749S Remus slip ons and Termi 54mm Full system - Written Nov ‘05
We’ve sold quite a lot of the hotter spec 749S models from ’04 and ’05. They’ve given us some agro with a stalling issue that we appear to have fixed with revised cam timing settings. The original spec is 106/109 centrelines, as a fix Ducati specified this be changed to 108/113, opening the lobe separation and increasing the overlap, in this case by 6 degrees. It’s not a very big change, especially given the figures we normally use for the Desmoquattro engines (where we might change the as delivered cam timing on a 916 by say 20 degrees on the inlets), but it fixed most of the initial problem bikes we had.
When the’05 model was released it was allegedly coming from the factory with this cam timing the first ’05 we got we checked under suspicion and it was spot on. Since then, with some bikes not responding as hoped to the new Ducati numbers, we’ve started using 113/113, retarding the inlets a further 5 degrees. This seems to have sorted them all out so far. It doesn’t seem to overly upset the power characteristics of the model either, not surprising given how over-cammed they are.
My theory on why they stall is that they don’t have enough ignition timing at idle. But, given I don’t have access to change the timing in the ECU I’ll never know. I’m sure someone at Ducati does, and the cam timing changes are the cheapest and easiest fix.
We’ve run a few different exhaust systems on them now DP/Termi asymmetric kit (the cheap one), DP/Termi 54mm full system (2-1-2, now much cheaper than they were) and some Remus slip on mufflers (the 996 style ones).
The first graph shows two all std 749S in green and red. The red bike is running 113/113 cam timing, whereas the green bike may be running 108/113 (I don’t remember) this may account for its more midrange/less top end somewhat. The blue curve is an all std 749 base spec bike for comparison.
Next up we’ll show before and after for the bike fitted with the DP/Termi 54mm full system the red bike from the first graph. This is one of the ’05 systems (for the bigger ’05 style swingarm) with the funny oval-ish fabricated pipe coming from the collector up to the mufflers. The next graph shows before in green, after in red, with power first then torque and air/fuel. A mixed result really, which is a bit of a pity. It would be interesting to tune out the midrange richness of the 54mm kit ECU to see how much power came back there, for which you’d need a power commander or the like.
As you can see from the torque curves with the 54mm kit fitted the bike really comes on around 8,000 RPM, and pulls hard from there up, especially from the torque peak of 10,200 RPM. It’s a real pity the lights go out at 11,000 RPM this thing would be great with a higher limiter of around 12,000 or so. Realistically, it shows how over-cammed these things are. I’d like to know what they were thinking when they came up with this combo, as I just don’t get it.
Moving on to the bike that got the Remus slip ons. A very nice kit as far as kits go, these were easy and straight forward to fit, which is a marked contrast to the similarly styled Casoli mufflers I had to fit to a 999. This bike is the green curve from the first graph. The next two graphs show power first then torque and air/fuel, with green all std and red with Remus slip ons fitted. As with the DP asymmetric kits there’s probably as much loss as gain at different RPM points, but it will be more responsive and they do sound better, so overall the result is a louder bike with similar performance.
The red after run has the air/fuel taken from the LH muffler, as the Remus mufflers give the same format as the DP/Termi asymmetric kits, where there is no crossover or connection between the two header pipes at all. I did some adding of fuel using the idle trimmer to see if it liked more. It did, which seems to be common to many 5.9M ECU bikes, but given the very small changes I don’t understand why they respond so much. The next graph shows power and air/fuel taken from the LH muffler, with green being trimmer set to +5, which was where we set it for the correct idle mixture of 5% CO. Red is with the trimmer raised to +15, blue with the trimmer raised to +25. Not a great deal of change, and certainly room for more. Bikes tend to give max power on his dyno at an air/fuel of 12.5 to 12.8, so it’s both too rich and too lean in places. Something a good remap should fix.
Of course, the RH is a bit different, although not quite as much as I was expecting. The next graph shows the green line from the previous graph LH muffler, trimmer at +5 with red being RH muffler, trimmer at +5. This is where the benefit of remapping each cylinder individually comes in.
The only runs I have for a DP/Termi asymmetric kit are after only, so for the next graph I’ll show the after runs with DP/Termi 54mm system, Remus slip ons, DP/Termi asymmetric kit and a base spec 749 with the same asymmetric kit (different ECU of course). The green (749S, Remus), red (749S, 54mm) and blue (749, asymmetric) curves show the same bikes as the first graph, with the added pink curve being a 749S with DP/Termi asymmetric kit. While all the 749S are down on power until 8,000 odd RPM compared to the base spec engine they do have a nice top end rush when they come on. It’s just a pity the base spec engine has so much more bottom end and the shorter cammed 749R more top end.