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Pops
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"F-USA officials have adjusted the horsepower limits for machines in the Formula Sportbike (750cc Superstock) and Sportbike (600cc Superstock) classes to suit the change from a Dynojet dyno to a Factory Pro Tuning dyno.

The Dynojet number for Formula Sportbike was 145 and the Factory Pro Tuning number is 122.

The Dynojet number for Sportbike was 115 and the Factory Pro Tuning number is 100.

The Thunderbike class pounds-per-horsepower limit has been revised from 3.8 to 4.0 horsepower per pound.

Factory Pro Tuning dynos read lower than Dynojet dynos. Factory Pro Tuning owner Marc Salvisberg maintains that his dynos produce "true horsepower" and that the readings given by Dynojet dynos are inaccurate and inflated.

Dynojet officials maintain that their dynos are accurate, and Dynojet has sold many times the number of dynos sold by Factory Pro Tuning.

The Factory Pro Tuning dyno at Daytona is being operated by Factory Pro Racing's Leigh Thomas.

Factory Pro Racing's Salvisberg claims that his dyno produces consistent readings without horsepower swings related to changing weather conditions."
 

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Blue is best
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Factory, Superflow and the new Dynojet 250 dynos are all eddy current braking dynos which tend to produce numbers that are significantly lower than the cheaper but much more plentiful inertia drum only dynos like the old Dynojet 150's. The newer dynos are much better at obtaining part throttle tuning due to the fact that you can actually load the bike anywhere in the rev range you want to, whereas an inertia drum dyno is only useable at full throttle.

Regardless of what number you get on a given dyno, the important thing is to use that dyno exclusively for tuning, if you switch dynos you will get different results that may not reflect what you have done to the bike.

As long as the Factory dyno is used exclusively in the series, everyone will be subject to the same numbers from race to race.

As a side note, the lower eddy current dynos results can usually be converted to obtain an inertia drum dyno result by multiplying it by 1.15 - 1.18. So, if you had a bike that read 122 on a Factory dyno, it would probalby an average of 140 or 144 on an inertia drum dyno just like the example above.
 

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Inertia drum dynos will never give accurate measurements because the inertia of the back wheel go into the equations. This is a problem of the principle that cannot be solved. So inertia drums are good for before/after comparisons but not for absolute measurements.
Also there is no such thing as a "conversion factor" from inertia drum to braking dyno because the inertia of the back wheel do change from bike to bike!
 

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I think that my ass dyno is the best there is.. and cheapest :lol
 

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Shadow... surelly true when it is going to the price. I have a refined "ass dyno" on my bike, an accellerometer. While I am not able to tell anything about the real performance, I am able to tell if a mod has some effect. Just accellerate the bike in 4th gear for example from 2000rpm to redline before and after the mod (same amount of gas in tank, same road) and I am able to tell if I got a gain in some rpm area.
However for purposes like remapping you need a dyno.
 

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Blue is best
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Also there is no such thing as a "conversion factor" from inertia drum to braking dyno because the inertia of the back wheel do change from bike to bike! [/B][/QUOTE]

The conversion numbers I gave represent an "average" you can use to obtain numbers that are more representative of numbers obtained by the older Dynojet dynos. They are not absolute engineered derived numbers but were simply obtained by comparison of dyno results over time.
 

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Juerg said:
Shadow... surelly true when it is going to the price. I have a refined "ass dyno" on my bike, an accellerometer. While I am not able to tell anything about the real performance, I am able to tell if a mod has some effect. Just accellerate the bike in 4th gear for example from 2000rpm to redline before and after the mod (same amount of gas in tank, same road) and I am able to tell if I got a gain in some rpm area.
However for purposes like remapping you need a dyno.
I know... I was making a joke :p
 

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I know... I was making a joke
I understood very well what you wanted to say, never mind ;).
Actually the ass dyno for most of us is all what counts: If you feel happy with the performance, why should one care about figures...
 
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