KahneFan Posted March 18, 2006 Report Share Posted March 18, 2006 I had a thought as I was cruising down the highway today. If a truck could have a tailgate that, similar to a Crossfire, had a tailgate that moved at a certain speed (i.e. 55+), could this be helpfull? I know it would appear strange at first, but f it helps with MPG and maybe HP(?). Basically imagine the top of the tailgate would be on a pivote of some sort (but could still open), and the bottom of the tailgate actually moved out about 3 inches or so, would this do two things; 1) Allow the air to pass through the bottom of the gate allowing less dead drag and increase MPG? 2) Give a healthy clean downforce to the rear tires to help with traction and maybe more HP? I have no idea if this would actually help with MPG or HP at all, which is why I was looking for the professionals input Even if it wasn't intigrated (SP?) with the truck, but maybe an add-on which you have to manually adjust your tailgate before the trip (less $$). Link to comment Share on other sites More sharing options...
Truck38 Posted March 18, 2006 Report Share Posted March 18, 2006 I know this is kind of nerdy but I was in engineering as my major in college it just didn't work out. BUT before I quit that, we had some homework problems with drag and stuff and we learned that at about 65 mph the air coming over the top of the cab doesn't hit the tailgate(on a full-size pickup). So people going 80 with their tailgate down don't actually save anything. But 65 and slower is were the savings are. If you're crazy enough when it is raining really hard go 70mph and watch the rain drops out the rear-view mirror. It should give you and idea as to how fast it actually is. Don't know if this helps but it might. We also did some stuff on the effects of A/C vs Windows down and how it effected HP. Link to comment Share on other sites More sharing options...
KahneFan Posted March 18, 2006 Author Report Share Posted March 18, 2006 I know this is kind of nerdy but I was in engineering as my major in college it just didn't work out. BUT before I quit that, we had some homework problems with drag and stuff and we learned that at about 65 mph the air coming over the top of the cab doesn't hit the tailgate(on a full-size pickup). So people going 80 with their tailgate down don't actually save anything. But 65 and slower is were the savings are. If you're crazy enough when it is raining really hard go 70mph and watch the rain drops out the rear-view mirror. It should give you and idea as to how fast it actually is. Don't know if this helps but it might. We also did some stuff on the effects of A/C vs Windows down and how it effected HP. So just tell the cops I was worried about the downforce on my tailgate? Is the dowforce below 65 enough to make a huge difference in MPG? I also have a crew cab, so the extra length of roof combined with the shorter bed probably puts my breask point closer to 55/60(?). Link to comment Share on other sites More sharing options...
Jason Posted March 18, 2006 Report Share Posted March 18, 2006 Its more the drag than downforce that is affecting your mpg. Link to comment Share on other sites More sharing options...
tps48 Posted March 18, 2006 Report Share Posted March 18, 2006 Its my experience that your right foot has more to do with your gas milage than your tailgate.....maybe get you some of those magic fuel line magnets that straighten out you gas molecules and add HP too. You probably could reduce drag by folding your mirrors in too.LOL Link to comment Share on other sites More sharing options...
Truck38 Posted March 18, 2006 Report Share Posted March 18, 2006 Is the dowforce below 65 enough to make a huge difference in MPG? The monkey is right drag is what's killing the mpg. The amount of drag is exponential for all those aggies out there than means it gets big really fast. The amount of drag is doubled from 50 to 70mph. Since most cars are in their top gear at 55(some cars as early as 40-45) all your doing past that is reducing your gas mileage. The more rpms without another gear the more gas you're burning. The length of the cab doesn't matter so much but the length of the bed would. Link to comment Share on other sites More sharing options...
Truck38 Posted March 18, 2006 Report Share Posted March 18, 2006 Its my experience that your right foot has more to do with your gas milage than your tailgate..... yeah that was more of what I was trying to get at, I guess that's why I never really tried posting things because I talk too much. Link to comment Share on other sites More sharing options...
1-Crew Posted March 18, 2006 Report Share Posted March 18, 2006 This was the subject of a recent Mythbusters episode.. Two identical trucks, identical route and speed and a fixed amount of fuel. One truck tailgate down, the other tailgate up. The tailgate up truck went a longer distance than the tailgate down truck.. Link to comment Share on other sites More sharing options...
Lonesome Ford Posted March 22, 2006 Report Share Posted March 22, 2006 Reverbation of the wind hitting the tailgate and comming back to hit the back of the cab, in effect pushing the truck. Hehe good theory anyhow Think about sand, gravel, trash, etc in the bed of your truck. Where is most of it when you stop?... against the front of the bed. Link to comment Share on other sites More sharing options...
arts22 Posted March 22, 2006 Report Share Posted March 22, 2006 I had a regular cab truck and when I had a truck load of people I would open the sliding window and the empty beer cans would fly in and hit the person in the middle. Ah, the good ole'days..... The air goes over the cab, hits the tailgate and funnels back towards the cab, making a circle of air in the bed. Link to comment Share on other sites More sharing options...
Truck38 Posted March 22, 2006 Report Share Posted March 22, 2006 I used to do that same thing, me and my brother would set people up for that. It was always a joke between us. Link to comment Share on other sites More sharing options...
tqj3 Posted March 22, 2006 Report Share Posted March 22, 2006 If you'll remember, we used to lie down in the truck bed to get out of the wind. There's kind of a bubble of air that circulates there, while most of the air flows over it, and over the tailgate. Dropping the tailgate moves that air mass down, and you end up with a lot of turbulence behind the truck, the kind of turbulence that causes drag. Some engineering students at the University of Michigan talked GM out of a wind-tunnel model of a pickup and ran some tests. Among other things, lowering the tailgate reduced fuel economy. But adding a shaped piece along the top of the tailgate, or increasing the height of the tailgate slightly, actually improved fuel economy. Air does weird things. Link to comment Share on other sites More sharing options...
REBELRACER Posted March 22, 2006 Report Share Posted March 22, 2006 it would make sense (the taller tail gate) if it is up.......if it is down it would seem like it would be like a sort of spoiler on the rear of the truck increasing the drag, and also decreasing the gas mileage...........wonder how one of those steel open web tail gates (gator net i think it is called) would factor in on the fuel milage deal..........seems like the wind would flow thru it so it wouldnt create drag, and maybe not decrease the fuel milage.......... Link to comment Share on other sites More sharing options...
tqj3 Posted March 23, 2006 Report Share Posted March 23, 2006 RebelRacer- That was the point: dropping the tailgate increases drag and hurts fuel economy. The open nets at the rear don't solve that problem; the fuel economy is still harmed by the increased turbulence and drag generated by having the tailgate down and allowing the air to move through the opening. Link to comment Share on other sites More sharing options...
KahneFan Posted March 23, 2006 Author Report Share Posted March 23, 2006 I don't know if I explained the original theory very well. Y'all are talking about dropped/open gates. I'm talking about the top of the gate staying where it is, and the bottom of the gate actually opening 3 or 4 inches to allow the air hitting the gate to follow it down and out, instead of bouncing back in... what would that do? Link to comment Share on other sites More sharing options...
Jason Posted March 23, 2006 Report Share Posted March 23, 2006 I think during a F1 telecast the other day they mentioned teams were using a spring loaded "wicker" between the upper and lower parts of the rear wing. At highspeed it lets down allowing for less drag and at lowspeed/braking it creates more downforce when it comes back up. Link to comment Share on other sites More sharing options...
tqj3 Posted March 23, 2006 Report Share Posted March 23, 2006 KahneFan- Most likely it would create massive amounts of drag both at the tailgate and behind the truck. Link to comment Share on other sites More sharing options...
KahneFan Posted March 23, 2006 Author Report Share Posted March 23, 2006 KahneFan- Most likely it would create massive amounts of drag both at the tailgate and behind the truck. Gotcha, thanks!! So, it may push the tires to the ground a little more, but it would hurt MPG. Link to comment Share on other sites More sharing options...
Bar2248 Posted March 23, 2006 Report Share Posted March 23, 2006 I know of this guy that was racing at Longhorn speedway and SA back in the 80's and back then they had those tall spoilers (roof high spoilers)... well the spoiler had a hinge on it but in teh pits it was legal, had pins in the back of it...at 45 mph the spoiler would lay back... people complained about it once teh car hit the track "hes cheating" well the tech official back then said "if you can find a way to check it while hes on the track and its illegal Ill throw him out, until then its legal in teh pits, so he can race!" the driver was told to change it beofre he came to SA, b/c if it laid back at Longhorn it would def lay down at SA! Also my dad took his spoiler off at the 1/2 mile in Altus, eveybody knew what he was doing (trying to get more speed down the straightaway, but he never made it down the front stretch spinning half way through the tri-oval and ending up by the tires off of turn 1. just thougth Iwould give yall two examples of some storrys I heard. Link to comment Share on other sites More sharing options...
lcpyltx8 Posted March 24, 2006 Report Share Posted March 24, 2006 I dont know if this was already said, i didnt read ALL of the posts, but i think i can come up for a resoning for this. My theory is that with the tailgate up the "drap" air that hits the tailgate has to go somewhere, so it folds back toward the cab. When it hits the front of the bed it the is "bent" again towards the sky. when the "newer air" coming over meets with the older air (air that origionally hit the tailgate), the newer air almost creates another "wall" so to speak and the air in the bed keeps rolling over and over creating a shell, so the air completely passes over the truck, tailgate and all. With the tailgate down, the air falls down onto the bed, never circulates and creates downforce and exits over the tailgate. I think the extra downforce would create some drag by making the truck seem heavier, using more gas. An example i can think of would be: i know i've been driving down the road and i see a truck pull up with nothing in the bed but a styrofoam (sp) cup and it just circles around and around and never gets blown outta the back. Idk, kinda confusing, but thats how i believe it can work. -Shawn Link to comment Share on other sites More sharing options...
Pacecar Posted April 17, 2006 Report Share Posted April 17, 2006 If Eddie Wallace shows up at TMS, it's because he has implemented the Renault active synthetic jet to reduce his aerodynamic drag. http://www.webwombat.com.au/motoring/news_...ica-concept.htm Link to comment Share on other sites More sharing options...
Budman Posted April 17, 2006 Report Share Posted April 17, 2006 That ad is just down right funny to read. "Hardcore headlights?", "That are said to ..... increase low-light visibility"......... well Duh! Link to comment Share on other sites More sharing options...
Ford27 Posted April 17, 2006 Report Share Posted April 17, 2006 Wow what a response but no, allowing air to escape at the bottom will not increase mpg,it will still cause turbulane drag not to mention the drag caused by the air rushing against the tailgate to replace the air that was lost through the opening. also the cushion of air is called a seperated bubble or if your a real nerd its called locked vortex flow. great now I feel like a nerd for knowing that..oh a tonnue cover is about the only way to increase mpg.usally about 5% depending on the truck and type of cover. Link to comment Share on other sites More sharing options...
Guest bigfat Posted April 17, 2006 Report Share Posted April 17, 2006 They won't work as well as my Solar Powered Flash Light. Link to comment Share on other sites More sharing options...
txtom Posted April 17, 2006 Report Share Posted April 17, 2006 If Eddie Wallace shows up at TMS, it's because he has implemented the Renault active synthetic jet to reduce his aerodynamic drag. Dang it, Larry, how did you find out about our latest Bandit Racing Project?! This one was so secret, even we didn't know about it! Link to comment Share on other sites More sharing options...
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