Ducati 620 Sport Base Runs, Mufflers, Etc

The new littly, the 620 engine is quite different in character to the old 600 carb engine. Given I spend quite a bit of time on a std 600M these days (and absolutely love it!), it’s something I noticed when I used the demo 620Sport for transport for a few days. With similar bottom end and midrange, the 620 keeps making power well into the top end. Not a huge amount of power still, but with a peak of 59 Hp std, it’s about 8 Hp up on my 600M in std trim.

For a full run down on the 620 engine, check the 2V comparison report. In short, however, the 620 has

• longer stroke – from 58 to 61.5mm, the old 750 crank.
• bigger valves – from 33.5 inlet, 30 exhaust to 41 inlet, 35 exhaust, the old 750 valves.
• different cam timing – earlier closing inlet mainly.
• fuel injection.

The main difference the fuel injection brings is the shorter inlet manifolds and larger 45mm throttles, compared to the old 38mm carbs. Both these features contribute to the improved top end performance, without reducing the lower end performance as happened with the 750 and 900 models when they went to fuel injection, although the cam timing also comes into play here.

We’ll start with a graph comparing the std 600, 620, 750 carb and 750 ie engines – in this case 600M, 620Sport, 750SS and 750SS ie. I’ve never dyno’d a 600SS with its smaller diameter 2 into 1 exhaust, so don’t know how they compare. 600M is yellow, 620Sport is red, 750SS carb is green, 750SS ie is blue. As you can see, the 620 is a little better at the bottom end than the 600 carb engine, while trouncing it completely above 7,000 RPM. On the road, it feels much more lively compared to the carbed engine, especially as the revs rise. I haven’t revved the 620 right out yet (there’s no point going to the 10,400 RPM rev limiter), but it gets to 9,500 pretty quick. It has that kind of engine nature that makes you hold on to a gear longer just for the sake of some more revs, and really is a very nice (and enjoyable) little engine to use. The power output is similar to the std 750SS carb, with the curve shape similar to the 750SS ie, not surprising given the number of inlet/head/exhaust components they share. Although it’s a while since I’ve ridden a 750SS ie, I’d have to say there wouldn’t be a lot between them in "on the road" performance.

The bike is perhaps a little let down by its suspension for serious sports riding, but that’s the nature of where the model is aimed I guess. Still very good fun to ride, and it surprises most who ride it with its enthusiasm.

Next up are power and torque curves for the 620Sport. Red is slip on mufflers and DP air filter kit, blue is slip on mufflers, and green is all std. Fitting the air filter kit caused a somewhat unusual effect when trying to get the bike off the line, although I’m not sure if the extra noise coming from the open lid was the main contributor. Something I’m sure you’d have allowed for after a couple of days of ownership. The noise is certainly worth noting here – just like my 851, the open airbox lid gives off quite a sharp noise in some conditions – opening the throttle generally – that will drive some people nuts. Something you either love or hate. It certainly does pick up the performance though. Having said that, I didn’t notice a huge increase when I went from all std to mufflers and air filter kit, but I certainly noticed it after I put it back to std. Funny how that happens sometimes. Doing the muffler and air filter mod makes the engine livelier, and even more fun to ride.

Next we’ll add some lambda curves. First up is std in green, slip on mufflers in blue and slip on mufflers with idle trimmer increased 10 points in red. Fitting the slip on mufflers hasn’t really made that much difference to the lambda curve, leaning it somewhat at the top end, but not significantly. I expected that increasing the trimmer setting (the trimmer is used to set the idle mixture – trimming up to suit mufflers, etc, is a bandaid solution for a too lean condition) would increase the power output (see the 800 report), but really didn’t make any difference power wise. So I’d have to say here that fitting slip on mufflers doesn’t upset the fueling enough to be of great concern at WOT. How it affects it at lower throttle openings is another thing. Duane did test and remap a 620 on his US trip, and this bike made about 5 more hp with his U59 ECU compared to the std ECU. The owners were also very happy with the improvement. So, as usual, the WOT dyno run doesn’t tell the full story. Given the 620 has the same intake and exhaust systems as the 1000, you would expect it to be far less demanding of, and less effected by them.

Now the same with slip on mufflers and Ducati Performance air filter kit. Green is all std, blue is mufflers and air filter kit, red is mufflers, air filter kit and trimmer increased 20 points. Again, adding the open airbox lid hasn’t made a huge difference to the lambda curve, and adding the 20 points on the trimmer has obviously richened the mixture without any difference to the power output. Apart from the odd "off the line" feel with the air filter kit, the bike felt quite good with this set up. But, pretty much all the 5.9M ECU bikes, especially the 620 and 1000 bikes I used as transport for a week, felt very nice in all std trim fuel mixture wise.

The next graph shows the changes with fitting the air filter kit, all other things unchanged. Even though the engine makes a little more power without the lid, it doesn’t make much difference to the mixture surprisingly. Green is std air filter, red is Ducati Performance air filter kit. The fact it doesn’t make much difference is a bonus in the sense of required mapping changes (or lack thereof). Whether or not the open airbox lid changes the part throttle fuel requirement due to changes in inlet tuning effect is something I don’t really know. Can’t imagine it would really.

The next graph shows the 620Sport with slip on mufflers compared to my 600M with slip on mufflers. The top end increase is pretty hard to ignore, but the 600M really responds to mufflers in the mid range, explaining the similar output there. 620Sport in red, 600M in green

The final graph is a road speed comparison for the 620Sport and 750SS ie. Both with slip on mufflers and air filter kits. With shorter gearing, the 620 is not very far at all behind the 750, an impression I got fairly quickly when riding the 620. On the road, the difference would be fairly minimal in general performance terms I would think. 750SS ie in green, 620Sport in red.

So there you have the little 620. It really is a surprising engine. Once again the combination of shorter duration cams with a little more lift and bigger valves has worked wonders over the whole rev range, with the addition of fuel injection topping it off.

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