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Better fuel mileage

4K views 34 replies 11 participants last post by  poolguy 
#1 ·
I just bought a dodge with the 6.7 liter in it. I already have taken off the egr and ran a straight pipe from the turbo back. Also running a h&s mini maxx. I want better mileage and was hopeing somebody could point me in the right direction.

Thank you.

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#2 ·
Light foot. Once your fully deleted there's really nothing else you can do. Unless you wanna spend big money and you still may not gain much. Turn your programmer up and drive with a really light foot and you should yield better mileage. Keep stock tires size and no lift.


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#4 ·
Need to update my sig, but I'm getting approximately 18.5 hand calculated, stock size tires with the winter blend diesel - These trucks aren't made for mileage, so I figure at 18.5, I'm doing pretty dang good. It was sitting around
19.5-20 with the summer blend...and before I wrecked it and did ~$19-20k in damage to her :buttkick: . Full synthetic oil seemed to make a small difference for me as well. Not an extreme amount, but I did notice a very slight increase in the way it ran.
Rundown of my Mods:

H&S Mini Maxx - Usually stick to running it on Wild power level, again I don't do any towing, and when I play around I am conscious of temps/pressures.

AFE Bladerunner Manifold - Didn't really notice a huge difference from doing this, MAYBE .2-.3 miles a gallon, and a little less grumbly idle/exhaust sound, and it looks good under the hood.

XDP Fuel Rail Plug - I did this because I was taking my stock manifold off and it was right there. I don't do any heavy towing, and I use my gauges on my Mini Maxx to monitor the rail pressure when I'm playing around. Heard too many horror stories of fuel being bled back into the tank and the truck not starting because of the banjo bolt.

4' Turbo back exhuast - Necessary for the deletes. Made a huge difference.

S&B Air Intake - Made the turbo whistle a little louder, slight mileage gains, not really noticable.

Sinister EGR Delete - Done at the same time as the exhaust (no longer needed the sinister EGR blockoff after I got the AFE).

I don't know what kind of mileage you're looking for, but driving with a light foot has been the only thing that really helped me other than the deletes.
 
#7 ·
I don't have the mini but remember reading a thread that stated not to run default timing at stock or mild tunes. Might be worth looking into.

Amsoil Direct
 
#8 ·
I researched it a bit when I was playing around with it - found a thread from H&S located here: H&S Performance :: Topic: Minimaxx adjustable timing (1/1)
...---Taken from HS Forum above........
"Although I cant really answer the techincal aspect of your question...I don't know that you going too see much advantage advancing the timing unless you have some more fuel delivery upgrades...I currently have mine set to the most agressive (5)...But I also have a FASS, injectors, and a modified CP3...The best answer you prob going to get is just to experiment a little and see what setting may work out best....

Technically, the adjustment only affects MAXIMUM injection timing. The only time the truck will actually go above lets say 20 degrees is at wide open throttle about 2000 RPM. The adjustment does not affect pulse width."

The timing is electronically controlled - adjusting the timing with the mini maxx probably isn't going to make a difference without an upgraded fuel system...

I will do a little more digging to see if I can find anything about running it on the default level. Thanks!
 
#9 ·
I thought it was HG failures due to the timing causing high DP. If I think of it I'll post back.

Amsoil Direct
 
#10 ·
I had the timing set on the the highest running on wild. I seemed to get a better fuel mileage. As of right now i am running through them at different levels to see what is the best. I really do appreciate all the help. I will be ordering my intake soon. Im either going with the s&b or the afe stage 2. I think im going to get the afe, just because i will be doing a injector upgrade and a different fuel pump.

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#13 ·
I have the first gen 6.7 in a 2500, 4 door long box. Im not even close to that mileage. I also have an automatic. Starting to think i should do a manual on it.


5" turbo back
Egr delete kit
H&s mini maxx


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#14 ·
So just some useful info for anyone who is interested. So I tried searching "mpg" on auto guide and nothing turned up- app still has a few loose ends... This was the first thread I could find with anything relating to mpg.

So I got a 07 6.7 mega 3500 with an HS mini max, a HS egr delete and bypass, a flow pro 5" turbo back cat and dpf delete and a k+n cai.

Prior to deletes, I would get 22-24 highway at sea level with no mountains or load on the truck.

Now I went on first roady without mountains or a load and on mild I recorded 18.75 mpg and on stock or no power I got 14.25 mpg on same speeds and flat Iowa/Nebraska flat highways with cruise...

So now it is 2:45 am and I am in Omaha heading to Denver and I am flicking it to wild to see what it does. I will report back in a few hundred miles...

By the way I am on winter blend now and was on summer blend with the 20-22...


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#16 ·
Get rid of that junk K&N. You have oil residue on your maf & ait sensors. That's what's giving you crappy mpg.

Clean sensors with maf cleaner or non-chlorinated brake cleaner. While your at it clean the map sensor on drivers side in the air horn, takes a torx head.
 
#19 ·
Use a dry filter only, diesels pull too much air stripping the oil out of oiled filters.

two on air filter box just spray off with cleaner I mentioned in earlier post, remove the one on air horn. spray with cleaner, reinstall, enjoy.

Were the MPG hand calculated or going off the over head display. Over head display is called the lie-o-meter for a reason. Although the lie-o-meter does have merit, if it drops like you say then the hand calculation would also.
 
#21 ·
K&N Air Filter Review - Debunking the Myths (and why OEM is better)

And if you don't believe the results, run your oil with an OEM filter and get an oil analysis done after X amount of miles. Change out your oil and filter to the same as what you had in there but this time run the K&N filter and see your silicon levels increase in your next oil analysis. The proof is in the pudding or in this case the oil.

K&N makes quality marketing, they don't however make quality filters.
 
#22 ·
Oh one more thing I forgot to mention before was I now have 287/75/17 and I use to have stock size. Would such a small increase in tire size make a difference like 3-4 mpg?

Pwr2tow I am cleaning sensors Sunday!

Thanks dudes. I love my truck so freaking much I don't know why I am ing about a 9,000 lb truck getting 18 mpg.... I guess I am just bored...


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#23 ·
Stock size to 285/75/17 is a pretty decent jump in size.

That being said, I just returned from a 1500 mile round trip in my 08 that was deleted in November.

Stock motor with Leveling kit and 285/70/17's - Hand calculated was average 15.4 mpg.
Stock motor, leveling kit, 285/70/17's EGR unplugged - Hand calculated 17.1 mpg
Fully deleted, H&S Black Maxx with Mild NO ATT tunning, 4" TBE, S&B intake, full synthetic fuild change prior to leaving on this trip - Hand Calculated 19.6 mpg. The over head was reading close to 24mpg at one point. hahaha I'd say 90% highway driving.

I noticed, on my 08 that i was getting absolute CRAP fuel mileage with the Mild ATT tuning installed. So I downloaded a different tune to my black maxx and i'm very happy with it. I was getting worse mileage with the previous tune that I was at stock. :doh:
 
#24 ·
If you didn't take into account the larger tires in your mileage calculation then yes, it will appear that your mileage suffered worse than it actually did. Because the larger tire turns fewer times per mile it will look like you've gotten fewer miles than you actually did. Find the "revolutions per mile" on the tire manufacturers website and compare that with a stock size tire. This is just a demonstration how to do the calculation...

[New Tire Revs per mile MINUS Old Tire Revs per mile] DIVIDED by Old Tire Revs per mile TIMES 100 = % Change

Take your miles on your odometer and increase them by the % Change you got in the calculation above. [Original Miles TIMES %Change] PLUS original Miles. THAT number is your new miles you can throw into the miles/gallons calculation.
 
#25 ·
This is a very good point. I spent a lot of time with a tape measure and my gps dialing in my Tire size to get my speedo accurate.
 
#28 ·
Thought I would share. Just checked my milage with mods in sig (2007.5 truck) after a 310 mile highway trip at 70 mph. Programmer set on stage 3 and mp-8 all the way up. Overhead read 23 mpg's. Hand calculated: 17.2 mpg's. As many are I am interested in getting the best milage possible and I'm gonna try this again on stage 2. Interesting info on the K&N filters. My 03 truck has had the K&N intake with the cone shaped filter for over 150,000 miles with no issue. However, I would love to tear it down and do some tolerance checks to see if there is any long term damage but until it breaks or dies gonna keep going with it.
 
#30 ·
More boost pressure always means more fuel to be used and higher EGT means more energy to the exhaust and not to the rotating assembly of the engine. Naturally aspirated these engines have 6.7L of displacement. At 14.7PSI at sea level the engine now has the equivalent of 13.4L displacement and at 29.4PSI an effective displacement of 20.1L displacement and you need the fuel to go with all that air.

Best fuel economy is with low EGTs and low boost with a light right foot. Or buy a Prius :confused013: :hehe:
 
#31 ·
That is very interesting. I never concidered that. One must also concider the temp. of the air going in. You just made me realize something. I have a boost fooler on my truck. I will have to do some experiments on milage with and without it. More pressure doesnt mean more air if its hot air.
 
#32 ·
If you really want to know then you'll need to use some gas law calculations which I'm not all up on anymore. Yes, with a higher incoming air temperature the mass will be less, but not substantially less than you think. AND our engines have a MAF and IAT sensors so the fueling will be compensated for with the incoming air temperature change. A boost fooler will allow you to overfuel the engine and run combustion more rich than you otherwise would be able to. Also, the boost fooler will allow you to run higher pressures than your turbo was designed and once you're out of the compressor map then all you're doing is heating the incoming air even more with very little increase in pressure.
 
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