800 Monster  Cam timing, etc, tuned with SFI - Written 05/06

When the 800M was first released we had a shop demo that I did a pipe and air filter kit series of dyno runs. It was quite lean with these mods, but 800 owners who I approached about tuning one usually said “maybe next time”, translating as never.  So when I had an 800 owner ask about tuning after he’d fitted an air filter kit and pipes I was keen to give it a go.  I do like the 800 engine – it’s what Ducati never gave the 750 the chance to be.

We tuned this bike using the SFI, mainly due to the fact that it’s much less time consuming to tune than the U59 (which I have never used on an 800, so it’d potentially be a full mapping job) and half the price.  This work was done in conjunction with a 10,000km service, belts, fuel filter, tyres and 14 tooth front sprocket so it was quite a big bill all up, hence the cost cutting on tuning.  I wasn’t sure how well the SFI would work, but it was worth a try.

We carried out the 10,000 service, replaced the fuel filter (as I always do before tuning on the dyno) and reset the cam timing to 108 degree inlet centrelines.  This is 2 degrees advanced over spec (110) and on this bike as delivered was 113 on the vertical and 119 on the horizontal.  So we advanced the cams 5 and 11 degrees.  The basic tune was set up as per usual, with the idle mixture set to 4.5% CO on both cylinders.

The owner had fitted the mufflers (Silmotor) and DP air filter kit just before bringing the bike in, claiming he felt it hadn’t really gained anything over all std.  And that it wouldn’t wheelie (the horror).  Assuming that it would be a bit lean this didn’t really surprise me that much – sometimes a lean engine will feel very flat.  The fuel filter was a little restricted, but nothing extreme as I was thinking may be the case.  I didn’t get to do a before run – we had a busy week with lots of rain thrown in, but given the changes (cam timing, tuning, gearing) we were making I was confident it would run a lot better when we were finished with it.

Tuning with the SFI 1047 is pretty straight forward.  I take the bike to the dyno and do 6 ‘sets’ of runs with both yellow and red pots set to positions 1, 3, 5, 7, 9 and 11.  Just as I did with the ST3 and S2R 800.  You could probably go 1, 4, 8 and 11 if you wanted to save a run, but that’s not such a big deal.  Usually a ‘set’ of runs will be 2 runs, with 3 or 4 at the first setting to make sure we start with a settled output – the first run or two of any dyno session are usually rubbish.

From these runs I choose the yellow and red settings and the RPM switch.  Then I ride the bike around a bit and play with the green.  Although this is something I’ll also tell the owner to fiddle with as he goes – there’s nothing like riding a bike regularly to get a good feel for subtle tune differences.

The previous 800 I tested had a lean peak around 6,600 RPM, being quite lean from, well, everywhere.  I was hoping the cam timing changes would even the air/fuel ratio under 7,000 RPM a bit to reduce the inevitable compromise the SFI brings.  The first graph below shows power and air/fuel curves for this 800 as modified, but with no fuelling changes in red and the 800 from the previous report with mufflers and air filter kit in green.  I had intended and expected these two curves to be fairly similar.  However, that’s not how it turned out - this bike was nowhere near as lean as the previous one, nor as powerful.  Why I really don’t know.  But on the bright side the air/fuel curve was very flat, just what you hope to see when you’re limited to the two WOT adjustment zones of the SFI. 

The next graphs show this 800 as modified with the fuelling richened using the SFI.  Setting 1 (no added fuel) is green, 3 is red, 5 is blue, 7 is yellow, 9 is pink and 11 is purple.  Power first, then air/fuel.  You can see the power increase the extra fuel gives as we get closer to the preferred air/fuel ratio of around 12.8 – there’s nearly 6 Hp more at 7,000 RPM.  This was obvious riding the bike as well – it felt very flat on the way to the dyno and much better on the way back.  It also wheelied quite convincingly too, like an 800 should with these mods and a 14 tooth front sprocket.

As I did in the S2R 800 report, drawing 2 black lines across the air/fuel graph gives us the clearest image of how the SFI satisfies the tuning requirements.  Below is the above graph with the horizontal and vertical lines showing our options re SFI settings.  Keep in mind for the air/fuel curves the lag in the Dynojet system – about 500 RPM in this case.  So any air/fuel trace realistically needs to be interpreted as moved 500 RPM to the left when you’re talking tuning settings.

In this case, the compromise range of air/fuel ratio is 12.4 to 13 (mean 12.7), which is pretty good.  Using a yellow setting of 8 and a red setting of 10 keeps us within the black lines, apart from the richness under 4,000 (really 3,500) RPM you get from the acceleration enrichment function in the ECU software.  And I’m not concerned about the extra richness above 8,500 (8,000) RPM shown by the vertical blue line – it’s pretty much all over by then.  At the red pot setting of 10 the air/fuel would be going into the rev limiter at around 12.1, where a little extra richness is not that big a deal.  The vertical red line gives us our RPM switch point – setting it as high as possible gives us 6,500 RPM on the graph, 6,000 RPM in reality and on the pot setting.

We could maybe run it a bit leaner on the yellow pot, as it makes the same power pretty much at settings 3 through to 11 up to 5,000 RPM, and over the whole RPM range at settings 7 through to 11.  However, in my experience, the bikes usually feel better on the road with the extra fuel.

I also did a couple more runs while at the dyno.  The first was differing yellow and red settings – I’d not tried that before – to see how closely it followed the curves with the yellow and red at the same setting.  I ran yellow at 5 and red at 9, with the RPM switch at 6,000 RPM.  The graph below shows both at 5 in green, both at 9 in red and the yellow at 5, red at 9 in blue.  As above, allowing for the lag in the air/fuel ratio it’s pretty much spot on, which is nice.

Next up was some green pot playing.  For this I ran the bike at a constant throttle in fourth gear at around 75 km/h.  I started with the green pot at setting 1, then went to settings 3, 5, 7, 10 and back to 1, holding each for a couple of seconds.  Just to see how much variation the green pot caused.  The graph below, plotted against time (the clearest way to show it) shows the flat plateaus each setting gave.  Starting out with setting 1 giving 14.1, setting 10 dropped the mixture to 10.6.  Comparatively, at WOT going from setting 1 to setting 10 would usually see an air/fuel change from 14.1 to 12.7 or so, depending on the actual fuel pulse widths and how the addition of 1.44ms translated into a % change.

The next run isn’t a run at all – I forgot to do it.  I was going to try runs at a constant yellow setting, but with varied green setting.  Just to prove to myself how the SFI works.  Which is that the yellow setting is added on top of the green.  Maybe I’ll remember next time.

In addition to the above constant throttle/RPM run, I did a bit of riding around to set the green pot.  The bike was definitely lean at part throttle, and overall setting 4 seemed to be the best compromise across the under 6,000 RPM range.  This gave final settings of Green: 4, Yellow: 5, Red: 11 and RPM switch: 6.  Of course, the owner is also welcome to have a fiddle with it as he see fit.

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