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Old 06-14-2018, 02:59 PM   #1
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Lost: 100 HP

I installed my ScanGuage D before a trip to Denver, CO. I monitor HP and have a question for those that have one installed on a Cummins L9. What is the max HP reading you have seen? Max I have seen is 256 HP when at 2100-2200 RPM, foot to the floor in any gear (2,3,4) under max load. Where did the other 100 HP go? If the HP reading is at the trans input/flywheel then it might be that the parasitic loss is the cause of the lower HP reading. In my last Chevy Duramax I had the Banks module and it would also show HP. I had asked Banks how the HP was determined and they said it was determined based on estimated values based on various inputs to the ECM/module. I assume the ScanGuage D does the same.
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Old 06-14-2018, 03:03 PM   #2
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I’ve often wondered the same. I’ve never seen above 230-240. That said I’ve only looked a few times and decided it was only making me sad. No idea in the details of how it’s calcuaktef. Not sure it’ll fit on a dyno lol

I just set mine back to MPG and monitoring temps and went on my merry way
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Old 06-14-2018, 03:11 PM   #3
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The 100HP didn't go anywhere, the ScanGauge HP reading is just a toy and has no real basis for what it reports other than what it "guesses" the HP could be based on sensor readings. There are no torque sensors that it's reading and then converting to HP.

Enjoy the ScanGauge, but don't put too much faith in those kind of estimates. I stick to raw sensor values, no need to calculate or convert anything.
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Old 06-14-2018, 03:47 PM   #4
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Originally Posted by DieselDrax View Post
The 100HP didn't go anywhere, the ScanGauge HP reading is just a toy and has no real basis for what it reports other than what it "guesses" the HP could be based on sensor readings. There are no torque sensors that it's reading and then converting to HP.

Enjoy the ScanGauge, but don't put too much faith in those kind of estimates. I stick to raw sensor values, no need to calculate or convert anything.
Drax is exactly correct.

The Scangauge has zero reference on how much horsepower is actually being made. It's about as accurate as those smartphone apps that measure horsepower.
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Old 06-14-2018, 03:51 PM   #5
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They are generally based on airflow #s from the MAF and RPM. It's a calculation not a measurement like a dyno or something. The typical model is MAF (g/s) *1.1 (on forced induction gas motor) Not sure about a diesel.

Also, realize engine HP and TQ are typically rated on an engine dyno not a chassis dyno. The chassis will have at least 15% loss in running gear...
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Old 06-14-2018, 03:56 PM   #6
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X3 on the Scan Gauge . That is why I went to the NEXIQ Blue-Link Mini.

I have a Scan Gauge for sale if anybody is interested. Only used one time.

Pm me if interested.
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Old 06-14-2018, 06:36 PM   #7
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Iím sure the drive line loss is +20%. As others have said itís just a tool.
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Old 06-15-2018, 08:27 AM   #8
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Anyone have a link to the ScanGauge scale?
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Old 06-15-2018, 08:51 AM   #9
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There was a previous thread on this same subject but could not find it. Same questions as to what Cummins advertises as HP and Torque as to what is actually being delivered and where its delivered and measured etc. I think it was on one of the HP and Torque upgrade threads. I think it ended in what the engine is " Capable " of and not what it actually does. Somebody feel free to correct me if Im wrong.
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Old 06-15-2018, 09:20 AM   #10
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There was a previous thread on this same subject but could not find it. Same questions as to what Cummins advertises as HP and Torque as to what is actually being delivered and where its delivered and measured etc. I think it was on one of the HP and Torque upgrade threads. I think it ended in what the engine is " Capable " of and not what it actually does. Somebody feel free to correct me if Im wrong.
Advertised HP and TQ is typically a bit of a legal thing. Not sure about RVs and heavy duty trucks, but there have been many law suits in other industries, so MFGs are generally very careful these days and use standardized SAE tests. They generally error on the conservative side since no two engines are identical in output.

Lawn equipment often does not even state HP anymore because of this. They just use engine size or tq as there is a bit less variance. This was triggered by lawsuits.

The engine needs to deliver the advertised HP and TQ under the SAE conditions on an engine dyno. What makes it to the wheels because of the drive-line and other drive-line protection strategies is where you get into a gray area (and that could be at play here, but doubt it). Most modern ECUs have something called torque management. It's used during shifts and other high load conditions to improve reliability. Some gears won't put out the same power as others... Another example is in cold dense air... it will keep the motor from putting out more torque than the drive-line should see.
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