996 Bips have been a bit of a nightmare for tuners, in a lot of ways they were
significantly stronger than the 916 engines they replaced but in one or two critical areas there were the potential for problems. The trick for the tuner is to get the
best out of the standard power producing parts of the bike without resorting to expensive new parts.
Brought out as a passenger friendly version of the 996SPS the bike was a bit of a stop-gap replacement for the then 5 year old 916. Styling and chassis were virtually
unchanged but a torquey 996 engine using a combination of SPS crankcases, heads, barrels and pistons with a 916 Bip crank design and gearbox.
The new engine was undoubtably stronger in places where the racers were becoming weak; the cases allowed a bigger bore without a reduction in strength;
the 916 ones are ok at around 916 cc but the cylinder stud spacing and case bolt spacing doesn't allow bigger bores without the resulting machining (opening the
crankcase holes) weakening the remaining structure unacceptably. The heads started the valve sizes at 36mm and thicker port walls allowed the porting
necessary to get the works racers to run 39mm valves with offset valve guides. All in all a good job of adding strength where needed for Superbike racing.
The problems are in the details; a new Eprom chip was designed, unfortunately the mapping included a spurious signal on the ignition advance curve; at around 3100
rpm the slightest increase in throttle leads to a sudden jump in the ignition timing, it looks like whoever designed the map intended there to be a sudden jump in fueling
but that is not what got translated into the actual map. The second problem came from the new con-rods; visually identical to the 916/748 pieces these steel rods
were slightly stronger; they needed to be because the piston they were trying to control are a lot heavier that the 916/748 pistons the earlier versions were living
with. This isn't a problem for the factory of course as the Superbike racing variant is allowed a new crank and heavy duty Rods.
Over the last few years the very irritating low RPM stumble has been dealt with by FIM who now market a revised (richened up) Eprom (Ultimap UM222) based on the
916 Senna Fuel Map as a single injector fitting for the 996; the 996 never really needed the dual injectors given to it, and it runs much smoother with this Eprom.
Without affecting top end power it loses both the erroneous ignition advance point and the problems of two simultaneous bursts of fuel each colliding with each other at low revs in the inlet tract.
The rods however are another point; they are stronger than the versions in the 916/748/ST4(same part) but they have a real problem with regular 10,000rpm plus
running, bikes fitted with higher than stock redlines can have a problem with rod breakage; it doesn't need much imagination to think how much damage is caused when that happens…….
So we have the ability to solve the fuel injection hiccup; we can try to live with the rods (fitting either stronger steel or Pankl titanium ones will cure the problem; its
just that either of these solutions can be quite expensive) so if a rod upgrade is not available what do we do?
Moving the power around
There have been
several race series where maintaining the standard redline is part of the rules, we took part in the 1999 British Production championship with a 748SPS where these rules applied. You rapidly learn to move
the cam timing around a little to get what you want, on the 748SPS where the standard bike has all its power in the last 1000rpm before the cut-off we moved the cam timing to boost the
power below its 11800 rpm redline when we built the engine. In the 748's case we could afford to lose peak because we just couldn't really use it there; we needed
and could lap a lot faster with more drive off corners.(Experience with a simple Stack recording rev counter on the following years 748RS showed a lot more
cornering around 6000 rpm ie 50% of peak revs, than you might believe).
Now into our shop one wintery day walks Ian Lear; Ian is going to move from racing a 900 Kawasaki in club racing to running in the Supertwins class on his 996Bip, the
major problem was that the budget was going to be small. Ian had already fitted a 45/50mm open intermediate Termignoni system and chip but the bike was standard.
Could we suggest a way to race it without major changes? There was no budget for heavy duty rods and the slipper clutch could come later…..we discussed the benefits of our Full Monty service including setting both motor and the chassis set up for track use.
Acknowledging that we were not going to sell Ian the SPS cams and Rods sitting on our parts shelf we decided to see if we could lift the power of the Bip lower down
its power curve without stressing the rods and give Ian a fighting chance by improving the torque available out of the corners. There is a natural assumption
that by trying for more power down low we would lose power at peak, and here is the key with this particular model, we don't think that the standard cam timing is
the limiting factor at peak. Just maybe we could have the proverbial free lunch and keep the peak power figure and develop more midrange?
We went off to the Dyno to get a base run and discovered a bike that was really hesitant at top revs with the trade mark 996 Bip stutter/power drop at 9100 rpm. (I
think it is a bit rich there and as soon as the bike has done over 5000 miles the wear on the valves seats conspires with the mixture to allow a misfire). If you look
at any number of 996Bip power curves they nearly all have the same hesitation/ misfire at the same point.
As soon as we got back from the Dyno the engine was hauled apart and given the Full Monty treatment; heads and barrels off, squish set at optimum, followed by
dismantling the head to clean the valves and valve seats then accurately setting all the valve clearances. After that it was the cam timing and fuel injection settings.
The cam timing we chose for Ian was not standard; its been set to try and get a few extra horses in the midrange, for that all important drive out of the corners.
Although not standard the cams on each cylinder are timed to within a degree of each other (something of an improvement on the normal 'up to 8 degrees out' spec
of some of the factory builds). To maintain a really smooth drive Ian was up for the FIM Single injector mod and to help further on the throttle response we modified the standard flywheel a bit.
This combination of build accuracy, good compression, along with the precision of the revised Ultimap eprom really improves the engines response to the throttle.
Once the engine was built it was back to the dyno; the revised timing was going to need some very different fueling to standard (the boost in torque we were looking
for was only going to come from the efficient burning of more fuel). From the first run we were obviously onto something. The top end was very clean and showed a
nice flat power band, the hesitation at 9k was gone and the engine revved freely through to its redline. We lobbed in 20% more fuel to start with; an awful lot and
while the engine made power it was clear that the richness would make the bike very unpleasant to ride any where other than at full throttle. We soon learned at
what throttle openings and revs the fuel was needed and where it wasn't………
This Dyno chart (click to enlarge) shows the best of the original base runs against the final one; a clear 8bhp improvement from the 'as delivered figures' at the top
end but with our revised cam timing still keeping a healthy improvement between 4000 and 8000 rpm. What is spectacular about this motor is a torque curve that
doesn't drop below 60ft-lbs anywhere between 4000rpm and 10400 rpm; tractor on reheat anyone?
Now for a little comparison, this chart (click to enlarge) shows the best run of the
Grunter Bip against the 996SPS we used in endurance racing in 2001. It's a fairly typical properly built 996SPS. We usually see identical power curves on both 996Bip
and 996SPS from the bottom to about 7500rpm where the SPS gains a few BHP. It feels more than that as the SPS revs up quicker. What we have here is a Bip that
has maintained its peak ie its only a few below a SPS at peak and made a bunch more torque in the midrange between 4500 rpm and 6500 rpm; a lot easier to get
out of corners and more importantly real power for normal users. We have also made it rev up and respond quicker so the differences between it and an SPS are reduced even more.
The last chart shows a comparison of two 'all-gear' runs, the first thing that is
obvious is the increase in power, the second is how a super flat Ducati power curve allows you to change gear and maintain full power, you may have 'only' 120bhp, but you have it all the time………..
So what have we got for our efforts; stonking midrange with between 60 and 74 ft- lbs of torque from 4500 rpm to the redline and nearly 120bhp with no falling off of
the power curve at the top end. This 996Bip came to us standard apart from a 45/50mm intermediate exhaust system and we provided a Full Monty, our Grunter
cam timing; a reprogrammed Fuel injection computer with an Ultimap UM222 eprom and a light weight exchange flywheel.
Not bad considering we didn't fit any 'tuning' parts……………
Now we wait for Ian's report after the first few track outings.
Neil Spalding ©2002
© Neil Spalding 2002. All rights reserved