Skid plate for the entire underside

[zaid3ssaf]

I am considering getting the entire underside of my Bravada covered with a skid plate. Well not the entire underside, but from the front of the transmission to the rear trailing arms alongside of the frame. Does anyone have experience with this? and are there any concerns about aerodynamics/airflow cooling components?

 

[Matt]

Why? What's your mission? You really only need the radiator and oil pan covered...I have an MDB bumper and skid plates for sale.

 

[zaid3ssaf]

For aerodynamics on the highway. I don't do any off roading. I get about 22 mpg highway right now but I am just experimenting to see if a plate would make a difference.

 

[TollKeeper]

I was actually doing some reading on this Friday..

A front bumper splitter, to push the air out to the sides, instead of getting caught under the vehicle, does help. You have to find a balance of how low to go, before it becomes a every day annoyance from hitting parking curbs, and dips in the road.

I also read that a simple bug deflector on the front of the hood can help. It catches some of the air, and pushes it up over the cab.

I have also heard that these work on cars and trucks, if placed correctly, and makes the air move, instead of tumble (creating suction).

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Airtabs™ are powerful vortex generators that reduce vehicle drag, save fuel, and improve vehicle safety by improving stability and mirror visibility in rain or snow.

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[zaid3ssaf]

I was actually doing some reading on this Friday..

A front bumper splitter, to push the air out to the sides, instead of getting caught under the vehicle, does help. You have to find a balance of how low to go, before it becomes a every day annoyance from hitting parking curbs, and dips in the road.

I also read that a simple bug deflector on the front of the hood can help. It catches some of the air, and pushes it up over the cab.

I have also heard that these work on cars and trucks, if placed correctly, and makes the air move, instead of tumble (creating suction).

Airtab | Aerodynamic Fuel Savers | Welcome

Airtabs™ are powerful vortex generators that reduce vehicle drag, save fuel, and improve vehicle safety by improving stability and mirror visibility in rain or snow.

www.airtab.com

on ecomodder, I found that most had mixed opinions/experience about vortex generators and bug deflectors. However, the bumper splitters seem to work quite well. I am considering the splitter alongside a belly plate. Perhaps I'll bend a long piece of sheet metal and drill holes in it to hold it to the frame with rivets.....or zip ties

 

[Mike534x]

I feel like doing an entire underbody skid plate would be a waste honestly, these trucks have the aerodynamics of a brick. I'm lucky to get 23 mpg on a good day with the V8, usually mine hovers around 19-21 typically. The thing that would probably help the most, is just reducing the the trucks weight by removing whatever it is you don't need.


Though I always wondered, if the gas mileage on these things would've been better if GM had used a 5 or 6 speed tranny with a higher rear gear ratio like they're doing now with the Yukon/Tahoe ( I think they started using 3.08 a few years ago?). Not sure if it would make a difference, but it seems to work well with the newer trucks (AFM/DoD aside).

 

[Mektek]

I was thinking of making a cover for the entire area behind the rear axle to make it more aerodynamically clean. The back bumper area adds drag like a sail. It also fills with debris when off roading. I imagine it would fill with slush and ice in cold climates.

 

[LikeEnvoy]

Mektek: "I imagine it would fill with slush and ice in cold climates."....

Yes it does. Every now and then a HUGE piece of ice comes loose and hangs down. I sometimes kick it gently until it breaks free and falls out. If it doesn't, I have to wait until the exhaust heat melts it enough to drop; sometimes a bump in the road helps.

 

[zaid3ssaf]

I installed a sheet of coroplast from home depot. It went from the transmission to the back of the gas tank. I went mudding few times and actually it kept the drive shaft and all the other components clean. The 36" wide sheet fits exactly from frame rail to frame rail. The GF says it's quite as far as road noise but I can't hear a difference.

I'll probably use another sheet to cover all the way to rear bumper but I haven't figured out the spare tire yet. Also I put a small sheet of sheet metal between the coroplast and the catalytic converter as a heat shield

 

[azswiss]

While reducing noise reduced airflow along the underside may result in lower heat transfer from the cat. Suggest you periodically monitor temps (use you hand) in the areas beneath, around & above the cat (i.e. interior floor, compare vs. areas not above cat). This will be especially important once the weather heats up again in the spring/summer.

 

[zaid3ssaf]

I think my catalyst is degraded anyway because I had P0420 that I bypassed. The sensor is working fine.

Wouldn't a hotter cat make it more efficient?

 

[azswiss]

My concern would be excessive heat build up due to reduced cooling and potential flamability of the coroplast sheet.

(Note: two of my personal mantras are "Only the paranoid survive" & "Trust but verify")

 

[TollKeeper]

I think my catalyst is degraded anyway because I had P0420 that I bypassed. The sensor is working fine.

Wouldn't a hotter cat make it more efficient?

Not if it gets to hot and melts the interior comb.

 

[zaid3ssaf]

I'll keep an eye on it with an IR gun. Alternatively, I can cut a hole to direct some airflow onto the CAT.

 

[mrrsm]

The problem you are actually facing here involves the daunting issues of Pure Physics and "The Demon of Energy Transfer".

There are Three Forms of Energy Transfer:

(1) Conduction
(2) Convection
(3) Radiance

In the same manner that you can look up at the Sun on a VERY Windy Day... and STILL feel its Powerful Heat upon your Face and get Sun Burned, regardless of having any Re-Directed Air Flow from above or below the Full Floor Pan, the Radiant Energy coming off of the Exhaust Manifold, Exhaust Piping AND an already excessively HOT Catalytic Converter (600-900 Degrees F) will constantly be getting absorbed by any adjacent Full Floor Pan.

So paradoxically, adding in a Floor Pan would act instead as a Heat Sink... completely defeating its usefulness in evacuating the escaping Heat Energy created by burning Gasoline with Air.

Besides this, in order for you to get any real Aerodynamic Benefit from adding that Full Pan underneath the vehicle... you would have to also add an Ogive shaped Nose Cone to the presently "Blunt Front" of your SUV (...think 9mm Bullet shaping here) AND be moving along at over normal highway speeds for it to begin to take any useful affect.

There is nothing wrong with thinking about making such modifications. But most of the time, the sheer reality of the Physics involved, along with 'Practical Necessity' will win the argument in the end in favor of keeping things "As Stock As A Clock".

 

[zaid3ssaf]

White coroplast is definitely not good for radiant energy. Stefan–Boltzmann law tells us that a radiation total energy radiated per unit surface area of a body across all wavelengths per unit time is directly proportional to the fourth power of the body's thermodynamic temperature T. Ie, the hotter the CAT, the higher the radiant energy, the more reflectance the white coroplast will have

While it's fun to see whether this modification has any aerodynamic effect on the mpg, the main purpose is to protect the underside of the vehicle from rusty salty midwest roads, especially evap and brake lines. I have to re-spray fluid film once a year. This year the film is still intact.

 

[mrrsm]

NP... Just answering All Three Questions you raised in your Original Post #1... :>)

"...and are there any concerns about aerodynamics/airflow cooling components?"

Not to put too fine a point on the issue... but you might want to review the Coroplast Materials Sheet at this Link as it indicates the product melts at 320 Degrees Fahrenheit... and know that Metal Plate you installed as a CAT Barrier may still absorb enough CAT Heat to become a problem:

https://www.coroplast.com/wp-content/uploads/Coroplast-standard-sheets-SDS-06-07-19.pdf

"Every Solution ...Breeds New Problems..." Arthur Bloch