Technical Discussion How to utilize dynomometer information

[Nth Moto]

With all of the discussion of dyno numbers lately from all the offerings to the Viper community, we (Nth Moto) thought it was wise to help educate everyone on how we as a community should properly utilize dynomometer information. This is by far and away one of the most misconstrued data points the performance aftermarket deals with and ultimately it ends up effecting the consumer negatively. Our objective here is to shed light and real data for people to see and understand, so people both in and out of the Viper community can have a better understanding of how these devices work, and how the results may impact your purchase decisions.

This information is a short summary of the culmination of our teams 30+ years of calibration experience working on dynomometers ranging from classic water brake units to advanced AVL machines inside OEM manufacturers. We continue to use both engine and chassis dynos depending on development and calibration goals.

The best way to start this out is to rule out the number one misnomer;

There are NO set dyno shop standards or rules applicable to dyno results around the world. Period. This means that one cannot factually state that Car #1 on a Dyno Model "A" will certainly dyno X horsepower on Dyno Model "B". A common form of that assumption is a Dynojet will read higher than a Mustang brand dyno, for instance. Additionally, one cannot take results from Dyno Model "A" and compare them to the results on Dyno Model "B" for any use other than entertainment and drama. Even the shape of the curve might be manipulated and/or altered by settings both in the software or mechanically that can skew results.

This doesn't mean dynos can't be calibrated to have comparable readings from cell to cell, it means there is no requirement between facilities around the world to do so.

You may be prompted to ask the question now, "But what about SAE, STD, and other standards of correction?" Ah yes, correction factors. Those factors are only applicable if the dynomometer software and hardware being used has the proper input information as well as a properly functioning and calibrated weather station, placed appropriately for the dyno cell, etc.

Need proof? I think we all deserve it, so Nth Moto did a little experiment for everyone. Below you will find dyno results between two Dynojet 248 chassis dynomometers in the Minneapolis metro area with one of our heads/cam/OEM ECU cars. For what it's worth, the lower reporting one is the one we use with our builds. Same car, same tune, same tire pressure, same relative elevation, and nearly identical conditions... you be the judge of what the information means. Did the car pick up power? No.

Now, should the car be advertised as a 650 WHP car, or a 696 WHP car? The car runs down the track the exact same way regardless of what the different dynomometer numbers report.

This is why the only number that has true relevance to the consumer is the gains produced via before/after testing of the build on the same dyno. Even that can have variance with conditions both climate and car related (water/oil temp for example), but it eliminates the majority of potential misinformation.

https://farm5.staticflickr.com/4301/36036034282_7c39879d69_o.png


https://farm5.staticflickr.com/4295/36161926876_eeb9d3e5ca_o.png

[uncaged_viper]

This is exactly why it's so hard to trust the marketing of various builds. Too many variances that allow for interpretation and misinformation. In the end, all that matters is the gap between the before and after. Nice post!

[donk_316]

TL;DR

Mustang Dynos suck! Haha!

Crank up the Dynojet!

[RTTTTed]

I'd also like to add that Bhp is the numbers that are not including friction and drag or powerloss through the driveline. Bhp numbers should be considered at least 13+% higher than Wheel hp

[Dan Cragin]

It seems like everyone uses Dynojet numbers as a standard. We use a Dynapack Dyno for all our tuning. It attaches to the wheel hubs of the car and allows us to load the car much better. This dyno is by far the best for tuning, but always reads higher than a Dynojet, so I typically give numbers from both dynos. Understand a dyno is just a tool, if you use the same dyno before and after your changes, and keep the variables about the same. You can measure the percentage of change pretty closely.

[Scott_in_fl]

So, with all of that said, how much power does the H/C package typically add? And how much power does the 9L package add? And, if you do both together, what is the gain over stock?

[mjorgensen]

So, with all of that said, how much power does the H/C package typically add? And how much power does the 9L package add? And, if you do both together, what is the gain over stock?

Arrow engine dyno new stock 620ish, H/C 720ish, H/C 9.0L 760ish All these will break in and loosen up 20-30+ hp in a couple thousand miles according to them.

Thanks Aaron for posting this, exactly why I TRY to not post numbers we get on a chassis dyno.

[Scott_in_fl]

Nice!

[Vegaskid]

I would think the delta shouldn't change between the before and after regardless of what dyno it's run on...but the evidence above proves otherwise

[Nth Moto]

I would think the delta shouldn't change between the before and after regardless of what dyno it's run on...but the evidence above proves otherwise

It would be expressed in a percentage, in which it's pretty darn close that way. However, every dyno pull (back to back) has a certain tolerance percentage for accuracy as well depending on the model, so that can compound it.


Arrow engine dyno new stock 620ish, H/C 720ish, H/C 9.0L 760ish All these will break in and loosen up 20-30+ hp in a couple thousand miles according to them.

Thanks Aaron for posting this, exactly why I TRY to not post numbers we get on a chassis dyno.

We still post dyno numbers but try to have track data to coincide with it. Our stock engine Twin Turbo builds making around 1200 WHP have been 160 mph in the 1/4 mile. Does that mean all 1200 WHP cars will do the same? Probably not.