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Project MPG: goal 30 MPG

52K views 143 replies 35 participants last post by  powerlifter405 
#1 ·
Truck:
Theft recovery Ford Super duty 2001 Ex Cab Short Box 4x4
3.73 Gears
295-75R-16 BFG ATs (started out with)
47RH HTS
93% Torque Convertor
Gear Vendors overdrive
2.01 to 1 Final Drive Ratio
70 MPH 8-9 PSI Boost, 700-800 Deg EGT, 1500 RPMs

Engine:
95 12valve
175hp
Stock head bolts to 150 ft/lbs
60 lb valve springs
Retainers and keepers
18 deg timing
No cam plate
AFC ahead stock star wheel location
5 X .012” Injectors 260 Bar
4K GSK
Coolant bypass kit
HX-35 14cm non-gated turbine housing, to 3” down pipe
Stock stroker exhaust 3.5”
AFE


I am shooting for 30 MPG and currently running around MI in weather in the low teens averaging 17 mpg. I have been driving it for about 3 months now since I finished it. I am attributing the low mpg to the hi boost numbers I am seeing? Truck may be too heavy, too much wind resistance, too big of an injector, or too tight of a turbine housing?

Things I am considering trying, each by itself to monitor changes:

Put some 235-75r-16s on it.... (gained 2 mpg to 18.9)
Change to another tire and rim combo? MT vs AT? More rim less tire?
Change out to a16cm housing and 4 or 5” exhaust (hopefully this this coming weekend I will do this)
Go down to a 5 x .010 injector (have them but last resort)
Build an air dam (I hear there are some guys on here that have had good luck)
Lower it (this will be after the turbine housing change)

Looking for some input from the guys that have setup their trucks for MPG.

Here are some pics

Drivetrain stolen



with the 235 85r 16s on it

Motor



Gear Vendors Adapter

Gear Vendors Installed

Crusing RPM

Cruising Boost and EGT with 235s


Any positive input is appreciated....
 
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10
#2 ·
Nice looking work so far. I like seeing a guy improve an abused piece of machinery.

Before we get too far, we need to know what you mean by "30 MPG." Is it a "snapshot" taken one time on a suitable piece of road? Is a one tankful average? If all you want is a snapshot drive 30 MPH down a 7% grad with a thirty knot tailwind. There is no shortage of guys that do that, but IMHO they are lying to me (I don't care - I know better by now), they are lying to the board, and worst of all lying to themselves.

This is how I measure it. Maybe you have a better plan.

I use a four tankful (roughly 1,600 miles) average on my daily commute. The commute is 35% urban/suburban (keeping up with traffic), 35% two-lane state roads (60 MPH plus or minus 10 RPM), and 30% Interstate (70 MPH plus or minus 10 RPM). I use my AIC's digital tach for precise speed setting. Averaging four tankfuls lets me average out variations in weather, traffic, and clumsiness in filling the tank. I use the odometer (my speedo is corrected for the tires I use) and the fuel pump and figure MPG the old-fashioned way.

Specifics in the next post.
 
#3 ·
OK. Specifics.

If you measure to an honest standard anything like mine, 30 MPG is going to be a tall order for a 4x4 with an automatic.

Judging by the clean conversion, you seem to be mechanically inclined. If you want 30 MPG, the automatic has got to go. The automatic is costing you at least 2 MPG by itself and forecloses some strong driving techniques.

Don't worry. Before long, the 12 valve and the GV will trash the automatic and you'll have an opportunity to install either a NV5600 or a ZF6-650. both come with SAE bellhousings.

Other than the fact if will cook you automatic the GV was an excellent idea although you final drive is actually 2.91:1 instead of 2.01:1. A GV is a 78% overdrive. There is a GV in my future this summer.

I wouldn't mess with my turbo. If you have enough boost that she doesn't smoke at highway speeds, I'd say stay with what you have. You may need smaller injectors. Your EGT is too high for good economy. You want to keep it below 600 degrees pre-turbo. I run at 500 degrees pre. I barely get any boost but she ain't smokin' yet, so I leave it alone. After the GV I may change my tune about the turbo.

At the moment, my guess is you are leaving 4.5-5 MPG on the table because your truck is as draggy as an Amish barn. You need to clean up that bed. A flat tonneau (hard or soft) will gain you 1.5 MPG. A sloped "fastback" bed fairing will help a lot. My rude, crude apparition improved the truck an additional 1.5 MPG over the flat tonneau.

An air dam helps. Look at Bonneville cars. They fight aero drag in a big way. Many of them have air dams that hang down perpendicular to grade. some people think they look dorky but they work. Mine was good for 0.75 MPG. For sake of practicality my air dam is made of 3/8" rip stop conveyor belt. Pricey and bearcat to fabricate but nearly indestructible. My air dam has hung 1.5" above grade but I'm gonna raise it to 3 inches this year. The rubbing annoys me.

You have to do something about those wheel wells. You may as well be poppin' a 'chute. You don't have to do full skirts, just fill in those big empty spots.

I presume you do the obvious maintenance stuff like airing your tires up to the rated pressure on the sidewall. I have firebombs, so I have to keep them rock-hard. Check your brakes for dragging. Sintered metallic brake pads are developing quite a reputation for edge swelling when a little rusty.

BFG Long Trails have the lowest posted rolling resistance. I don't use 'em myself. The firebombs give good all-around performance. OEM tires are probably the lowest rolling resitance tires commonly available. One parameter of rolling resistance: Quieter tires tend to have lower rolling resistance. Making sound requires energy. You know where that comes from.

Chuck the automatic and clean up your aerodynamics and you'll be in the mid-20s. Then the going gets tough.
 
#7 ·
I'll be watching this but I live by another motto. As I'm sure Redstroke knows from his other fummins, it's not about miles per gallon but SMILES PER GALLON. :D
 
#8 ·
If smiles per gallon were paramount a Z06 Corvette would be a much easier path to take.

Don't sweat the ratio. I'm calculating from the back of the transmission.

The big question for right now is: "What do you mean by 30 MPG?" A snapshot? A long term average? A WAG?
 
#9 ·
Well for now the goal is get to where you are 27 in the summer and 24 in the winter. I drive around 17 miles to work one way everyday about 4 miles to get to the x way then 11 @ 70 mph then .5 mile off to work. I think anything in the 25 range is sufficient and possible on a tank average. The 30 mpg is kind of a goal that if I could hit a tank avg a couple times on longer trips I would consider the project a sucess. My hope is with finding the right turbine housing and injector combo as well as taking your advise on aerodynamics (lowering, air dam, and bed cover) I can get in your 24-27 range. Then to gain the last mpgs to 30 use drugs. The hydrogen thing seems to be a hoax for a diesel anyways, so water/meth, CNG, or propane would need to be experimented with. Anyways that is what I invision, I am going to do all I can with fuel then cheat the rest of the way. LOL LOL

Hope that clarifies my goal.

Thanks

Adam
 
#10 ·
OK. Now I see. The goal of 25-27 in summer and 22-24 in winter is quite realistic.

Some things that are really right about your truck:
The GV overdrive: Good gearing on demand.
Right sized tires: OEM-size tires are optimum for MPG. Bigger diameter gets worse mileage because of the higher rotational moment of inertia and rolling resistance. Smaller tires make the engine rev up too much. The boys at the factory aren’t complete fools. Ask me how I know this. Buying and trying a lot of tires, that’s how. Maybe a good idea is a set of winter tires and a set of summer tirees. Gnarly lugs for Michigan snow. Road pattern tires for warmer weather. My OEM-type firebombs have been a good all-around compromise.

Stuff I would recommend:

A stick shift is a solid 2 MPG there for the taking. I have always been amazed how guys who will take on the complex problem of engine swaps are intimidated by an auto-to-manual transmission swap.

I think you are over-injected. Try driving to hold 600 degrees. If you can’t do it (give yourself a couple weeks to get the knack) you are over-injected. I routinely run 500 EGT, 2-3 psi boost, and 1700 RPM @ 70 MPH. EGT is a function of fuel burn. Less fuel burn (better MPG) means lower EGT. I would not mess with the turbo til you get EGTs down.

Given you have a 4x4, I don’t think a air dam is in order. I lowered my 4x2 4 inches in the front and 6 inches in the rear and my air dam is on the ragged edge of being too big. I don’t think a 4x4 can be lowered without fab work that would make Jesse James (the bike builder) flinch. On a 4x4 it would look like the mainsail on Old Ironsides, and add more frontal area than the reduction in coefficient of drag it will make. Maybe a belly pan (another thread is going on this subject) might be a better idea for a 4x4.

Some sort of bed cover is in order if you want to get to the mid-20s on a regular basis. For me a hard tonneau added 1.5 MPG and my lewd, crude fastback added another 1.5. Hopefully, you can make something nicer than I did.

Compared to a Dodge or Chevy, the Ford is definitely heavier. There is a price to be paid for that sturdy construction and it is weight. But fuel is cheaper than repairs to cheesy trucks, IMO.

I would not mess with auxiliary fuel (CNG, propane) until I got the No. 2 where you want it. I don’t know about MI, but here on the frozen steppes of central Indiana, propane is more expensive than No.2 on a $/MMBTU basis. Before doing propane or CNG, take a long hard look at how much advance you are running. Propane (once blowtorched into ignition) has a very fast flame front and has been known to put windows in crankcases.

Something very cheap to do is adjust the nut behind the steering wheel (the driver). Read Beating the EPA - The Whys and How to Hypermile - CleanMPG Forums
This guy is the guru of high MPG drivers. He does things that only the truly insane would do and his site has a load of politics I don’t care for, but he has the goods. He has been verified as squeezing over 100 MPG out of a first-generation Honda Insight and 47 MPG out of a gas Ranger pickup on public roads, and does it on a routine basis. Most of the link is written from the standpoint of a hybrid, but read it and find the stuff you can (will) do and use it and discard the rest. The driver matters a lot. In Michigan I would not recommend driving real slow. People there might shoot you. Here in Indiana they’d just throw a chair at you.

For me, my testing season is mid-May to mid-September. No doubt later for you, but that gives you time to make your mods and practice any new driving techniques you can do before you try a real test.

Send me a PM with an e-mail address and I’ll send some .jpgs of my fastback bed fairing.
 
#12 ·
Dave’s recommendations:

Get rid of auto:
I chose the auto because rowing gears in traffic is a pain, so I am going to stick it out with the auto being that it is a built trans and upgraded 93% efficient convertor it should hold up fine and be as efficient as an auto can get. I understand your point but I see plenty of D-maxs getting well into the 20s with Allison’s so I think it is feasible with my auto.

Lower EGTS (too much fuel)
I did change over to a 4” DP and 5” exhaust this weekend I did not change the turbine housing and I will check mileage again. I also tested my CAC system and found 2 leaks one was a big one so that should help mileage a bit. I can run about 650 deg at 55 and 750 at 70 after checking mileage I will decide on the 5x .010” injectors, I just hate taking power out of this thing!

Tonneau Cover
I thought myth busters busted this one? Sounds like your data does not support this with your total improvement of 3mpg with your fastback, that is a nice increase. I was thinking of just taking off the tailgate and checking mileage for a tank before buying a cover. Thoughts?

Air Dam
I see you think the dam would be too big on the front of a 4x4. From the bottom of the stock black plastic dam to the ground it is 14.5” so really I could lower 12”. I don’t have a problem fabbing one up to extend the existing black plastic one if you think it would help?

Lower ride height
I can prob get about 2” out of the front and 4” out of the rear, or do I just do an air dam below the bumper and leave the ride height alone?

Wheel wells being parachutes??
Um full skirts? Don’t have a clue about this? Are you talking about actually filling in the top portion of the fender opening with plastic? How do you do that without looking really weird?

Tire Pressure
I was running at 65 went to 80 PSI now and will go to 100 takes forever to air up to that pressure.. Went thru all caliper slides and checked pads already so good there..

Additives:
I am running 18 degrees of timing and yes I agree, get as far as I can before using additives, small amounts of these are usually ok it is when people try making 100hp on an additive that they get into trouble.

Adjust the nut behind the wheel
I will take a look at the link once I get a chance, I have been driving by the boost and pyro gauge as much as possible, this is not nearly as fun as driving like you stole it, but keeps you busy. I am the guy complaining about slow drivers so I sure do not want to become one, but rather just drive more conservative.


Here is a link, this is another Cummins conversion but in a 2wd ½ ton short box dodge. He is running about 700hp, twins, bigger injectors than me, 30 degrees of timing, and 3.21 gears I believe. He has averaged 55mpg at 60 mph which is equivalent to a Cummins idling. I am trying for around half that so I wonder if the truck weight and aerodynamics is what is killing me? Competition Diesel.Com - Bringing The BEST Together
 
#18 ·
Dave’s recommendations:



Lower EGTS (too much fuel)
I did change over to a 4” DP and 5” exhaust this weekend I did not change the turbine housing and I will check mileage again. I also tested my CAC system and found 2 leaks one was a big one so that should help mileage a bit. I can run about 650 deg at 55 and 750 at 70 after checking mileage I will decide on the 5x .010” injectors, I just hate taking power out of this thing!
From my conversations with Dave, decreasing the EGT's by changing the exhaust leaves you burning the same fuel for lower egts. in other words, if you change the exhaust, take a note of the EGT drop, and try to make your 600* goal that much lower :eek:

Tonneau Cover
I thought myth busters busted this one? Sounds like your data does not support this with your total improvement of 3mpg with your fastback, that is a nice increase. I was thinking of just taking off the tailgate and checking mileage for a tank before buying a cover. Thoughts?They did, but that was for tailgate up vs down. with a tonneau cover, the swirl area is still there, just smaller and therefore more aerodynamic. the fastback virutally eliminates the swirl, leaving only the space behind the tailgate.


Lower ride height
I can prob get about 2” out of the front and 4” out of the rear, or do I just do an air dam below the bumper and leave the ride height alone?
If it's a 4x4, I doubt this could feasibly be done, but feel free to prove me wrong ;)

Wheel wells being parachutes??
Um full skirts? Don’t have a clue about this? Are you talking about actually filling in the top portion of the fender opening with plastic? How do you do that without looking really weird?
Think Honda Insight. (go google pictures of it)

Adjust the nut behind the wheel
I will take a look at the link once I get a chance, I have been driving by the boost and pyro gauge as much as possible, this is not nearly as fun as driving like you stole it, but keeps you busy. I am the guy complaining about slow drivers so I sure do not want to become one, but rather just drive more conservative.
Most of us who drive for mileage still do 65-70 on the freeway. you still have to consider your own safety.


Here is a link, this is another Cummins conversion... He has averaged 55mpg at 60 mph
Obvious BS claim... maybe if he was running it halfway on propane and half on diesel, but then he's not counting the propane... or methanol, or whatever else he's putting in it.
see replies in red
 
#14 ·
OK. We have a 4x4 SC Short box Super Duty with a warmed-up Cummins 12v and an automatic transmission, a GV overdrive, and roughly OEM-size rubber currently getting just shy of 19 MPG. Completely plausible so far.

The goal is 24-27 MPG in a combined-duty commute. I’m there, so I know it can be done.

But the automatic will be retained as well as the oversized injectors which cause excessive EGT. A tonneau or fastback bed fair seems to be unacceptable if I read this correctly.

Red says he can lower the truck 2” up front and 4” in the rear, and put an air dam on it. Auxiliary fuels seem to be on the table.

OK. Good luck. Keep us abreast of progress.
 
#16 ·
Yes the auto will be retained, the injectors can go if need be, a tonneau should not be a problem I was just asking if removing the tailgate would net a similar gain?

I also checked alingment and I was toed out, now toed in 1/8", so less resistance there too should help.

Thanks for your input this far, I appreciate your help Dave

So far I am at 280 miles at a 1/2 tank so I am improving since the mods this weekend.
 
#15 ·
Obviously, I failed to make myself clear on the subject of bed covers.

When I first got the truck I got 18 MPG. Dead stock. Open bed.
I put an A.R.E. hard flat tonneau and my MPG jumped up to 19.5 MPG.
I took off my A.R.E. and put on my homemade “fastback” cover and my MPG jumped up to 21 MPG.

So, I concluded that my homemade bed cover gained me 3 MPG versus an open bed. Sorry if I wasn’t clear.




On the Dodge.

Step back and think about the claims. We have a half-ton pickup with a 1,200 lb 700 HP engine and he is claiming to get 34% better MPG than the highway mileage for a 2010 VW Golf TDI diesel, 15% better MPG than the highway mileage for a 2010 Toyota Prius, and 28% better MPG than the claimed highway mileage for a Honda Insight.

Is it just me, or do you guys detect a whiff of rodent?

Now I don’t see the Dodge being anymore aerodynamic than Red’s Ford. Yeah, its probably 1,200-1,500 lb lighter.

I think the big difference is that the Dodge guy is lying and Red isn’t.
 
#17 ·
Yeah it is hard to believe but Jeff Garmon is a stand up guy as well. Just using his info as a bench mark for my setup.


So here is a question:

What gauge indicates better mileage?
Boost shows engine load, less boost less load
EGT also shows load lower EGT less load

So is the goal to have both gauges as low as possible at 70? Does increased RPMs mean lower mileage?

GV Engaged
70 mph
1550 rpms
6 PSI Boost
750 Degrees

GV Disengaged
70 MPH
2000 rpms
9 PSI Boost
650 Degrees

As you can see the boost and EGT flip flop based on RPM, which is more efficient?

Second point:
If the goal is to have both gauges as low as possible, twins may be the solution. A higher volume of more efficient air without the increase in boost effectively keeping boost low and egts at a minimum, just pondering this as a possible solution as well.
 
#20 ·
I'd be curious to see what a three-tank average in his truck on Dave's route would pull. Too bad those comparisons never happen.
 
#24 ·
3.5" to 5"

Hole in boot

7" Tip

As of today the fan is removed

3" DP to 4" down pipe

Testing for boost leaks
 
#25 ·
Looks good! How's your mileage been lately?
 
#26 ·
Not worth a poop.. Avg 18 driving normal to slight conservative...

This tank I am checking with the only change being the fan is now removed.
 
#30 ·
Yeah you are prob right, I am just trying to get the air flow opened up to ensure it will never be an issue. The truck sounds like its got a pair now but has an annoying drone at 1500 rpms.

Dave the plan is 1 tank to see if the fan makes a difference, then a bed cover (cking craigslist), then lower the truck 2". I am also swapping to a set of 20s for a week to see if the more rim, less tire concept has any backing.

Just traded a 6bt for a 4bt so I am going to start collecting my 4bt ranger parts if this project cannot get mid to high 20s I am defaulting to a 4x4 ranger. Gonna try like heck for 25-30 with a 4x4!
 
#29 ·
Dave, do you think the 5" will increase pressure due to less velocity?
 
#34 ·
I assure you the larger rims will definitely hurt your mileage. Even if they weighed exactly the same overall they have a higher Moment of Inertia.

I have swapped to large rims twice and both times I lost a significant amount of fuel economy.

On my Jetta tdi I bought the trickest, lightest 18" wheels out there to replace the stock 16"s. The overall weight was exactly the same w/ the tires mounted. I lost like 4 mpg (not a huge % on that vehicle).

Cheap little rims w/ skinny little hard as a rock tires will get you the best mpg, not to mention the best braking and accelerating (removing absolute traction from the issue).

When I added 20s to my PSD, I seriously thought my chip had been turned off it made it so much slower. I'm certain that some of the mpg advantage of the Duramax compared to the new Fords is all in the rim size the manuacturers choose as OEM.
 
#35 ·
well, more has to be considered than just size and weight.
You have to think about what distance that weight is at, as well as how this effects the tire, sidewall, etc.
personally, I would think going to a larger rim with a similar OD tire should help mileage.
this is, as usual, based on no data.
 
#37 ·
I believe they make Carbon fiber 22's. full prepreg construction, and four or five pounds each...
if you have 20 grand per wheel...
and a car light enough to put those on LOL
I disagree with the idea that it's always more with larger rims.
now, toss on similarly larger tires, and then yes, of course.
 
#38 ·
Rotational moment of inertia goes up with the square of the increase in radius. You double the radius, the moment of inertia goes up four times.

Increase radius 10%, you increase moment by 21%.
 
#39 ·
Well if everything was the same the fan gave me 1.1 mpg, best now is 20.7 mpg.

Now I am trying the 20s
Weights:
235 85 r 16 on stock 16" rims, tires about bald 57lbs each
305-50r20 on 20x10? 89 lbs each

Judging by the width of the 20s contact patch to the road I would assume there would be more drag let alone the extra rotating weight, so am not expecting a mpg change, but it is worth a try, and it looks cool!

Dave what do you think of the air dam pics below? I will paint this black and put it on once I get a baseline for the 20s.











 
#45 ·
Well if everything was the same the fan gave me 1.1 mpg, best now is 20.7 mpg.

Now I am trying the 20s
Weights:
235 85 r 16 on stock 16" rims, tires about bald 57lbs each
305-50r20 on 20x10? 89 lbs each
Assuming these tire set ups have the exact same overall diameter I'm looking forward to seeing exactly how much mpg the 20's do cost.

I'm going to gander 2.1 mpg. I look forward to hearing back from your testing.

Are all tests run w/ no AC?
 
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