dyno.  I'm not convinced the fuel
pump is really at issue, as many here (including me) have dyno'd over
300WHP with the stock pump.  

> 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...

A dyno run might change your conclusions of the data you put together.
I'm not sure what I see in your data concludes 'better' anything.
Remember too, as IAT increases Air Density Ratio Decreases > less fuel
required.  IME, that k24 is a robust unit as many have abused it, but
the upper limit is 2.4PR.  At 2.5PR, the half life of that turbo just
sucks, btdt.  If you look at the 2470 Turbo map, it doesn't show any
lines above 2.2PR.  As I indicated, it can run 2.4 with pretty good
efficiency for instantaneous hp, but it's spinning at 140krpm, which is
what KKK considers terminal velocity.  At 2.7PR, you aren't at a very
good efficiency of that turbo (understatement), as demonstrated by your
own data....

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

.....  3 seconds of boost your IAT temps are already more than double.
Extend that 'on boost' profile on a dyno, I'd doubt you could complete a
run without popping somthin....