87
GS Intake Manifolds and Cat Code Plug “Hop Up” An
R1100RS/RT! - Rob Lentini
Many BMW “Oilhead” riders spend big bucks chasing more horsepower with
expensive exhaust systems, magic Motronic microchips, even camshaft and
head modifications. I’ve wondered whether many of these riders have defined
what it is they want to “improve”?
I don’t know about you, but absolute high RPM power is NOT why I purchased a
BMW. Superior broad torque, “user friendly” power delivery and fuel economy is
what I seek in an engine. Top speed advocates often perform expensive
modifications to a BMW for only a modest peak horsepower increase. Then the
machine may be less rideable and reliable on the street. Not my style, thank
you! I prefer strong roll-on power for normal every day commuting, sport riding
and touring.
When I learned about a simple way of getting almost 5 more peak mid-range
horsepower from my ’94 R1100RS while increasing and smoothing power
delivery from 3000 to 6500 RPM for less than $35, I was all ears! Here are the
facts…
Anthonie Mans posted an interesting test on the Internet BMW Riders/Oilheads
lists performed by “Das Motorrad”, a Euro motorcycle magazine. All that was
done to a stock R1100RS (same engine as in the RT) was to give it a
dynamometer baseline run and then replace the intake manifolds (black tubes
connecting the airbox to the throttle body intakes) with those from a GS. Then
they dyno’d the RS again. Here were their reported results in Newton Meters of
Torque and Metric Horsepower:
RPM Torque (GS tubes) Torque (RS tubes) HP (GS tubes) HP (RS tubes)
2000 86 87 24 25
2500 85 86 29 30
3000 92 89 41 39
3500 90 89 44 43
4000 92 83 52 47
4500 96 96 62 62
5000 102 99 73 72
5500 106 102 82 80
6000 101 96 86 81
6500 92 92 87 87
7000 86 91 86 90
7500 79 85 84 90
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