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Tech Tip: Low Cost Improvement for Fuel Injected BMW’s
Published in the Australian Ulysses Motorcycle club -
Hills Branch
Newsletter
I became an owner of a BMW R1200GS in April of
2008 as a replacement to a Japanese four cylinder motorcycle and was not
entirely happy with the behaviour of the big twin at low engine speeds. A modern
four cylinder can hold top gear down to near idle, whereas the GS really needed
to be kept around 3000 rpm and even then the motor could get cranky when hot or
playing in Sydney commuter traffic.
To me, the engine seemed to be tuned too lean, probably a side effect of meeting
all the appropriate emission requirements. This “crankiness” encouraged a bit of
searching on the internet to discover a way of adjusting the fuel injection.
Initially I looked at an add-on computer, this gives significant control of
injection parameters but can become complicated and expensive very quickly,
especially if custom mapping is performed on a dyno. Think $800 plus !
Also some of these by-pass the exhaust gas oxygen sensors undoing the research
performed by the factory to get the injection correct for most circumstances.
Another way of changing engine parameters is to introduce an error signal into a
sensor used by the fuel injection computer. The computer will then adjust the
mixture to correct the error and in this way it’s possible to make the motor run
lean or rich within certain limits. A good candidate is the airbox temperature
sensor as this is one of the inputs for cold starting.
A bit more research turned up the “Booster Plug”, made by an ex-MotoGuzzi
mechanic in Denmark, and the price looked right at USD$149.95 including shipping
to anywhere. Mine arrived around 10 days from order and, as I am a bit anal
about making things look original, took about an hour to fit.
That was back in September, since then I’ve done a few country runs and ridden
in city traffic, a total of ~3,000KM’s and the change is quite noticeable.
Around town I can now use a gear higher in most circumstances with the motor
running smoothly down to 2000 rpm. Torque is improved and carrying a pillion or
luggage is now much easier. Moving away from rest does not require as much
clutch slipping either. Fuel consumption is largely unchanged as the mixture is
only running around 5% richer at low engine speeds.
So I’m convinced, the Booster Plug fits most fuel injected BMW’s, have a look at
the website: http://www.boosterplug.com/
Below are a couple of photos showing the GS installation.
Cheers,
Chris Sweet
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