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Issue link: https://magazine.cyclenews.com/i/128347
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MOTOGP
Round 15
Octobe r 17, 2004
World Cha mpionship Road Race S er ies
Tech Talk:
Firing Order and Such
It was obvious In the era of the Big Bangtwo-strokes of the 1990. that a close firing order
- or, to put it another way. uneven firing intervals - had a benefit for the tires. for traction
and for "ride r-friend line ss." The same thing has become obvious again in the MotoGP class,
nagged not only by Yamaha's "virtual V-four " M I for Valentino Rossi but also the revivalof
Ducati's previouslystill-bom Twin Pulse engine.
The difficult thing is pinningdown an explanation, a quest I have pursued all year.
Colin Edwards (45) charged the entire race and eventually finis hed fourth,
passing Alex Barros on the fina l lap.
Edwards (45) lea d s countryman
Hayden (69). Hayden came from
14th on the grid to finish sixth.
A new one in Australiacame from Aprilia racing director Jan Witteveen.
"With our two -cylinder two-strokes, we fired them simultaneously Witteveen said. "If
,"
we spread that out by one or two degrees, it would make little difference, but 10 degrees
apart made a big difference in rider feel and effective performance . I believe it is to do with
the way the tire heats up. With uneven firing, you get local hot spots and cool spots,
though the average temperature of the tire is the same."
In this way you get a luckydip, with some power pulses coincidingwith grippier
proportions of the t ire .
There may be something in this, according to Dunlop tire designer Dave Watkins - if
only because there really is a mystery.
"We understand what causes grip and how to improve it," Watkins said. "But there has
never been a detailed scientific explanation of the actual mechanism of grip - of what actuallyhappens, step by step , with the chemical reaction between the tire and the road surface, and the friction against the road surface."
What they do know is that at the moment a power pulse strikes the tire , "there is an
almost insta ntan eo us temperature increas e. in excess of 700 degrees boost in the fract ion
of a second."
If the tire snatches or slides through that part of the contact patch, "the temperature
increase gradient is much higher," he said.
For this reason, local temperature variations could be a factor, Watkins agreed.
The probl em with pinning down the reasons for it all is that the time intervals are so
small, but mo re understanding wou ld give tire engineers an im portan t tool. For the ti me
being, however, that understand ing remains as elusive as the Holy Grail.
MICHAEL S COTT
Johan
Dov izioso heading the pack as the riders
crossed the line for the first time.
Lorenzo was in the group , and as
Locatell i held a watching brief a second or
so behind, the trio of youngsters were
making all the running and e xchanging the
lead frequently. Lorenzo led over the line
for a spell, Dov izioso tak ing over from
laps seven to 12, then back again. Stoner
seldom saw the fro nt out on the trac k and
never over the line.
Towa rd the finish Locatelli closed up to
join in the last lap battle, but the othe rs
stretched their legs again and he was left
behind as they started the final lap,
Dov izioso in front.
Stoner dived to the lead at turn one;
Dovizioso pushed back underneath him at
Siberia comer, after the Honda Ha irpin ,
with Lorenzo also push ing into second .
One last chance remained, and Stoner
took it, regaining second at the tight , lastright MG corner.
The final drama played on the run to the
line. Dovizioso was safe enough, by inches ,
and it looked as though Stoner had second
- until Lorenzo's Derbi came alongside, to
be judged inches ahe ad over the line.
Locatelli was 2.4 secon ds adri ft in
fourth ; Steve Jenkner prevailed in a threestrong all-Aprilia battle for fifth, finishing
inches ahead of Hector Bar be ra and Gino
Borso i. Mike di Meglio won out in the
ne xt big gang .
Dovizioso is even more of a champion
than he was before, w ith a marg in of 91
points over Locatelli, 273 - 182. Lorenzo is
closing on 170, pushing Barbera ( 177) to
eN
fourth , w ith Stoner fifth on 14S.
AUSTRAUAN GRAND PRIX
PHI U IP ISlAND, AUSTRAUA
RESULTS: OCTOBER 17, 2004
MO TOGP Q UALIFYING: I. Sere Gibemau
( "lO.122): 2. Valen hno Raul (1:30.222): 1. Lori. Capi"""
(1:10.b I3): 4. Colin Edwards (1:30.b25); 5. Mal