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Re: [ST] Can + Tune



Mike Benzon wrote:
> I seriously doubt the ride to the dealer with the new can will do
any harm
> to the motor. After all, the FI will compensate for the reduced back
> pressure. I ran a couple of days with my SS can before the dealer
was
> available to download the proper tune. He said that it would only
effect the
> smoothness of the motor running.

The concern is that the freer-flowing exhaust will cause a lean
running condition.  My take:  It's unlikely to make any difference if
you ride moderately.

and Kieth Winter added:
> You're probably right, as long as it's a 2002 or newer 955i
> engine with the O2 sensor; the earlier models did not have
> the sensor and therefor could not compensate for a
> difference in back pressure, etc. because they could not
> take a reading on the exhaust gas composition.

My understanding is the O2 sensor controls the idle fuel trim below
1500 rpm.  The system lacks the inputs (from a maf sensor, for
example) for full-range control.  Instead it recieves data on throttle
position, rpm, barometric pressure, coolant temperature and others and
selects fuel delivery, timing etc. from a 'map' (the tune) for those
conditions.  Add a freer-flowing can and the map needs to be tweaked
for optimum operation.
- --
Rick in Oregon
'01 Sprint ST




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