Comparing chassis dynos

[n8in8or]

The shop that I dyno'd my Tahoe at (Force Engineering in Plainwell, MI) just put out a video where they compared their Mustang dyno to another shop's Dynojet chassis dyno using their turbo Coyote Mustang. I think it's super interesting and a good watch so I wanted to share it. It's easy to get swept up in raw numbers that you get from a dyno (I'm guilty of this as well), but this really drives home the point that a dyno is a just a tool and not an absolute and is most useful for comparing A-to-B changes.

He also compared a Dynocom and will be posting that video soon, when he does I'll add it to this thread.

Note that this video is best watched on a screen larger than a phone so you can see the numbers that he's referencing in the graphs.

Enjoy!

 

[Twisted Steel Performance]

He states it well.
I know most engine builders use engine dynos and have no faith in chassis dynos, this shows why.
Now if folks want to see real world type numbers look for a engine dyno shop and a builder that is willing to have a motor they build go through a 50-100rpm per sec step pull up & down, I've seen a few motors that didn't make it, the circle track builders are the ones that do this type of pull mostly...

Good info Nate....

 

[Will L.]

Look at that, a guy not out to push the money making narrative from so many ripoff tuner shops. Nice.

If you take a look at 9:50 you can follow up the chart to see that both dyno operators were not cheating the numbers by correction factor also.
5252 rpm is mathematically where hp and torque will always cross. If not the dyno operator is lying to you. This is regardless of engine or wheel dyno.
So if you wanna see what your “not gonna hit 5252 rpm 6.5 is, you need to see it with a different motor pushing without adjustment between them.

Like anything, don’t instantly shoot the dyno man if you catch him being off a little - but point it out and don’t accept improper factoring. Being off a few hundred rpm can be a legit mathematical mistake. But many shops do obvious huge ones that if the customers know what is up- they get busted quick. On Nov 15 a guy sent me and a couple others a YouTube video link and it took stoping the video a couple times to show how bad this guy was lying.
First pic, notice the far left column of graph is 1000 rpm, first column next to beginning of lines is 2,000 rpm, each line going up is another 1,000 rpm.


Now, looking at the second picture- you should see the hp & torque lines cross at 5252 rpm. But they don’t. They cross clear up at 7,300 rpm area. And in that video the guy talks about how they had to run the car in top gear to get the most power. And the fater the wheels spun the more hp and torque the car made. Nonsense.




Now back to the video Nate posted- look at the graph that has the two dynos being shown. Although because of the differences in how the dynos measure- both show the hp & torque cross at 5252 rpm. In other words these two dyno operators aren’t trying to lie by factor correcting.

 

[93detroit]

I have a short marked off strip for acceleration to test changes (I am WAY rural). I also have my choice of small, steep mountains to climb to get out of the valley that I live in. Load up the gooseneck with a known load and see how she does.