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Exup and exhaust cam timing

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Re: Exup and exhaust cam timing

Postby acotrel » Sat Apr 15, 2017 2:42 pm

As I understand it, this dyno is commonly used for bikes :

http://www.dyno.com.au/dynotech/dynotech-motorcycle

If you do a bit of research, you will find that the calibration is fiddled so that the Yamaha V max reads it's specified 135 BHP. All other bikes are then measured relevant to the specified value for the V max.
If they have done that for the horsepower figures, how good are the torque measurements ?

In Australia all scientific measurements are usually related back to the standards maintained by the National Measurement Laboratories. Anything else is suspect.
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Re: Exup and exhaust cam timing

Postby Rohan » Tue Apr 18, 2017 10:20 am

This sounds like BS, what happened before the V-MAX was around !

Yamaha claimed 113 rear wheel hp, so to get 135 hp they would have had to 'fiddle the numbers' !!
When it came out though, this was well more than most anything else about....

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Re: Exup and exhaust cam timing

Postby acotrel » Tue Apr 18, 2017 2:33 pm

I'm talking about inertia dynos, not the Heenan and Froud type. In the old days the calibration was done ultimately with a dead weight tester. With the Dynotech dynamometer, it appears they attempted to do this , however when the figures appeared unrealistic they put the Yamaha V Max on the dyno and used a fiddle factor to make it give the maker's specified figure. That in itself is OK as long as you use the dyno in a comparative way and only claim precision rather than accuracy. My question is still about torque measurement. Over the years I have had a lot to do with motorcycle 'experts' - most of them are opportunistic bullshit artists. I could take my bike over to the dyno which is about 80 Km away, pay my money and achieve WHAT ? As you know very well, most of the guys don't even know the scientific basics, let alone the maths.
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Re: Exup and exhaust cam timing

Postby Rohan » Tue Apr 18, 2017 3:26 pm

The computer does all the maths.
Rolling road dynos do rear wheel horsepower.
Engine dynos do engines !

The computer can give real time readouts of torque and hp,
those mice inside can add up and calculate real quick. !
Caution should always be a byword when comparing results between different dynos/operators,
but using the same one each time you'd hope would/should be fairly consistent.

You really should go and see it done, even if the doubting thomas's in you don't/won't/can't believe...
Its fairly simple science to figure out power from acceleration, and with accurate timing its tough to fudge the figures too much...

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Re: Exup and exhaust cam timing

Postby Rohan » Tue Apr 18, 2017 4:22 pm

Dyno numbers - all done on the same day.

https://s27.postimg.org/urmg979rn/horsepowers.jpg

'puter can figure out the top speed reached too.
Presumably on the rev limiter, since there is nothing to limit the speed apart from the engine itself...
Some pretty tall gearing there.... ( And no air resistance !)

All relatively recent machinery, apologies for the lack of brit iron.
Didn't notice if any of them had exup !

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Re: Exup and exhaust cam timing

Postby acotrel » Thu Apr 20, 2017 4:26 pm

When I am next near Myrtleford, I will go and visit the dyno guy. However I won't have any great expectations. I've seen too many of the guys who are involved in motorcycles in Victoria. Most of them are dangerous bullshit artists whose main interest is in your hip pocket. In the end what I need is a before and after - cause and effect. So it probably involves a lot of road trips.
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