L5P GVW 24k+ I have a Curiosity - Chevy and GMC Duramax Diesel Forum
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post #1 of 22 (permalink) Old 02-11-2020, 11:54 PM Thread Starter
TheLachlan
 
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L5P GVW 24k+ I have a Curiosity

Attached you will find my approximate route for the trip we completed this last Monday. Pics of trip computer, scale ticket, and truck/trailer setup also included.
Cruise was set to around 78-80mph most of the time.

Here is my situation and question to anyone who knows.

We travel alot for work and are full time RV'ers. Our travels could well bring us over most of the western 2/3rds of the country eventually. Planing on pulling this 5th wheel quite abit this year. Truck is mechanically stock, pulls great, that stretch of I-10 we did has multiple fairly long grades of 2% and it never even downshifts for 2%, once we hit 3% it does sometimes. Power is not really and issue, sure I'd love more but I could live with this. Fuel mileage is where its getting pretty thirsty I feel. On level road it gets around 7-8mpg at 80mph. At 70mph it gets about 1-1.5mpg better or so.

Would a Derringer help, and if so how much?

Deleting is out of the question right now but I am curious if there are any other reputable tuners out there, including the Banks Derringer, that would help me get better mpg while towing without having to swap ECM's etc.
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2018 L5P Z71 LTZ
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post #2 of 22 (permalink) Old 02-12-2020, 03:07 AM
touchracing
 
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That's a good looking setup you have there. I find I get my best mileage towing at 65 mph.

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post #3 of 22 (permalink) Old 02-12-2020, 03:49 AM
JimmyD
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That's a good looking setup you have there. I find I get my best mileage towing at 65 mph.
Me too.

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post #4 of 22 (permalink) Old 02-12-2020, 06:11 AM Thread Starter
TheLachlan
 
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Thank you for the replies.

I one of those guys I guess.. I would really struggle to get myself down to 65 in a 75 or a 80... May have to consider that though

Anyone know about how the Derringer or tuning options would impact the numbers at 75-80?

2018 L5P Z71 LTZ
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post #5 of 22 (permalink) Old 02-12-2020, 06:24 AM
rockn69
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I pull the same size rig @ 65 mph & get 11-12 mpg, try slowing down, your tires are not rated for 80 mph you'll have bigger issues than fuel mileage.

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post #6 of 22 (permalink) Old 02-12-2020, 07:12 AM
jdwarren
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Quote:
Originally Posted by TheLachlan View Post
Thank you for the replies.

I one of those guys I guess.. I would really struggle to get myself down to 65 in a 75 or a 80... May have to consider that though

Anyone know about how the Derringer or tuning options would impact the numbers at 75-80?
BLUF: I don't own a Derringer. What follows is pure pontification, albeit arguably well-informed pontification.

I don't know about the effect on fuel economy, but I'm extremely skeptical that it would offer improved fuel economy. The goal of those tuners is to increase power, not necessarily fuel economy. Your vehicle's drag coefficient, the speed at which you're traveling, the weight of the rig, and the grade you're ascending determine the power required. Fuel consumption is approximately linear with power, and it's very unlikely that there's any tuning that could allow the engine to produce the same power with less fuel consumption. That would be a thermodynamic miracle, to be honest.

Additionally, if you run the stock configuration, you can be confident that the engine isn't going to turn itself into kibbles and bits even at WOT with a load because the factory tune was set up specifically for that scenario. As soon as you deviate from that configuration all bets are off, and you'll have to be extremely careful about how hard you push the truck with a load, especially in hilly areas. Personally I like being able to set my cruise control when I have a trailer hooked on and let the engine and exhaust brake handle things. With a tune your cruise control may inadvertently run the engine at maximum HP (beyond design HP) for an extended period of time while ascending a hill, which is a recipe for disaster.

This is why the engines in the commercial variants are generally tuned for lower max HP; since they're generally expected to be run at max output continuously (not just for a few seconds under hard acceleration without a load), it's safer to keep the engine at a lower power output. It seems a bit ironic but it makes sense.
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post #7 of 22 (permalink) Old 02-12-2020, 07:23 AM
kiwi lml
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Well I don't think your gonna get much better than what you have now. I don't see a programmer/inline tuner really doing much for you as far as towing mpg.

I just went on a 2000 mile trip over Christmas with my fifth wheel (grossing just under 24k) and I averaged right at 9 the whole time. And that's with truck in my signature here.

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2016 lml chevy ccsb. Last december installed a HSP compound turbo kit with a stainless diesel 5 blade S475 over stock. And a exergy 10mm cp3 conversion kit but still stock injectors and transmission. 5" flo-pro exhaust with no muffler and tuning is done with EZ Lynk by PPEI.
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post #8 of 22 (permalink) Old 02-12-2020, 07:41 AM
JimmyD
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I have done 2, 1400 mile round trips at 24k gross towing the camper. Towing at 65 MPH my mileage is a pretty steady 10 MPG, bone stock.

09 GMC SLT Dually
Steel Gray Metallic
All options except sunroof

Mods so far:

Alcoa 19.5s with Michelin XZE, Centramatics,Tow Mirrors, Chrome Grill Overlay, Rear underseat storage, Mudflaps all corners, 20% Window tint, 6" Oval Steps, B&W Turnover Hitch, B&W Companion Hitch, Sulastics, GM Campaign #PIT3009J, Wireless Console Charging, Bilstein 5100s, Raptor 3602RL
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post #9 of 22 (permalink) Old 02-12-2020, 07:58 AM
MIkey52
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Yep, aerodynamic drag is a squared function, double your speed and square the drag.
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post #10 of 22 (permalink) Old 02-12-2020, 11:53 AM
kiwi lml
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Yeah speed will make the most difference for sure. My trip was all around 75 mph, if I would have been at 65 I'm sure it would have netted a mile or two better.

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2016 lml chevy ccsb. Last december installed a HSP compound turbo kit with a stainless diesel 5 blade S475 over stock. And a exergy 10mm cp3 conversion kit but still stock injectors and transmission. 5" flo-pro exhaust with no muffler and tuning is done with EZ Lynk by PPEI.
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