Ducati 851 SP3

In my opinion, one of the prettiest bikes Ducati has ever built (even if it has got black wheels ). The 851 and 888 SP series bikes are also lots of fun to ride, with quick revving engines begging for a thrashing.

There is a bit of a story to this one that is worth telling.

This particular bike came in for a major service and a "running on one problem" with one rather loose and one broken cam belt. No reflection on the owner, he had just been given some not so correct advice that unfortunately cost him a bit of money. After the service, he claimed the bike did not have anywhere near the grunt it had previously. Believing we had done the job correctly, I could only guess the difference came from the new, correctly adjusted belts. On all Ducatis, loose cam belts advance the cam timing in a static setting, and, it would appear, when the engine is running. Which makes them go better. I explained that the belts would have slowly lost their tension without him noticing a performance change, and now it was back to how it would have been originally. He then requested that I loosen the belts off to the tension they were before the service. This is definitely NOT an option. I suggested that to regain its previous performance, he should get the cams dialed in.

At this point it was becoming clear we had a very good ( and very much liked ) customer going bad, so I told him to leave the bike with me and I would see what I could do. Having previously checked the cam timing during the service, I knew we had enough offset keys in stock to get the cams about where I wanted them. On a quiet Saturday morning ( it's amazing what you can get done when no one interrupts you ), I used the required keys to dial the cams. Doing this reminded me why we don't use offset keys on all our cam timing jobs. They can be inaccurate, inconsistent and very annoying.

But I digress ( it's a habit ).

I then asked the owner back to ride the bike ( without telling him what I had done ) and tell me what he thought. His verdict was most positive. My next suggestion was a revised eprom. The ECU used in the early fuel injected Ducatis is known as a P7. The great drawback of these is that you cannot make and store changes to the mapping. Any change you make is lost every time the ignition is turned off. It is possible to solder in an additional circuit board that allows infinite changes to any point of the map, but this was about double the cost of a custom eprom.

In addition to this, the P7 won't respond to resetting the TPS base value higher as it resets its zero value every time the throttle is closed. Also, the throttle bodies lack airbleeds, meaning all the usual tricks to richen the bottom end have as much effect as a withering stare and a little blue language.

The main reason for the new eprom was that the bike was particularly hard to get off the line, and generally unhappy tooling around. I figured I could make it both easier to ride and go harder at full throttle. So I rode around with the FIM hand held terminal race-taped to the fuel tank and worked out what I wanted. With this info, Duane burnt a custom chip and we were in business.

The power curves of the various states are shown below. The post service, std state of tune curve is green. The cam dialed curve is blue. The extremely minor differences between these two curves ( except between 6,500 and 7,500 RPM ) make it difficult to believe that I had actually made a difference. To the guy who owned and rode the bike, however, the difference was night and day. A good example of what the dyno doesn't show.

The red curve is with some more fuel added. The improvements you see with this line were not overly noticeable to the owner. Sometimes it's like that.

(dyno graph courtesy of DYNOBIKE, (03) 9553 0018)

At this point he was happy again. Which made me very, very happy.

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