Dyno gurus out there. Keep in mind, I do not have nefarious intentions with these questions. I would just like to know.

How can chassis dyno numbers be manipulated by the operator? Can numbers be artificially lowered or raised at will? How much is user error a factor in abnormally high or low numbers or are these things designed to minimize/remove operator error? I know different dynos yield different results based on how they calculate hp/tq (i.e Dynojet vs a Mustang, etc.) Is one type more prone to user error and/or easier to manipulate?

 

seems like a sore subject

 

Software set up, hardware changes, incorrect calibration, incorrect weather correction factors....etc.

Yes

Dyno set up, calibration, strapping, fan placement, and actual run procedure can all play a roll in power figures recorded. Each one of these factors open it self up to "user error".

Some of these machines are MUCH easier to manipulate then others. For example, a dyno jet 248 is basically just a spinning drum in the ground that measures acceleration. This makes it harder to alter set up and power figures. A dyno dynamics dyno however can use the simple key combo of "ctrl + X" to scale the whole graph by what ever factor you would like.




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Tony
Thanks for your reply. What specifcally about the 'run procedure' can give abnormally high figures?

 

Mustangs can be manipulated as well with factors like roller weight and parasitic multiplier.

Not hard to do and throws numbers way off.

Mitch

 

We have a Dynojet AWD setup, the MD's can be manipulated, much like Mitch said, to just about whatever you like, however they all load each car differently.

Pay attention to what correction factor is used as well, not all dyno charts are printed equally!

We specifically use SAE for reporting any dyno numbers, a good example is when hammer hit 915rwhp SAE, it was nearly 950rwhp on STD correction. Always look at the curve, before the numbers.

Look for real world performance numbers, such as the popular 60-130 and 1/4 mile timing breakdowns, while they can vary due to driver ability, pay attention to data logs to see how the car pulls through the gears.

 

^^Again, thanks for the input.

What's your take on this graph?

 

Man, that looks pretty ragged in the higher rpm's.

 

Also remember with that chart the smoothing value is at 20. It ranges from 0-100 so not much smoothing hence the jaggedness.

Using smoothing is something for another debate but very helpful in determining problems in the power band.

We have found that leaving a lower smoothing in Porsches really helps us to see detonation and where cars are pulling timing back, as apparent in huge dips in the curve that maybe missed when smoothed way out IE-80 or so.

Mitch