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MPG improvements through aero mods

66290 Views 647 Replies 28 Participants Last post by  steve05ram360
Recently I'd seen a Chevy with with wheel splats (or mini air dam) in front of the rear wheels. I'd seen this long ago on the Audi TT I had and often wondered if there was any benefit to doing something like that to the ram. Well it appears Chevy felt it did contribute somehow to mpg improvement. Took a look at my trucks rear wheel openings to see if it was feasible to add one back there that dose not look obnoxious. Seems like it may be worth trying.

Another mod I'd thought of doing was adding a strip of plastic to close off the gap between the frame and the outer body panel, between the wheels. That would be out of sight, not sure if there would be any benefit or not in that area. Recently I read a writeup on the Ecodiesel that had a higher FE version of it, 2wd and it had side steps... side steps... really? They apparently felt it had an improvement.

Further reading (and getting back to) wheel well aero drag had me realize I have the rear fender liners. Not sure if that reduces drag back there or not when compared to the 1/4 liner that the truck came with. One of the thoughts I had once upon a time was to experiment with an louver on the fender liner in an effort to relieve some of the turbulence that occurs in the wheel wells.

At some point in 2018 I am going to revisit/install the 2nd air dam I had under there once upon a time. I plan to add the rear wheel front splat. That 2nd air dam was not even noticeable unless you knelt down and looked for it. AFter lowering the truck down I would expect it to have more of an affect on airflow under the truck. When I went from 3" spring to 2" spring that air dam started rattling, it was not prior to the spring swap. That told me airflow was actually hitting it. Any benefit from it I never did test for.

New Rams... I noticed a while back that that they had a seal setup somehow between the cab and the bed. I've looked at some of the truck liner seals to see if something could be had that would be cheap to pop in there but have yet to find one that would work ok.

I am thinking it will be hard to detect any change on any mod that is done as it will be a small change by itself. Collectively however it may be easier to detect. How? I'm thinking it will be easy to use the Torque app I use daily and record before and after data, looking at the calculated load on a longer loop that can be easily repeated. Where I"m at up in WA I can jump on the hiway and do an out & back easily to collect data for a 40 minute run... using CC of course and starting and stopping the log at the same points on the hiway.

Anyways, any thoughts or ideas out there worth discussing?

Disclaimer.... motivator, an evil one I will admit is to try and come close if not match the wifes new Mazda CX5's mpg of 24 mpg. Probably not gonna happen but time will tell. Remember, lighter wheels going on, going back to stock height and e-fans going in are in the near future and my truck was consistently getting low-mid 20's for mpg before the fan clutch gave me the finger. Its said that leveling kills approx 1 mpg, the fan is good for 1~1.25 mpg, lighter wheels???? unknown. If I get those 2 mpg from those 2 mods that should put me up into the 22-22.5 mpg range tank to tank (city & hiway combined).

Edit: Adding article link with useful info...

Front air dam re-installed

V2_0 of the air dam

Look @ pic, velocity of compressed airflow -> rear exit of truck.

Truck aero study

V2_0 Air Dam...

Blowing the vortex part 1

Part 2

Part 3

Part 4

aero mods thread... this is where I document what I tried.
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· Diesel Filled Veins!
5,772 Posts
Here's my take:
1) The electric fan will only offer reduced fuel use because it moves less air. To move X amount of air, you will require X amount of power. Using electrical power to do that is more inefficient than the fan currently on there.

2) Aero mods MAY help but the change will probably be imperceptible unless you have access to a wind tunnel with highly sensitive equipment.

3) Lowering the front from a leveling kit, is always a good idea in my book, but that's personal preference.

4) You really want to increase the efficiency your truck uses fuel, learn up on thermodynamic systems and how efficiency can be increased. The secret is to have as high inlet temperature as possible, and as low outlet temperature as possible. Your intercooler needs to go, that will give you the largest fuel efficiency increase. Next insulate the intake tubes/system from the turbo compressor all the way to the intake plenum, this will keep the intake charge as hot as possible. If you're really inventive, you could preheat the intake charge with exhaust gasses in a heat exchanger you're on the right track! Now for the exhaust side, dodge does pretty good as they are using the heat from the engine combustion cycle to turn the turbine in the turbo. You could try finding a turbo that will utilize the heat more, but diminishing returns because it generally means you'll be compressing more air (which you won't want more air because that uses more fuel). And your FINAL solution to best in class fuel economy, drive like a hypermiler freak. Easy on the acceleration, coast into stop lights trying to time them so your truck doesn't stop moving, as few service brake applications as possible (these brake applications are fuel energy being expelled as heat energy through the brakes).

4) If fuel mileage is the goal, skinnier tires, higher pressure.

· Diesel Filled Veins!
5,772 Posts
Replies inline below in red...
The incoming air temps thing: the truck takes IAT into effect when choosing a place on the fueling map to use. The truck calculates incoming air mass and matches the fuel to it. The intercooler isn't giving you anymore consistent IAT than if it wasn't there, it is there to cool the air from the compressor so sometimes it's not able to cool as much (high engine load) and other times is might not be hardly cooling anything. Better efficiency by conserving the heat of compression rather than consistency in IAT - science :D

As for hypermiling, I know very little, I'd go nuts trying to practice it. But, every application of brakes is wasted fuel energy. And I think coasting in gear is probably more efficient than throwing it into neutral because you are conserving the energy used in the compression of air whereas in neutral you are using fuel to keep the engine alive.

And yes, tire pressures are important for safety reasons. For me, a consistent wear across the face is more important than anything. This provides the safest tire and easiest wear on tread. When Dodge jacked up my rear winter tires to 80PSI I told them to lower to 50PSI, TPMS be damned (although no light illuminated, I was right, they were wrong, haha).

· Diesel Filled Veins!
5,772 Posts
Good info there for sure. I would think the IAT sensor may be slow to react, but not sure I would agree with the heat soaking of the sensor itself. I would say once the intake is heated up from the compressor heat, the IAT swings will smoothen out a bit. Also, if the IAT saw higher than actual temps, you'd just be on the leaner end of things - thus saving fuel. I can't honestly see any reason why eliminating the intercooler would cause any adverse effects and only increase your fuel economy. It is there to shed head and get the incoming air charge as dense as possible, thus allowing more fuel to be added.

As for compensating for the incoming air temp, the ECM has to, these trucks run from -50*C to +45*C (-58F to 115F) and have to accommodate for those atmospheric temperature swings, why not a temp swing from the compressor? I will concede the compressor temp swings will happen a lot quicker whereas the atmospheric temps will swing a little slower so perhaps the ECM can't compensate that quickly. BUT, the IAT does swing already with the compressor loading or unloading and the ECM does just fine. Think going up a hill and you're adding fuel, truck does just fine, then when you let off and the IAT is much less (thanks intercooler) the truck still does just fine.

Heck, I'd give the intercooler delete a serious consideration for fuel economy improvement if that was my goal. But then again, I'd consider an old VW if economy was my thing.
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