R1100, R1150 and R1200 Alpha-N Fueling and the Dyno: Post #5
As I mentioned above, Roland and Terry collected BMSK data with the GS-911 while making 8-10 passes at a dyno lab. One of the items reported by the BMSK to the GS-911 is a parameter called Engine Load. It is reported as a percentage of the maximum torque load that the engine can produce.
From the Air Charge chart in Dyno post #1 (essentially the same information as Engine Load) you can see that 80% is typical maximum charge at WOT for our type of engine.
In addition to the GS-911 data collected on the dyno, Terry has set me dozens of test-run GS-911 files from his R1200GSA including some where he has accelerated in 4th gear at WOT--same as on the dyno.
On the chart below you can see that the max engine load on the dyno was ~63% and the max engine load on the road was ~70%. This is another way to see that the dyno is under-loading the engine due to a lower inertial load than an actual riding load. Also note that on the dyno, the engine load doesn't reach 60% until 3500 to 4000 RPM. This is another indication that less than full HP and torque is being measured.
The dyno measured a peak 95HP and 74 lb-ft torque. If you scale up those numbers by 70/63 (road load/dyno load) you get 105 HP and 83 lb-ft torque, which is the R1200GS spec. I don't know if this is coincidence or if the dyno might have gotten the right answer if it had a full riding load but I wanted to point this out.
If you look at the engine load before WOT you see that riding down the road in 4th gear, 1800 RPM yields a 35% load. The BMSK senses 0% load in the seconds before WOT on the dyno. This difference has much more bearing on the measurements than the 63 vs 70% load issue. The reason is that the BMSK commands very lean operation at light loads, resulting in an under measurement of torque below 3500 rpm. The solution to the problem is to add a small static load to the dyno (by asking the dyno operator for it ahead of time). You might even be able to apply the rear brake just before WOT, to keep the fueling where it belongs.
In the charts in Dyno post #2 you can see that most riding is in the 2000-4500 RPM range. You can get a much better measurement of torque in this range on the Dyno if you properly load the engine during the test.