Re: avoiding turbo conflicts

[Orin Eman <orin@wolfenet.com>]

> Our cars do have fuel and spark maps optimized for what the factory
> specifies. Generally speaking, they aren't going to be terribly
> aggressive, depending on what car you have and the amount they can
> compensate for your driving may be limited (motronic aside). The turbo
> ecus do contain the necessary data to run more boost-to the limit of the
> pressure transducer. The spark and fuel curves are probably going to be
> extensions of the standard pattern and not be any more aggresive. 

The stock MAC11 ECU _DOES NOT_ contain any mappings for above 1.5bar
manifold pressure.  The stock pressure transducer goes to 2.0 bar.
In addition, the fuel curve only has two vectors, one for low boost
and one for high boost.  Neither accounts for higher than stock boost.
You would be relying on the fuel distributor's capacity.

Those with knock sensors will be relying on the knock sensor to
prevent detonation.  You will very quickly hit its retard limit
using 1.8bar and the stock timing maps.  If you are lucky, it
will switch to the regular fuel map, allowing a whole lot more
retard.  Unfortunately, this causes a loss of performance
off boost due to the retarded timing at all points on the map.

I had to take _12_ degrees of timing out of the MAC11 table
at some points on the map to stop detonation... most of the
sub 3k rpm boost points in the table are set to a
default value - the stock configuration simply doesn't
go there!  Oh, you might not go there in your acceleration
runs, but get an uphill freeway stretch and guess where you
will be...  I have some data aquisition logs that show the
timing and onset of knock quite nicely.

> running excessively lean. Very wrong. I was not running lean in the least
> bit. EGT temps were high, but safe (due to higher boost). Air fuel meter
> showed a slight lean condition, but safe and well within acceptable. Many
> turbo cars will lean at boost, anyway and mine what just a hair under.

But you don't want to be running lean at all, you want to be running
rich.  That's what the stock ECU settings are for stock boost.
I'd be worried if I wasn't getting 0.7 to 0.8 V at least out
of the O2 sensor under boost.

Still, the later engines don't seem to mind too much.  Do it
to an UrQ and the inevitable burnt exhaust valves will occur
that much sooner.

Orin.