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MPG improvements through aero mods

66292 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...
http://media.gmc.com/media/us/en/gm...news/us/en/2013/May/0516-gmc-pickup-aero.html

http://www.pro-touring.com/threads/101460-Designing-Aerodynamics-for-Track-Performance?



Front air dam re-installed


V2_0 of the air dam



http://www.audew.com/AUDEW-Universa...rotector-Lip-Splitter-Body-Spoiler-p-130.html

Look @ pic, velocity of compressed airflow -> rear exit of truck.
http://www.buildyourownracecar.com/race-car-aerodynamics-basics-and-design/3/


http://www.autospeed.com/cms/article.html?&title=Modifying-UnderCar-Airflow-Part-1&A=113181

http://www.autospeed.com/cms/article.html?&title=Modifying-UnderCar-Airflow-Part-2&A=113182


https://www.curbellplastics.com/Sho...93-in-x-48-in-x-96-in)-Haircell-P1-Fire-Rated

Truck aero study
http://people.cst.cmich.edu/yelam1k/asee/proceedings/2011/DATA/7-155-1-DR.pdf


V2_0 Air Dam...

http://www.cumminsforum.com/forum/3.../2412082-diy-air-dam-v2_0-a.html#post28028746


http://ecomodder.com/forum/showthread.php/rear-diffuser-1831-3.html

http://ecomodder.com/forum/showthread.php/underbody-panel-testing-12747.html


Blowing the vortex part 1
http://www.autospeed.com/cms/article.html?&A=113216

Part 2
http://www.autospeed.com/cms/article.html?&A=113217

Part 3
http://www.autospeed.com/cms/article.html?&A=113218

Part 4
http://www.autospeed.com/cms/article.html?&A=113219


aero mods thread... this is where I document what I tried.
http://www.cumminsforum.com/forum/3rd-gen-non-powertrain/2449106-aero-mods.html#post28435634
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Discussion Starter · #41 ·
I would highly recommend using self adhesive CCF gaskets in different thicknesses for the different areas you want to close off, particularly the cab/bed space, as you would NOT want any sheet metal scratching paint as the bed and cab move differently from each other while driving. The CCF tended to be either black or dark grey and would also not be very noticeable in those spaces.
Wouldnt use sheet metal, looking for a seal similar to whats below for both the bumper and the bed/cab area... The bed/cab seal would need to be enough to come up to but not touch the cab. Might be tough to find something to work right. I know the ecodiesel has it so I will start there and see how the bed is shaped on the inside lip. Maybe its as simple as buying that strip and slapping it on there. The front would be very similar to below...



 

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Maybe a weatherstrip type stuff like you’re showing Steve but with an adhesive backing. The new rams have it. Next time I have one in the shop I’ll lookup the part number.
 

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Discussion Starter · #45 ·
for the bed area there is a nice lip to use that folds in towards the center of the bed, I was figuring that lip would allow for an easy install, thinking about it more it may be difficult to find the right type of seal to extend back towards the outer edge of the bed, so your thought of a tape seal may be a better way to go.

Either way, that lip is where to mount the seal.
 

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I know bed toppers are not a favorite of most folks but i had a chance to buy one that matched my truck color for a tenth of original cost, so I did. It solved 2 basic problems i was going to have on a trip involving a couple thousand mile trip over a 4 or 5 day stretch. I built/modified a mobility chair lift for my wife's power chair and installed it in truck. Naturally I needed a way to weather proof the setup, and to provide a level of security simultaneously. The topper did both at once.
A side effect of the topper was an increase in MPG, I gained overall for the trip about 1.5mpg. Reading of the dams and other tips in this thread has me wondering if i should lower the rear of my truck the inch or two it needs to sit level, and possibly do the gasket. I know there is a tremendous amount of air that rises between the cab and bed, enough to blow over a big screen Tv that did not stick above the cab. (long story).
My truck has 3.73(I think) gears, at 55mph it tachs around 1650 or so. Knowing that rpms are the bane of MPG's I installed a Gear Vendors overdrive, now at 160 or so i run around 72mph. Fuel mileage did not change, I suspect the sheer aerodynamics of this fat truck at that speed killed any mpg increase I would have seen.
My F250 with powerstroke had the GV overdrive and it gained almost 3mpg when installed, was hoping for a simlar increase.
My best MPG to date is around 25.8, driving 50-55mph on country roads in mild traffic and nearly no towns for stop and go. If I could get to that point on interstate where 70% of my driving is i would be pleased beyond beief. At present I am hovering at 20.5-21.8 MPG consistently. My fuely report has a couple errors in it governing the total overall MPG, i lost a receipt last year on 28 or so gallons, and have had a couple of bozai runs with the enclosed trailer keeping the overall average down.
 

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Discussion Starter · #47 ·
1.5 mpg is a pretty good jump, even with the added weight of the shell. I owned a shell in the past on another truck, it was great for crashing during fishing trips to various spots over several days. If you can tolerate the bed being covered like that then great, I cant. I used to have a snugtop hard cover that had its bright spots with better weather sealing and providing weak shelter for crashing at trailheads. I got tired of the locks breaking on it and eventually sold it in favor of the Pace Edwards Jack Rabbit I have on there now. Now I cant imagine not having it. Being able to roll it up and dump in a yard of bark for the wife is priceless...

On your truck, if you can tolerate higher coolant temps, a 2010-12 200*f stat ($30 @ napa) is good for ~.75 mpg. Also since your an MT truck, you can drive up intake temps with a front cover (~$100 iirc at Genosgarage.com or home made for ~$25) and further bump mpg. I found ~100-110*f is awesome for stock programming. You might also benefit from that lower air dam mod. Not sure if a reverse level will benefit mpg or not. Maybe someone else might know.
 

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according to temp gauge in truck it already runs 200-210 constantly. I thought about a winter cover but have not done that yet. My F250 has a cover and it certainly heats better in winter but seems like the mpg dropped on it when fully closed. I figured(apparently guessed wrong) that i was blocking air flow enough to make the fan work harder, making engine work harder to pull it.

The lower air dam is a nice touch, I like the looks of it and will attempt it when it gets warmer outside
 

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Discussion Starter · #49 ·
If you can monitor IATs & the Ambient temp sensor in the OEM airbox, any temp difference below 25*f will keep the fan from engaging for air temp. If it exceeds that 25*f difference then you can hear the fan clutch engage off and on. Sounds like you may already have a 200*f stat in there.

Feel free to post back some results when you get the lower dam installed...I am sure many would want to hear results.
 

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Question... Does a shell offer better mpg gains vs a tonneau cover?

Doing some reading and have found some different styles of vortex generators. The airtab being one of them, illustrations show how it reduces the low pressure zone aka LPZ behind the trailer. If the shell offers better mpg vs a tonneau cover question is why? I would think the added height at the rear would increase the LPZ...

Airtab | Aerodynamic Fuel Savers | Order Page


This design

Individual VorBlade Unit

is said to be effective for side winds. This has me curious to know if it may be effective with the turbulent air under the truck.

Also read an article about a ferrari that uses he flow off the cab area, fed thru the body and out the rear near the tail lights, towards the middle. The usage there was intended to break the LPZ behind the car. This was allowing higher speeds with less HP.

New rams have the exhaust under the rear bumper... was the intent to flow hot air into the LPZ in an effort to reduce the LPZ size? Seems to me the LPZ size reduction might be the best bang for the buck if it can be reduced. Wondering if the Vorblades could be used on the frame to control the flow under the truck and under the bumper in an effort to reduce that LPZ...

random thoughts not wanting to get lost... (all it takes these days is a trip to the fridge hahaha)
 

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The LPZ is quite evident at the back of the topper. I pulled my enclosed trailer at a speed higher than I am comfortable admitting to rescue a friend in distress. I had forgotten to latch the window and it kept opening up to almost horizontal at anything above speed limit +25%, it does not attempt to open itself when not towing, although admittedly I have not had it above 3 digits since towing.
 

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Question... Does a shell offer better mpg gains vs a tonneau cover?

Doing some reading and have found some different styles of vortex generators. The airtab being one of them, illustrations show how it reduces the low pressure zone aka LPZ behind the trailer. If the shell offers better mpg vs a tonneau cover question is why? I would think the added height at the rear would increase the LPZ...

Airtab | Aerodynamic Fuel Savers | Order Page


This design

Individual VorBlade Unit

is said to be effective for side winds. This has me curious to know if it may be effective with the turbulent air under the truck.

Also read an article about a ferrari that uses he flow off the cab area, fed thru the body and out the rear near the tail lights, towards the middle. The usage there was intended to break the LPZ behind the car. This was allowing higher speeds with less HP.

New rams have the exhaust under the rear bumper... was the intent to flow hot air into the LPZ in an effort to reduce the LPZ size? Seems to me the LPZ size reduction might be the best bang for the buck if it can be reduced. Wondering if the Vorblades could be used on the frame to control the flow under the truck and under the bumper in an effort to reduce that LPZ...

random thoughts not wanting to get lost... (all it takes these days is a trip to the fridge hahaha)
I have seen lots of those on the side filler panel on semi-tractors, and studying the dirt patterns after driving in rain iit appears they merely swirled the air and dropped at least some of it back on the corner of trailer.
 

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Discussion Starter · #54 ·
Yeah I've had the same issue with the last truck I had that had a shell (dakota QC), busted latch on the rear door and it would open up on its own often. It was quite irritating.


aero graphics pics....





An FYI for anyone looking to do the 2nd air dam... was out earlier looking for parts, had a chance to look at a stock height 2500 4wd, took a pic, then took a shot of mine for comparison and noticed the 2nd air dam looks like the top of it lines up with the bottom of the OEM air dam.
 

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More reading... this one is long and geared towards racing but does explain a lot

Designing Aerodynamics for Track Performance

I read an article about the FE ecodiesel model, one of the comments was that it used side boards. In the article above there is discussion in post #6 regarding side splitters... part of its function is to keep airflow from rolling under the body. This I am guessing is to minimize turbulence under the body. My truck has always had the tubular side steps (tubular shape is bad according to the write-up linked) and I've thought of adding a plate of some sort to close off most of the opening that exists between the step and the body. Now I see why I should go ahead and do it.


Also, I looked at the back of the truck by the tire area and think something can be done in that area to change flow exiting from under the truck. Thinking something like this with directed airflow to make it effective...

 

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Someone mentioned how many small things can add up, and while I don't know which change did what, the result was a whopping 43% improvement in mileage.

Had lots of time to ponder fuel economy (or lack thereof) during bi-weekly 1,000-mile trips, and after installing an aftermarket bumper, something had to be done.

Ended up grafting most of the stock bumper onto the bottom of the aftermarket one, and got a narrower and lower enclosed V-nose trailer (based on the bug splatter on the front of the old one), not much taller than the shell.

Inspired by the results, I then installed a 6-inch wide strip of conveyor belt onto the lip of the factory air dam, for an extra four inches hanging down.

I probably have the mileage results from that air dam add-on in the log, but can't remember for sure now. The 43% overall improvement I'll never forget.
 

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Someone mentioned how many small things can add up, and while I don't know which change did what, the result was a whopping 43% improvement in mileage.

Had lots of time to ponder fuel economy (or lack thereof) during bi-weekly 1,000-mile trips, and after installing an aftermarket bumper, something had to be done.

Ended up grafting most of the stock bumper onto the bottom of the aftermarket one, and got a narrower and lower enclosed V-nose trailer (based on the bug splatter on the front of the old one), not much taller than the shell.

Inspired by the results, I then installed a 6-inch wide strip of conveyor belt onto the lip of the factory air dam, for an extra four inches hanging down.

I probably have the mileage results from that air dam add-on in the log, but can't remember for sure now. The 43% overall improvement I'll never forget.
That is a tremendous gain. What mileage are you seeing after these mods?
 

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Discussion Starter · #58 ·
Someone mentioned how many small things can add up, and while I don't know which change did what, the result was a whopping 43% improvement in mileage.

Had lots of time to ponder fuel economy (or lack thereof) during bi-weekly 1,000-mile trips, and after installing an aftermarket bumper, something had to be done.

Ended up grafting most of the stock bumper onto the bottom of the aftermarket one, and got a narrower and lower enclosed V-nose trailer (based on the bug splatter on the front of the old one), not much taller than the shell.

Inspired by the results, I then installed a 6-inch wide strip of conveyor belt onto the lip of the factory air dam, for an extra four inches hanging down.

I probably have the mileage results from that air dam add-on in the log, but can't remember for sure now. The 43% overall improvement I'll never forget.
someone did something similar with a 2nd gen truck IIRC, also mentioning a 4 mpg bump. Reading the racing link I posted earlier, I 100% believe that blocking off the front would give that much of a bump.

side pics of my 2nd air dam taken today...



 

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That is a tremendous gain. What mileage are you seeing after these mods?
As I recall, it got me to around 10 mpg. I need to dig up the log book for that one and get the real numbers (I sold it a few years ago). Should dig up some photos of the frontal area modifications, too.

Also, it was a 2010 5.7 gasser, but that doesn't really matter as far as the mileage gains goes, as they were all due to aerodynamics.
 

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aerodynamics are certainly a factor for me, when I first bought the truck it was a bone stock '05, 6spd with 3.73 gears. running 55mph roads i could knock on 21mpg, interstate it fell to under 19 hanging with the 75mph traffic. I added a Gear Vendors and can run 74mph at around 1800. Fuel mileage did not come back to the 22 with that single change. Once the weather breaks where I can roll my old antique butt around on the ground I am going to do the front dam idea shown above. I like the look it adds if nothing else.
 

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