Need Help Interpreting Dyno Results on 5.3 with 6L80

The.Sundae.Drive · November 14, 2019

Need some Dyno expertise. I am used to manuals and this is my first time dynoing an automatic.

Because of the 95 mph limiter on the truck (due to the weak drive shaft and probably the tire speed rating), the dyno tech said that the stock truck won't hold 4th so he is forced to do a 1st through 3rd pull. He will then do the same thing after my modding and tuning so I can see how much more power is made (this was a baseline tune). Because of this, the dyno was graphed vs MPH instead of RPMs and I am not sure how to calculate my actual HP because of the gearing (I believe for the 6L80 the gearing is as follows: First: 4.03. Second: 2.36. Third: 1.53. Fourth: 1.15. with 4th being the closest to a 1:1?). Is there an accurate way to pull out the actual power numbers from the MPH graph since it is graphed vs MPH instead of RPM (65 to 95) while accounting for the transmission gearing and rear? The Dyno Graph is attached. Thanks for the help!

truckguy82 · November 15, 2019

Torque and hp meet at 5252 rpm on every dyno no matter what.

So if you know what mph corresponds with 5252 rpm is, you can do some basic math and convert the rest of the mph into rpm.

truckguy82 · November 15, 2019

Nevermind, didnt look at it close enough

i think that graph is worthless. Peak torque should not be that far to the left.

it’s like that dyno starts at 4k rpm

VdellaV · November 15, 2019

For what I can see:

Around 91 MPH is 5252 RPM

Engine RPM and Ground Speed are linearly proportional

With Simple rule of thirds:

Graph Starts at around 3751 RPM

Graph Ends at around 5482 RPM

This numbers seem pretty stout for a Stock Baseline, nice

VdellaV · November 15, 2019

9 minutes ago, VdellaV said:

For what I can see:

Around 91 MPH is 5252 RPM

Engine RPM and Ground Speed are linearly proportional

With Simple rule of thirds:

Graph Starts at around 3751 RPM

Graph Ends at around 5482 RPM

This numbers seem pretty stout for a Stock Baseline, nice

Therfore, you can calculate the RPM at each graph step, in the graph:

65 MPH is 3751 RPM

68 MPH is 3924 RPM

71 MPH is 4097 RPM

74 MPH is 4270 RPM

77 MPH is 4444 RPM

80 MPH is 4617 RPM

83 MPH is 4790 RPM

86 MPH is 4963 RPM

89 MPH is 5136 RPM

92 MPH is 5309 RPM

95 MPH is 5482 RPM

And therefore visually figure out how much Power/Torque you have at each RPMs

Peak torque seems to be around 360 ft-lbs at 4100 RPM

Peak Horsepower seems to be around 330 HP at 5350 RPM

These numbers seem to be at the wheels, and they would be pretty stout, what mods do you have on the truck ??

truckguy82 · November 15, 2019

Sunday drive

you are the ****in man

yes!! Finally

Nitrousbird · November 15, 2019

I would find a new dyno operator. Just dyno in 3rd. Not ideal, but better than going by MPH. And why is he shifting through gears? Get to the gear you are going to dyno is at a low RPM, mash it to redline and let off.

The.Sundae.Drive · November 15, 2019

21 hours ago, truckguy82 said:

Nevermind, didnt look at it close enough

i think that graph is worthless. Peak torque should not be that far to the left.

it’s like that dyno starts at 4k rpm

I was kind of thinking it worthless as well except for a straight comparison of the exact same thing after modifying.

The.Sundae.Drive · November 15, 2019

19 hours ago, Nitrousbird said:

I would find a new dyno operator. Just dyno in 3rd. Not ideal, but better than going by MPH. And why is he shifting through gears? Get to the gear you are going to dyno is at a low RPM, mash it to redline and let off.

I was wondering as well. Pretty established tuner tho and apparently he does it this way for all the trucks

The.Sundae.Drive · November 15, 2019

19 hours ago, truckguy82 said:

Sunday drive

you are the ****in man

yes!! Finally

Haha I'm glad that video helped you out! That rattle was driving me nuts.

19 hours ago, truckguy82 said:

The.Sundae.Drive · November 15, 2019

21 hours ago, VdellaV said:

Therefore, you can calculate the RPM at each graph step, in the graph:

65 MPH is 3751 RPM

68 MPH is 3924 RPM

71 MPH is 4097 RPM

74 MPH is 4270 RPM

77 MPH is 4444 RPM

80 MPH is 4617 RPM

83 MPH is 4790 RPM

86 MPH is 4963 RPM

89 MPH is 5136 RPM

92 MPH is 5309 RPM

95 MPH is 5482 RPM

And therefore visually figure out how much Power/Torque you have at each RPMs

Peak torque seems to be around 360 ft-lbs at 4100 RPM

Peak Horsepower seems to be around 330 HP at 5350 RPM

These numbers seem to be at the wheels, and they would be pretty stout, what mods do you have on the truck ??

Ok cool! Did you base the 91 mph off of 4th or 3rd gear? I think they may be pretty close to one another. My motor is pulled or I would have done a street run to see my RPM at the speed. I had zero mods done as was checking my stock numbers before throwing in the new cam and ported heads from GPI. This is why I am concerned that the numbers aren't accurate as they seem pretty high for a base truck. I know the transmission gearing would throw it off some tho?

VdellaV · November 16, 2019

2 hours ago, The.Sundae.Drive said:

Ok cool! Did you base the 91 mph off of 4th or 3rd gear? I think they may be pretty close to one another. My motor is pulled or I would have done a street run to see my RPM at the speed. I had zero mods done as was checking my stock numbers before throwing in the new cam and ported heads from GPI. This is why I am concerned that the numbers aren't accurate as they seem pretty high for a base truck. I know the transmission gearing would throw it off some tho?

This pull should be in third gear. In fourth at 5400 you would be going faster than 130mph

The numbers seem to be a bit high for a stock truck, BUT don't worry Too much about the numbers on the dyno. After your truck is done, you can see the results and calculate the percentage of improvement. This is what your truck should be putting out stock:

http://gmauthority.com/blog/2013/07/lingenfelter-performance-puts-the-2014-silverado-on-the-dyno-with-video/amp/

What i do recommend is that you keep a close eye on the people working on your stuff. And don't be afraid to ask them all the questions and info you want to know

flyingfool · November 17, 2019

try using your OBD2 port in conjunction with a scanning software, like torque app. I am getting the same numbers as your base dyno just using a $7 blue tooth scan tool. Torque app should also be able to do graphs, i set my gauge for numerical output, i get 320hp i stock form doing a pass on a deserted road in town. my street dyno run was in a 5.3L on 91 octane, 6 speed, 3.75 gears and 33" tire. truck shuts off at 100mph

davester · November 17, 2019

1 hour ago, flyingfool said:

try using your OBD2 port in conjunction with a scanning software, like torque app. I am getting the same numbers as your base dyno just using a $7 blue tooth scan tool. Torque app should also be able to do graphs, i set my gauge for numerical output, i get 320hp i stock form doing a pass on a deserted road in town. my street dyno run was in a 5.3L on 91 octane, 6 speed, 3.75 gears and 33" tire. truck shuts off at 100mph

Um, that's not a "dyno run". That's just speeding on a public road.

There's no sensor in your truck that measure how much torque and/or horsepower it is generating, anywhere in the drivetrain. Any numbers your app is showing to you are just a rough approximation of what power your truck should be generating, if everything is working properly, likely under ideal circumstances.