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Old 01-14-2015, 02:03 PM   #11
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Re: Exhaust Backpressure for 5.4 V8 required?

I've never quite reached 15 mpg during any trips with my 5.4L van. My overall average for 12k miles is probably closer to 12.5-13 based on how we drive it.

265/70-17 tires
3.73 gears
never been loaded down significantly
I drive conservatively (i.e. slow, in no hurry, easy on the acceleration)

My conclusion, after owning many Ford V8s and many Chevy V8s, is that Ford can't make a V8 that gets decent fuel mileage. Chevy can do it. Our old Tahoe got 20+ mpg on road trips loaded to the gills. Ford cannot do it. Why do you think they made a turboed V6? Because they can't make a V8 get better than dog crap mileage...

That's how it is. I don't think you can expect much along the lines of fuel efficiency from the 5.4L in any vehicle let alone a vehicle that has the aerodynamics of a barn.
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Old 01-14-2015, 05:00 PM   #12
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Re: Exhaust Backpressure for 5.4 V8 required?

Quote:
Originally Posted by mgmetalworks
I've never quite reached 15 mpg during any trips with my 5.4L van. My overall average for 12k miles is probably closer to 12.5-13 based on how we drive it.

265/70-17 tires
3.73 gears
never been loaded down significantly
I drive conservatively (i.e. slow, in no hurry, easy on the acceleration)

My conclusion, after owning many Ford V8s and many Chevy V8s, is that Ford can't make a V8 that gets decent fuel mileage. Chevy can do it. Our old Tahoe got 20+ mpg on road trips loaded to the gills. Ford cannot do it. Why do you think they made a turboed V6? Because they can't make a V8 get better than dog crap mileage...

That's how it is. I don't think you can expect much along the lines of fuel efficiency from the 5.4L in any vehicle let alone a vehicle that has the aerodynamics of a barn.
Truth!^^^^^^ Also, CarringB can explain about adding an intake on a V10 vs. the 5.4l. No one makes one for a 5.4 that I know of, and supposedly it doesn't do any good to let more air in anyway. I dunno, but he has explained it. I gave up and just bought the 5-Star. Also 3.73 gearing in mine which I forgot to mention. If you don't like your 5.4's fuel mileage then buy an old 460 like I did! You'll then appreciate the 5.4's MPGs then.

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Old 01-14-2015, 05:23 PM   #13
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Re: Exhaust Backpressure for 5.4 V8 required?

Quote:
Originally Posted by 86Scotty
Truth!^^^^^^ Also, CarringB can explain about adding an intake on a V10 vs. the 5.4l. No one makes one for a 5.4 that I know of, and supposedly it doesn't do any good to let more air in anyway. I dunno, but he has explained it. I gave up and just bought the 5-Star. Also 3.73 gearing in mine which I forgot to mention. If you don't like your 5.4's fuel mileage then buy an old 460 like I did! You'll then appreciate the 5.4's MPGs then.

Just so you know K&N makes an intake for the 5.4L 1997-2012 Part #:77-2570 which lists the 6.8L and 5.4L E350. Also AFE makes an intake for the 6.8L 1997-2005 E-Series vans part #:54-10542. CarringB has said in another thread awhile ago that the AFE will work on the 5.4L as well.
Cheers
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Old 01-14-2015, 10:21 PM   #14
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Re: Exhaust Backpressure for 5.4 V8 required?

Wait, I thought he said the AFE would NOT work? Maybe I read wrong.
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Old 01-14-2015, 10:52 PM   #15
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Re: Exhaust Backpressure for 5.4 V8 required?

AFE will work. The V10 and 5.4L have the exact same intake. But that's also why I don't think it would provide any benefit. The intake is already designed for the V10, and the V8 sucks 20% less air at the same RPM, and actually makes peak power even lower than the V10 does so it usually isn't wound up quite as high. Now... stick a Lightning/Harley-Davidson supercharger on your 5.4L, and I think the AFE would really help.

FWIW our 5.4L E350 has 3.55 gears, which is probably worth close to 2 MPGs over 4.10 gears.
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Old 01-15-2015, 06:49 AM   #16
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Re: Exhaust Backpressure for 5.4 V8 required?

Wanted to second or third the intake comments.

I had a 5.4 Quigley Class C RV, 4:10 gears, 12,000LBS getting 6.5 - 7 MPG

I added the K&N intake. It made no MPG difference, none, nada. It did make the cabin loud as hell though. Couple it up with open exhaust and you'll need ear protection!

5 Star tuning made the van more fun to drive, and did maybe increase MPG a little.

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Old 01-15-2015, 07:50 AM   #17
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Re: Exhaust Backpressure for 5.4 V8 required?

Quote:
Originally Posted by mgmetalworks
That's how it is. I don't think you can expect much along the lines of fuel efficiency from the 5.4L in any vehicle let alone a vehicle that has the aerodynamics of a barn.
I just wanted to correct an incomplete statement by mgmetalworks: Dave Whitmer, the Mileage Moderator at PowerStrokeNation.com, called my van an "Amish Barn."

It's part of the diesel forum over there, but some of the aerodynamic stuff, gearing info, tire size discussion may be of interest to the OP and others:

http://www.powerstrokenation.com/for...splay.php?f=27
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Old 01-15-2015, 08:07 AM   #18
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Re: Exhaust Backpressure for 5.4 V8 required?

I agree with CarringB on the supercharger. A buddy of mine has a Lightning with a supercharged 5.4l. It's unbelievable. It's totally modded past just the supercharger but it's insane. There is a lot of power to be had with a 5.4, but most likely not in a van.

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Old 01-21-2015, 04:59 PM   #19
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Re: Exhaust Backpressure for 5.4 V8 required?

Quote:
Originally Posted by mgmetalworks
I've never quite reached 15 mpg during any trips with my 5.4L van. My overall average for 12k miles is probably closer to 12.5-13 based on how we drive it.

265/70-17 tires
3.73 gears
never been loaded down significantly
I drive conservatively (i.e. slow, in no hurry, easy on the acceleration)

My conclusion, after owning many Ford V8s and many Chevy V8s, is that Ford can't make a V8 that gets decent fuel mileage. Chevy can do it. Our old Tahoe got 20+ mpg on road trips loaded to the gills. Ford cannot do it. Why do you think they made a turboed V6? Because they can't make a V8 get better than dog crap mileage...

That's how it is. I don't think you can expect much along the lines of fuel efficiency from the 5.4L in any vehicle let alone a vehicle that has the aerodynamics of a barn.
Chevy has been using displacement on demand, or cylinder deactivation, or whatever they are calling it nowadays, for a long time. When you can run a V8 on 4 cylinders the BMEP doubles which can make the engine run more efficiently at light loads. Fiat/Chrysler has been doing the same with Hemi V8, and Honda runs their V6 on 6, 4, or 3.

Ford on the other hand hasn't pursued running V8s on fewer cylinders, which makes them less efficient at light loads. I've gotten as high as 15 to 16 MPG with my V10 a couple of times, but engine was very inefficient running around 50 HP. Even with a 5.4 liter V8 it's hard to gear high enough to load the engine enough.

Think about a GM of similar displacement running as V4. To match same BMEP as V8 the engine would have to run at half speed. And since normal may be 2000 RPM, it's not practical to gear up so it only runs at 1000 RPM. The engine can't run that slow anyway because it wouldn't have enough torque.

Bottom line is Ford thinks smaller displacement with turbos is a better way to ensure high-enough BMEP to make engines run efficiently.
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