How to improve Dodge Ram Van from 12mpg? [Belly pans?]

[ahanix1989]

Hey everyone, this is gonna be a fun project.

I happen to own a fullsize Dodge Ram Van. 5.2L V8, 4-speed automatic, LT235/75R15 Severe Snow Service tires... this thing was designed for towing and cargo, not high efficiency.

This spring I'll be restoring it. Ripping out the interior panels and putting new insulation and carpet in, painting the exterior, and while I'm there... I want to do something about the fuel economy.

I've spent plenty of time under that van. There is a TON of space underneath. I don't even need to jack it up to replace the shocks, I climb underneath and there's 28" of space from the ground to the floor panel.

Everybody who has done belly pans has been on more efficient vehicles. I mean, one of the cars tested was already getting pretty near 100mpg... so belly pans can't help much more than that thing is already doing. Right now, during winter, I average 11.8mpg. During summer, I get closer to 15. "Driving variances" doesn't really apply, it's ALWAYS 11.75 to 11.83 mpg, no matter how I drive.

Considering the significant amount of space under that van, I'd imagine it has absolutely horrible airflow. Even if I could squeeze 0.5mpg out of some coroplast-crafting, that'd be pretty decent. I don't know all the details of the design though, especially around the tires.

With the front control arms and rear axle, should I be encasing them (jacking up the van so I know the lower limits of the control arms), or should I just have the pan angled to have the air "jump the gap"?

Lots of pictures to help illustrate:
License plate is well-deserved
Front suspension can't be good for airflow.
Exhaust doesn't hang that low anymore, but still gives an idea of body height. Doesn't show floor height
Goes with the above picture, this is how high to reach the bottom of my frame
View looking from the middle towards the front. Poor airflow I'd imagine
View looking from the middle towards the rear. I'm sure this could be improved, even if I have to ignore the area with the driveshaft

As you may have noticed, some pictures are old and that van has been modified numerous times. Usually on a really low budget (lol tailpipe? more like failpipe) but this time I want to do things right.

But you guys are the experts on this. What would you all recommend?

[rmay635703]

Air dam on the front perhaps, but I own a 01 dodge ram crewcab v8 (5.2ltr) it gets the same FE as your van 11 city 15 highway.

I am able to get a little above 18 highway using a scanguage and fiddling with the throttle.

I can also get 20mpg city if I have lots of rolling hills and situations where I can almost coast to a stop. Normally though I can only do about 14 depending on how far I have to go and how cold.

The 5.2 dodge in neutral coasting gets about 20mpg right down to 10mph, so needless to say coast almost to a stop to improve FE. You only need to be moving about 5mph to get above 11mpg in neutral once the motor is warm.

Another thing, GET AN ENGINE HEATER. The 5.2s hate cold weather and use over 2gph of fuel just idling when its cold and the FE crazynes continues a long while after you get going until the motor heats.

Also I've found on my 5.2 that the truck takes off SSLLOOWWly if I just press the accelerator pedal in, if I waver the pedal in and out a small amount rapidly just before I take off in earnest the truck takes off much more firmly and at better FE, another thing if you are accelerating, just accelerate fairly hard the 5.2 gets about the same FE accelerating hard (assuming you did the pedal trick) as it does accelerating slowly.

Good Luck and its best to test with a scanguage

[womprat]

Anyone tried boat tailing on a van? I don't think I've seen it yet, but a partial kammback on the top and sides might help.

[Andyman]

It should help if you install summer tires after winter is over. Snow tires usually have high rolling resistance. Check if your ignition timing is correct. Make sure the engine warms up to normal operating temperature. If the heat feels weak you might need to replace the thermostat. Check the output from the oxygen sensor to see if the fuel mixture is correct. It should have about 0.5 volts after it warms up. If it's not working right it should turn on the "check engine" light. Replacing the oil in the differential with a slightly lower viscosity synthetic oil should help in the winter. There's a lot of other things you could check out. Read about the 65+ Vehicle modifications for better fuel economy - EcoModder.com if you haven't already.

[rmay635703]

Originally Posted by ahanix1989

Hey everyone, this is gonna be a fun project.
Right now, during winter, I average 11.8mpg. During summer, I get closer to 15. "Driving variances" doesn't really apply, it's ALWAYS 11.75 to 11.83 mpg, no matter how I drive.

But you guys are the experts on this. What would you all recommend?

You can do better than 11.75mpg with a stock 5.2 even in town but you need to rework your route usually. You also need an engine heater if your trip is shorter than 10 miles or you simply can't get the things to do better without extreme measures driving wise. I would estimate that this motor even with many aero mods would see little benefit in the winter on short trips without a magnetic or gel blanket heater on the bottom to keep things warm

Also how much air pressure do you have in the tires? I can get about 2-4mpg better with 60psi (depending on how far I am allowed to coast and what speed)

Your vehicle has a lot of inertia even one stop and go reduces fuel economy even on short trips by about 1-3mpg as measured by my scanguage. Think about the number of times you stop and from what speed. Think of the # of times you have to use brakes. The potential fuel economy on this vehicle is only around 18mpg-20mpg steady state & better P&G, even in the winter but you can't actually reach that except if you have a long trip with no stops.

The main issue I have with my trip is that I can't coast far enough on my trip into work and around oshkosh. To get 20mpg you need to be able to coast down fully at every stop. If you ARE NOT COASTING DOWN TO 8 MPH you are not getting your full FE potential and stopping straight from anything above 20mph kills fuel economy massive (I am talking experience)

If your vehicle is OBDII beg/borrow a scanguage if you can afford it. You will see there is a lot to be gained on a 5.2 from driving technique alone, especially at lower speeds.

One last thing, if you coast to a stop always coast in neutral never in drive, dodge has the motor set to burn more fuel in gear; sometimes on the highway almost double in gear compared to neutral.

Lastly this post was not to discourage you, I am just stating facts about your vehicle, aero is only going to be the most effective if you can get the motor warm and only if you are driving about 40/45mph much of the time. Grab the low hanging fruit first. If you have a lot of stops you need to be able to coast down as much as possible regardless of your aero situation. And lastly 5.2's don't like being babied when you accellerate, either accelerate or drive a steady speed but nothing in between when you are in gears below 3rd. Generally firm acceleration but not to the floor accelleration. And don't diss wavering the accelerator pedal before taking off from a stop, its worked now in 3 dodge vehicles, must be some strangeness with the computer and slushbox.

Good Luck
Ryan

[ahanix1989]

Wow, just woke up and already tons of great information! I'll have to tackle these one at a time...

@rmay635703:
Unfortunately the only similarity between the trucks and vans is the powertrain... You didn't mention if yours was 2WD or 4WD, and that obviously has an impact on weight differences. We both seem to get the same mileage, but aerodynamics is my focus at the moment, and our vehicles are too different in that regard
It's been running Mobil-1 Truck/SUV oil for a while, but a lot of people are suggesting I switch to Valvoline, which I plan on soon. I've done some little things just to make the engine breathe better (Dynomax exhaust, modified the intake manifold, 180° t-stat)
As far as overall powertrain health... the engine was replaced with a warranted 80,000 mile engine a couple months ago, transmission was rebuilt 2 years ago, and the axle was serviced and swapped to limited-slip months ago... so everything should be good.

The old engine had a heater but it didn't help much. Maybe I need a bigger one?

@Andyman:
Tires are simply too expensive for me to keep two sets, plus getting ahold of another set of four chrome factory rims is a challenge. There's also few options for LRR truck tires... that flying brick weighs 5,000 pounds, so it needs strong tires. Thermostat is good, heat is enough to make me sweat in below-zero outdoor temps... It's OBD-II and my check engine light is off. If I use a code reader I only occasionally get a "Transmission Temperature Out Of Range" (too cold, not enough to trigger a CEL)

@rmay635703 (Again. Didn't see the last post):
Right now I have my rear tires at 45psi, front at 42. They're rated for 55 max cold. Also, you work near Oshkosh? I'm just south of Fond du Lac, and I drove up to Oshkosh every day for work! I've noticed the engine "feels" more efficient giving it some gas, not just babying it. I installed a tach to keep track of engine speed and I usually have it at 2000rpm (±100) when accelerating until it hits overdrive. At 2,000 those engines put out 105hp and 275ft-lbf of torque, so they definitely have some power available!

I'll at least try smoothing out airflow leading up to the control arms, and I will definently have to try the wavering. A good portion of my drive is up or down a large hill, so neutral coasting sounds like it could be helpful. I wonder if the wavering at a stop improvements has to do with the low idle speed... mine idles at 500rpm, but wavering the gas would bump it up to 1,000 before trying to move the car. I'd imagine if you don't waver the pedal, trying to accelerate from 500rpm is just wasting gas.

Hard to discourage me when I've got nothing to lose trying

[rmay635703]

Originally Posted by ahanix1989

Wow, just woke up and already tons of great information! I'll have to tackle these one at a time...

@rmay635703:
Unfortunately the only similarity between the trucks and vans is the powertrain... You didn't mention if yours was 2WD or 4WD, and that obviously has an impact on weight differences. We both seem to get the same mileage, but aerodynamics is my focus at the moment, and our vehicles are too different in that regard
The old engine had a heater but it didn't help much. Maybe I need a bigger one?

@Andyman:
If I use a code reader I only occasionally get a "Transmission Temperature Out Of Range" (too cold, not enough to trigger a CEL)

@rmay635703 (Again. Didn't see the last post):
Right now I have my rear tires at 45psi, front at 42. They're rated for 55 max cold. Also, you work near Oshkosh? I'm just south of Fond du Lac, and I drove up to Oshkosh every day for work! I've noticed the engine "feels" more efficient giving it some gas, not just babying it. I installed a tach to keep track of engine speed and I usually have it at 2000rpm (±100) when accelerating until it hits overdrive. At 2,000 those engines put out 105hp and 275ft-lbf of torque, so they definitely have some power available!

A good portion of my drive is up or down a large hill, so neutral coasting sounds like it could be helpful. I wonder if the wavering at a stop improvements has to do with the low idle speed... mine idles at 500rpm, but wavering the gas would bump it up to 1,000 before trying to move the car. I'd imagine if you don't waver the pedal, trying to accelerate from 500rpm is just wasting gas.

Hard to discourage me when I've got nothing to lose trying

Our vehicles are much more similar than you can imagine, mine has a cap and actually has WORSE aero than your van, mine is 2wd and approx the same weight.

Try to air the tires to 60psi and suffer the ride, assuming you aren't driving in tons of slush.

Also I have been known to place a magnetic heater on the transmission Both the motor and transmission need to be warmed, best to place a blanket on the oil pan and transmission or if you have a garage You do need to make sure the heater is the type that can't burn anything though.

Also these vehicles do quite well up and down hills, unlike most here I burn going up the hill, throw in neutral before the crest and coast down. Steeper hills work better and my scanguage shows a definate improvement done correctly. Remember though you need to map out your trip, neutral coasting works best for me around 35-50 mph and you don't want to loose huge amounts of speed so if the hill is insufficient it won't work very well except at low speeds both around the hill and through the hill.

Also wavering the pedal a small amount before taking off seems to make my truck grab in and take off harder with much less pedal, you can actually feel the motor pushing harder with each small movement, it might only apply to those of us who need a tuneup but both my friends and my 5.2 behave that way. I have always known on OBDII to push in the pedal slowly when you need hard accell instead of just slamming, perhaps its computer/sensor related?

If it works for you free tip I get around 5mpg accelerating when I do this instead of 1mpg accelerating when I just push in.

Also aero is very important but equally so is technique, trouble is if your on highway speeds AKA 40mph+ the only thing you can do is drive really slow and gently press your pedal in going down slight inclines and slowly and gently release the pedal going up minor inclines. This is how I can get 18.5mpg. Without I get a tad below 15. Faster than 55 is troublesome for FE in these rigs unless you have a tailwind.

Good Luck, the only direction you can go is up

[aerohead]

The sticky with seminars and mod data has a section on bellys.You might get some quanta there.
CAR and DRIVER attempted a bellypan on a Dodge van and it was basically a wash.They surmised that only an intricately crafted pan would be effective,something they were not willing to take the time for.
All vehicles will behave differently.

[aerohead]

Originally Posted by womprat

Anyone tried boat tailing on a van? I don't think I've seen it yet, but a partial kammback on the top and sides might help.

18-inches of tail on a VW Transporter was good for about 4-mpg at 55-mph.

[thatguitarguy]

Originally Posted by ahanix1989

"Driving variances" doesn't really apply, it's ALWAYS 11.75 to 11.83 mpg, no matter how I drive.

"Driving variances" always apply. You can aeromod and engine mod to your hearts content, but it has been shown over and over on this site that the biggest improvements come from adjusting the way you drive.