So lemme see, that's cam timing sorted, filtration upgraded (for hp if not small animals), improved velocity stacks....time to head to the dyno to see if I'd russled up a few more ponies.
And here's the result:
I'd basically achieved nothing! Seriously... what....the...hell?!
If anything I'd gone slightly backwards...but realistically both dyno sessions had documented a correction factor of "0", therefore the tests hadn't been standardised for differences in air temperature/pressure/humidity so I wasn't going to take the slight drop as gospel...the bottom line was a big fat "0" in the improvements column.
To say I was frustrated and confused is not going to surprise anyone.
Having said that, there is some useful info there:
- the torque peak has definitely been shoved further up the rev range, from 7000rpm to 8200rpm, so the valve timing has had the desired effect
- torque is hanging in there and therefore hp is actually climbing with revs when the rev limiter kicks in at 10000rpm
It was also interesting talking to the dyno operator, who just happened to be fresh over from Italy and operated as a race mechanic at a high level. He was skeptical of the extended intake trumpets theory, pointing out the Factory mantra of shorter trumpets for high end hp. Hmmm, obviously more investigation was required...
The other issue we discussed was the 10000rpm rev limit, not exactly ideal when I had 748R heads/cams fitted and a 748R makes peak power at 11500rpm. I'd built the engine to a spec (H-beam Ti conrods, balanced etc) to rev but the current ECU eprom just wouldn't allow it, and any eprom that did allow those revs (I actually had some on hand) would be set up for the SP or Corsa type dual injectors per throttle body which I didn't have. More investigation required there too!
In the meantime it was what it was and still made +20hp over a stock 851 Strada....but it was still frustrating. But another race meeting loomed and what better way to relieve some of that frustration than by figuratively and literally wringing the bloody thing's neck.
I had a slight setback at a tuning day the day before. I took the 749R out just to get back up to speed and get used to the new chicane that enabled bikes to again race at Barbagallo/Wanneroo, only to experience a lil' low side in the very first session.....yes, I was that guy. In my defence it was quite a cool morning (7degC overnight), you do 3/4 of a lap without ever touching the left hand side of the tyre, and I was to find out later (thankfully with no further harm done) that my "you beaut" tyre pressure gauge read approx 4psi low. Roll all that together into a snowball of cold track, cold side of a tyre that will be even cooler due to over-inflation and a few laps in I tipped left for the first time in 40seconds, brushed the brakes and "SPLAT!", I'm sliding along the tarmac. Aaaaah shit! Things could have been worse, with only minor damage, but I really didn't need any more work, or any more cracks in my crumbling confidence (insert heavy sigh here).
On the way out the gate I stopped in at the weightometer they have set up for the 4 wheel brigade, curious what the the 749R weighed (minus a few grams of fairing, peg, gear lever and 'bar, doh!). First weighing me holding the bike up, then subtracting my weight alone, arrived at 172kg. Draining 4L of fuel (3kg's @ 0.75kg/L) once I got home gave a ready to roll weight, minus fuel, of 169kg. Interestingly Ducati also provide an "in running order minus fuel" weight in their workshop manual: 194.7kg. She's not particularly light compared to an IL4 600 but she's not bad for a Ducati.
The next day I'm praying to Termignoni (the Roman god of racing) to exorcise the demons as I get ready. Again, not so many Golden Era bikes turn up but I do get to share the track with some very cool machinery: TZ750, GSXR7/11, NSR250, hotrodded GSX1100 etc.....
.....it just wasn't for very long. Rolling back in after taking it easy in the warm-up/1st qualifying, I glance down and notice smoke wafting up from the LH exhaust tail pipe: oil is dripping onto the exhaust.
Investigations in the pits lead to an unusual culprit: oil from the crankcase was being pumped into the airbox and then dripping down over the engine. My day was done before it really got started....again....and I dragged my sorry arse back home.
But not before stopping in at the weightometer again: using the above method she came in at 175kg, minus the measured 4L of fuel equals 172kg. Not too bad for an ol' girl....
But what was going on with that bloody oil? I mean it had been on the dyno just days before with no issue, so what was going on at the track?
Assuming the worst, first up was a compression test. Vertical cylinder:
Horizontal cylinder:
A healthy desmoquattro engine should be between 130 - 160psi, with the cylinders pretty even. I actually expected a tad more given the 748R heads and 96mm Pistal pistons (926cc)....but I have unshrouded the valves which would have cost a bit of compression. All things considered sitting at the high end of the healthy range, and both cylinders virtually identical, that side of things seemed tickettyboo.
So I turned my attention to the small OEM crankcase oil/air separator installation, nothing like the big Corsa units, but they were only so large to minimise pumping losses not because of excessive amounts of oil. Those oil/air separators also did away with the crankcase PCV valve, which I still had fitted in the OEM position. I couldn't magic up a Corsa setup but I could move some way towards it...
This is the airbox, with the breather hose entering bottom right:
That hose formed a sort of "kangaroo tail" looping up slightly to the exit of the oil'air separator. I wondered if small amounts of oil residue would slowly build up in that low point before burping up into the airbox?
So I rerouted the hose over the vertical cylinder head so oil drained back to the separator, and made a "Corsa-lite" PCV to sit at the airbox rather than down at the crankcase. This would add the volume of the "breather box" and hoses to the crank case volume, slightly minimising the pressure pulses.
I had in mind something like the 748RS setup which has a "cored" (straight through, no valve) breather at the crankcase, connected to a a breather box under the seat/tail, and that venting into the airbox via this valve....
...fitted in the 748RS airbox like this:
Fortunately I already had a cored RS crankcase breather sitting on the 999RS engine. But the 748RS breather valves are just impossible to source. And you can't just use a normal Ducati valve because of the way the fittings are oriented such that for it to flow the right way you have to somehow connect a hose to the large threaded fitting that normally screws into the crankcase, hmmmm.
One answer is to pick up one of these later plastic breather valves:
You then machine off the threaded portion and cut it in half along that line around the middle. Then flip the top portion containing the reed valves and using hot melt glue or similar, bond it together again. This means you can use the hose fitting and the valve flows the right way. So you end up with a plastic version of that unobtainium 748RS unit above:
But would it be enough?
And did you notice the now short intake trumpets? I was starting to get my head around the dynamics involved here, and more research had shown the intentions/effects of the different lengths. Much of what I wrote in earlier posts about the 'stacks/pressure pulses etc was actually formed in this period: longer stacks bring the torque peak down the rev range, shorter push it further up the range. So the earlier advice I was given about 1098RS stacks on a 1098 losing power was absolutely correct....because a stock 1098 is designed to make max power at just 9500rpm, nowhere near where the RS stacks are designed to work, and the cams/heads won't allow the thing to breathe and rev to a point where the stacks come into their own.
So it's all about the parts of the package complimenting each other, not just throwing cool parts at a bike when the parts may counteract each other....which is what I kinda did with adjusting the valve timing then lengthening the stacks. Every day is a school day....
