SBK Rules

Two things of note. It seems that everyone in WSB is running some kind
of traction control but refusing to talk about it. And it seems to be
generally buried in the ECU where it's going to be extremely hard to
ferret out. Traction control is banned in AMA (right?) but surely AMA
and SBK Suzukis are running the same ECU? Troy Corser has admitted
running traction control while Mat can't say anything.

Secondly, Yamaha with Emmett in the UK have made a jump in performance
this year after experimenting with firing orders. And WSB has just
banned big bang, altered 1000-4 firing orders.

Now both of these look to me like technical areas where racing could
improve the breed and lead directly to better road bikes. Is this being
handled right?

 

Secondly, Yamaha with Emmett in the UK have made a jump in
performance

You can't experiment with firing order with ECU alone. You need to
modify camshafts for that.

 

And or crank shaft.

/MBE

 

Not necessary. Certainly not for an inline four. Probably not
for a V4 (dep. on whether rods are sharing crank pins).

To modify a four-pulse inline four, which typically has the inner two
and outer two pistons already moving in tandem, I leave it as an elementary
exercise for you to figure out.

 

But doesn't a "big bang" 4 cylinder engine have 2 pairs of "closely"
firing" cylinders - not a 2 pairs of simultaneously firing cylinders?
Necessitating offsetting of the "closely firing" crank pins, cams &
ignition timing?

Bummers

 

Allegedly, Virgin Yamaha are using stock crankshaft (required by the
rules) but are firing the pistons as 2-1-1-gap. The Motec ECU can
already do this, so they just had to get some cams made up, and they
were already sourcing their cams from one of the many custom engineering
places in the UK. The exhaust tuning isn't as good, the engine makes
less power and torque on the dyno. But it cut a second off the lap
times. Go figure.

 

That's easy. It's probably just doing what a big bang config is
supposed to do: let you get on the gas earlier with a more controlled
slide, so you're simply on the gas more than the guy who might be
putting out a tad more power. Also keep in mind that peak horsepower
number is just one point on the dyno graph. You gotta look at the
whole integral of the curve in usable rev range to really know the
difference.

Another thing that might be happening is a different ram air effect.
Airbox pressurization is a tricky thing and lab testing does not always
produce the full picture. I remember reading an article on what
happens in stock airboxes as far as big twins vs fours. The twins were
having a harder time because of "the big gulp" effect which was causing
the airbox pressure to go wildly up and down, whereas the fours were
"sipping" the air at a relatively smooth rate. Of course, SBK rules
allow all kinds of airbox tinkering, as well as different cams and
valves, so it may be that they've figured out how to use that gulp
effect to their advantage and tap into a big-bang or big-bang-like
motor's airbox resonance better than that of a screamer.

 

I thought the theory behind Big Bang was well understood by now - it
generates a series of 'microslides' at the tyre, but then has a long
enough gap for the tyre to 'recover'. There's no need for the mumbo
jumbo above.

 

My point exactly, it may have and undoubtedly it has been tested/used.
I'll leave it as a more advanced exercise for Michael Sierchio to figure it
out.

/MBE

 

Your thought experiment is beside the point -- is a crankshaft change
from stock permitted by the rules? If so, there are many options. If not,
there are still a few ways to implement a modified power pulse 4 cyl
engine.

 

No kidding? Microslides? Longer time for the tire to recover? And I
thought it was magic that let you get on the gas earlier with big bang.
Thank for clearing that up for me.

 

No and Yes. Which is why Virgin-Yamaha have just messed with the
cams/ignition to create what is probably a 2 together, one, one, gap
firing order. You could also do 2,2,gap gap or 2, gap, 2, gap. I believe
the first was too hard on the gears and the second didn't give enough
benefit.

[1]Note that I have a really hard time imagining firing orders in my
head. So the alternatives may not make sense at all.

 

The rules say (see http://www.fim.ch/en/default.asp?item=26# ):
2.4.6.20 Camshaft
Camshafts may be altered or replaced from those fitted to the homologated
motorcycle.
2.4.6.21 Cam Sprockets or Gears
Cam sprockets or cam gears may be altered or replaced to allow the degreeing
of the camshafts (see also Art. 2.4.6.18).
2.4.6.22 Crankshaft
Crankshaft may be altered or replaced from those fitted to the homologated
motorcycle.
Crankshaft stroke must remain as homologated.
Polishing or lightening is allowed.
Balancing is allowed of the crankshaft, rods and pistons.
SBK 71
*1000 cc Three and Four cylinders machines:
The following modifications are allowed to the homologated crankshaft :
a. Bearing surfaces may be polished or a surface treatment may be applied.
b. Balancing is allowed but only by the same method as the homologated
crankshaft. (for example heavy metal i.e. Mallory metal inserts are not
permitted unless they are originally specified in the homologated
crankshaft.)
c. Attachment of aftermarket ignition components or sensors is permitted.
d. Balance shaft may be removed.

The rules don't seem to say that crankshafts, cams etc *can't* have
their components *offset*!

 

I have a really hard time imaging your firing order descriptions

 

They don't say they can, either -- hence, a change in offset angle
from the homolgated crank is forbidden.

 

Well, I _think_ I saw somewhere that the new rules do specify an minimum
angle between two cylinders firing on a modified motor. That kind of suggest
that it might be leagal to alter the offset today.

/MBE