Exhaust valve

In the exhaust of the recent Ducati models there is a valve very similar to a butterfly throttle in an early carburettor. This valve is controlled by a small servo motor just behind the right hand side fairing panel with two cables.

cablesThese are the cables after removal from the bike.

In my opinion anything that causes a restriction in the exhaust of any engine will reduce efficiency – that is power and economy. The valve is opened and closed by an input from the bikes electronic control unit (ECU) so cannot be just disabled without the ECU throwing up an error message on the dashboard. That means that if you disconnect and remove the cables the servo will not tell the ECU that valve is working due to a lack of resistance on the servo. There are two ways around this, one is to fit a metal profile to the servo so that it thinks there are cables there and the other is to fit a small electronic box instead of the servo which does the same electronically. The electronic box is obviously the preferred method as the servo can also be removed.

Before paying out for the electronic box I thought that I would see how different the bike feels without the exhaust valve operating.

coverThe exhaust valve is behind this cover on the right hand side of the bike. Remove the heel guard from the footrest (two bolts 8mm spanner) and then the three bolts holding the cover. The bolts in mine are non-standard aircraft titanium bolts that weigh in at about a third of the steel ones.

valveThe valve is now revealed. Mine is wire locked in the open position, but that is just the aircraft engineer in my as it is spring loaded in that position anyway. The two holes to the left are where the cable ends were fitted, and the wire locking goes to the cable guide.

Rather than buy a metal profile from ebay I made one up from a piece of mild steel so the servo motor will only turn as far as it would have done with the cables fitted. I won’t show you a picture of the profile as it is just temporary to allow me to test the result and I can return everything to standard if required. The purpose of the exhaust valve is, as far as I can understand, for noise emission checks and the bike does sound a little louder with it disabled.

When I departed for the 100 km road test I noticed the difference within a few hundred meters. We have a rough track from our house before we get to the road and on that track is a small hill with a bend on it. First gear and no throttle is the normal way to negotiate this obstacle. Before, the Ducati would threaten to stall and stutter on this bit of track, but what I did not know was that the exhaust valve was moving. Now the bike was much happier going around the bend at slow speed. Out on the road there was very little difference in sound that I could hear, but my wife was with me on her BMW F800ST and very noisy exhaust! I would say that the bike felt much better at lower revs when riding around town and now pulls much more smoothly from down around the 3000 rpm mark, something it would not do before.

I have now ordered the electronic servo motor eliminator for the US via ebay and will leave the bike as it is until that arrives. When this is fitted I will completely remove the servo motor and put it in a box with the cables. That box will probably sit on a shelf in my garage for the next thirty years as none of us like to throw stuff away!!!!!!

I will give a link to the eliminator once it arrives and is fitted.

If you are interested in a girls outlook on biking then have a look at my wife’s blog HERE



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