Pickup trucks and bed aero

[bandit86]

Been looking at the aerodynamics of pickup trucks since I bough an 03 ram diesel last week. The ram 1500 has a tiny little spoiler on it that the 25/3500 series don't, it cleans up airflow and guys claim a half mpg increas from this straight bolt on part. There is also a short flat piece that goes behind the top of the cab and helps redirect airflow over the open box. Supposed to work I can't find real use numbers

Today I saw a truck with a softtopper on it. It's like a convertible top, folds out of the way when not needed. The guy had the sides off, just the top was up and I was wondering if a straight piece of wood might be enough, even curved from the top of the cab slanted to the back of the tailgate.

Second thing I wonder about is the dam in the front, the trucks being so high off the ground what if the dam was more sloped backwards

[kach22i]

The chin spoiler really should not be any lower than the lowest thing on the underside which can grab air. My S-10 4x4 has been raised a little by a previous owner, and the chin is about 7-1/2" off the ground.

Chin Spoiler:
Chin Spolier - fast/easy/cheap/effective - Pelican Parts Technical BBS

If you have a cover on the bed, then yes air flow will trip over the top of the tailgate lip. On my older truck I re-directed it there on purpose with a roof wing. Your truck has an arc in the roof which does the same.

Rear Spoiler:
Rear Spoiler on Pick Up Truck - Experiment - Pelican Parts Technical BBS

Roof wing:
http://ecomodder.com/forum/showthrea...1-a-19525.html

From what I've reading and been seeing on pick-up truck wind tunnel pictures, they have addressed many of the issues you questioned. However, one of the wind tunnel pictures of the Ram has been said to be photo-shopped. I have no verification of that, it's just what another forum member claimed/observed.

http://s184.photobucket.com/user/kac...?sort=3&page=1

[PaleMelanesian]

http://ecomodder.com/forum/showthrea...bums-3541.html

[PaleMelanesian]

http://ecomodder.com/forum/showthrea...down-9732.html

Originally Posted by MetroMPG

So, in conclusion: a giant ugly air dam apparently has a greater positive effect on drag than rolling up the the driver's window.

[skyking]

I bellypanned my 96 diesel, used various grill blocks, and even made a testing aeroshell for it.
The trouble is, I have not run it any significant amount of time to collect data. I had more efficient rigs to drive. When it moves these days it is towing something heavy or large or both.

[kach22i]

Originally Posted by skyking

96 diesel, used various grill blocks.......

If you ask me, grille blocking a Diesel is dancing with the devil.

I cannot see how the benefits would outweigh the risks.

[skyking]

Not at all. One of the things about a truck like mine is huge excess cooling capacity.
It was designed for a worst case scenario of making a continuous 180 HP while towing a 9300 pound load up a steep grade at high altitude on a hot summer day.
Real world loadings are paltry, by comparison. I ran it all last winter with NO cooling fan, for example. Then I started blocking the grille off to see what heated up. I have instruments for transmission temps, EGT, intake temps, you name it.
Now I have a couple of electrics that I run on low speed when towing the 5th wheel.
Last week I took it up to 5000 feet on a cool day on Rainier, towing an empty 3500 pound flatbed trailer with the fans turned off.

[kach22i]

I stand corrected then.

[Diesel_Dave]

Yeah, I've run (unloaded) in 100 deg F heat with the grille 100% completely blocked off and didn't overheat the coolant. That requires several other efficiency improvements (EOC P&G and others), but illustrates the point.

[kach22i]

I drove a 1986 Diesel Golf from 1985-1990, put 80,000 miles on her (purchased new). At around 60,000 miles it blew a head gasket, which apparently they were known for. Mostly covered by the extended warranty I purchased. It was an expensive policy and an expensive repair - I broke even.

I don't think my electric fan ever went on, even had the dealership check it in the first few months of ownership because I thought that it was odd and perhaps broke.