Mark wrote:
>I based that statement on dyno testing we did on my '94 and
>'96 RS125 roadracing bikes. Two exhaust cans, one 2" longer
>than the other, otherwise identical. HP difference was in
>the noise range of the dyno and not repeatable.
I know it is not necessary for me to explain the effects of exhaust
length, inner diameter, backpressure, etc. on the powerband of a motor.
I will say that given the fact that the limitations imposed on the
exhaust systems of F500s are construed to limit the power potential of
the motor package (short Y-pipe dumping into a single exhaust, etc.),
that any variances from these constraints have the potential to alter
the powerband of the motor and give one motor package an advantage over
another. It is often advantageous to sacrifice peak horsepower for
torque and vice versa.
I can site evidence of large variances in the power produced at both
high and low rpms between different pipe designs bolted to the same F500
motor and chassis (both Rotax and AMW) on the same weekend (most
recently at Road Atlanta 3 weekends ago on a Rotax-powered KBS MkV). It
is a fact that a change in the shape and length of a F500 exhaust can
result in the motor producing more power at certain points in the
powerband. The fact that your dyno testing with an RS125 did not show
noticeable gains does not erase this verity, but rather hint that the
cans you were testing were probably not the bottleneck of your exhaust
system.
>So you really think that the folks in question had those
>cans on there to increase power?
I think, as I have said many times, that the folks in question had those
cans on their cars for other reasons (obviously noise abatement), and
did not check the rules closely enough to realize that their cars no
longer complied with the silencers in place. The fact that the
infractions offered the potential to alter the performance of the motor
is simply one of the reasons that the exhaust systems were ruled
illegal. This is similar to my example of mounting a turbocharger to my
car in an effort to reduce the exhaust noise.the intention of the
modification does not make it or the potential benefits legal.
>You're certainly not implying that above.
I have stated all along that the fact that the cars in question were
illegal according to the rules was likely an oversight on the part of
the owners, and probably not an attempt by the owners/drivers to gain
some unfair advantage. On the other hand, the fact that the illegal
items offered the potential to alter the performance of the cars does
not change. It would be very difficult for a protest committee or me to
discriminate between an unknowing/unintentional violator of the rules
and someone whose intentionally sought a performance advantage yet was a
good enough actor to give people the impression that the rules
infraction was unintentional. The end result is that potential for one
bad apple does ruin the bunch.
>I'm sorry, I was in fact assuming this to be the case, based
>on the ease of which it could be fixed. So you're saying
>that the protestor went over and told the protestee that
>"I'll protest you if you don't fix your exhaust" prior to the
>runs?
>
>If so, I apologize for misleading everyone. I find it hard to
>believe, but there are stubborn people everywhere. :-)
I have heard both sides of the story from the people involved and I know
that each feels they are on the proper side of this argument. I can tell
by your comments that you have not done as much. It is misleading for
you to present your assumptions as fact.
J. Brett Howell
www.PebbleMotorSports.com <http://www.pebblemotorsports.com/>
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