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Discussion Starter · #1 ·
I was just wondering if anyone could tell me how much difference there is in power from load bearing dyno numbers vs. inertia drum dyno numbers. One would think that the load bearing dyno would help the truck build up boost for the pull, which will equal more power. I was just wondering if this is the case?????? :dunno:
 

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idk but when i was out at Sheid Diesel Extravaganza they had both and it seemed like there were more trucks making bigger power on dunbars drum dyno than on scheids load bearing dyno
 

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Load dynos generally show higher power readings when operated properly.

The reason Dunbars Dyno was showing better results than Scheids is Dunbar knows what he's doing when running it.
 

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Discussion Starter · #5 ·
I own an inertia drum dyno that I use for tuning cars here are my shop. I know its not the ideal setup for tuning anything with a large, slow spooling turbo. With these trucks where the entire pull only takes 3 seconds there really isn't enough time to reach full boost. I have been seeing 35ish psi at the end of the pull.

So basically what I'm asking is are the load bearing dynos producing more power due to loading down the truck to make more boost?? Not is the guy operating the dyno fudging numbers.
 

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I own an inertia drum dyno that I use for tuning cars here are my shop. I know its not the ideal setup for tuning anything with a large, slow spooling turbo. With these trucks where the entire pull only takes 3 seconds there really isn't enough time to reach full boost. I have been seeing 35ish psi at the end of the pull.

So basically what I'm asking is are the load bearing dynos producing more power due to loading down the truck to make more boost?? Not is the guy operating the dyno fudging numbers.
The answer is yes. However you can simulate that a little by riding the brake on the truck a little in the beginning of the run
 

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Discussion Starter · #7 ·
The answer is yes. However you can simulate that a little by riding the brake on the truck a little in the beginning of the run
Yeah I have tried that a couple of times, but I believe that when you touch the brake it unlocks the converter which makes the numbers lower and not accurate. I could be wrong. :dunno:
 

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Yeah I have tried that a couple of times, but I believe that when you touch the brake it unlocks the converter which makes the numbers lower and not accurate. I could be wrong. :dunno:
Thats why you only do it initially. You dont ride the brake the entire time. Just long enough to get it to start to spool
 

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Discussion Starter · #9 ·
I'll give that a shot next time I strap the truck on the roller. Thanks. :)
 

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You can make a dyno read whatever you like. So "knows what he's doing" isn't necessarily what it sounds like. "Knows how to fudge numbers" might be a better choice of words....
Dunbar uses a 1.02 correction factor, which on my dyno run was a 10.01 difference in uncorrected. He showed me the computer and pulled up my results. My 1.02 correction factor numbers were 560/1110 and my uncorrected number was 549.98/109X. Then he showed me standard correction, which is what a lot of dyno operators use. That was 571/1133. I guess it just depends on the operator and what correction factor they use and what load they use....
 

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An inertia dyno such as the common dynojet measures power and torque via the acceleration of the roller. The roller itself is a mass equivalent relative to the vehicle being tested. It works great, but isn't adjustable.

A dyno with a brake, such as the mustang dyno that has an eddy current brake, can get away with a smaller roller, as it has a power absorption unit that can account for additional power through adjustable resistance. The main benefit is different testing methods available to use with tuning vehicles such as steady state testing, rpm field testing, and programed simulations.

The correction factors are generally used to compensate for different environmental factors such as temperature and humidity. This way vehicles can be relatively compared across the world, but the dynos do need to be calibrated due to variables such as friction forces from bearing wear.

Horsepower/torque numbers can have variances due to added load especially on turbo vehicles, but generally, the main change I've seen is where in the powerband its produced.

In my opinion, find a dyno that's local to you and use it every time so you can see the improvements for your ride from modifications you've done. If you want to compare numbers with others on a competitive side, then get together and run on the same dyno. For general comparisons, just use the same correction factor. Just my thoughts.
 

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Dunbar uses a 1.02 correction factor, which on my dyno run was a 10.01 difference in uncorrected. He showed me the computer and pulled up my results. My 1.02 correction factor numbers were 560/1110 and my uncorrected number was 549.98/109X. Then he showed me standard correction, which is what a lot of dyno operators use. That was 571/1133. I guess it just depends on the operator and what correction factor they use and what load they use....
dunbar doesnt "use" a correction factor. the dynojet uses it. automatically. he can print your results corrected or uncorrected. its dependent on conditions ..this year ive had a couple dyno runs with negative correction factors. load dyno's typically read lower, because the time it takes to make a run on a load dyno is much longer than an inertial , therefore air intake temps are higher at peak hp/rpm than it would be on a dynojet. the thing about a dynojet is, basically the way it works, the dumbest person in the world could run it and its still accurate. load dyno's CAN be manipulated.
 
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