PoWeRtRiP

http://forums.evolutionm.net/showthread.php?t=181046

O.K. so anyway. I get this months Hot Rod magazine in the mail. There is an article in it, "The Truth Meter". It's about the Mark Dobeck, the originator of the Dynoet. Basics of the story is he was just building kits to re-jet carbs back in the 1980's. He needed a way to hook a large piece of equipment to a motorcycle and test AFR's and such. Well since that was impossible he decided to make a portable roller to run the motorcycles on to use his test equipment. He then got an idea to make this portable roller calculate HP.

At the time the most powerful motorcycle being built was a V Max. Here is the story from there, just a paragraph:

"Dynojets final number-fudge was arbitrarily based on a number from the most powerful road-going motorcycle of the time, the '85 1,200 cc Yamaha V Max. The VMax had 145 advertised factroy hosepower, which was far above the raw 90 hp number spit out by the formula. " (*not a quote->they are talking about the formula that they came up with to figure out the hp based on the time it took to accelerate the rolls of the dyno they built) "Meanwhile, existing aftermarket torque-cell engine dynamometers delivered numbers that clustered around 120. Always a pragmatist, Dobeck finally ordered his Chief Engineer to doctor the math so tha the Dynojet 100 measured 120 hp for a stock VMax. And that was that: For once and forever, the power of everything else in the world would be relative to the '85 Ymaha VMax and a fudged imaginary number."

Anyway, the proof is in the story about what I was thinking lately. Pick up the March 2006 issue of Hot Rod and read for yourself.

The Dynojet numbers mean basically nothing. It is a tuning tool to make baseline runs from and measure you gains. The actual numbers are inflated and that is FACT based on the inventor himself.

quote-david buschur

interesting post by dave buschur on the evom forums. given our recent controversy over the magical 300whp number on a dynojet, i consider this to be relevant.

my main question is to any engineers out there. Is this true? What is the proper calculation for determining WHP, and which dyno most accurately represents the real numbers?

Alberto

iTrader: (14)

I highly doubt Dynojet the company has maintained the same BS application to come up with hp/tq numbers as they "supposedly" did 20 years ago. Interesting story but I think its "bsflag:

PoWeRtRiP

you never know. thats why i put it up here. i know we have at least one person on the board who works for a dyno seller. plus many of the shops are quite familiar with these devices.

im not convinced this is true either, but im more than willing to hear an explanation as to how the dynojet arrives at its numbers, and just how accurate they are.

phunk

iTrader: (21)

i dont even care if its true... all that matters is that the dynojet numbers are what everyone else uses for comparison... if you wanna claim titles in country where everyone thinks dynojet, then you have to do it on a dynojet. thats all there is to it. who cares if its accurate to real mathmatic HP... dynojet numbers are just what we are used to computing and deal with in our head.

phunk

iTrader: (21)

oh but BTW its highly unlikely that this is true anyway. I have dynoed literally hundreds of stock cars on a dynojet. They never make anywhere near what they are flywheel rated at the flywheel from the factory.

This wouldnt be the first BS i have seen published... but either way.

fahrenheit350

iTrader: (15)

I was just reading that part where you said "i know we have at least one person on the board who works for a dyno seller" and it dawned on me that my co-worker use to build and maintain dyno's. I'll get more info for you and his background on it.