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Old 07-12-2011, 05:55 PM   #1
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Question Loss of Gas Mileage any thoughts?

Put the new MBRP exhaust on the truck. It has good sound and power but have already noticed a drop in MPG. Any thoughts?
2011 SCREW 5.0. I was getting 17 to 18 on highway and now getting 15 to 16 on Highway.
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Old 07-12-2011, 05:58 PM   #2
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you like the way your engine sounds. [/thread]
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Old 07-12-2011, 06:14 PM   #3
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you like the way your engine sounds. [/thread]
I hear what you are saying but I am not laying into it to hear the sound. I actually do 50 miles to work all highway and use cruise and have noticed the decease. Maybe the decreased back pressure messing with the computer?
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Old 07-12-2011, 07:26 PM   #4
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I remember modding cars years ago and telling myself and my friends that I put the new intake, exhaust, ____________, _____________, ___________, and ___________ on to increase my gas mileage.

I was kidding myself, my MPG went down with every modification; the power on the other hand was noticeable.


As much as it pains me to say this, Ford is probably spot-on with how they have these trucks tuned down to the diameter of the exhaust pipe. With the big push in the past five years for fuel economy, they really have to push the limits. My 5.4 got 20.1 mpg on a recent highway trip (including some mild 4x4in at the end of the drive). No way I would want to touch anything to make that worse.
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Old 07-12-2011, 07:40 PM   #5
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Your computer on the car is programmed to see a given value changing the exhaust will change that value causing the computer to see a different value and adjusting according to what it is prgrammed to do.. In this case more fuel...
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Old 07-12-2011, 08:03 PM   #6
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What is the value you refer to?

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Old 07-12-2011, 08:23 PM   #7
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Won't the computer eventually adjust - re-learn the new settings?

If not, I got a tuner from 5 star. Loaded the 87 Performance tune. After I got done playing around, my mileage increased 1 to 1.5 mpg.

Was going to load the others (87 economy and 87 tow/haul) but decided that the perf tune rocks and left it alone.

I get to pop around and have fun when I want to but still get great mpgs when I need it.

Wait a while and see if the computer re-learns it. If not, and you can afford it, try the tune. I love mine but it can be pricey.
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Old 07-12-2011, 08:54 PM   #8
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These systems on our trucks are fine tuned to factory parameters. Any time you change something it will have an affect on performance one way or the other. There aren’t very many if any things we can do to improve on fuel mileage. My 2009 fuel injected Harley Davidson is the same way. Everything is computer controlled.

Some times we learn thing the hard way but some folks are willing to sacrifice factory performance for looks and sound in this case.

I knew my fuel mileage was going to suffer when I replaced the stock 18" wheels and tire for a set of stock 20's. Sure enough, my fuel mileage has dropped about 1 to 1-1/2 mpg because of the added weight and width of the wheels and tires.

Last edited by shortride; 07-13-2011 at 07:02 AM.
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Old 07-12-2011, 10:50 PM   #9
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What is the value you refer to?

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The vlaue is the combined set of computer sensors on the truck. o2 sensor before cats after cats, exhaust temp, exhaust pressure and so on. In the current engines there are more then 50 sensors that are pre told from the factory to operate fuel based on what the sensors indicate. So if you change one thing, like a thermostat then a bunch of sensors will change there behavior. There not smart or super computers and do not learn anything. They have to be told everything so they adjust accordingly....
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Old 07-12-2011, 11:07 PM   #10
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I had the same expearence on my 09 when I put a MBRP cat back system on, new set Goodyear tires and a K&N filter..I lost MPG after all my improvments..waited till I had gone threw a few drive cycles..still lower mpg. put the stock exhaust back on and stock air filter...mpg came back...
I have no plans to make any aftermarket inprovments on my 2011...
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Old 07-12-2011, 11:07 PM
 
 
 
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