Daytona RS Exhausts, Tuning and stuff

Written 07/13

Summary: Daytona RS dyno runs with open exhaust, eprom tuning, influence of 1.6M ECU idle trimmer setting and comparison to Sport 1100i.

I found some dyno runs for a Daytona RS from the old Dynobike dyno and recently dynod another on the new dyno so thought I’d put some runs up.  Both bikes are running Staintune mufflers, and I believe they’re both running the Mistral crossover that’s sort of a “Double Z” style, in that the pipe from one side runs across under the gearbox to the other and where the two pipes cross in the middle they’re open to each other.  I ran something like this on my Sport 1100i at one point and even made my own version, but neither worked quite as well as the full system I made which had a crossover much like a Termi or Staintune full system.

Bike one, run on the old dyno, was running a CSTN eprom which I believe is one of Will Creedon’s that I’d modified a bit in ways that I don’t recall now.  Otherwise it ran a std airbox.  My main playing with this bike was to see how it was running, and then, based on that result, I think I decided to adjust the idle trimmer to see what influence it had.  Red is with the trimmer set for the desired 5% CO idle mixture, which corresponded to around -120 degrees counter clockwise from the centre point.  Blue is with the trimmer full rich or 135 degrees clockwise from the centre point.  As you can see it was still too lean, but better and that indication is what I would have been looking for at the time.  As an aside, I had been told they made 100hp, and back in 1997 that was pretty cool out of an aircooled 992cc twin.

The variation in fuelling is at a guess up to 20% at low rpm and more than 5% at the top end.  So you can see how important the idle trimmer setting is to the overall running of the bike.  The variation at lower throttle openings will be greater too.  The issue this brings in service is that if the bike an eprom was developed on wasn’t set up properly then using that eprom in another bike carries no consistency of setup.  It’s the predominant reason I have an expectation of failure whenever I sell an eprom for a Guzzi.  And why I recently changed the Sport 1100i eprom I sell to be consistant with the original eprom in terms of idle trimmer setting.  At least that way the new eprom makes the theoretically desired changes from how it was.

Next I’ll compare this bike to my Sport 1100i and BMW R1100S.  I had the opportunity to buy either the Sport 1100i or Daytona RS when I bought mine back in 1998.  I went with the Sport as it was around $3,000 cheaper from memory, and the next graph makes the rider in me happy that I did, although the hot it up side of me always had a thing for an RS and how much power it might put out, regardless of relevance.  Blue is the RS, red my Sport 1100i with the full system I made, ported, decked and dual plug heads, open airbox and tuning to suit and green is my R1100S with the Staintune full system and Ultimap eprom fitted (it didn’t dyno well with the big duct fitted) .  Power first, then torque.

The torque curve makes the difference really obvious.  You’d almost call the Sport’s torque curve a little peaky on its own, but the comparison with the RS makes it look much better.  The RS’s almost flat torque curve from 6,000 to 8,000 rpm clearly shows its high rpm potential, but the hole under 5,500 rpm you certainly feel on the road and that would and does annoy me.  I’ve not dynod a std cam Daytona or Centauro, but the C kit cams in the RS certainly live up to their old school big cam characteristics.  The new 4V motors feel fairly similar, although the last Sport 1200 4V I rode revved much faster I thought.  The BMW motor is nearly 100cc bigger than the Daytona, and a bit bigger than the Sport (1064cc), but its curve is super smooth and on the road it felt like the Sport 11 – open the throttle, away it went.  But its peak power is disappointing next to the RS, and it did sound crap.  I know I’ve said it before, but my Sport 11 was one of the best sounding bikes I’ve ever ridden.

Finally the second RS, run on the new Dynobike dyno.  I believe this bike came into Moto One some years ago and at the time had the cam timing reset to 108 degree inlet centrelines.  I’m not sure how much they were moved, but I have a memory of them being advanced 5 to 8 degrees.  It wasn’t tuned at that time due to time constraints and we didn’t have an Ultimap eprom on hand to suit it anyway.  In the time since then the owner had fitted an Ultimap UM431 eprom himself.

So this time I changed the fluids and fuel filter, set the throttle bodies and idle mixture and headed off to the dyno.  We did some wot runs with fuelling changes and part throttle runs and then I modified the eprom mapping as required.  Overall it was lean – the new eprom was richer (and generally quite a bit) apart from an area of light roll on under 3,500 rpm.  The first graph is power for base fuelling, +10 and +15%.  The rpm trace was dodgy for most runs, but the limiter comes in at around 9,400 rpm or 138 mph and 6,000 rpm is 88 mph.  Blue is std UM431 fuelling, red is +10% and green is +15%.

Feedback from the owner was that the power delivery was much smoother with the new eprom, which is always good.  One comforting thing I realised when modifying  a V11 map and comparing it to many other 1.5M and 1.6M Ducati and Moto Guzzi air cooled engine maps is that the temperature corrections on this eprom are quite normal, unlike many of the others I checked (early V11 especially).  More on that in another report.

There was one run with a functioning rpm trace, so I’ve compared it next to the runs from the first bike, showing both power and torque.  Given this new dyno reads at least 5% lower (13% it seems for my 750M) the outputs don’t exactly compare, but the shapes are completely consistant and that’s reassuring.  Blue is this bike with +10% fuelling, red the previous bike with the trimmer at full rich. So it seems the 108 cam timing hasn’t changed the shape of the curve or hurt the top end.  It’s a bit like the Ducati 750 F1 Laguna Seca, they’re so over cammed that any change is almost negligible on a dyno run.