R1100S With Boxer Performance Cam Sprockets

This R1100S came in to have the cam sprockets from Boxer Performance fitted, so I took the chance to do some before and after runs. I wasn’t expecting a huge difference, but was curious to see what showed – as I’d expect many others are too. The sprockets advance the cams 9 degrees, and are a pretty cheap and simple mod aimed at improving performance in the range most people use most often. A mod for the realists, if you like.

Ultimap have an eprom to suit the Boxer Performance sprockets with the std exhaust and the Induct, plus with the Staintune exhaust and the Induct. However, this bike had the std air duct, plus a Vandelinde exhaust and eprom. Duane has tested an S with the Vandelinde and Induct, but never got to the sprockets as well. Not that this was any use to us here. Usually the Induct requires quite big mapping changes due to the change in airflow it gives, whereas fitting the sprockets is no where near as dramatic.

Also, the eprom that comes with the Vandelinde exhaust has a reputation for being rich through the mid range. Why I don’t know, just the way it is. So I was expecting to see that on this bike. It is the first time we’d seen this bike, so I have no idea of what has been done to it in the past. Given the air/fuel trace and the mileage (17,000 km) it may be ready for a fuel filter. Something we’d replace at the 20,000 km service.

To the graphs. Red is after, green is before. Power is first, then torque and air/fuel. The change in air/fuel ratio is of the order of 4% at the maximum variation. Not a huge amount, but something that, if changed, would be just noticeable to the regular rider of the bike I’d expect. Although, in reality, it’s probably the sort of variation you’d get with different types of fuel, that sort of thing. I would expect the base air/fuel to be richer with everything as intended, so the variation shouldn’t be a huge issue. Especially as the Vandelinde eprom appears to be too rich anyway.

The improvement isn’t large, and I’m sure the drop at the top of the graph will be interpreted by some as a catastrophe by some (that’s what people do). But unless you’re running it over 7,500 RPM often (and need the power over 7,500 RPM) it’s not really a big issue. And there’s a pretty consistant 3 – 5% from 2,500 to 6,500 RPM. The biggest change I noticed when we were doing mine all that time ago was the improvement in part throttle response. Just makes them feel stronger in the lower rev range, especially helping drive out of corners.

What you make of it is up to you.

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