Throttle Position Sensor - Rob Lentini - BMW R850 Maintenance Manual

Throttle Position Sensor - Rob Lentini

Note: the following information has been updated in the "Zero = Zero R1100
Throttle Position Sensor Tuning" article in the Super Tuning section of this
manual. The following information is intended primarily for people who wish to
adjust their TPS but do not want to change the factory sealed throttle body stop
screw on the throttle body.
Here's what I know about Throttle Position Sensor (TPS) settings on my bike an
R1100RS. I also suspect that this information will apply to the R1100 GS, RT,
and R also.
Locate connector #1 on your TPS - it is to your right as you face the TPS or the
rear most connector (red/white wire). All of my readings were taken with a high
quality Fluke 79 Digital Voltmeter (DVM) with the positive lead to the TPS and the
negative to the engine block. I used a paper clip to probe inside the TPS
connector. Readings may be taken with the engine running or not, though I
observed a very slight (2-3mv) change between the two states. Ignition must be
on, engine cutoff switch in the on position, and the sidestand retracted to make a
reading.
The voltage range at #1 is .370 - .400 volts at idle to a smooth increase with
throttle to 4.77 volts at about 1/3 throttle opening. There is no further increase to
wide open throttle. Thus this part of the TPS appears to control idle and off-idle
primarily. Publicized idle values as set by the BMW analyzer are the source of
the above .370 - .400 figures. These values appear valid, though changes to
individual machines may be advantageous.
It appears that for machines operated primarily at higher altitudes (above
perhaps 4000 ft.), setting pin #1 TPS voltage to .370 or even slightly lower can
improve performance. Conversely, if a machine is operated at sea level, #1 could
be set for .400 to fatten up the fuel/air mixture slightly.
Performance-wise here is what I observed and concluded:
-TPS #1 values of .370 or less reduce surging, reduce throttle response, and
increase backfiring tendencies. Too low a setting could cause pinging,
overheating, and catalytic converter damage.
-TPS #1 values closer to .400 or even slightly above don't necessarily increase
surging, but they do improve throttle response and reduce backfiring. Too high a
setting could violate emissions regulations, damage a catalytic converter, and
increase fuel consumption.
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