S4Rs Monster With 50mm Termi Kit  - Written August ’06

The newest big monster, the S4Rs runs the same 998cc Testastretta engine as the ’05 999.  Meaning it has a deep sump and S model cams with the base model style ‘heavy’ crank and steel rods.  The only real difference between the 998 or 999 series engines and the monster series engine is the throttle bodies’ diameter – 54mm with shower style injectors on the Superbike, 50mm with under throttle injectors on the S4Rs.

The throttle bodies are the same as the ’06 model ST3, and are functionally the same as the old single injector 4V throttle bodies used on everything from 888 until S4R.  I thought the injectors were the same end feed IWP069 injector as the 748R, 998 and 999 shower injector throttle bodies (the biggest Weber make of the style), but they have a different colour band on them (pink instead of yellow) so I’m not sure now.  They also have a cast in TPS, like the 749/999 series.  How much difference these smaller throttle bodies make to the power output of the S4Rs I’m not really sure, as I’ve had quite a bit of variation from 998S engines over the few I’ve dynod and this bike, with the power kit fitted, fits within the range of those 998S.

The Ducati Performance Termi kit consists of a 50mm diameter full system, air filter kit and ECU.  The DP ECU differs slightly from the original DP ECU in that it does not run closed loop.  I assume those behind the DP kits, clearly marked “For off road use only”, feel there’s no need to meet the road requirements.  As you would.  The kits do, however, come with baffles in the mufflers and a little label stating TUV certification.  Not that they sounded overly quiet with the baffles in though.  These baffles are made from tube about 25mm OD and maybe 125mm long with capped inner ends.  The tube has a group of holes at the capped end, not enough for you to think that they’d allow any power to get out, but they obviously do.

To the graphs.  Green is all std, red is DP kit with the baffles out, and blue is DP kit with baffles in.  As you can see, the kit clearly makes a big difference – 11 Hp at the peak, 14 at 7,000 RPM and 13 at 8,000 RPM and adds 500 or so RPM before the limiter comes in.  Even with the baffles in it’s much better for most of the RPM range, and surprisingly close to the open muffler curve.  There are a couple of things that stand out – the dip at 5,500 RPM with the 50mm system and the hole from 4,000 to 5,500 RPM with the 50mm system and baffles in.  Some people will no doubt get all stressed about these dips and need an answer about why they’re there, but that’s just how different exhausts work.  Power first, then torque and air/fuel.

The air/fuel for the baffle in run appears to have quite a bit of lag – the baffles only let the probe sit in the end of the muffler around 125mm and would effect the sample reading speed quite a bit.

Riding the bike the difference is clear – it goes much harder.  All std the bike certainly felt quite nice, with a good top end, but it just didn’t go that hard.  Rolling it open around 4,000 RPM in second gear it would pull smoothly to the rev limiter, but wouldn’t lift the front wheel.  With the kit fitted, the front wheel starts to lift around 6,000 RPM and the rising torque curve keeps it lifting up to 8,000 RPM.  By which time I’d shut the throttle and changed gear.  Opening the throttle again in third will hold the front up very nicely – it’s certainly the most impressive Ducati I’ve ridden ease of high speed wheelie wise.  Very impressive indeed, albeit not so much license retention friendly.

Compared to the S4R, in all std trim there’s not much between them until 9,000 RPM, by which time it’s all over for the S4R and the S4Rs powers away.  S4Rs is green, S4R is red.

I had this report written soon after we did this job, but the bike came back before I got to publish it to have the cam timing reset.  So instead of writing a new report, I’ll continue this one.

All the S cam Testastretta engines I’ve checked have had the cam timing retarded.  At some training in April ’02 they told us the cams should be about 6 degrees retarded, and to this day they still haven’t fixed it.  This bike had the inlets retarded 2 and 5 degrees over spec with the exhausts retarded 3 degrees.  Given the exhausts were both set at 108 from the factory and my aim is 107 I didn’t bother changing them.  The inlets were reset to 107, advancing them 7 and 10 degrees over as delivered.

We also pulled the flywheel and machined it down.  Well, I fitted one I’d done earlier – we have a spare 3 phase alternator flywheel so we can do it as a changeover.  It also allows me to machine a few down at once when I get some spare time (which these days doesn’t seem to happen) as the set up time is a major part of the time it takes to do the job.

So the changes were inlet cams advanced 7 and 10 degrees and lightened flywheel.  It was pretty responsive before, but is now a little on the outrageous side.  This bike represents temptation in its most simple form for me – the exhaust note, the induction roar and the performance are simply delightful.  But I’m nowhere near responsible enough to own one.

Anyway, the after.  I took it to the dyno and did some runs with more fuel using the idle trimmer function of the Mathesis.  It’s a bit lean around 4,000 and 8,000 RPM and a little rich around 5,000 RPM.  But overall it’s not too bad, and really only needs more fuel under 4,000 RPM, which is somewhere you probably shouldn’t be using WOT.  And if you roll it open at 3,500 the acceleration enrichment will fill the hole anyway.  At some point in the future we may tune it using an Ultimap U59 ECU, depending on how the owner finds it overall.  First up I’ll show the after runs of power and air/fuel with the fuelling as was – the idle mixture setting didn’t change – and with the idle trimmer raised 60 points.  Green is trimmer at -5, red is trimmer at +55.

Next up is before and after cam timing reseting, showing power and air/fuel – the trimmer setting is the same for both runs at -5.  As you can see, the air/fuel is leaner down low and richer up higher – what you expect for advancing inlet cams – but overall the change isn’t that great at all.  Green is before, red after.

Adding the initial all std run to the above graph shows how much better it is overall.  Green is all std, red DP 50mm full exhaust kit fitted and blue with DP kit and cam timing reset.  At 8,000 RPM it’s over 18 Hp better than all std.  Power first, then torque.  The angle on the torque curve from 5,500 up to 8,000 RPM is fairly obvious when riding it – the more it revs, the harder it pulls.  It’s a pity there’s that hole around 5,500 RPM though.

Compared to the S4R is replaces, the Testastretta engine has the valve area to make better power, and in this case the bigger exhaust really helps too.  But the S4R engine is still good through the midrange.  The graph below shows this S4Rs in green and two S4R – both with cam timing, airbox, exhaust and tuning mods in red and blue.  Red is std cat box, DP slip on kit and idle trimmer raised, blue is Spareshack header, Staintune slip ons, air filter kit and U59 ECU.  Power first, then torque.  A S4R with the ‘Corse’ kit – 50mm exhaust, SPS cams, etc, I’d expect to go pretty close to equaling the S4Rs.  But by that time it’s probably cost about the same and wouldn’t have those lovely Ohlins.

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