Perhaps a silly question (and maybe in the wrong forum) but trying to figure out how to "properly" dyno our trucks due to the speed limitations and get accurate numbers.

In particular, looking to dyno a 2010 1500 (6L80 transmission) with OEM driveshaft and speed limited tires (T rated) which precludes a run in anything close to 1:1 for gear selection. How are the numbers adjusted with 2nd gear pull to get something accurate?

No, have never run a dyno (and it sure as hell won't be me on the controls) just trying to learn. Are the specifics for transmission gearing, tires and rear-end ratio all entered for the dyno to compensate?

Like I said, noob question...


Allen

 

Probably wont be accurate at all. Does the truck have mods or is it stock?

 

Doing a lot now that will wrap up with a dyno tune...

Allen

 

Numbers will be low. My truck is was tuned in 2nd instead of 3rd and numbers came out @ 574/575. Tuner said would've been north of 600 if he would’ve tuned in 3rd.

 

On an OEM driveshaft, don't go over 100mph. You're on borrowed time if you do.

 

I would not even attempt a dyno tune with stock drive shaft

 

Ok... Seems every so often there is confusion on how a dyno works and what complications are introduced by different dyno types, gear ratios, operators, etc... Assuming your eddy brake/strain gauge/vehicle RPM pickup (mustang) or drum radius/mass/reluctor (dynojet) are calibrated properly, you can rest assured the force imparted by the tires onto the drums will be accurate. In that event, it doesn't matter what gear or whether or not the converter is locked because that torque and power is what reaches the wheels in those conditions. Now the reason people want to dyno in 1:1 or as close to it as possible, whether they understand why or not, is due to the reduced friction that occurs inside the transmission when there is no underdriving or overdriving taking place. When you underdrive (or overdrive, which nobody really dynos in for hopefully obvious reasons), there are additional gear meshes and bearings that are moving rapidly relative to each other, which use up torque that would otherwise make it to the tires. An easy example is the 4L80e...in 1st gear at 5000rpm, your intermediate shaft is rotating relative to the other geartrain in the opposite direction at over 12000rpm. That consumes energy. So 1:1 is the preferred ratio because it nets the highest numbers due to less friction. But that doesn't mean the numbers in other gears are inaccurate (again assuming the operators know wtf they are doing). Those numbers are just lower than they should could be because of...physics. But its still the amount of power/torque that actually reaches the ground in those gears.

For the nuances and differences between inertia-based dynos and eddy current dynos, we can save that for another lesson o.O