2014 DRW 68RFE - New Raceme Ultra - Full Delete - MPG baaaad!!!

[TH-64]

Rolling resistance goes up with heavier and/or larger tires. I lost 1.5 - 2 mpg with one size larger tire. Lots of guys claim better milage with 120 tune and baby the throttle. I do this with a 12,000# trailer and no problems. Just don't let Junior drive it.

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[elcubano]

If I could continue the picking y'all's brains - do you guys have any idea what a regear goes for these days? May end up at 3.73. no romping the truck. Easy easy

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[elcubano]

Ended up having Chrysler and dealer give my truck back, charge me for the rental and tell me that 12mpg on factory tires unloaded and 7-9 mpg pulling any kind of trailer is within spec. So I'll be dumping more money in it if I'm stuck with it. Intake manifold, plenum, throttle body delete. Etc

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[TH-64]

I installed a stage 2 intake, BD intercooler and intake tubes, intake horn, grid heater delete... a ton of money... and barely got a blip on fuel economy. If I were you I'd spend the money on custom tuning geared towards fuel economy. It would be money well spent and pay for itself putting on your kind of miles.

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[elcubano]

Thanks man!

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[TH-64]

Others here can help you with regearing ideas, but I know with mine it's happiest at 1800 rpm. I lock out 6th gear most of the time.

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[brandonjansen]

Just read through this entire thread and I'll pick out some of the issues I think need to be further addressed.

Not yet. Can't even consider it until I get the truck running right

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This was in response to IGOTACUMMINS asking if you had WARP tuning or not. Honestly, that's the wrong response and attitude. Your tuning could be the biggest issue in why the truck isn't running right and why you're getting the mileage that you're getting. Getting a good quality set of custom tunes could actually solve all of your problems if the tuning really is the main cause. Now that being said, I don't think that tuning is your only issue. But I do believe that it's part of it. You'd be FAR better off getting a good set of tunes from Ray at Double R Diesel. Not only for mileage gains but for overall driveability of the truck as well. This will likely make the biggest difference out of anything you could do.

Ratlin, all my numbers are evic, 12.9 hwy if hand calculated on my second to last tank. Possibility of all the numbers being skewed high. Best tank when new was pushing 650 miles do about 20 but that would have included T least some city driving.

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I hate to break it to you, but this right here is your biggest issue. The EVIC isn't reliable even on a completely stock truck. Since you never hand calculated you literally have no idea what it got stock. I guarantee it wasn't the 25 mpg unloaded and 17 mpg loaded that you were claiming. That's simply far too high for what your truck is. So referring back to those numbers as your "base" is not correct because they were not reliable. This is why I ALWAYS recommend guys hand calculate if you actually want to know what your fuel mileage is.

Running 255/80 17, speedo calibrated. 80 front 70 rear

3.42 gears

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I'm assuming you calibrated your speedometer with your RaceME. No issues there. But have you actually checked it with a GPS to confirm that it's correct? I've found quite often that entering the correct size tire for what you're running in a tuner does not actually calculate the speedometer properly. You need to play around a bit and double check with GPS to confirm. For example, I run 37's on my truck but in my tuner the tire size is listed at closer to 35" to actually make the speedometer correct.
If your speedometer is out then your odometer and trip meters are out as well which will completely skew any numbers that you even hand calculate. First step is confirming that it's actually correct and reading properly to what a GPS is reading.

Also, what tires are you running? Most guys that swap tires go with something more aggressive than stock which obviously means more weight as well. That weight alone is one of the biggest factors in decreased MPG with aftermarket tires. It's not all about the size. On a DRW this is obviously even more of an issue as you're spinning two more tires than the SRW trucks.

If I could continue the picking y'all's brains - do you guys have any idea what a regear goes for these days? May end up at 3.73. no romping the truck. Easy easy

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Approximately $2500-3000 to regear the front and rear diffs with all the required parts, labor, etc. With the miles your truck has you'd likely want to replace all the bearings while you're doing that so I'd expect you'd be on the higher side of that estimate.

So I'll be dumping more money in it if I'm stuck with it. Intake manifold, plenum, throttle body delete. Etc

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I wouldn't bother with messing with any more of the airflow stuff at this point until you get some of the other items sorted out first. Intercoolers, charge air pipes, throttle valve deletes, etc aren't going to be a waste of your money without first addressing tuning. You'll see little to no gain out of doing them.


So to sum it up, should your truck be getting the low fuel mileage you're claiming? No I don't think so. But there's a handful of things that need to be double checked or done to help solve this issue that you haven't gotten into yet.

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[elcubano]

Just read through this entire thread and I'll pick out some of the issues I think need to be further addressed.



This was in response to IGOTACUMMINS asking if you had WARP tuning or not. Honestly, that's the wrong response and attitude. Your tuning could be the biggest issue in why the truck isn't running right and why you're getting the mileage that you're getting. Getting a good quality set of custom tunes could actually solve all of your problems if the tuning really is the main cause. Now that being said, I don't think that tuning is your only issue. But I do believe that it's part of it. You'd be FAR better off getting a good set of tunes from Ray at Double R Diesel. Not only for mileage gains but for overall driveability of the truck as well. This will likely make the biggest difference out of anything you could do.



I hate to break it to you, but this right here is your biggest issue. The EVIC isn't reliable even on a completely stock truck. Since you never hand calculated you literally have no idea what it got stock. I guarantee it wasn't the 25 mpg unloaded and 17 mpg loaded that you were claiming. That's simply far too high for what your truck is. So referring back to those numbers as your "base" is not correct because they were not reliable. This is why I ALWAYS recommend guys hand calculate if you actually want to know what your fuel mileage is.



I'm assuming you calibrated your speedometer with your RaceME. No issues there. But have you actually checked it with a GPS to confirm that it's correct? I've found quite often that entering the correct size tire for what you're running in a tuner does not actually calculate the speedometer properly. You need to play around a bit and double check with GPS to confirm. For example, I run 37's on my truck but in my tuner the tire size is listed at closer to 35" to actually make the speedometer correct.
If your speedometer is out then your odometer and trip meters are out as well which will completely skew any numbers that you even hand calculate. First step is confirming that it's actually correct and reading properly to what a GPS is reading.

Also, what tires are you running? Most guys that swap tires go with something more aggressive than stock which obviously means more weight as well. That weight alone is one of the biggest factors in decreased MPG with aftermarket tires. It's not all about the size. On a DRW this is obviously even more of an issue as you're spinning two more tires than the SRW trucks.



Approximately $2500-3000 to regear the front and rear diffs with all the required parts, labor, etc. With the miles your truck has you'd likely want to replace all the bearings while you're doing that so I'd expect you'd be on the higher side of that estimate.



I wouldn't bother with messing with any more of the airflow stuff at this point until you get some of the other items sorted out first. Intercoolers, charge air pipes, throttle valve deletes, etc aren't going to be a waste of your money without first addressing tuning. You'll see little to no gain out of doing them.


So to sum it up, should your truck be getting the low fuel mileage you're claiming? No I don't think so. But there's a handful of things that need to be double checked or done to help solve this issue that you haven't gotten into yet.

Thank you. Going through all of this now.

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[RamIt]

The taller tire as you know will gear even higher which with 3.42s is kinda a trans killer if you like to beat on the truck a bit. But that can also improve mileage. What will negate that mileage gain is the 12.5 wide pushing more ground surface. Kind of a wash, or maybe slightly worse in my opinion, and if you like to romp on it now and then, I'd stay away from 35s with 3.42s, and that's my personal experience.

This is a very good point. 35x12.50s is more stress on the transmission, mostly due to weight and rolling resistance. However, I run 35x12.50s on mine (34xxx into em) on a 120hp WARP tune and things are excellent. So there is a bit of a grey area here on the tire side of things. But I can tell you that I did see a noticeable loss in MPGs with 35x12.50x20s (approximately 2MPG average)

Rolling resistance goes up with heavier and/or larger tires. I lost 1.5 - 2 mpg with one size larger tire. Lots of guys claim better milage with 120 tune and baby the throttle. I do this with a 12,000# trailer and no problems. Just don't let Junior drive it.

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Again, same thing. Most larger tires are going to have a big weight disadvantage (something I am addressing with my truck tomorrow). But @TH-64 is right here about the 120HP tune. The higher HP tunes do generally see better MPGs than the lower HP tunes. But that doesn't mean I'd throw a 200HP tune at your truck and tow with it.

I installed a stage 2 intake, BD intercooler and intake tubes, intake horn, grid heater delete... a ton of money... and barely got a blip on fuel economy. If I were you I'd spend the money on custom tuning geared towards fuel economy. It would be money well spent and pay for itself putting on your kind of miles.

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Agree 100%. Airflow upgrades aren't going to help here without the supporting tuning and other mods.

Others here can help you with regearing ideas, but I know with mine it's happiest at 1800 rpm. I lock out 6th gear most of the time.

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I disagree with the intent of locking out 6th gear. However, without WARP tuning, this is what most people are dealing with. With WARP, I never have to lock out 6th because my tuning won't even shift into 6th gear until 65 MPH anyways. (This applies for city driving as well, my tune is set up to hold 4th gear around town to prevent lugging)

@elcubano You've got a laundry list of items to focus on with getting your situation squared away to your liking. But as I and others have mentioned, you really need to start with the tuning because thats where the magic happens. Get Ray to work you up a tune that meets your needs and I'll bet you you'll see an instant change in power and efficiency. Trans tuning will do wonders for you on the economy front.

Also, in regards to your tires, I would advise you stick with a OE size (both width and diameter) and go with a E Range 10 ply tire. But read through this thread, http://www.dieseltruckresource.com/f...-tires-220066/ ( @IGOTACUMMINS feel free to redact if not allowed, best resource I could find on this topic) as it focuses on guys who Hot Shot their trucks and need long lasting tires.

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[elcubano]

Excellent info. I'll get with Ray before doing anything. What's his email without hunting it down?

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