Happy Dyno?

[Shonky.]

I am getting close to having my car tuned and while I understand the dyno's role is for tuning, not bragging, I really would like to see the difference the tune make to the cars output.
So I guess it's fair to say I don't mind if the end number is accurate or not, just that the % increase as a result of the tune is accurate, so that when I go for the next round of mods and repeat the exercise I have a good idea of which parts contributed what to the end result.
So, how does one create a "happy dyno"? What parameters are adjusted? Are these available on the printout that is supplied to the customer?
I would imagine there is a strong incentive for tuners to "adjust" the dyno between the stock and tuned runs to inflate the performance gain and therefore the perceived value.
Is it possible to verify that this has not been done from the dyno printouts?
Clearly I don't know squat about the operation of dynos, so would like to know a little more before I jump into it.

[Nikked]

The dyno's arnt really adjusted between stock and modded...

But, some dyno operators adjust all the gizmos and can create happy numbers, some do this to take into account drivetrain losses etc...


Street machine had a good artical on dynos, and have a few suggestions for helping big numbers appear, 2 of which are...

-lowprofile rubber
-thninner oil

[yift]

as long as the AFR's are within spec you will be making the correct power.

i have seen alot of tuners run vehicles dangerously lean in order to boost power outputs which are cowboy antics.

[Shonky.]

Yeah, I wouldn't want to be pushing for the biggest numbers at the expense of safety, which is kinda why I want to learn more about it.

I think it is sometimes appropriate to adjust ramp rates etc, but I would like to understand this so I can distinguish between attempts to correctly compensate and shenanigans

[prasac]

at the bottom of the dyno sheet you will see things like AT, RR, BP. when you adjust the air temp, barometric pressure, hmidity it will increase the power. dyno's work on a calculation method of power production on a perfect day. say for instance you dyno on a very humid 40C day, you will read less power, the dyno will then compensate and show the power it would make on a nice perfect humidity 19C day for instance. this should explain it better http://wahiduddin.net/calc/cf.htm

picture of a dyno sheet, notice at correction it has all the details and provides a 5.16% correction, so the car really made 95rwhp and the correction was 5% so it would bring it up to 100rwhp


here is a dyno dynamics readout, all the data is on the bottom, the correction factor that Dyno Dynamics uses would actually show a lower figure than the Mainline would as they use a different calculation.

[Psi-Pop]

Here is a good thread that a sponsor has put up to show how they can be manipulated.

http://www.fordforums.com.au/showthread.php?t=11362400

[ratter]

The applied correction is not a calculation that is decided by the dyno company, it is a calculation set by the SAE (Society of Automotive Engineers), but there can be different standards than can be used and each has a slightly different calculation, on some dyno's, the operator can choose with standard is used. The mainline sheet above shows that the standard J607 was used.

[Shonky.]

That's awesome, thanks guys!

So it seems as long as the same SAE standard is being used on both runs then the dyno implements the appropriate correction factor for the conditions and gives a true controlled comparison?

So these atmospheric conditions are entered manually, or measured by the dyno?

Also the Mainline output is very easy to interpret, but can someone explain the fields on the bottom of the Dyno Dynamics one?

I guess BP = Barometrice pressure, RH = Relative Humidity, AT = Air Temp

Accred # is the SAE standard used is it???

What are RR, TN, CK and CF?

[Shonky.]

Originally Posted by Psi-Pop

Here is a good thread that a sponsor has put up to show how they can be manipulated.

http://www.fordforums.com.au/showthread.php?t=11362400

Thanks, saw that one when searching before starting this thread

[ratter]

My mainline has an automatic weather station that sends updated information to the dyno computer multiple times per second, some dyno's the operator has to manually enter figures from a third party weather station and the dyno computer prompts the operator every hour to update if necessary the weather figures.
The air intake temp sensor has no bearing on adjustments to the correction being applied, it is there only to record temps that the engine see's

[Shonky.]

Thank you.

I guess in either case (auto or manual input of weather) it is recorded on the sheet for review, so if the values seem extreme you could ask.

Cheers again.