Front splitter Rear spoiler

[myth]

Don't throttle me to bad for this. I figured it would be better ask in here then any other forum. Lets talk about spoilers and splitters on trucks. Im mainly curious to see how well they work in an autocross situation. Does a rear spoiler do as well without a bed cover? Just thinking about future plans.

[Sales-TCI-Eng]

We plan to go 200mph with our c10 so aerodynamics and downforce will be important. For autocross speeds...….it is highly unlikely that #bigwangs and splitters are going to make much difference.

I've spent a lot of time looking up info on truck aerodynamics. There's not much out there specific to trucks so for our truck we are just going to try to apply the basics.

At highway speeds the air exiting the back of the cab will still "land" behind/above the tailgate. Directing that air to a specific wing height/distance is going to be the trick at any given speed.

Still curious to see if anyone has first hand experience though.

-J

[myth]

Some aero would help your truck for sure. I too did some digging on truck aero and came up short. I understand what you are saying about the air coming over the cab. I have done a good bit of looking into spoilers and it is said that even at slow speeds(30 mph) there is still down force to be gained. But if you cant get it to hit the spoiler then it does no good. Thank you for chiming in.

[CSG]

For the rear spoiler Tape some stringers on top of your tailgate and see what the air is doing at speed. As far as a splitter, I wonder if you can get it low enough to do any good without it looking bad.

[FlyDoc]

I don't see why they would not help, air flow over, and design of each are specific to vehicle and use. you design for your C-10 will defiantly be different than for a Corvette.
I have a '65 C-80 long hood, Fire truck. I have the rust free cab and fenders, kept the cool brackets and hardware from the tanker box. the truck has a massive 12000 original miles! I purchased the truck for the 348W motor to put in a 64 Impala convertible. my son claimed the fire truck so it will become a race truck with a nice interior.

[Adam_T]

I'm curious about this too. You see them a fair bit on open boxes and am wondering how effective they actually are and how high they need to be?

[CSG]

https://afinemesh.files.wordpress.com/2014/01/autodesk-flow-design-truck-streamlines.jpg

I see a lot of different results with different trucks but interesting none the less

[Frank ZX]

I have been curious of pickup truck aerodynamic myself. I have talked to a few people semi familiar with aerodynamic in general. From my understanding, taping strings of yard all over a truck and videoing will help understand whats going on. I would give anything for some wind tunnel testing of my truck.
My truck relys on some airflow for cooling the supercharger heat exchanger mounted in the bed.
I have a bed cover and a rear spoiler. I'm not too sure how much it helps.
Now a front splitter I feel does help at low speeds and heres my experience. I had a homemade splitter on my truck at one time. I turn off a highway onto a side road nearly daily. With the splitter my truck made the turn at 55mph easily.
It was damaged from parking too close to a curb so I removed the splitter. While making my usual 55mph turn I noticed the frontend pushing to the point It scared me.
I do think a front splitter Could help atleast some trucks.

[Frank ZX]

We plan to go 200mph with our c10 so aerodynamics and downforce will be important. For autocross speeds...….it is highly unlikely that #bigwangs and splitters are going to make much difference.

I've spent a lot of time looking up info on truck aerodynamics. There's not much out there specific to trucks so for our truck we are just going to try to apply the basics.

At highway speeds the air exiting the back of the cab will still "land" behind/above the tailgate. Directing that air to a specific wing height/distance is going to be the trick at any given speed.

Still curious to see if anyone has first hand experience though.

-J

See my previous post. As my truck is sat up right now coasting @ 70mph off a 6% grade my truck picked up speed . Before the same grade and mph it actually slowed down.
Keep in mind I added a few tricks like bearing spacers so that could have helped parasitic drag instead of aerodynamics.

[cornfedbill]

Years ago when I was at GMC Truck, they were working on a Bonneville Sonoma for marketing. They ran a lot of wind tunnel tests the the GM Tech Center in Warren.

They found that covering only the rear half of the bed was best for reduced drag.

Unfortunately they did not supply any results for spoilers and downforce.

At low speeds such as in autocross, it will take a large spoiler to make much difference. Look at some of the CAM and Good Guys autocross cars. They have tall spoilers that sit at a high angle.

I don't have any experience with a splitter. But my experience with an air dam that nearly touches the ground is that they can be quite effective down to about 50 mph. The lower the air dam, the more effective it is at low speeds. To make this work you need to limit the air bypassing it through the grill.

So I would assume a very low splitter with a lot of horizontal surface area in front of the air dam that it is attached too could be effective at low speeds.

[Sales-TCI-Eng]

See my previous post. As my truck is sat up right now coasting @ 70mph off a 6% grade my truck picked up speed . Before the same grade and mph it actually slowed down.
Keep in mind I added a few tricks like bearing spacers so that could have helped parasitic drag instead of aerodynamics.

70mph is pretty fast, definitely above most average autocross speeds. However, those types of tests are fun/interesting so long as you can remove as many variables as possible. I like the string idea.

I'm real curious how much back pressure and turbulence is at the windshield base. We may delay cutting holes in the hood until we know where they need to be, or at least where they shouldn't be. We've been told at least 12" forward of the base but that was based on S10 which doesn't have nearly as steep of a windshield as the earlier trucks. I will most definitely be messing around with different things on #ctwin.

-J

[cornfedbill]

I'm real curious how much back pressure and turbulence is at the windshield base. We may delay cutting holes in the hood until we know where they need to be, or at least where they shouldn't be. We've been told at least 12" forward of the base but that was based on S10 which doesn't have nearly as steep of a windshield as the earlier trucks. I will most definitely be messing around with different things on #ctwin.

-J

I would be very interested to understand what the holes in the hood do for downforce. The hood on my old Vega with a very large air dam that nearly dragged on the ground had a significant pressure differential. It was enough (the hood opens in the rear) to compress the hood spring at highway speeds. Holes in the hood may balance the pressure and reduce downforce.

It depends if the goal is to reduce drag or to increase downforce. The Laws of Physics do not allow us to do both. If you are autocrossing, I would guess that downforce is king.

[Sales-TCI-Eng]

I would be very interested to understand what the holes in the hood do for downforce. The hood on my old Vega with a very large air dam that nearly dragged on the ground had a significant pressure differential. It was enough (the hood opens in the rear) to compress the hood spring at highway speeds. Holes in the hood may balance the pressure and reduce downforce.

It depends if the goal is to reduce drag or to increase downforce. The Laws of Physics do not allow us to do both. If you are autocrossing, I would guess that downforce is king.

We're planning on going 200mph with it so drag is a major concern.

I'm just trying to keep any unused air from entering the engine compartment. Planning on sealing the intercooler to the core support, the radiator to the intercooler and the hood vents to the radiator. The radiator will be laid over roughly 45 degrees though.

Oh and it will have a belly pan.

[cornfedbill]

We're planning on going 200mph with it so drag is a major concern.

I'm just trying to keep any unused air from entering the engine compartment. Planning on sealing the intercooler to the core support, the radiator to the intercooler and the hood vents to the radiator. The radiator will be laid over roughly 45 degrees though.

Oh and it will have a belly pan.

Okay. That makes sense. Then I would consider covering only the rear half of the bed like GMC did. They spent a lot of time in the windtunnel.

If it were me, I would have a long spoiler hanging off the rear with very little angle to it to get the air to flow smoothly off the rear.

Take a look at this example. The taillights make it look like the spoiler is part of the bed. Actually it hangs rearward quite a bit.

164519

[HUSTLESTUFF]

https://www.allpar.com/racing/missile/aero-testing.html

String Theory. Probably a little easier with go-pro's these days

[Northern Bel]

I saw this “truck” go over 200.
https://www.hotrod.com/articles/uncatchable-the-land-speed-rat-rod-truck/

This one too.
https://www.safety-kleen.com/about-us/news/performance-plus-motor-oil-helps-jesel-racing-set-land-speed-records

[aventino68]

Working through my aero issues, where did everyone end up with rear wings. From what I've looked at online trucks are a real mess with respect to flow breaking up behind the cab. Most doing Pikes Peak where huge aero is needed for the thin air give up on containing or controlling this and make do with a rear wing up out of the dirty flow. Quite the opposite of the Truck racing but that's probably constrained by rules. Thoughts?