SaintLos

Newer trucks have cabs that are designed to form this "air cushion" within the bed. I remember driving at 75mph and having an empty styrofoam beer cooler do somersaults within my bed, sometimes reaching as high as the cab itself, but never leaving the bed ....I've seen older trucks that do actually get better mpg with the tailgate down (un-scientific observation of older rigs I've driven)

8100hammer

I have a roll up tonneau cover("access cover" type). And run without tail gate and full tonneau. Does not weigh that much ethier, just 4 alum rails, 2 with rip your fingers off velcro. Don't think it weighs more that 20 lbs. best of both worlds at the strip!!

Black Blown 02

I ran the numbers through a calculator I found. http://www.nightrider.com/biketech/accel_sim.htm

13.54 @ 103.46 with the tailgate removed C/D-.5596
13.52 @ 103.92 with tailgate up C/D-.5304
13.49 @ 104.45 with tonneau C/D-.4967

Don't know how accurate those #'s are, but according to those, it's more worth losing the weight than keeping the tailgate or tonneau. Considering 100 lbs = .1 off ET.

Blown Yellow

I am actually in the shop right now trying to squeeze every last pound
out of my truck so that I can hit the track for the first time and check my numbers. I am running a snug top cover with full box carpeting and it is the last item I am scratching my head about. I would think that the at least 180 pound difference that losing it all has to make a way bigger difference than the possible aero dynamic losses of removing the items.

Maybe I will do a run right now with everything on, then strip everything of and do a back up run.

Martin

Sportfish

There are two diagrams with the R&T article which depict the wind tunnel air flow. With the tailgate up, it shows the air flowing over the cab and bed in smooth lines, and the air from under the tuck exiting smoothly at the rear. The two air streams merge a few feet behind the tailgate. With the tailgate down, the air flow drops into the bed about midway back and then some turbulence occurs as it flows off the tailgate. The air flow exiting from under the truck is disrupted and is lifted up and reversed over the tailgate instead of flowing straight back to meet the upper air flow.

One thing to keep in mind when attempting to compare wind tunnel results to track results...wind tunnel testing employs pretty constant factors and results are repeatable. Track results will of course vary from day to day with weather conditions, with your reaction times, and how much junk is still laying around in the bed from the party the night before.

tooquick2beslo

I knocked off 2 tenths when not having the tailgate on. I picked up 1 mph also.
I always take my tailgate off when I go to the track.
I have also tried it with the tailgate down and that didnt show any increases at all.

Sportfish- I laughed hard at the last sentence of your post. The **** from the party the night before.....hehahaha

zippy

well, you are also leaving out weight transfer. if you leave the tailgate on the truck and put it down, you gain the leverage of 45lbs at the back of the truck over not having it at all. this is the same reason the old timers use to move the rear axle forward, more overhang. if traction isn't an issue, remove it without a doubt. another thing to consider is that the newer trucks are built with the tailgate in mind, but that doesn't cover all years.

TheOtherDodge

Keep in mind that a wind tunnel test uses air speeds that are not the same at the track. I am not sure what air speeds they use, but remember, you are starting out at 0 mph and wont get to around 60 mph for around 6-7 seconds (depending on truck). So there are a few things to consider about "the tail gate issue": will the savings in weight (without it) overcome the worse drag coefficient (that does not take place for about 6 seconds or so)? Will not having that weight in the back hurt traction enough combined with the worse drag coefficient to over come the weight loss?

I really think the only way is to do it at the track and every truck will be different based on what kind of times they run to begin with.

OBXMarine

iTrader: (2)

Here ya go!

https://ls1tech.com/forums/showthread.php?t=175338

Sportfish

That's a good point and the article doesn't give any of those details. One would assume they did their testing at typical highway speeds, so the drag coefficient effect wouldn't be nearly as applicable in the 1/4 mile as it would for gas mileage on trips. Perhaps the weight factor of a tailgate is more important than the DC for track performance, except maybe for those 100+ MPH screamers like PARISH8, or if you happen to be in Florida during hurricane season.