Normal value for Engine Load %?

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disallow
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Normal value for Engine Load %?

Postby disallow » Tue Nov 16, 2010 7:31 pm

Hey all,

As I've mentioned in other posts, I've noticed a drop in fuel economy that I thought coincided with my changing from P265/70R16 Coopers to P265/75R16 REV02s. I've dropped from 19/23MPUSG to about 14/17MPUSG. So pretty significant.

I'm wondering if there is a deeper problem here. I have the Superchips Cortex, and one of the features is a real time display of J1939 parameters such as Engine Coolant Temp, Advance angle, Vehicle speed, etc etc, and also includes a parameter for Calculated Engine Load %.

Normally, when cruising on the highway at 65mph, the Engine Load shows about 50-60%. I mentioned this to one of the engineers at work, and his eyes nearly bugged out of his head. He said he'd never seen anything over 25% in his experience. However, the truck seems to be running great otherwise, no weird shifting, no hesitation, and I pull my massive camper with it with seemingly no issues.

Does anyone else out there have a Cortex or other tool that tells them what the ECU is calculating for engine load? Or does anyone know what the normal value of this parameter would be?

I tried a few things on the way home today. Engine load at 65 MPH was 50-60%. When I clicked off the O/D, engine load dropped to 40%. When I downshifted to 3rd, it dropped even more, to about 35%.

Does this seem normal?

Comments appreciated. Wondering if I have a binding transmission/diff/transfer case. Like I said, no issues apparent in driving, seems normal in all ways, acceleration is great, power is great. Reverse is fine.

Thanks!
t


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pathology
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Postby pathology » Wed Nov 17, 2010 12:14 pm

I notice that this happens in winter, and always assumed it is due to the gas stations using 15% ethanol gas in the colder months (less bang for the buck). I'm getting a net economy of 16.5, though I've only had my PF for 2 weeks. I'm hoping I get the hang of driving it more efficiently.

GbayPathfinder
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Postby GbayPathfinder » Wed Nov 17, 2010 3:58 pm

pathology wrote:I notice that this happens in winter, and always assumed it is due to the gas stations using 15% ethanol gas in the colder months (less bang for the buck). I'm getting a net economy of 16.5, though I've only had my PF for 2 weeks. I'm hoping I get the hang of driving it more efficiently.
It could be as you suggested above, but consider that as the weather gets colder the engines air/fuel ratio is running richer for a longer period of time to ensure that it warms up to operating temperature (which coincidentally takes longer in cold weather). Plus the fact that the other fluids within the vehicle (i.e. transfer case and rear diff fluid) are also thicker when cold causing more drag on the engine.

Just my 2 cents

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pathology
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Postby pathology » Wed Nov 17, 2010 4:57 pm

Agreed, all of the above!

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disallow
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Postby disallow » Thu Nov 18, 2010 8:30 am

pathology wrote:I notice that this happens in winter, and always assumed it is due to the gas stations using 15% ethanol gas in the colder months (less bang for the buck). I'm getting a net economy of 16.5, though I've only had my PF for 2 weeks. I'm hoping I get the hang of driving it more efficiently.
My numbers are an average for any time of year. I am aware of winter blend issues. I don't think that is it, and certainly wouldn't account for a 25% drop.

t


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