Lost: 100 HP

hook47 · 06-14-2018, 02:59 PM

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.

FOURWHL · 06-14-2018, 03:03 PM

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

DieselDrax · 06-14-2018, 03:11 PM

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.

kfergiez · 06-14-2018, 03:47 PM

Quote:

Originally Posted by DieselDrax

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.

wfo9 · 06-14-2018, 03:51 PM

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...

joet19711 · 06-14-2018, 03:56 PM

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.

mikew968 · 06-14-2018, 06:36 PM

I’m sure the drive line loss is +20%. As others have said it’s just a tool.

**bclemens** · 06-15-2018, 08:27 AM

Anyone have a link to the ScanGauge scale?

The Renegade · 06-15-2018, 08:51 AM

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.

wfo9 · 06-15-2018, 09:20 AM

Quote:

Originally Posted by Mountieman

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.

joet19711 · 06-15-2018, 09:38 AM

This is a guess calculator. We have 350 BHP

Wheel Horsepower to Crankshaft Horsepower Guestimator

hook47 · 06-15-2018, 10:54 AM

Interesting web site. If I put in the 256 hp I saw on my gauge, it comes up with 320 hp at the crank which is the same hp rating as others have reported their unit has; the same rigs that have had the ECM uprated to a higher level.
I also agree with another post, that the ECM can/will derate under certain conditions such as shifting and perhaps in certain gears. The ECM simply uses various inputs to determine what the power is and adjusts fuel accordingly. The number displayed should be at the crank or xmsn input shaft. I kind of believe the input shaft can measure input torque which could then be relayed to the ECM to adjust power as necessary.
Since the 256 hp indicated should be at the crank/input shaft that leaves 94 hp loss forward of the crank for parasitic loss. Just seems like a lot. Or, maybe the engine really isn’t producing the placarded 350/1000 after all.

I've emailed the ScanGauge folks for their input on this question and will pass along any response.

wfo9 · 06-15-2018, 11:42 AM

Quote:

Originally Posted by hook47

Interesting web site. If I put in the 256 hp I saw on my gauge, it comes up with 320 hp at the crank which is the same hp rating as others have reported their unit has; the same rigs that have had the ECM uprated to a higher level.
I also agree with another post, that the ECM can/will derate under certain conditions such as shifting and perhaps in certain gears. The ECM simply uses various inputs to determine what the power is and adjusts fuel accordingly. The number displayed should be at the crank or xmsn input shaft. I kind of believe the input shaft can measure input torque which could then be relayed to the ECM to adjust power as necessary.
Since the 256 hp indicated should be at the crank/input shaft that leaves 94 hp loss forward of the crank for parasitic loss. Just seems like a lot. Or, maybe the engine really isn’t producing the placarded 350/1000 after all.

I've emailed the ScanGauge folks for their input on this question and will pass along any response.

I've been into the code on a few ECUs... never seen or heard of or seen one with input torque from a strain gauge... Granted all my experience is with performance gasoline engines, so it is possible there are some things in the HD diesel world that are different, but I seriously doubt it. It would be very problematic and expensive to build in a tq measurement device. It's all based on airflow calcs from MAF or VE and MAP. There are several different models and they are generally pretty accurate these days with good MAFs. Still nothing like an engine or chassis dyno where there is an actual measurement.

joet19711 · 06-15-2018, 11:58 AM

Quote:

Originally Posted by hook47

Interesting web site. If I put in the 256 hp I saw on my gauge, it comes up with 320 hp at the crank which is the same hp rating as others have reported their unit has; the same rigs that have had the ECM uprated to a higher level.
I also agree with another post, that the ECM can/will derate under certain conditions such as shifting and perhaps in certain gears. The ECM simply uses various inputs to determine what the power is and adjusts fuel accordingly. The number displayed should be at the crank or xmsn input shaft. I kind of believe the input shaft can measure input torque which could then be relayed to the ECM to adjust power as necessary.
Since the 256 hp indicated should be at the crank/input shaft that leaves 94 hp loss forward of the crank for parasitic loss. Just seems like a lot. Or, maybe the engine really isn’t producing the placarded 350/1000 after all.

I've emailed the ScanGauge folks for their input on this question and will pass along any response.

For me: the 350 BHP on mine is taken from the Blue link mini data reader
BHP is at the crank. So the guess is, how much HP is lost from the crank to the wheels? The calculator comes up with the guess of 291HP, based on rear wheel drive and a 5 or more speed tranny.
The only true way is on a Dyno. Besides, HP and torque are two different things.

DieselDrax · 06-15-2018, 12:06 PM

Quote:

Originally Posted by joet19711

Besides, HP and torque are two different things.

They do two different things, but HP is calculated using the formula (T * RPM / 5252) where T = Torque.

If you make a peak of 350bhp @ 2,000 RPM then you are making 919ft-lb of torque @ 2,000 RPM. If there were a torque sensor at the trans input, which there isn't, then it would be very easy for something like the ScanGauge to report both torque and HP.

hook47 · 06-15-2018, 04:27 PM

Used that formula way back in my aviation days. Useful.

Here is the response I just got from the ScanGuage folks (Linear Logics):

"The horsepower reading on the ScanGauge is similar to the Banks module. The ScanGauge uses different sensors to calculate the horsepower. There is a horsepower adjustment located in the advanced set up menu that you can use to adjust the reading to a more accurate value. If you have any questions, please let me know"

I guess I'll give it a try. Heck, I could just change the out put to read 500 hp

. That'll get me up the hills faster

FOURWHL · 06-16-2018, 08:07 AM

Wow! that scangauge really is a nifty little box. Can even add HP? I didnt even know that!

hook47 · 06-16-2018, 05:28 PM

Yep, sure can add HP. You can find the settings under the FHP menu. Set mine to 1000HP and took it for a drive. Wasn't paying attention at a stop light and didn't notice the cop car beside me. Light turns green and I burn rubber for a 100 feet! Got pulled over, got a ticket, dialed the HP back to stock.

FHP=Fake Horse Power

The Renegade · 06-16-2018, 05:41 PM

So in terms an idiot can understand, does the engine have the advertised hp of 350 or is it just impossible to know for sure?

hook47 · 06-16-2018, 05:56 PM

Can't answer that question for a fact. But when I first had my DX3 I didn't think it had much power, especially going up hills. Then, at around 3K miles it just started pulling much better. Still have to anticipate hills, but almost night and day different. At this point, comparing apples to oranges (past experience with P/U diesel pulling 5th wheels at 27K GCW) I think that it produces the rated HP/Torq by virtue of observed performance at about 36K GCW. In other words, it does what I think it should.

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